First off, it's a 89 MAF TPI.
I was fighting a false lean condition about 6 months ago and I finally fixed it after changing a blown driver's side intake manifold gasket. I now have the same problem. My vacuum with the blown intake gasket was about 16in at idle and it is currently between 16.5in and 17.5in at idle. Having changed all the intake gaskets three months ago could I rule out a vacuum leak? I have sprayed all around the TPI and have found nothing. I have checked my fuel pressure also and it is good, 50psi at idle with the vacuum line unplugged. I have also checked the pressure under load by taping the gauge to my windshield while driving. I made several WOT and the fuel pressure read right at 50psi. The problem is only under throttle with load, my idle o2 and BLM are good, even if I rev it. Under almost an loaded throttle my o2 drop down very low and WOT drops down to 0volts. Does it sound like a fuel starvation problem? Could I have another vacuum leak? Thanks for any help.

BTW I installed new fuel injectors in one year/7k miles ago for a unrelated problem. Here is a link to my log file: http://www.fbody.com/members/Formula355/log.CSV

EDIT: I forgot to add why I believe it is a false lean. My emissions are through the roof, 6x on HC and 4x on CO. My buddy was behind me and he said my car smelled very rich. My gas mileage has dropped to about 12mpg. This may be a curve ball, but my idle also smells very rich even though my numbers say its running good.


[Modified by PLANT PROTECTION, 7:42 PM 10/20/2002]

 

How old is the 02 sensor?

 

By "O2 reading is fine at idle" what do you mean. What values are you getting.

 

O2 is brand new. My log file will tell all. The o2 at idle bounces back and forth between .7-.3 or so......normal amount of cross counts.

 

I noticed in your log file that you're allways in closed loop mode. My car doesn't switch between open and closed either, can't remember which it stays in.

Just thought i'd point it out, sorry i can't help :cheers:

 

I started the log after the car went into closed loop, about 3min. Its not supposed to swap. I think my o2 is working correctly seeing tons of oxygen in the exhaust and some other problem is causing it, but my question is what?

 

I just took a second to look at your comments. If you are sure there is no vacuum leak at the intake then that most likely points to exhaust or header flange leaks. Then you still have the low vacuum readings at idle. It is starting to sound like you have 2 problems and the other may be a cat converter that is starting to clog and cause to much back pressure, giving the low vac at idle.

I had some cracked headers that gave me one hell of a false reading on my Grand National. The air passing by the cracks was literally sucking in outside air and giving false readings on the 02's. Good luck :D