Sputtering

**SS201** · 11-17-2010, 11:27 PM

Alright guys,
I am having problems with my car again. I beleave it's the same problem I have had since last year. Last year I had to change my fuel pump becasue I was having a sputtering problem during heavy accelaration or cold starts, it even stalled on me a few times during a stop at a red light. I changed the fuel pump and it quit for a while. A year later, almost to the day, it starts to sputter again during heavy accelaration or cold starts. My car is now showing a Service Engine soon light, when hooked up to a code reader it shows: Lean bank 2. It showed the same code last year. Last year I even changed the O2 sensors. This year I already changed the fuel pump again but still it sputters, not as bad as it did before the pump change but it still does.

What is the diagnosis for my car. What else could be giving me that same problem?

A little history for my car, it has a Texas Speed Ms3 cam (going on 15K miles), LS6 GM Air intake, 2nd - 4th gear clutch pack, A4, 3600 Stall. Before the cam it was ran with Nitrous during a few drags and fuel pump of course. Everything else is stock.

**Jay37** · 11-18-2010, 02:03 PM

What is your fuel pressure at the rail?

**pajeff02** · 11-18-2010, 03:04 PM

When was the fuel filter last changed?

**Cutlass** · 11-18-2010, 04:23 PM

A lean code can set from a vacuum leak, dirty/clogged/partially clogged injectors, bad MAF sensor, or low fuel pressure among other things.

**SS201** · 11-19-2010, 01:47 AM

Well I am going to get my fuel pressue reading this monday or sunday on my days off. I changed teh fuel filter when I changed the fuel pump just to make sure.
I had the MAF sensor checked last year and it worked ok. I changed it out with my friends (LS1 T/A).

What's the best way to check my injectors and vaccum?

**pajeff02** · 11-19-2010, 03:08 AM

Carefully inspect the all the vacuum hoses for breaks. You will want to pay particular attention to the PCV assembly. The connection on the side of the throttle body and the union at the back of the passenger side head seem to be the most failure prone points. There is also a collection of small hoses back by the PCM.

Nominal fuel pressure is 58 p.s.i., but it can range anywhere from 55 - 61 p.s.i. or so and be ok. Make sure pressure is checked across the operating range as it may appear ok at idle, but under demand you could have a fuel volume issue. If you can get a scanner on the car, check your fuel trims and see where they are at. You should find Bank 1 (driver side) and Bank 2 (passenger side) short term fuel trims (STFT) and long term fuel trims (LTFT). You want these to be close to zero, maybe plus or minus 3 or so at the most. A skewed fuel trim will confirm an issue.

Let us know what you find.

**jamessr** · 11-19-2010, 01:46 PM

clogged cats

**Jay37** · 11-21-2010, 09:49 AM

one way to check for a vacuum leak is put gasoline in a spray bottle and lightly spray any area that could be suspect to a leak, and if it is leaking you will have a rpm change, simple but effective.

**Cutlass** · 11-21-2010, 11:46 AM

Originally Posted by Jay37

one way to check for a vacuum leak is put gasoline in a spray bottle and lightly spray any area that could be suspect to a leak, and if it is leaking you will have a rpm change, simple but effective.

That seems extremely dangerous. I prefer to use carb or throttle body cleaner

**pajeff02** · 11-21-2010, 02:55 PM

Originally Posted by Cutlass

That seems extremely dangerous. I prefer to use carb or throttle body cleaner

Agree. I would never use gasoline.

**SS201** · 11-21-2010, 04:23 PM

Originally Posted by Cutlass

That seems extremely dangerous. I prefer to use carb or throttle body cleaner

Ok I see, that seems pretty simple actually.

**Jay37** · 11-21-2010, 05:09 PM

Hope your not a smoker.

**0rion** · 11-21-2010, 08:35 PM

Originally Posted by Cutlass

That seems extremely dangerous. I prefer to use carb or throttle body cleaner

Originally Posted by pajeff02

Agree. I would never use gasoline.

propane works well too and is fairly safe

**0rion** · 11-21-2010, 08:36 PM

check everything these guys have told you and if your fuel pressure is low it could possibly just be a crack in the hose going to the pump.....that's no uncommon on the 99+ cars. They will also blow that venturi hose off. Did you cut the bucket or use a racetronix set up? and do you run the car down to empty on a regular basis?

**pajeff02** · 11-22-2010, 03:08 AM

Originally Posted by 0rion

propane works well too and is fairly safe

I have used that as well trying to track down a wandering idle on our Corvette.

**SS201** · 11-23-2010, 01:40 AM

Originally Posted by 0rion

check everything these guys have told you and if your fuel pressure is low it could possibly just be a crack in the hose going to the pump.....that's no uncommon on the 99+ cars. They will also blow that venturi hose off. Did you cut the bucket or use a racetronix set up? and do you run the car down to empty on a regular basis?

Ok I checked the fuel pressure at the rail, it is stable at 58 psi even during hi revs (on park). I also sprayed carb cleaner around the air intake manifold and fuel rails including each fuel injector and did not have any change in idle. All the hoses appear to be ok not cracked and intact. I just chaged my fuel pump to a new walbro 255 lph pump. The way it was installed the previous owner had cut the bucket. i just reinstalled it the same way, quick disconnect and connect. I have not had but a few hundred miles on this new pump, going about a month with it actually. I have not let the fuel tank go less than half since I have had this new pump. It appears that the sputtering is worse when the engine is cold. Once it warms up to operating temp it almost doesn't do it. I did however have to replace a valve cover gasket about two months ago on the passenger side, the side that gives me the lean code. Could that be something to take into consideration with this problem?

I read a post somewhere on this forum about valve cover breathers, could that help any? Also a oil catch can? Could that be giving me a lean code or somme kind of timing retard?

**SS201** · 11-30-2010, 09:36 PM

bump

**Smittro** · 11-30-2010, 09:49 PM

I did'nt see any mention of a tune in the list of mods..

**Danger731** · 12-01-2010, 02:42 AM

don't forget bad gas....

**SS201** · 12-01-2010, 08:07 PM

Well of course it does have a tune, LS1 tuner i think LS1 edit. I have been using it dayly still as mild as possible. I have gone through about 4 full tanks of fuel ( without going past half tank). Sputters during cold start mainly, once it warms up it goes back to regular running. On full throtle sometimes it will sputter.

A local guy told me to change the spark plugs to NGK TR5 b/c the NGK TR6 are too cold and could be making a difference.