lean

**LS1MuNkY** · 05-09-2008, 07:43 PM

so ive been having problems with my car first i thought the 02's were bad after the header install and they werent got a street tune and it ran crappy still. then i got a dyno tune and it put out 212rwhp and 304rwtq lol. my tuner said the car runs fine at a normal speed but when i give it gas it runs off the chart lean. so i changed the fuel pump and filter thinking it was that and it still runs shitty. and suggestions would be greatly appreciated thanx
Aaron

**Y2KPewterSS** · 05-09-2008, 07:54 PM

Did you put new 02 sensors in?

**mo gomez** · 05-09-2008, 08:00 PM

sounds like a mass air flow issue but i am guessing without knowing what you have got other than headers and a custom tune with a new fuel pump and filter.

**Fbody4ever** · 05-09-2008, 09:05 PM

Okay, so I don't know too much about OBD II, but from my training; put it into cold start mode, and see if it still runs lean under throttle. If it does, your looking at a hardware problem. If the problem disappears, then start testing your electronic stuff.
Cold start mode= no electronic controll over fuel and spark, the computer puts all that stuff into a pre-determined factory setting which should yeald a 14:1 ratio (oxygen content).
I have been hittin' the 12 year old scotch, so I may not b 110% rite now

**LS1MuNkY** · 05-09-2008, 11:04 PM

yes i put brand new o2's and the maf is fine i have no clue what it could be its getting zero fuel when i get on it all injectors are fine so im lost lol

**sic2001** · 05-09-2008, 11:35 PM

So Im having the exact same problem. replaced fuel pump/filter,o2's, dyno tune and all that and car still stutters under light load and runs fine when its cold. This same problem is all over the threads under different titles and NONE of them have a solution to the problem. If you find one please letmeknow what it was. I had a head cam job done and it did it before and after so....

**LS1MuNkY** · 05-10-2008, 06:31 AM

yah its real frustrating i just put lt,ls6 intake,plugs,wires,tsp y pipe,and a lid and it doesnt budge. im probably going to sell it now seeing is that i cant stand cars that dont seem to have a solution to the problem

**jigger1166** · 05-10-2008, 06:47 AM

Make sure your air filter is clean.

Are their any DTCs set?

Has anyone checked their MAP (manifold absolute pressure) sensor readings, or their TPS (throttle position sensor) readings?

Make sure your MAF (mass air flow) sensor isn't contaminated with excess oil from your K&N filter. Sometimes people apply too much oil to the filter, and it gets sucked out and contaminates the MAF sensors, giving inaccurate readings.

**0rion** · 05-10-2008, 08:13 AM

Have either of you guys physically checked your fuel pressure at idle and under load?

**jigger1166** · 05-10-2008, 08:26 AM

Originally Posted by 0rion

Have either of you guys physically checked your fuel pressure at idle and under load?

They both said that they replaced the fuel filter, and pump, so I'm thinking that the fuel pressure isn't the issue.

But, was the fuel tank module (including the fuel pressure regulator) replaced, or just the pump replaced? Cause the fuel pressure regulator could be the problem.

**LS1MuNkY** · 05-10-2008, 11:28 AM

just the pump and filter were replaced

**0rion** · 05-10-2008, 11:52 AM

the first thing I would do is verify fuel pressure both at idle and at wot to see what's going on there first. Then I would make sure the injectors are all firing like they should. Pulled the plugs lately to see if there was one specific cylinder leaning out? I'm not saying rule out the MAF and things like that, I would just start basic and work your way to that point. Make sure first that you're getting fuel to the injectors and that the injectors are all firing properly then start looking at sensors.

**sic2001** · 05-10-2008, 02:48 PM

I tried to replace the fuel pressure reg but no places but dealership seems to have them. To top off a great day I took the clerks word that he gave me the correct fuel pressure gauge, got home, hooked it up to find out whats REALLY going on and bam...wrong hook-up! So Im going to watch a movie, say a couple prayers then get the right gauge and let ya know what I get at WOT and idle...and everything inbetween...

**jigger1166** · 05-11-2008, 04:24 AM

Originally Posted by sic2001

I tried to replace the fuel pressure reg but no places but dealership seems to have them. To top off a great day I took the clerks word that he gave me the correct fuel pressure gauge, got home, hooked it up to find out whats REALLY going on and bam...wrong hook-up! So Im going to watch a movie, say a couple prayers then get the right gauge and let ya know what I get at WOT and idle...and everything inbetween...

Is your "Service Engine Soon" light on? Any DTCs ?

**LS1MuNkY** · 05-11-2008, 04:47 AM

my ses light came on but it gave me a p0131 and p0151 front o2's but they are working fine i just put them in there brand new. when we hooked up to the dyno everything was fine so idk i think im going to sell my baby and get back into bikes.

**Cutlass** · 05-11-2008, 08:18 AM

Originally Posted by LS1MuNkY

well he spotted two misfires on #3 and #5 which i fixed and he deleted the rear 02's i fixed all that but he said my front 02's werent giving a reading. no cats the ses light is still on

Did you ever fix this problem from your previous post?? If the front O2s don't work right then you could run lean. Follow a standard 02 sensor diagnosis to help determine if there is a PCM,sensor, or wiring/connection problem.

Also did this problem happen instantly after the header install or was it weeks later, several tanks of gas later,etc? I'm just trying to help narrow this down further and further.

**LS1MuNkY** · 05-11-2008, 10:17 AM

i eneded up buying all new o2's again and the o2 extensions so those are reading fine now. and the misfires were from bad wires. and it happened right after the install

**Cutlass** · 05-11-2008, 03:26 PM

Originally Posted by 0rion

the first thing I would do is verify fuel pressure both at idle and at wot to see what's going on there first...

Agreed. Thats the first place to start.

Other then that, here's some suggestions from a Lean diagnostic trouble code chart:

Visually/physically inspect the following items:

• Vacuum hoses for splits, kinks, and proper connections. Refer to Emission Hose Routing Diagram .

• Crankcase ventilation valve and/or system for leaks. Refer to Crankcase Ventilation System Description .

• Contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• PCM and sensor grounds are clean, tight and in the proper locations.

• Air induction system after MAF sensor for vacuum leaks.

**sic2001** · 05-12-2008, 06:28 AM

So I went and bought ANOUTHER fuel pres, gauge...wrong hook-up and Im not going to cut the line to put their stupid shrader valve in so Im just going to go with the dealership, the mechanic there is really good and Im with Munky, I dont even want the thing back if it cant run right.

**Spaz** · 05-12-2008, 11:39 AM

Originally Posted by LS1MuNkY

so ive been having problems with my car first i thought the 02's were bad after the header install and they werent got a street tune and it ran crappy still. then i got a dyno tune and it put out 212rwhp and 304rwtq lol. my tuner said the car runs fine at a normal speed but when i give it gas it runs off the chart lean. so i changed the fuel pump and filter thinking it was that and it still runs shitty. and suggestions would be greatly appreciated thanx
Aaron

every one says sea foam to clen the injectors... start with the cheapest fix first...