2G GST Idle and Acceleration Issues

[knifeparty118]

Ok I'm working on this car for a friend, and I'm used to 1G problems. Here is exactly what's going on. Any help would be appreciated.

The original problem was a dead battery, and a CEL for IAT sensor. I cleaned the sensor, which was dirty from the FIPK Oil Kit, and cleared the CEL. Now that those two problems are fixed I'm having some Idle and Acceleration issues.

The car is bone stock except for a K&N FIPK. It is a 1996 GST with 114,000 miles. It has a new OEM T-25 turbo, about 10,000 miles on it. I have already replaced the fuel filter as well. I also bypassed the Fuel Solonoid and ran the FPR straight to the intake mani. I also topped the tank off with 93 octane, and ran STP Injector cleaner through.

At idle, the A/F gauge stays dead lean. I know that you can't use that as a means of tuning, but I'm not tuning the car. The Idle is also erratic. It will sit at 1,100 RPM for a duration of about 5 mins, then settle to 450-550. During low throttle/low RPM driving, everything runs smooth, except the A/F again stays pegged red. Over 3,500 RPM, at light throttle, the gauge will move to just before Stoich, and when you go WOT it will peg rich and taper down to stoich, until about 7PSI, then buries the gauge back to red, sometimes it wont even register. While this is happening the car will backfire once or twice, but other than that it pulls smooth to redline, just not hard. It feels that the timing is being pulled out completely.

If anyone has any suggestions please let me know.

Im thinking its maybe the fuel pump, but there isnt any noise from the rear passenger area. My only other thing I havent checked is fuel pressure, which I will do later tonight. I figured I would ask around and see if anyone has experienced this before.

Thanks,

Matt

 

[absolute_DSM]

Id check the O2 Sensor just to be safe. Then check the knock sensor since you say you think timing is being pulled. Might as well check the timing with that to make sure it on.

Also check your plugs.

And after that, check this for idle surge - http://www.dsm.org/how-tos/tttt/tttt3.html

 

[knifeparty118]

I checked the plugs already, and they are getting white. I just switched the MAF unit with one from my 1995 3000GT VR4, and the car ran alot better. I know its probbly calibrated differently but the idle stabilized to 900-1100RPM and the A/F Gauge was working again (Blinking back and forth). Under acceleration however, the same problems were repeated, as the gauge pegged lean (12 PSI on stock T25), and 2-3 harsh pops occurred before timing pulled out and acceleration almost halted as RPM's climbed.

Is there a chance the MAF is dirty, and sending a poor signal? Also, would the O2 sensor (pre-cat or after-cat) affect the idle, and fuel delivery to such a degree? To me it seems that the car is just running out of fuel. I'm going to swap out the MAF and O2 sensors tonight to confirm, but after checking everything I'm running out of ideas. Has anyone ever seen a fuel pump drop volume without failing?

Thanks,

Matt