Verify the fuel pressure ... for yourself ... at 5K in high gear. Shops usually check with the engine not even running. If you don't have a dyno handy then do it on the road with the pressure gauge taped to the outside of the windshield. Make sure that the gauge attached with genuine fuel hose, not low-pressure hose.
----- Original Message ----- From: "Chuck" <[EMAIL PROTECTED]> To: "miatapower List" <[email protected]> Sent: Sunday, July 20, 2008 10:45 AM Subject: persistent lean on a 94 > z0-pHey gang, I'm helping a buddy diagnose a persistent lean condition > on his stock 94. We could use some help on this... > > His 94 has a stock fuel system and stock ECU, with a narrow band O2 and > AF meter. > > The car is running quite lean almost all the time. It shows a normal > dithering on the AFR meter at idle and a very light cruise. It's lean > at any rpm above 5000 and at any more than just light throttle (cruising > or very light acceleration in low gears). If we go WOT from idle, it > stays rich until 2000rpm and then goes dead lean, and stays lean until > the rev limit. Power is down significantly, but it does not ping. It > doesn't misfire except, it always has an extra hesitation as it passes > through 5000rpm. > > Here's what we've done for diagnosis so far: > > ~ swapped MAF with known good unit - car ran slightly worse (slight > misfire at med throttle angles) > ~ swapped NBO2 with known good unit - no change. > ~ verified voltage at fuel pump - ignition on and FP jumped in the > diagnostic box, blue/red wire had 12V, yellow wire had 8V. Grounds had > continuity. -- by the way, what is that yellow wire for??? > ~ cleaned all ground points (didn't look too bad to begin with). > ~ clamped fuel return line after FRP - no change in running or AFR meter > reading. > > A local shop said that they verified good fuel pressure and swapped in a > known good fuel pump - I have not verified any of this myself. > The same shop said they swapped ECUs with no change - I haven't been > able to verify this myself either. > > At one time the car had a JR SC, so the AFM harness and TPS harness have > been spliced at one point, but seem to have good continuity. > > Any ideas? We're stumped. > > -Chuck > > > _______________________________________________ > Miatapower mailing list > [email protected] > http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower
