5.3 Runs Rough, Wont Go Above Idle, And Dies

jgaff · June 27, 2011

I have a 2002 Tahoe with a 5.3 in it that has developed a problem that I am having trouble narrowing down. The problem first occured at the end of a two hour trip. I was backing into a parking space when it started running rough, wouldn't make any power, wouldn't go above idle, and eventually died. I tried to restart it immediately and it would act like it would light off and immediately die. I let it set about ten minutes and tried it again and it started right up, and ran fine on a five mile trip, a twenty mile trip and about an hour and a half into the trip home it acted up again. I was going down the highway this time when it happened. I just lost power and it didn't matter where I put the throtle, it just kept slowing down and not reacting. I pulled over and shut it off. Left it off for a minute or two, restarted it and it ran fine the last thirty minutes home.

The problem that I have is that it didn't turn on any check engine lights or store any diagnostic codes. I am thinking that it might be the throtle position sensor, but that is only a guess. When we were plugged into it, it was showing the TP which I assume is throtle position at 0% while it was sitting there running at idle. I was thinking that it would be low, but above 0% since it was running, but have nothing to compare it to.

Any help on fixing this would be greatly appreciated, and might save my wife from going and trading it tomorrow, as she is not very happy about it, and is scared that it is going to quit her and our kids. Thank you in advance for any suggestions or advice on what you might think is the problem!

God Bless! JGaff

greentourismo · June 27, 2011

that definitely doesnt sound right...tps will usually be at around 10% at idle, and the driveability problems definitely sound like they could be related to a bad tps. The only odd thing about it is that being way out of spec should cause an engine light, but you cant always rely on that.

TexasAl · June 27, 2011

The symptoms definitely sound like the TPS sensor. Remove it, and have it tested at a local parts store (I know Autozone can test it). That will at least make sure it is working properly. If I am not mistaken, I think they test the resistance with am ohm meter.

Yeah, here is a video on how to do it:

http://www.youtube.com/watch?v=IsX5q3jBeBQ

Hope this helps.

jgaff · June 27, 2011

I was talking to a friend of mine, and he said that he thought that it could be narrowed down to the Throtle position sensor, map sensor or mass air flow sensor, but again, I have now way to tell which one. Anyone know any of the symptoms of either of the other two sensors?

TexasAl · June 27, 2011

I've already told you how to test the TPS sensor, so that can be eliminated with five minutes of your time.

The MAP sensor can be simply disconnected, and the computer will go into a back up system with predetermined values to replace the ones from the map sensor. It will allow your engine to at least run.

The MAF would also give you problems at idle, so I doubt it will be the culprit. It can be tested at some auto parts stores as well, or you an test it yourself.

http://www.youtube.com/watch?v=NRIDW0xRmYo

Sir Dan · June 27, 2011

My neighbor's 2002 yukon recently had a similar problem. It ended up being a bad battery. It would start and die right away. Wierd though, cause up to that point, there were no symptoms that the batt was going bad, it just went.

jgaff · June 27, 2011

Thanks for the reply and links TexasAl! I checked for post this morning without refreshing and didn't see your post until after I posted my next question.

Would you know what the Throtle position percentage should be on this 5.3 L engine at idle? We had my friends diagnostic computer hooked up to the Tahoe last night and it showed 0% with the engine running at idle. Is that correct, or should it be at a slightly higher value?

I will run the TPS test on it tonight after my wife gets home with it to see if it has any bad spots in it's range of motion. Thanks for your help! JGaff

greentourismo · June 28, 2011

that definitely doesnt sound right...tps will usually be at around 10% at idle, and the driveability problems definitely sound like they could be related to a bad tps. The only odd thing about it is that being way out of spec should cause an engine light, but you cant always rely on that.

07sltcrew · June 28, 2011

Not to hijack the thread but that's what my truck does randomly. It will start up and then die. Usually it will start if I try it 2-3 times and then I wont have a problem sometimes for weeks or months.

I'm going to do a battery and TPS test this weekend see if either of these could be the culprit.

My neighbor's 2002 yukon recently had a similar problem. It ended up being a bad battery. It would start and die right away. Wierd though, cause up to that point, there were no symptoms that the batt was going bad, it just went.

jgaff · June 28, 2011

I am starting to think that it might be a fuel pump problem. My experience with fuel pumps are that they usuall go all at once, and are done, but know occasionally that they get weak and don't completely quit. The reason that I say that I am starting to think that it is a fuel pump issue is that if it was a sensor, I think it would cause the engine light to come on and store a code. Anyone agree? I kept getting an engine light last fall due to a leaking manifold gasket, and it caused the engine light to come on almost every time that I started it up, and it wasn't running near as bad as it was when it quit me this time.

Does anyone know what the acceptable fuel pressure range is on the 02 tahoe with a 5.3 flex fuel enine? Will low puel pressure cause the check engine light to come on and store a code? I am planning on checking the fuel pressure tonight, but don't know if it ok or not until I know what the acceptable pressure range is. Thanks again for everyone's help! JGaff

jgaff · June 29, 2011

Well, I tested the Throtle position sensor tonight, and there is no problem with it. Same with the mass air flow sensor, no problems there either. We changed the fuel filter and it was pretty dirty, but not terribly restricted. Tested the fuel pressure and it was about 48 psi at idle and it looked like the regulator was working when you throtled it up. I guess that I am back to square one on diagnosing the problem.

I am thinking that changing the fuel pump is probably my next move unless someone else has a better idea. That being said, does anyone know where I can find detailed instructions on removing the tank and changing out the fuel pump on this 02 tahoe?

Thanks again! JGaff

TexasAl · June 29, 2011

48 PSI at idle sounds a tad low. I don't know what the exact specs are , but I remember it being around 52-60 psi. Here is what I would do. Check the fuel pressure again after leaving the truck parked overnight, and see what results you get. Then, run the engine for about 20-30 minutes, and check your fuel pressure again. Hopefully it will start acting up, and you will see the fuel pressure drop dramatically. If it does, this will verify that it is in fact the fuel pump.

txab · June 29, 2011

Specs for a Flex fuel code "Z" engine are 48-54 PSI. Key on, engine off

Keebs · June 29, 2011

When this is happening is there heavy black smoke from the tailpipe? I had a similar problem and it turned out the intake manifold gasket had to be replaced. The smoke started out intermitently and got worse and worse as time went on.

jgaff · June 29, 2011

When this is happening is there heavy black smoke from the tailpipe? I had a similar problem and it turned out the intake manifold gasket had to be replaced. The smoke started out intermitently and got worse and worse as time went on.

No smoke at all, and I replaced the intake manifold gasket last winter, so hopefully that is not the problem.