chaotic

hello i have a 1990 ls 400 with 161,000 miles.. i am noticing a ping when i press on the gas slightly... i have always run premium gas in it... can anyone tell me of any possible problems?? someone told me it could be the computer i hope not....

SharpLS-96

Could be a number of things.
How long has it been pinging for?
When was your last complete tune-up?
Possibly bad 02 oxygen sensors.
You might have some water in your gas from receiving a bad batch of gas.
Could also be just the switch over from winter gas to summer gas in your local area.

I would try using a can of octane boost at your next complete fill up and see if that makes a difference before you start messing with the computer.

chaotic

Its been pinging for the last couple of months but seems to be getting worse... i put sone octane booster in but it didnt seem to make a difference........

SharpLS-96

Who told you it might be the computer?
I am leaning towards that now as well since you tried octane booster and said it's been a few months and getting worse.
Could still be bad O2 sensors but that's a 50/50 shot.

hyperopt

chaotic,

Sounds like the same problem with my 90LS. Early 90LS has a tendency to ping when slightly gas but the ping goes away after that. My guess is Lex engineers advance the timing a bit too much when slightly throttled to give a good punch feeling (acceleration) and smoother engine at the expense of denotation, which becomes noticable when the car aged. My 91LS doesn't give a good punch when slightly throttled nor does it ping.
I tried swapping the ECU between 90&91, and as I predicted the car with 90's ECU pings. I permanently replaced the 90's with a used 92's ECU and she happily consumes regular gas without any ping. Read the TSB if you want more info on this subject. Let's us know the results!

clark

Was the 92 ECU a simple replace on the 1990 or was there more to it than that? What does a used or new ECU go for?

chaotic

Could you let me knoe where i can maybe find a used ecu, and about how much do they cost?

hyperopt

90-92LS ECUs are 100% interchangeable. I can't speak for the 93&94 but I don't see why not. I got the ECU on eBay for ~$160 on a good day.

phillipin

bringing this back from the dead, but my 90 has the same problem, light gas and 1200 rpm and it will ping slightly, nearly 150k miles....i'll have a shop check my o2 sensors

I'll retard the timing soon and if that doesnt work i'll pick up a 92 ecu