Running Rich

bleucamaro · 07-31-2006, 11:13 AM

My '89 S2 is running rich off of idle. At idle, it runs fine (~800RPMs 14.7 AFR, smooth running). As soon as the TPS goes from idle to transition state, it goes full rich (8.2 AFR). I've done some searching and most rich condtitions point to a hanging injector, FPR or vacuum leak.

If it was a vacuum leak or FPR issue, would the condition feel like such a light switch?

There are several relevant modifications to the car that I've tried to rule out, including: 2 bar MAP sensor (outputs similar voltage to AFM at idle and just off idle), GM type intake temp sensor (similar resistance to AFM), Innovate LC-1 wideband w/ gauge, and I'm using an SMT-7 piggyback and can see live data on screen and nothing looks out of the ordinary.
I also have 55lb injectors (siemens, low impedence).

The change in mixture is definately TPS triggered and is night and day. Any suggestions?

Razorback1980 · Razorback1980's Garage

Do you still have the TPS switch? If so, have you checked it?

bleucamaro · 07-31-2006, 12:48 PM

Yes, TPS is functioning propperly. When it comes off the idle circuit, it goes rich.

Schumi · 07-31-2006, 01:42 PM

I had the exact problem in my 8v 24S. It was faulty FPR and Damper. Just so happened that both were bad at the same time. FPR was runnning full pressure nearly all the time off idle and both the reg and damper were actually leaking fuel into the vaccum side. I was told that they might be the problem when I posted I had fuel smell coming out of the vaccum lines. I pulled on the vaccum line off of the regulator and gave it some gas, small amounts of fuel spirted out. Same thing on the damper.

I replaced both with new bosch parts and it solved the problem.

There are also other things that could cause it but I would check those.

bleucamaro · 07-31-2006, 02:18 PM

Thanks for the tip Schumi, I'll look at that when I get home from work. I was suspecting a vacuum leak, but thought it would run rich at idle too, and a more analog enrichment from full vacuum to ambient. Again, the symptom is like a switch, boom, full rich.

bleucamaro · 07-31-2006, 10:30 PM

Well, the FPR looks fine, not leaking, and it wasn't a problem before the install, but it seems I have a decent vacuum leak at that connector. I hooked up a vacuum gauge and saw 22inHg at the line and only 17inHg with the FPR connected. I'll try some new vacuum line to that site tomorow.

Razorback1980 · Razorback1980's Garage

Is your O2 sensor connected and working?

bleucamaro · 08-01-2006, 06:20 AM

Quote:

Originally posted by Razorback1980
Is your O2 sensor connected and working?

Yes. Wideband signal going to piggy-back and narrowband signal going to DME. was working fine before addition of MAP sensor, IAT, and injectors.

bleucamaro · 08-01-2006, 10:17 PM

I fixed the vacuum leak and got absolutely no improvement. I double checked the O2 to make sure there was a good connection and its fine. I also connected the O2 sensor to the laptop and tweaked it for a leaner running condition and it went to the leaner AFR at idle, but super rich again just off idle. Then I started to screw with the calibration and it went all the way lean (wouldn't idle, or rev, bucking. . . shut 'er down!) I'll recalibrate tomorow before anything else and see if that at least gets me back to square one. Then I'll put the original injectors back in and see what that gets me. After all that, I'll open up the DME looking for fried traces or busted solder joints.

Anything else I should look at?

I'm very strongly believing that this is electronically caused, and thus electronically cured.

bleucamaro · 08-04-2006, 12:05 PM

Just as an update I got the car running better now. The culprit was a bad calibration on the wideband O2 sensor. Now I can start tuning it so it doesn't get so rich when getting into boost.