Yeah, pinging also. it does it whether it is on 91 87 or 101 octane. Not so much on the 101. But bad on the others.
101 is unleaded race fuel here. I have some for my camaro and put a tankful in the celica to see if that would fix the problem. It didn't completely.
Pinging is usually due to low octane gas, carbon buildup or hot spots in the cylinder. Something is causing the fuel to ignite on it own without the spark plugs. There might be some kind of fuel additive that can help remove the carbon.
The larger problem is the motor will only rev to 4000 and then it acts like it hits a rev limiter. The car hesitates upon acceleration. When floored the intake has pulsing sounds coming out of it. At light to full throttle it pings. Starts easy, idles irratic ( just dies then starts back. Doesn't completely die, just enough to hear a major miss.) Besides that, it is very reliable, gets about 20 mpg, no other wierd noises from the motor (rod, main knock, or valve clatter.)
I tried B12, never tried sea foam. I ran a half gallon to a full tank twice. I soaked the intake manifold with a 16 oz spray can. When I started it after that, it obvisiously ran rough, but it sounded like a piece of metal traveled down the exhaust pipe from manifold to tip and then it was gone. I looked for something but never saw anything. I have a straight through muffler is why it didn't get stuck in the muffler. Then while it was running, I poured a 12 oz can into the brake booster line while it was running. That was all done in the last 3 months.
When I replaced the timing belt on my 92 GT I placed it on Zero degrees.
It pinged like crazy.
At Idle, trying to rev to 4,000 RPM's the engine would do as you describe and would cut back.
All I did was retune the engine with a vacuum gage and solved my problem.
You can try adjusting the timing with a timing lamp.
yes this is caused by carbon build up on the valves. simple fix
this is cause by driving around for years in too low of a gear like 5th at 60kmh/35mph or an example. there is not enough heat to burn all the carbon out of the chamber. if your car is maual drive around town in 2nd gear or auto too i suppose. also euther auto or standard take your car for a real burn p the highway, 1st till red line 2nd till redline and so on this will heat everything up and burn off the exess carbon. i work for as a mechanic and this is nessicary we do this to many vehicles to get rid of pinging caused by carbon build up. also if your car is running not 100% buy some kleen flow injector cleener and put a whole bottle in a quarter tank of gas before you go and give the engine a work out.
i hope this will help it should