Idle or Missing Problems

[lestion]

Hiyas again gang,

My 96 turbo KA is alive and kicking, with a couple of what seem to my thinking to be 'minor' problems. I am currently runig 10 psi of boost and the car is out of hand fast. The one thing I can't seem to get past is this idle problem. The car will idle fine when it is cold, but once it's warmed up, and the idle drops a bit, the engine gets rough and the idle is VERY unstable. It 'hunts' for an idle speed and will eventually die (maybe 30 seconds at a stop light). I have talked extensively with Jim Wolf and we have gone through the paces i.e. checked fuel pressure, adjusted both up and down, checked for vaccum leaks on each side of the manifold, adjusted MAF location and seal techniques to check for air flow problems. I have double and triple checked timing settings, checked valve tappet clearance, run a pocketlogger to check O2 sensor voltages and tried to keep the car in closed loop operation under load to see what settings come through. Here is what I have determined thus far: MAF at idle=1.15-1.19 V. O2 Front sensor seems to be cycling at factory spec.

Lemme give you all a rundown of the vehicle so maybe to paint a better picture:

Forged Rods and Pistons 8.0:1 compression255 LPH WalbroDenso 660 cc injectorsJWT ECU Flashed for Z32 MAF and Densos listed aboveZ32 MAFGreddy type S BOV recircing into intake tube AFTER MAF, but BEFORE compressorIACV hose fitted to charged air pipe just before Throttle BodyValve cover breather to MAF/Compressor tube AFTER MAFT3/T4 hybrid stage II compressor wheel/ .48 exhaust housingApexi generation I AVCR

The boost gauge, BOV and Boost Pressure Sensor are all plumbed into the FPR control line from the back of the manifold on seperate T's.

So with all this please let em know if ANY of you have any ideas on what could be the problem. The car 'feels' like perhaps there is a miss in it up to about 2000 rpms, after 2k, it just pulls like a banshee. I would love to turn this thing up to 17-20 psi like its been built for, but I am afraid to until I have this problem sorted out. Any ideas would be greatly appreciated!! HELP!

Thanks all, sorry this was so long, but I figured, the more info you had, the better it would aid in diagnosis.

Marc

[WDRacing]

What do your plugs look like??

[Structure240sx]

too rich? maybe an egr problem? with my hotshot header my egr wasnt in and i had idle problems. check the plugs

[lestion]

Hey guys,

Plugs look good...just the right color. I took some additional measurements with the pocketlogger just to check out trims and whatnot. Short term fuel trim at idle is anywhere from 2-25% to the positive side, under power or under boost the short term fuel trim is at -15 to -19%. It looks like the computer is for some reason setting fuel trims way high to the rich side during idle, then backing out fuel as I boost or am under load in vacuum. This may have something to do with the injector size, being as I built this thing to run high boost levels and made fuel arrangements to accomodate this. Would kind of explain the backing out of fuel at only 10 psi of boost, but I cant figure out why the idle would be so rich, something has to be signaling the ECU to richen the mixture unless I am totally off on my understanding of these things? Also, I have tried introducing vaccum leaks into the MAf and the manifold which would lean things out, but it didn't have any affect on the idle whatsoever. I am totally perplexed. Any ideas that I am not for reason seeing in my current state of confusion?

Just for the record, the EGR system is not even installed, but both the local dealer, and Jim Wolf agree this would not cause this condition. I don't know enough about EGR systems to speak on this myself.

Thanks a million guys for trying to help me with this.

Marc

[WDRacing]

I'm not familiar with 2-25% fuel readings, I'm only used to tuning with actual A/F ratio's. If your running that rich under 2000 then you might need your chip flashed again. Cause it doesn't sound like its programmed to run without boost and those big injectors. Cause it sounds to me like its starting to lean out once boost comes on allowing the car to actually run. You should throw it on a dyno and see what the A/R's are like, You'll probably benefit from some serious leaning out.

WD

[groundhogday1976]

Are you venting your BOV to the atmosphere, or are you recirculating it? If you're venting to the air that could be your problem.

[bedbull]

Are you venting your BOV to the atmosphere, or are you recirculating it? If you're venting to the air that could be your problem.

__________________

also have you checked on the engine ground i had a problem like that and it turned out to be the ground so now i have more than i need so no more problem

[lestion]

I am recirculating, the idle seems to have smoothed out a tad with some timing adjustments, but I am afraid thats a 'band-aid' and not the real issue, I am going for dyno work next week I will let you all know what I find out. Thanks!!!

Marc