bottesini

iTrader: (1)

Need some help brainstorming an issue.

The car had a P0357 (#7 bad coil) code. Ended up changing the plugs and finding the PCM connection was loose. The car ran great sat for a few days and then I drove it again with no problem.

After sitting at work for the day the car started up and began having lean issues. On a cold start the idle is very lean and eventually once the car heats up returns to normal. It currently runs fine for cruising and holds around 14.7 afr. However, it hesitates at WOT and runs around 16 + afr.

No codes are being thrown and I have checked the fuel pressure and it holds steady at around 60-65 psi at idle and under load.
I have not found any vacuum leaks and the idle does hold normal.

I have also changed the fuel filter with no luck.

Any ideas?

sjsingle1

iTrader: (1)

lots of places where a vacuum leak can occur and maybe cause a lean condition....that you would not suspect otherwise

intake gaskets...
throttle body gasket
valve cover gasket
original PCV hose setup ( the worst leak IMO )

the rubber type gaskets GM uses are great til they get old and shrink and flatten out....lose all sealing

Blade22225

Are you using your o2 sensors to diagnose the lean condition or are you using a wide band? Every time I had a o2 sensor fail it started reporting a false lean condition and would make the car ran like s**t.

RPM WS6

iTrader: (3)

Some good suggestions above. Another possibility would be weakening injector(s). Sounds like fuel pressure is great under load, so I think you can rule out the pump and filter.

ddnspider

iTrader: (26)

Should be pretty easy to pull the #7 plug and see if its rich or lean and that'll tell you if its spark or fuel related.

bottesini

iTrader: (1)

Older pic and some things have changed, but essentially what I have.

All of my gaskets were replaced when I put in the 416 and this was a sudden change. Happened while the car was parked in just a few hours. On my check for problems I could not find any vacuum leaks and the idle becomes normal once the car has warmed up.


I have a wide band. The O2s are not throwing out any codes.

bottesini

iTrader: (1)

80 lb/hr injectors that are less than 2 years old and the fuel pressure stays constant. I actually bought a new Walbro 340 thinking mine might be going out before I put a gauge on the rails.

Going to try taking the rails off this weekend to make sure the injectors and rails don't have junk somewhere.

Blade22225

Neither did mine.