Chevy GMC 7.4L Misfire Wont Start and Lean Code Diagnosis

[@AP9311]

Tim, great video. I do own 454 and 350 Suburbans. Most extremely common problem is intake gaskets fail due to deathkill stuff (Dexcool) injectors failure by the poppet valves gets harder by heat and cool cycles due their location inside the intake. By having new multi port injectors instead of Central Port. Solved problems with leaky injectors and low vacuums etc. Plus oil leaks on the oil cooler lines going to the filter housing. Super common! Thanks for showing this video, Tim!

[@EXOVCDS]

That truck is good for 10 videos at least! I'll cross my fingers for you that they give you the go-ahead!!

[@ThecardoctorTV]

Indeed! Hydro boost leaking, upper and lower BJ’s outer tie rod ends, idler and pitman arms, complete exhaust system, injectors, regulator, upper and lower intake gaskets, fuel pump, valve spring, battery hold down, RR inside tire flat, oil cooler lines, ignition coil circuit code, etc. maybe a feature length film is in order. Haha. I don’t think they are going to do it. The cost exceeds the value I’m pretty sure. Sad deal.

[@EXOVCDS]

LOL.

[@ThecardoctorTV]

haha

[@ThecardoctorTV]

I polished the radiator cap and placed it on a new truck for them.

[@wyattoneable]

That's one heck of a good trick. Love it! You did a great job getting this guy a heads up on the work that needs to be done. Too bad he just bought it. Now the real cost is upon him. :(

[@ThecardoctorTV]

I get the feeling they are just going to drive it till it kills someone.

[@ginaberrie2608]

@@ThecardoctorTV that is horrible. I really loved the video, I'm having some issues with my 454 k3500 hence why I'm here. However, that comment... just wow. So what kind of vibes did you get from the truck owner that would lead you to make that comment? I mean there are options for the owners. They could fix it, seems like issues that could be fixed offer several weeks and be do-able. They could off the truck on someone else, much the same is what happened to them (although not my choice) they could part the truck out, they could make a trade to someone handy looking for this kind of project.. Hell, they could surprise you and hire you to fix it, maybe they have the money to do that now, maybe they will just slap it on the credit card. I mean there are far better options other than driving it till it KILLS someone. I just didn't like that. Sorry, just my thoughts, the comment kind of shocked me, completely unexpected.

[@allanwilson6188]

I have a 97 Chevy 5.7 it has po300 code misfire. I have replaced distributor, rotor, plugs, wires, ignition module, coil, crankshaft sensor, map sensor, fuel filter, spider injector and fixing to put a cam shaft sensor in it. The check engine light comes on and the next day it goes off its driving me nuts "help"

[@elliottmorris6439]

I wish you would finished a follow-up video for this truck. I have a 2000 k2500 with a 7.4 and at was having similar issues, I replace upper and lower intake manifold gaskets, all injectors, had 6 hole Rochester, TPS. It started running lean bank 2, missing on cylinder 2 at first, lost all power, rough start, blew oil out back. Now after all the time parts and work. Run lean bank 2, horrible missing cylinder 1, mild on 2.

[@cotytownes5353]

Im having same issue with mine after doing same parts minus the TPS but also did new plugs, wires, distributor, and coil

[@vanessacederlund7629]

@@cotytownes5353 real bummer I am having same issues I have a 2000 7.4l / 454 big block. L29sfi. I am just learning about. It's a 2000 GMC reg cab long bed. Came with a factory gas/ natural gas option . I ot it used aand they took 100 gal nat gas tank off and left the nat gas pump of whatever ontop or intake. It's losing power , higher rpm at lower speeds. Speedo is not accurate when trk is acting up, breaks aren't normal horrible gear like sound from top of fuel tank. Sounds like a wind tunnel in the intake housing but , the oil looks like new even at change time can anyone explain the problem? Can reset the brain so I get correct codes? It reads o2 bank 1. All the stuff happens at once . What's the connection?

[@Jwat731]

Did you ever complete fix the issue? I’m having the same issue with my 98

[@jreyman]

I don't think the truck was a lemon, rather the previous owners were the real problem. The 7400 Vortec doesn't have major problems, unless it's been severely abused.

[@PwnyDwn]

I also have a miss I cant track down on a VI gen 454. Inherited a 96 3500 GMC from my dad when he passed this year (covid/cancer) and the poor truck is just running like hell. No power. Pops and rattles.. rug idle. I've replaced plugs, wires, cap, rotor, fuel filter, fuel pump... hell everything basically.. still dead miss

[@benkanobe7500]

Great Video. I just subscribed! I have a question: Where do I get that nifty vacuum tool? I want one.

[@willb273]

I have two 454 motors, and one bad TBI upper (One upper makes both motors work, the other upper does the same thing, motor runs for 30-45 seconds then starves for fuel and stalls, all else remains the same). I rebuilt the bad uppper with new injectors, new gaskets, and a new fuel pressure regulator, no avail. Same issue, motor runs for 30-45 seconds, then starves for fuel and stalls. Any idea what could be causing my issue?

[@willb273]

@@rarefruit4173 second engine had low compression on three cylinders. Did a valve job and it got a lot better. Still chasing gremlins, but it runs and drives. Has an erratic idle (bounces continually from 800-1200 rpm), and doesn't make as much power as the port engine, but it runs, and stays running. Seems to starve for fuel, not sure why, everything is new, including the pump.

[@MShrader211]

So you never did pull the valve cover off to check for broke or bad valve spring?

[@125sm3]

They were seen coming when they purchased that truck. Horrible when people get sold these lemons. Truck is fit for the scrap yard. Great video and loving the shades !

[@ThecardoctorTV]

Agreed. I would have gladly kicked the tires for them but this stuff happens. Super sad deal.

[@juansantiago8968]

I got a 2000 gmc 3500 hd with 7.4 n it turned off on me as I was driving I changed the coil n crank sensor n it still will not start n I checked the fuel pressure n it's good u have any ideas ?

[@stevenmarn4385]

Check the wires that run along the top of the motor in the back. Might be burnt up

[@mikeanderson1994]

Your the man tim keep it up👍

[@ThecardoctorTV]

Thank you!

[@haywardsautomotive6156]

That's a sweet exhaust system Tim! Put a sparkplug in the exhaust and you can have some cool flames and a few throttle snaps and I bet you can blow that muffler clean off...just saying...never done that when I was a bored teenager. It clears up any exhaust restrictions also :D

[@ThecardoctorTV]

Hahaha. Nice. I’ll have to recommend that upgrade to the customer. They have decided to drive it till the wheels fall off I guess.

[@handy__andyy4026]

Hi there sir! I'm interested in seeing the broken valve spring as I have a 99 k2500 suburban with 7.4 and it has a small misfire on #4 at idle. Around 8 misfires every misfire counter cycle. Where did you pinch off fuel lines at? Transmission hump? Can you pinch off those flex lines there? Thank you for the great videos and keep them coming!

[@ThecardoctorTV]

Have you tried the exhaust test yet?

[@handy__andyy4026]

The Car Doctor no, it has duel cats to single muffler and exhaust all the way back to end of truck. Would I notice it with full exhaust?

[@BigDog50001]

She’s a beauty.

[@ThecardoctorTV]

One in a million.

[@jeffarmer4428]

Cool stuff , where did you get the vacuum gauge ?

[@ThecardoctorTV]

That is an atlas brand from a long time ago. Don’t think they make atlas products anymore.

[@zx8401ztv]

I wonder why they didn't get it checked by someone before parting with the cash :-(. Since one valve is faulty, i would expect the rest to be suspect, could be an expensive mistake they made.

[@ThecardoctorTV]

The overall condition isn’t good. Probably not worth fixing. They relied on someone who said they were a mechanic and helped them out with the purchase but I’m not sure they got sound advise. I told the owner I would check any future vehicle free of charge if they plan on looking for a replacement. Heartbreaking

[@zx8401ztv]

It's a shame they didn't ask you from the start, they would have saved a packet if they payed you to do a general checkover of the heap... i mean vehicle, i got that right the first time lol. I found a family run motorcycle repair shop, i did not have the time to repair my machine and be at work at the same time. They were worth every penny, a decent repair from decent people :-). Much like yourself, you do a decent job thats affordable without the customer selling a kidney lol.

[@LaramieJim]

Very interesting. Never see tech check exhuast suction. I have a feeling this vehicle is fully depreciated. Thanks Car Dr, I learned something today!

[@ThecardoctorTV]

Yes but have you ever seen a tech who sucked?

[@LaramieJim]

Low skills! Yes

[@rdp2370]

Hey Tim, who makes that PCV test gauge? Any part number?

[@ThecardoctorTV]

It was an old Atlas brand and I got it whena Chevron I worked at was closing. Haven’t seen one since but I’m sure they still make them.

[@adamthatguy454]

Did you ever fix the exhaust sucking issue? If so, what was it? I still have basically the same issue on a 2000 GMC 454/7.4. Bank 1 is ok, but bank 2 sucks (split dual exhaust). I've rebuilt the heads, replaced all gaskets, all new injectors, new pressure regulator, new O2 sensors, new distributor, coil, plugs, wires, new PCV, cleaned IAC and MAF, cleaned the lifters, etc. I suspect one of the lifters because there was one or two that seemed to have weak check ball springs.

[@enriquetorres6069]

Lower intake is definitly a commen problem i have a 99 suburban with the 7.4l and it has the same problem . Cauases it to flood after warm up Nd hard starts 😥.

[@ThecardoctorTV]

Yes and also the fuel system leaks causes the same.

[@enriquetorres6069]

Yea hopefullly when i do the lower intake i want to do all the injecters and F.P.R other than that trucks a tank.

[@wrotedog]

4:55 sounds like a leaky injector or regulator

[@chadharmon5716]

What's that white stuff curly?

[@ThecardoctorTV]

On my face?

[@chadharmon5716]

The Car Doctor 🤦‍♂️😆 referring to the snow ❄️

[@edb.3313]

Feel sorry for this guy Tim. Big loss there. 🤢

[@ThecardoctorTV]

6000-7000 estimate of repairs. Super sad. Truck might be worth 3000 on a good day.

[@ThecardoctorTV]

A bit more but a considerable savings but they don’t know how to repair their own vehicle. Probably 3000+ in parts at least. Don’t forget we live in Alaska. See a comment below for a short list of some of the problems I identified. It’s pretty bad

[@حسامحسام-ج3ض3ذ]

Wher are you from

[@ThecardoctorTV]

I live in Alaska.

[@fieldsofomagh]

Just by googling problems with that vehicle, it might have made them aware of the potential faults. Prevention is always better than cure. Sooo many issues !!

[@aissaaneslyes3566]

thank god that it doesn't suck you inside the engine lol

[@ThecardoctorTV]

I know. I felt like I was surely going to get sucked up that exhaust pipe. That would have made for a real viral video!

[@3735geez]

At least he has mufflers. Mine is just cats and loud

[@elcheapo5302]

A GM product that sucks. Imagine that!

[@ThecardoctorTV]

Funny.

[@bbkmm1]

LOL, Cherry Bomb on a work truck, what are these guys thinking? Of course, they don't have the money to fix the real issues.

[@ThecardoctorTV]

A real bomb might have been a better choice.

[@bbkmm1]

True that Bro. This is a recycler's wet dream. How's the weather in your neck of the woods? I notice you are getting bright sun again. It must feel good.

[@ThecardoctorTV]

Yes, much more daylight and getting warmer. Fish will be running soon!!!

[@alfredopaez9097]

👍👍👍❤️❤️❤️