Extremely Lean condition

[Marc87GN]

I finally was able to hook up my laptop using Turbolink. The car has a terrible idle.

These are some of the numbers. I have to go to work so I don't have time for all of the specifics.

TPS - .45
IAC - 77
MAT - 75
Idle - 750 rpms - 850 rpms
MAF - 6 kg/m
O2 - 39-46 mv
BLM - 128
CTS - 176

I have a heated O2 installed so it was closed loop. normally the O2 mv jumps all over the place to show the computer correcting. Any Ideas on what is the common cause for this would be helpful.Could the IAC count be causing this very line condition at idle and why wouldn't the computer correct for this?

 

[Turbo Brian]

A vacuum leak will cause an extremely lean condition and a poor idle. Check all of the vacuum hoses and zip tie them. If that does not solve the problem, other places that have been found to leak include the plenum base, and the Egr valve. There are also other places for a vacuum leak. Good luck.

 

[ijames]

You say it was in closed loop, but were both the closed loop and learn flags on? With that O2 for any length of time in closed loop the BLM (integrator) should have been all the way up to its maximum value, usually 150, and if the learn flag was on the BLM should have also been maxed out, not still at 128. Also, the IAC at 77 is very high for idle, which means the ecm is adding lots of air and you probably don't have a vacuum leak. If it used to idle okay and you didn't change anything so the throttle stop is probably still set okay, start by pulling the IAC motor out and the uppipe of of the throttle body and wash the insides of the throttle body and as much of the intake manifold as you can reach, and the iac passage, with about a can of carb cleaner. Also hose off the tip of the iac but don't pull on it or scrub vigorously as it's pretty delicate and expensive. Put it all back together, start it up and warm it up, and then change the oil to get rid of all the carb cleaner that will make it past the rings.

 

[MistaScott]

Ignore the idle o2. You should be looking at BLM. O2 can only tell you if you are lean or rich not how lean or rich you are.

 

[Marc87GN]

OK, I made some adjustments and recorded about a 15 minute drive. I adjusted the Idle screw and TPS.

New idle numbers,

Idle Rpms 725-750 in P
IAC Count 19
TPS - .43
O2 Volts 95-805
Mass Air 4gs - I read an interesting artical about this at the Thrasher website. Basically the K&N under the hood is throwing off the TPS readings.

Int - 138
BLM - 150 drops to 132 off idle and to 128 above 1,000 rpms
CTS - 188
MAT - 99.5 Hot and humid today. Big mouth cold air is next.


The thing that concerned me was getting 3-8 degrees of spark retard at 3000-3200 rpms even the O2 reads over 800 mv. I think it was related to the Bosch platinum plugs because they run hot to clean themselves. I replaced them with CR43TS AC Delcos tonight, took a turn out of the waste gate & bumped the fuel pressure to 46 psi. Otherwise, the car runs great and is much more responsive. So far since I bought the car 2 weeks ago, I changed the injector harness, ign module, coil pack(twice- long story), wires to 10mm, plugs, bought turbolink(awesome tool), heated O2 & installed line to boost gauge properly(was leaking). I have waxed it 5 times and the looks I got on the street was amazing. It hasn't been out in 2 weeks and I drove it home at night.