Detonation on acceleration question?

Hi guys,

Need some help here. I was unable to find help using the search. When I accelerate lightly and lug the motor at low RPM's, I hear heavy detonation, or pinging. It only happens when the motor is under 3000 RPM's and is making about 5 psi of boost.

I use only good 93 octane gas, and my car was tuned up within the last year. I scanned the computer and found no codes. It never did this before, just started this week. I thought I got a tank of bad gas, so I drove until it was empty, and then filled up from a different station.....still detonating. Under hard acceleration, I don't hear it at all.

Any ideas? Sorry about the long post, I really want to fix this. I know that detonation is not good for head gaskets!!! Thanks guys.

Randy

Anyone have any ideas? Thanks.

detonation

My 89 has a knock sensor,I think yours does also.Maybe a bad sensor.

spark knock

could be few causes,, If your car is an auto matic ,,powerbraking can stretch the timming chain wich could cause your problem. Does it run at a slightly different temp than before?? Also does it boost as it normally did before??Could possibly(hope notbut) have a crack in one of the pistin skirts.Try a little octane boost. if it goes away your timming has moved,(stretched chain maybe) If it doesnt help may be a mechanical failure like a cracked skirt since it isnt showing codes. Also put car into gear and put foot on brake and slightly gas up the engine just under load and see if she misses a little ,If so Plug wires could be bad.

good luck Jim (vetteman)


89 SC
76 vette
84 vette
87 vette
70 GT Torino

I had a major problem with that on my 89. It was stolen and got to fix it entirely.

1. Get a cylinder balance test to if see one or more cylinders are bad.

2. Definitely check your EGR valve (if app.). Replace if your mileage is high or you have heavy carbon deposits.

3. Run some injector cleaner in the tank. Berryman's seems to work well. Redline offers a product as well. Partial

4. Pull and inspect your plugs to see whats going on inside your motor!

5. I've heard of a worn TPS causing detonation due to high resistance.

6. Vacuum leaks can take in unmetered air in the system. Check the underside of your rubber intake tube and make sure your crankcase intake tube is completely sealed. Check for cracked vac lines, etc.


Good luck.

mine did it when egr wasnt working right and with colder plugs and colder thermostat i can run 87 octane with no pinging and it rips prob close to 250 hp , pinging is really hard on headgaskets i would try to fix it soon

Thanks guys, excellent help. I am putting plugs in it tomorrow, along with some injector cleaner and a 180 thermostat. I'll let you guys know if it fixes it.

Thanks.

Update:

I fixed it tonight! I replaced the plugs with Autolite double platinums, replaced the fuel filter, installed the 180 stat with water wetter, and I installed the intercooler fan kit. It runs nice and cool now, and no more detonation.

Thanks for all the help and advice guys, this website is awesome.

Randy