I was wondering if anyone could take a look at this log in Excel and see if they can determine why my '88 L98 is running rich, needs a quick pump of the gas on a cold start or else it stumbles or dies, and also is hard to start after being driven and sitting for 4-ish hours (like at work). The car has new Bosch fuel injectors (the yellow ones, I think the type III?) and a new MAF power and burn-off relay, a new o2 sensor, and I'm pretty sure I replaced the CTS as well. I'll be replacing the spark plugs as soon as I'm able. The car has 80k miles and I run 91 octane. Also, without the cable plugged in, in park it idles at around 600 and in drive at around 400 which I know is not normal. Thanks for the help

 

Since you have replaced so many parts already. Your down to leaking ninth injector, leaking fuel pressure regulator. Or bad tps !

 

Thanks for the response. My TPS is being reported as perfect, so unfortunately that's not it I don't think. I haven't tried unplugging my ninth injector since I replaced the new relays, so maybe I'll try that. But would that affect it after it's warmed up?

 

Here's an updated log with the ninth fuel injector unplugged. Not much change that I can see, besides it being a little harder to start cold, obviously.

 

If it's leaking you would be running rich.

 

I suppose I'll invest in a fuel pressure gauge soon and see what I can come up with with the FPR. Thanks for your help

 

Try unplugging the vacuum line off the fuel pressure regulator. Let the car idle for a good minute or so like this. If you see any fuel coming out of the fuel pressure regulator, you have a tear in the flap of the fuel pressure regulator.

This releases pressure during shut off (which makes it take longer to start and sputter for a second or two while the fuel goes from the tank to the engine). It also releases fuel into the engine during a hot shut off, like at a gas station.

 

Thanks for the suggestion. I finally got around to changing the plugs and wires and the idle while in gear is almost perfect, so that probably rules out the FPR now. The IAC is still reporting 160 in gear and 70-90 in park, and the BLM still reports 160 and INT still hits 140 even though it's running rich, so I'm gonna try changing the O2 sensor and seeing if that'll fix my false lean.

 

Have you not done the IAC reset and base idle adjustment?

Idle Air Control
Tools needed:

Torx bit # T-20
Paper Clip
Small Punch

Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the ‘A’ and ‘B’ pins.

Turn on the ignition, but don’t start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.

Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).

If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.

 

You could have a lean condition,a injector partially plugged . I would suspect drivers side. This would cause the ecm to over compensate and run rich.