Chevy 4.8L Vortec Common Engine Problems
Meet Jake
Jake is a founder of 8020 Media and has been creating automotive content online since 2017. He has been the lead writer for Chevy Trucks and has transformed it from the old and outdated site it was into what it is today. Jake creates a ton of GM related content for the 8020 Media YouTube channel and specializes in Duramax and Vortec information but has a wealth of knowledge across all GM cars and engines. Jake believes the L5P is the best diesel on the market today.
The 4.8 Vortec was the base engine option for Silverado and Sierra trucks for years, until it was eventually replaced with the 5.3L Vortec as the base motor.
The 4.8L is actually just a smaller version of the 5.3L engine, with less stroke and less displacement. That engine is known for reliability which is great news for reliability and longevity of the smaller 4.8L Vortec.
The 4.8L Vortec is actually considered to be the more reliable of the engines, since it does not use active fuel management. However, the engine does still have a few common problems such as knock sensor failure, water and fuel pump failure, and intake manifold leaks.
Engine Variations
- LR4 (Gen III)
- 1999-2006 Silverado and Sierra 1500’s (as well as 2007 “Classic” models)
- 2000-2006 Tahoe and Yukon
- LY2 (Gen IV)
- 2007-2009 Silverado and Sierra
- 2007-2009 Tahoe and Yukon
- L20 (Gen IV)
- 2010-2013 Silverado and Sierra
These engines were also used throughout various Chevy Express and GMC Savana sprinter vans during these years. In the L20 version, the Tahoe and Yukon were upgraded to the 5.3 Vortec while the Silverado and Sierra remained on the 4.8 platform. Surprisingly enough, the LY2 platform was the only Gen IV Vortec engine to not feature variable valve timing.
Chevy 4.8L Vortec Engine Problems
- Faulty intake knock sensor
- Water pump failure
- Fuel pump failure
- Intake manifold and gasket air leaks
If you would rather consume this content via a video, check out our 4.8L Vortec Common Problems & Reliability video below:
1. Intake Knock Sensor
The engine knock sensor sits on the intake manifold and is responsible for sensing vibrations caused by the engine. The knock sensor, as you could guess, functions to detect and prevent engine knock. If you ever hear a “knock” or “ping” noise on your 4.8 vortec, it’s likely engine knock which is caused by pre-detonation.
The sensors responsibility is to detect this knock and then alter the ignition and engine timing to prevent it from continuously happening. The knock sensor is known to go bad or become faulty and throw check engine lights. When you have a faulty knock sensor, the engine thinks it needs to alter timing despite there being no timing issues, which can lead to a number of performance issues.
Faulty Knock Sensor Symptoms
- Check engine light and fault code (P0332 and others)
- Cylinder misfires
- Engine vibration, primarily at higher RPM’s and speeds
- Knocking or pinging noise from the engine
- Rough acceleration, poor acceleration, and bad fuel economy
Replacement Options
Fortunately, if you have a faulty knock sensor, the solution is usually as simple as replacing it. The knock sensor is about $50 and is a relatively easy DIY.
Replacement Part: GM Knock Sensor
DIY Replacement Video: https://www.youtube.com/watch?v=zGmAQVPxvi4
2. Water Pump Failure
Water pumps are an integral part of an engines cooling system. The water pump is responsible for flowing coolant throughout the engine cooling system to keep engine temps down. Heat is one of the most threatening elements to engine longevity. Therefore, failed water pumps can become serious problems if not dealt with once a problem arises.
On the 4.8 Vortec, the water pumps aren’t necessarily a common issue on low-mileage engines. But, most of these engines still around today are high mileage, and that is when these tend to become a problem on these engines. Usually around 150k mile mark is when you will experience water pump failure, or begin to notice that the water pump is becoming slightly less effective.
Water pumps can fail for a number of reasons: the internal impeller deteriorating, the pump bearing breaking, housing cracking, a bad gasket, etc. However, failure symptoms remain the same despite the reason for failure.
Water Pump Failure Symptoms
- Leaking engine coolant
- Engine overheating
- Water pump is making squeaking noises inside the engine bay
- Check engine light combined with reduced power or quick overheating
Replacement Options
Again, this is fortunately a cheap repair with most water pumps coming in below $100. The DIY isn’t overly difficult, but it can be if you do not have the proper tools. For most car guys with some DIY experience, it should be relatively easy to replace your water pump.
Replacement Part: 4.8 Vortec Water Pump
DIY Replacement Video: https://www.youtube.com/watch?v=dQUiXlFbUno
3. Fuel Pump / Control Module Failure
The 4.8 Vortec uses a sequential multi-port fuel injection system, which is jargon for saying that the fuel system uses a fuel pump to send fuel to the injectors which then sprays fuel into the intake ports.
When a fuel pump fails, it either stops sending fuel to the injectors, or it cannot keep the fuel pressure high enough. Obviously, when it stops sending fuel, the engine gets starved of fuel. When the pressure is too low, the injectors can’t properly spray enough gas in the engine causing it to run lean and misfire.
While there have been a number of instances of people killing 3 fuel pumps in a matter of 10,000 miles, this is very rare. For the most part, the fuel pumps hold up until 150k miles or so until they begin to fail or noticeably deteriorate.
Outside of the pump failing on its own, the fuel pump control module has been known to go bad on the 4.8 and 5.3 Vortec’s. The control module is responsible for communicating with the fuel pump and telling it how much fuel to send to the injectors. When the control module fails, it relays incorrect fueling info to the fuel pump.
Bad Fuel Pump Symptoms
- Engine misfires
- Running lean air-to-fuel ratios
- Engine “surges” or acts jumpy during acceleration
- Loss of power or rough idling / acceleration
- Poor fuel economy
- Engine won’t start (if fuel pump fully fails)
4. Intake Manifold and Gasket Air Leaks
Similar to the 5.3 vortec, the 4.8 has some somewhat common issues with the intake manifold and the gasket for it. The intake manifold control the flow of the air entering the engine and distributes it to each of the 8 engine cylinders.
On both of these engines, the manifold is made of plastic which makes it prone to cracking. The mainfold can crack or warp from excessive heat or also from being overtorqued. Most of the time, problems arise from common wear and tear as they sit right next to the engine where there is a lot of heat produced. The gasket for the manifold wasn’t designed very well, and naturally, gaskets deteriorate.
A cracked manifold or a bad gasket causes air leaks. When air leaks, it leaks prior to getting to the engine. When this happens, the engine doesn’t get as much air as it needs, which causes it to run rich air-to-fuel ratios and causes a number of performance related issues.
Intake Manifold and Gasket Leak Symptoms
- Poor idling, stuttering
- Slow engine starts or trouble starting
- Loss of power and lack of acceleration
- Check engine lights for rich/lean bank codes
4.8 Vortec Reliability
The 4.8L Vortec is a complete workhouse and overall a very reliable engine. The problems mentioned above aren’t truly very common and only tend to become common at high mileage, which is expected with any old engine. With proper maintenance and frequent oil changes, these engines can usually last 250k-300k miles.
Overall, the engine blocks are considered bulletproof and are very strong. The transmissions on these vehicles usually last behind the 200k mile mark as well, but sometimes might need to be rebuilt once you get to that mileage. Outside of the engine, the only thing to consider is various other maintenance on these cars as they get to high mileage. Usually by the time you get beyond 200k, you’re going to need to star replacing suspension components to keep your car road safe.
Nice overview thanks. At 175K throttle body sensor, purge valve and a/c core have been replaced.
I have a 2011 Chevy Silverado 4.8 vortec I have misfire power 307 I changed plugs I move around coils, wires and injectors engine light still on the dash and engine misfires on load up any idea what else it can be cylinder 7 has between 175 to 200 psi I don’t know where to turn
Change your fuel injectors if you already did the tune up and the coils the injectors and spark plugs work together
Did you ever figure it out? I have a 2010 Chevy Silverado 1500 and I’m having the same issue. The engine code says cylinder 8 misfire. I’ve changed spark plugs, spark plug wires, coil packs, fuel injectors.
I had about the same issues with 2013 5.3 New plus new intake gasket swapped coils and plug wires random misfire check engine light blinking not good
Finally replaced plug wires with new AC wires problem solved
Have you had any issues besides the throttle body sensor during the life span of your truck? Reason I’m asking is because I recently purchased a 1500 with a little over 181k on it and so far I have a list of things that need to be done to make it a 100% reliable but as far as I can tell it’s in pretty good shape besides some minor cosmetic and interior and a few things that a 20 year old truck would need in the first place.
My 2005 GMC Savana has 65,000 miles and throws a code of random misfire change the plugs coil packs and wires and still does the same thing wondering if anyone else has had similar problems
if you change plugs and coils and still that you should change crank sensor it will give you random mis codes
I had a 2001 Silverado 1500 with the 4.8 engine. I occasionally got codes as well. My mechanic did some research, and found out that some of the exhaust manifolds had a casting flash problem. The unremoved casting flash would heat up and cause a localized hot spot and caused the sensor to throw a code. unusual comma i know period this was a mechanic who was quite diligent about his research period i have not seen the casting flash issue mentioned in any articles period but comma he had a bulletin on it.
Possibly could be a fuel injector or the wire harness or it could be the injector spider web too dffect intake will have to be pulled to get to it good luck
Check the 4 common problem’s with that engine and one of them is the knock sensor 50 Dollar part it will cause misfire codes and hesitate on take of or at high speeds for it controls fuel pocket buildups in the cylinders..
If you take care of it properly it will last mine is at 287,000 miles
I recently purchased a 1999 1500 4.8 liter from the original owner. This truck has 350000 miles on it. I replaced the original shocks and replaced the tires. I also replaced the AC. Other than that the truck runs almost as new. The engine pulls strong and uses no oil. Transmission shifts crisp and doesn’t leak. If I didn’t use it to work out of and keep miles off my 19 f250 I would consider restoring it. It’s that good. I plan on driving it for a few years then handing it down to my grandson
My 2003 Silverado.was my grandfathers! Its an amazing 1st truck with a good engine! Good choice!
My dad’s, now my sons 2000 silverado just died. 451xxx miles, all original. Tranny went out. Too rusty and too many miles to spend the money on. Found an 06 with 50K on it for a good price, but not the same truck.
Since I last posted the transmission went out in my 99 Not bad with over 350.000. I went ahead and spent the $ since I couldn’t replace the truck for the cost of a rebuild It has developed a small exhaust leak that I will check into but it’s still running strong I wish my 93 Vette was this reliable
Dang nearly half million miles, that’s crazy!! My father in law, recently handed down his ‘99 Silverado ext cab, 277,xxx miles on it, you can’t even hear it running!! Shifts great, he’s had oil change and put water in it!! I like it, I just hope she (my wife) keeps it!!
Ken,
I have the same truck I bought new in 2003. At 150k I started towing a 28ft travel trailer a few weekends a year and a 20ft ski boat. Drove it in Atlanta traffic 76 miles round trip until it had about 200k on her and handed her down to my daughter in 2013 to drive to school. No issues but with the miles and daughter wanting the truck, thought it was a good time to
Get a new one. Daughter named her Sally. Sally got my daughter through high school and then went off to college for 4 years with her. After graduation my daughter married and moved into a new home. Her husband worked locally and was in need of a newer car so I signed Sally over to them officially 2 years ago. She now has 264k on her and is still as quiet as a sewing machine. Truck looks brand new still. Sally stole my daughter’s heart and it will always be a part of the family. Ive installed 2 alternators on her, a water pump, new shocks, upgraded stereo, replacement gauge cluster due to step motor issues, center arm rest, and a circuit board that caused the AC not to run on high. Other than that, tires, spark plugs, and oil. Best truck I’ve ever had…
She has an actual name given to her by the factory if it’s a cat eye pull the trim right above the cluster and you’ll see mine is peggy 309k running strong
They are with preventive maintenance but you must keep the maintenace
I have a 2009 Chevy Silverado with 4.8, I have 203,000 miles. Just started shifting hard from 1-2 gear, check engine light comes on throws PO700 then will clear on its own, the next day engine light might or might not come on until next day. Think I have a loose wire, can anyone help me with this? Other than that the truck looks great and I have nothing but good things to say about this truck
Reset trans controls module: find on internet. Tcm evenually will wear out.
My 2010 is showing the stabilitrac and traction control light. If it’s the 4.8 with no AFM what suggestions do you have?
Try replacing the negative battery wire. I know a bunch of 2010 that this fixed alot of electrical issues.
I have a 2006 4.8 Sierra. Couple issues 1st being when I roll the windows up the lights will dim meaning all of the lives headlight – don’t lie also also went to put put right front back together after it flew off caliber path caliber pad’s hub assembly Caliber bracket at 8:45 at night got the parts low and behold they were too small was curious if somebody changed front axle and made it in HD because that’s the parts that fitted the regular parts were too small
Could be steering position sensor,mine was.Clear the lightusing the trip odometer button on the gage cluster,if it is that the light will come back as soon as you move the steering wheel.Its located at the base of the steering column,totally doable as a DIY,just look up video on youtube .
Mine did same , replaced the break light switch on break pedal . 12 bucks on Amazon . That’s what mine was .
check the the code for this!! …have it scanned!! mine 2010 Silvy 1500, was a PITAss TC/ST “lights”/”ding dongs” for over a year!!… no tire pressure sensors at fault… scanned code told me “steering wheel position sensor”… never would figure thered be such a thing… replaced!!… “ding dongs” went away for good!! omg Im sooo glad. thanks – DTM
My 07 sierra just rolled over to 329000 an runs like a champ. Never one mechanical problem. Great pickup
My 09 has 32500 just replaced the map,maf,tps but still running like a champ tonka tonka
My ’09 4.8 L motor in a Chevy Silverado Truck, does NOT have Knock Sensors under the Manifold! On this truck they are on the lower side of the engine block, left and right. What did go out on mine, 25k, is the water temperature sensor. It ran real rough for about a month until a kind mechanic at O’Reilly’s Autoparts gave me the tip! Too, I am learning the hard way, 33k, to have the Transmission oil flushed. IOW do NOT follow the manual which states under heavy use the build is good till 50k, and under light use to 100k. That’s rubbish! In south Texas, hot and humid, I now watch the transmission temperature all the time! I am thinking of installing a transmission oil cooler!
Twice in 3 years I smell the burning transmission oil, and being an idiot I ignored it, relying on the dealership certified service to spot and recommend. Still don’t know if I damaged my auto transmission, but lesson learned. It will now be changed every 25 k or, 3 years.
If you bought a new Chevy truck, take my hard earned advice. Change the brake fluid every 2 years; the coolant every 3 – 4 , transmission fluid every 3 years / 25 k; engine oil, irregardless of what the silly computer says, twice a year, or when it says 40%, about 4 k miles. Don’t only rely on GM inspection, listen to your truck!
If I did it again, a new truck, I would change the transmission oil every 3 years or 25k miles, new filter and gasket, but leave the flush till it shows it needs doing.
Great truck BTW! No doubt about it.
I bought my 2003 Chevy extended cab 4×4 4.8l May of 2020. Been a great truck! It had 175,500 miles on it when I bought it. It now has 188,200 miles on it. I had the U joints replaced, the entire front suspension replaced, tune up, Synthetic Oil changes and a water pump replacement as well. The Air is as cold as it was brand new. My ears are cold when I get out. And it has great heat. The stereo has been replaced also. I plan on seeing how many more miles I can get out of this Chevy! Love it!
I’m up to 360.000 on my 99 with the 4.8. I did have to have the transmission rebuilt this year but it was $well spent. I’m looking forward to seeing how many more miles I get out of this great truck. It is a daily driver that I work out of. So far the engine has been a workhorse
I have a 2000 Silverado w/ 275,000 miles…great truck, rebuilt tranny at 270,000…problem I have now, p0300. Started at p0308. Swapped with cylinder 7 and code went to P0300 miss everywhere…I replaced plugs and wires and coil pack on cylinder 8..still have p0300. I have been reading and I understand it’s a generic code, could be vacuum leak causing it, or a knock sensor, or a oxy sensor..? Dang, I am in a place I don’t want to be….anybody out here have a suggestion…I haven’t had to deal with a shop in a long time…my other ride is a Astro van..2001 ….thanks for any suggestions….
More than likely the knock sensor
had a buddy who owned a 4.8 and his knock sensor needed replaced. sounds like the exact same issue. id try that before you go paying astronomical labor rates
I have a 2004 Chevy Tahoe I bought new and she yes I said runs like a champ with 375k on the original engine. I did have to replace the tranny at 260k but damn can you blame it for going out. She made it through my sons High School years and now is back in my hands. I have had to replace basic stuff including water pump but it is all to be expected. The 4.8 liter is a great motor and I will drive Natty Blue till the sweet end..
Thanks for the info! I replaced my fuel pump in the early 12400s, but my truck has had problems with it since 115k. Runs amazing now
Thinking buying a 2011 chevy silverado 2wd ls 4.8 v8 165kmiles for my landscape business I plan to start is there a thing I should replace right away to avoid any issues later on
just do your oil changes, maintenance, and tuneups with plugs, wires, and coil… run a scan on it during these maintenance times to be sure a problem isnt slowly creeping death upon you…
I have a 2011 4.8 v8 in mine and it starts rough and ticks while it cranks and when it starts its missing and has a check engine light on i heard that it is running “rich” but i would like to find out for sure any suggestions that it might judt be a sensor or something
Knock sensor
By the looks of it, you all really like the 4.8 engine. This is good news as I am doing research on a 03 z71 Tahoe 4.8 with 220,000 miles on it.
I have also have 04 4.8 Tahoe with 225k first car was family owned whole life runs like new only things have to had done a throttle body, center console and basic Mantince
I recently bought a 2012 Silverado with 60 k miles on it, the previous owner treated that truck like a baby, When traded in the dealer went over it did new brakes and shokes and the general engine. The body is new truck perfect. and great foe a singlke door the only thing is the farmer who owned it had all lettering removed,,SOO I don’t know iy its a Z71. I’m a 40 year Navy vet 90 years old I love this thing and plan to drive it till I’m 100 WHOOOOYA!!!
I purchased a 2006 Chevy Silverado 1500 4.8 Crew Cab back in December 2018, it had 135,000 miles. The previous owner had lifted the truck 4” and put 35” tires on it. Truck runs great! I did have to rebuild the transmission which was around $1100 with a small shift kit. Then come to find out the transmission guy said it went out because whoever did the lift didn’t extend the drive shaft and it was almost 2” short which was another $450 for that. I did change the rear end gears to 456 because that’s what was recommended because of the lift and the big tires. I also had to replace the front driver side wheel hub being it totally broke off and caused the front tire to turn sideways. Luckily we had just gotten off the freeway so we weren’t going very fast. The only thing holding the tire on was the brake caliper and break line. Repaired that and it was somewhere around $150. Over all the truck runs great and I get guys complimenting me on it all the time. I have also installed a Super Chip tuner and that makes a pretty good difference with the trucks performance. I have driven it to Florida and back with no problems either way towing a good size loaded down car trailer and fixing to head back to Georgia with a travel trailer very soon. She’s been a great truck and just kicked over to 180,000 miles. GREAT TRUCK OVER ALL!!
I have a 04 silverado with 161000 miles so far years ago replaced the break lines knock sensors probably around 120000 still go in and out and water pump at 150000 been a great truck bought it brand new no plans off getting rid probably pass it down to my son also have a 15 with 113000 love my silverado trucks
Just hit 467,xxxKm’s or 290,000miles and just replaced the fuel pump.
My 2010 has the 4.8 and it’s a bad little mother I’ve beat vettes and chargers and mustangs and it’s a extended cab with almost 300,000 miles on it
04 Silverado-1500-5.3L-4×4
Had 70,000 when bought, now has
198,000 miles, replaced cracked Y in heater hose, only because factories plastic, and a couple relays… routine maintenance, oil changes, plugs, packs, grease, fluids, brakes… hands down best truck ,for any occasion, I’ve ever owned… I’ve owned Ford, Toyota, Dodge… etc…, I’ve liked different things about different trucks more than others, this is by far the most well rounded Gas powered truck of my lifetime. Daily driven work truck, hauls 12 ft trailer daily, every winter pulls 10-20 vehicles out of tough spots, She does better in the cold, I have no kind of “upgrades” accept for lower suspension… My daughter turns 16 this year and will be getting this truck, says it’s hers anyways!!
Just bought a one owner 2003 4.8 with 109000 on it runs good it sat awhile a a little rust. Changed out front lower and upper new knuckles, hubs, rotors and calipers replaced rocker panels and cab corners, and all new brake lines. Cold air intake and plug in tuner and truck went down for first time on me for Vehicle Speed Sensor thought would be a pain, Haha ten minute job. Do all the work myself can see paying someone if I got two hands
Thank you, Jake – super well written article.
Mine’s an ’04 Sierra with 300,000 km’s. Great little shortbox and I don’t want to part with it yet. Do (does) you (or anyone here) know what might be happening with the coolant? It seems to be disappearing very slowly (fill up reservoir once every two months). I can’t seem to see any drips. I really hope it’s not because the old girl is hungry….but how can I tell?
The engine light is now just something I ignore – have a strong hunch that it has to do with fuel canister stuff.
Sincerely,
Doug from Canada
Hey Doug – some of these Vortec engines are known to experience what people call “phantom” coolant loss because there are no visible signs of coolant leaks. We actually have this happening on our 5.3 Vortec in our 2002 Suburban right now – been going on for 50k+ miles, we just fill the coolant up every so often. But zero signs or leaks, no drips, etc. so we just live with it.
Head or intake gasket
Well, that’s comforting – I shall wait until (and if, that is) things get worse….maybe the squeaky belt is trying to tell me that it gets a little wet from some sort of tiny drip somewhere that never gets to hit the ground…..
Love reading your stuff – concise and loaded with knowledge. If I’m ever lucky enough to cross paths with you and your crew (in the USA somewhere, I’m guessing), I’ll be sure to leave you with gifts of hospitality from Canada (please don’t hold Justin Trudeau against us….).
Sincerely,
Doug Thomas
Canada Doug,
Try some coolant dye (ACDelco 1149323 or 10-5046 from amazon) with a cheap blue flashlight. The leaks will glow.
My mystery leak was a little water pump drip that would evaporate off the top of crank pully casing. It intermittent and really starts leaking after the truck heats up. Probably from the weep hole.
Regards,
USA Doug
Bought a 2002 GMC 4.8 V8 2whl drive pick’um up (brand new), and still driving it today.. Has 250,000 miles and that 4.8 is still going strong. Been a great little truck. Major problems have been the tranny, replacing the fuel pump (in the gas tank), replacing the front wheel bearings @190,000. It’s not a work truck, however my daily driver and tows my popup camper 2,000 GVW. About the best vehicle I’ve ever owned.
2010 4.8 Silverado 246k still a beast! Never been towed. Work truck, a few years ago on a cold winter morning, she got sick. Cough, stumbling, no power. My neighbor, who was an old hot rod guy and well respected mechanic was getting his paper. I flagged him down and he asked what was going on. He said he would be at his shop in about 30 min. 2 miles away, took unhooking batt. 3 times to get it there. He started cleaning TB and messed with ECM a while, He closed it up and said ” I will be back in about 20 min’. I don’t know what he taught that engine but it has run like a scalded assed ape ever since! Seriously considering a 4.8 swap for my ’79 C10.
If you go and join chevy legends club by chevrolet u will see people who has hit 1million on body frame and alot of 500k original motor and bunch cool stuff
Bought a 2007 regular cab LT with 20k in 2009. Now have 184k. Runs like it did the day I bought it. Religious about oil changes with Mobil 1 synthetic at least every 7000 miles. Replaced master cylinder and both rear wheel cylinders and psg. Side window switch twice-that’s it. Every gas station fill-up I get an offer to buy it. Looks spectacular. I hope to go to my grave still driving this truck!
just got a 2004 silverado 1500 stcd cab…beautiful with 77k on it…has a couple dead gauges that will be addressed with new stepper motors….however, i keep getting a 307 code – new plugs, wires, coils…still 307…cleared code and it came right back with the next run….where should i go next?…ty
Hi John,
I believe you’re referring to P0307 – cylinder #7 misfire. Were you receiving that fault code before replacing plugs, wires, and coils? You could try swapping the plugs and/or coils with another cylinder that isn’t misfiring to see if the code follows to the new cylinder.
Otherwise, I’d consider the fuel injector. Plugs, coils, and injectors are definitely among the top causes of a single cylinder misfire. With only 77k on the 4.8 Vortec it’s unlikely to be anything more serious. However, if the fuel injector isn’t the cause it may be time for more extensive testing like compression and leakdown to ensure there aren’t any internal issues with cylinder 7.
Best Regards,
Jake
exactly… and exactly %100 my issue… led to “top end” rebuild w/head gaskets leaking too…
my ’10 1500 5.3L AFM 120K Miles 3/15/23 – @ about 110K Miles, cylinder #7 misfiring for over a year (mechanic at he the time told me, “After my research, that problem is gonna solve itself.”, … contd replacing spark plug #7 every 2 months… then it became every 2 weeks, then it wouldnt fire over at all… time to do something… discovered oil in the crankcase (not good). While having my oil changed (for what I thot was the last time), I had them look underneath… and it was wet!! (tech said “Im not kidding ya bud its wet under here.”… head gaskets leaking… led to #3 cyl eventually began misfiring as well… time for a diagnosis, and for what I thot was gonna be a trade-in upcoming?? … final diag after leak-down/compression check to make sure bottom end wasnt “hurt”… engine was “coked-up”/carboned up… pics showed #7 and #3 intake valves weren’t seating due to carbon and clogged valves… no amount of FI cleaner will do the trick to remove/remedy issue, plus both head gaskets were leaking…. I was quoted $2,000.00-$2,500.00 to “freshen” the top end… well… after all that. plus other parts/issues and a fine-toothed comb in addition…, $5003.65!!! IF Id have known it was gonna run double what was estimated, Id have dumped the truck, and got another one in the afterthot of this repair. I will say in defense of this “extreme intense repair” for a modern truck, its runs like a flaming ass cat!!… screw gas mileage!! … we’re at 350 HP from 315 HP, plus down 2 cylinders, I have a “gun runnin amish” truck now. Haaaa!! I can boil all 4 tires in 4wd for 100ft now in this truck, and I did it in the alley at the shop on asphalt that did the work as I was leaving and they watched in awe… LOL!! I guess I’m married to this “bitch Silvia” for a while now, until it rusts out, and that wont be long either… maybe two years since I live in rusty PA. But whatta difference now that its running on all cylinders and cleaned up like new… the smell outta the duals is a clean burning “demon alcohol” smell, because I run 105-110 octane E85 ethanol in it one fill-up per week to keep it clean burning…then I use “unleaded 88” E15 (%15 ethanol) for normal driving to do work, then when I want some fuel mileage on trips (if that exists anymore LOL!!), Ive found that 89 octane mid-grade E10 fuel gives me the best fuel mileage (if theres such a thing after this “rebuild”?). Haaa!! truck will run on vodka or “shine” now. LOL!! Hahahahaa!!… thanks – DTM – (now 10/20/23) 133,000+K miles – still running strong and fuel Mileage is starting to mellow out and get more efficient… ONLY thing I let the garage DO at this point is, the “oil changes” because one, its their baby, and two, they use BG “EPR ” additive to treat the old engine oil first, then let idle for 10 minutes at 1200 RPMS, then drain, then do the oil/filter change with synthetic oil (Ams Oil 5w-30) in my truck to keep the “rings” loose because the rings were “tight”/clogged as well with carbon. After $5,000.00+ spent its like new under the hood, maybe better…. truck will rust away before the engine blows at this point. How I see it…BUT it GOES!! Haaaa!! good luck… I spent too much….my problem but its fixed…