Intermittent P0171 and p0300

[chevy1500]

hello guys i have a 07 tahoe LT non flex 5.3. And im having a issue diagnosing this lean issue i have on the left bank i changed the intake gasket checked coil packs and swapped out MAF sensors oh and i checked the compression and its good and the fuel psi was 45 with the key on engine off and I can see the needle bleeds off to about 30 psi but the truck starts right up oh and it has a slight rough idle im stomped

 

[Big Mama]

I think the psi should be around 60 but I’ll double check. The culprit could be the intake gasket you just changed only takes a little air to do that. Have you tried spraying some carb or intake cleaner while it’s running to check for idle pick up?

 

[chevy1500]

I think the psi should be around 60 but I’ll double check. The culprit could be the intake gasket you just changed only takes a little air to do that. Have you tried spraying some carb or intake cleaner while it’s running to check for idle pick up?

Yes i done all that is possible and no change at all

 

[chevy1500]

Also when i started up the truck the psi went to 60 psi and the needle was jumpy and when i rev it doesn't move and stays at 60 psi

 

[HiHoeSilver]

Also when i started up the truck the psi went to 60 psi and the needle was jumpy and when i rev it doesn't move and stays at 60 psi

Your KOEO pressure is a touch low, but if you're 60 running, I'd look elsewhere first. Do you have a scanner to see the fuel trims?

 

[Big Mama]

It wouldn’t happen but there also may be an injector that’s a little clogged. The spray in cleaner may not do a lot but some seaform in the next few tanks might be an inexpensive way to see.

 

[HiHoeSilver]

It wouldn’t happen but there also may be an injector that’s a little clogged. The spray in cleaner may not do a lot but some seaform in the next few tanks might be an inexpensive way to see.

This is where I'm looking, too. If you can see your fuel trims and the short term comes down as you get on it, there's a vacuum leak somewhere. If the short term is getting worse as you raise rpm, you've got a fuel delivery issue (or a goofy MAF, but you said you checked that). Since your pressure seems reasonable, I'd clean the injectors.

 

[chevy1500]

This is where I'm looking, too. If you can see your fuel trims and the short term comes down as you get on it, there's a vacuum leak somewhere. If the short term is getting worse as you raise rpm, you've got a fuel delivery issue (or a goofy MAF, but you said you checked that). Since your pressure seems reasonable, I'd clean the injectors.

I talked to a chev tech at the dealer and he said 45 psi with KOEO is pretty low it should be in between 50 and 60 and my truck only leans out when im driving so im still on it

 

[chevy1500]

Changed fuel pump still rough idle and still getting the intermittent pending p0171 code then after i shut the engine off and turn truch back on the pending code is gone smh

 

[chevy1500]

This is where I'm looking, too. If you can see your fuel trims and the short term comes down as you get on it, there's a vacuum leak somewhere. If the short term is getting worse as you raise rpm, you've got a fuel delivery issue (or a goofy MAF, but you said you checked that). Since your pressure seems reasonable, I'd clean the injectors.

I looked at my short fuel trims this morning when i get on it it bank 2 shows higher than bank one

 

[HiHoeSilver]

I looked at my short fuel trims this morning when i get on it it bank 2 shows higher than bank one

What kind of numbers are we taking about?
How high are your long terms?

When you get on it do the short terms go negative at all, or do they go higher than they already are?

 

[chevy1500]

What kind of numbers are we taking about?
How high are your long terms?

When you get on it do the short terms go negative at all, or do they go higher than they already are?

The short term on bank 2 goes to 7/8 and bank 1 goes to 5 and it subtracts alot

 

[HiHoeSilver]

The short term on bank 2 goes to 7/8 and bank 1 goes to 5 and it subtracts alot

Your 0171 is a lean code, so the upstream sensor is seeing too much air or not enough fuel. The computer is correcting by pouring more fuel. It's forcing the long term trims up and setting the code.

As you increase RPM you are in less and less vacuum, so your short terms are going to move one way or the other.

If the short term trims are going down as you get on the gas, you have a vacuum leak somewhere.

 

[chevy1500]

Your 0171 is a lean code, so the upstream sensor is seeing too much air or not enough fuel. The computer is correcting by pouring more fuel. It's forcing the long term trims up and setting the code.

As you increase RPM you are in less and less vacuum, so your short terms are going to move one way or the other.

If the short term trims are going down as you get on the gas, you have a vacuum leak somewhere.

i wonder where could it be i did the carb fluid trick no change i changed the intake gasket no change but youre right about the vac leak somewhere be cause it feels like it at idle

 

[HiHoeSilver]

i wonder where could it be i did the carb fluid trick no change i changed the intake gasket no change but youre right about the vac leak somewhere be cause it feels like it at idle

It's possible to have one big enough at the exhaust manifold to cause some bad numbers, but i don't see it causing the misfire code.

 

[chevy1500]

It's possible to have one big enough at the exhaust manifold to cause some bad numbers, but i don't see it causing the misfire code.

It threw the 0300 code only one time so no more misfires all im dealing with is the shaky idle and the intermittent 0171

 

[Big Mama]

Still sounds like an injector or two?

 

[chevy1500]

Finnaly have the freeze frame and im still stomped smh

 

[Tonyrodz]

Sub'd

 

[M1Gunner]

HOLY $@&! Your long term FT B1 is stupid high about maxed out. There’s your problem. It’s having to dump fuel to B1 to compensate for B1 lean condention. So think about things that will only effect one bank... intake manifold gasket etc.