HELP: N/A pinging, need help diagnosing...

URIN 2ND · 11-18-2005, 04:46 PM

Hey gang...

I have an '88 N/A that has a pinging issue. Trouble is, I'm not sure where to look next for the possible cause. At moderate/heavy throttle, she pings on 91 octane.

The car was pinging when I bought it earlier this year. Since then, I have replaced the TPS, DME temp sensor, O2 sensor, flushed the fuel system and balanced the injectors, and recently replaced the H/G and T-belt (finished that yesterday).

The car is still pinging even though the head and pistons are totally clean of carbon deposits and I have brand new OE plugs. I only run 91 octane in the car, and it has a stock chip. The timing should actually be *retarded* slightly since I had 30 thousandths decked off the head to raise the compression, which should actually help fight off pinging (this is not the cause of the pinging, as it was pinging when I bought it months ago).

What are my likely/possible causes?

Are there any other external sensors I can check/replace, or could the DME itself be faulty? Or is it possible that my FPR/dampener/fuel pump may have an issue causing it to lean out above a certain load or RPM? For some reason I seem to remember messing with the TPS adjustment and having some sort of effect on the pinging, but this was a while back and I cant' recall for sure...was this my imagination or could TPS adjustment be a factor?

The car runs beautifully otherwise (aside from needing a waterpump because the bearing is shot and the waterpump pulley wobbles). I just don't know what to check next. If anyone could help I'd appreciate it! Thanks so much!

URIN 2ND · 11-18-2005, 05:57 PM

...Bueller???

Jeff Laurence · 11-18-2005, 06:03 PM

knock sensors?

Eldorado · 11-18-2005, 06:57 PM

maybe throw a bottle of injector cleaner into your gas?

URIN 2ND · 11-18-2005, 09:12 PM

1) N/A 8V cars don't have knock sensors!

2) The fuel system is clean enough to eat out of, literally (if you don't mind the taste of gas, anyway). Has no impact on the pinging.

I think it's a sensor or computer related issue, but I'm not sure which ones impact ignition timing and/or fuel delivery...ideas???

EA425 · 11-19-2005, 07:22 AM

Just a guess, but a bad catalytic converter will definitely cause pinging. Sometimes you can hear a bad cat rattling from underneath at idle. Also sometimes if you give it a thump with a rubber mallet or something you shouldn't hear any loose pieces inside, but if you do it could need replacement.

CJFusco · CJFusco's Garage

Do you have any aftermarket performance add-ons, such as a chip?

Try running it with higher-octane gas and see if the pinging is still there.

URIN 2ND · 11-19-2005, 04:25 PM

Cat is new, stock chip, and 91 octane is the highest we get here.

Ugh! This is really annoying. I'll leave an update if I find anything tomorrow.

EA425 · 04:33 AM

Maybe low fuel pressure?

You could also try changing the FQS setting to see if less timing, or more fuel helps. If that helps you could go down that path to troubleshoot the timing/fuel issue - or maybe just leave the FQS set at the position that helps