1989 L98 Coupe

I have been having an extremely rough idle for the last three weeks. The car will run extremely rough throughout the RPM range. It will range from 500 to 1800 RPM if left alone and will usually die if the throttle is touched. It is blowing black/carbon exhaust which will make your eyes burn. At the outset of this problem I got one code which was rich exhaust (duh) but it hasn't thrown a code since (unless i disconnect a sensor to troubleshoot).

I've replaced:
O2 sensor
Wells MAF (thought that would do it...no luck)
AFPR (40# w/vac 45# no vac)
fuel injectors
fuel pump screen
fuel filter
Cat converter
Plugs, wires, cap, rotor (good spark to all cylinders)
good compression (170# +/- 5#)

What's left? I am at the end of my rope. As an aside...my current ECM says remanufatured on the case so I am assuming there have been problems before. I have only had the car 4 years. Also...after about 2 weeks of trouble shooting I noticed that the ground wire to the ECM (one of the two under the batt...the stranded one not the braided one) was disconnected. I thought I had the problem licked and connected the wire, checked the ground to the ECM (~9ohms), started the car...and same old problem. Could that ground having been disconnected have blown the ECM?

Any other ideas...i'm tired of replacing components with no results. Thanks
:U

 

You need to get a scanner on that car to see what's going on. Otherwise you will be chasing parts forever.

The 89 does have a bad ecm, but your problems are not the classic symptoms. The orginal ecm was a 1227165 which had problems, 16198259 is the replacement part and is a better ecm.

Check voltage at the TPS and see if it is 5V or if it is higher, like 12 V. This could be an indication that the ecm has given up the ghost.

But I really think you need to get a scanner on that engine and see what's going on. Could be anything.

Let us know what you find.

Pete

 

Like this :crazy:

Sorry I couldn't resist

Pete offers good advice on the scanner. When you ground terminals A and B on the ALDL do you get a code 12? Another thing you might try is replacing the MAF relays. This is a common problem on TPI vettes. Did you try unplugging the MAF to see if that helps?


[Modified by 89vette, 7:54 AM 5/2/2002]

 

I swapped out the MAF with a new one and have run the car without it with little or no change. I have not checked the MAF relay but will try tonight. I do get a code 12 when I short the diag term.

When you say "scanner" are you talking about Diacom software? I really don't want to take it to a dealership because all of this started after it was there last (for a ground/battery drain problem that was never found, they may have disconnected something!!) I am more than willing to buy the software/hardware. Is Diacom the best...is there a better one out there...where can I buy it. (I know ecklers sells it for $299)

 

Your Idle Air Valve could be malfunctioning or more likely, there is carbon build-up blocking the hole. Take the throttle body off the car, remove the IAC and clean all the holes. Reassemble and reset the IAC by reading the tech tip and Let us know how it runs.

 

If you go to the tuning / prom burning section: read the FAQ for information on free software and inexpensive cables.

Hate to even mention this, but Jiffy Lube often offers scanner (they use auto x-ray) service for a fairly low rate I think. But you will have to know what to look for when you go, because other than a code I would not expect these places to be able to actually look at scanner output.