I picked this car up about a month or so ago now, its had this problem since then, Interested in what is causing it. It does not do it all the time... maybe half the time. car is stock.

I recently did a complete tune up, new Dizzy, cap, rotor, icm, plugs, wires, o2 sensor. and replaced the maf that just failed.

I accidentally had the timing 6 degrees advanced (wasen't thinking when I was setting it) despite being a total dog it did not ping at all like that. I ended up dialing it back to 6* BTDC like it should be. It got my power back however with it came the pinging it had before all this.

when it does it if i don't get off the gas fast enough it will set the SES lamp, however i do not know the code at the moment. I have gotten a knock sensor code in the past though.

Can a bad knock sensor cause this?

thanks
-chris

 

try premium fuel

 

way ahead of ya there. been running midgrade, recently switched it up to premium no change.

 

I'm going to guess that you made a mistake in your initial post. I believe that you meant that when the timing was retarded that it did not ping; is that correct?

Was the distributor itself replaced? If so, why and by whom? What was the reason for replacing the distributor and not simply the cap/rotor?

if it was replaced, was the same style used?

You have a timing issue. You could also have build up in the combustion chamber which would cause this. You can try Sea Foam and then replace the plugs again in a week.

 

It could be a bad knock sensor.

 

No, I seriously had it advanced 6* past tdc and despite being dog slow it did not seem to ping, currently its at the factory spec 6* btdc. I replaced the dizzy, reset the timing when I did. I know its bang on. I replaced the dizzy because the wiring inside going to the icm was all corroded. The replacment distributor is a factory style reman.

 

I do not know if the '87 LG4 has a knock module, but if it does, replace it. My '87 TPI ESC (AKA - knock module) module died and it was pinging like a ****.

Old / bad knock sensor will cause pinging too.

CG

 

I should clarify, this is for my LB9 IROC not my LG4 SC. I'll have to update that thing.

perhaps I'll change that knock sensor when I get a moment, its cheap enough.

 

Yes, the knock sensor is cheap. The ESC was about $70 though. I happen to have one used (but good), only 1.5 years old. I'll let it go because I just did a 350 swap for my 305. If u want the LB9 ESC, just pay the shipping.

CG

 

Hey so I am having a similiar issue with my 86 iroc with a tpi 305. It was rebuilt about 2k miles ago and it pings only under hard acceleration at about 3k rpms and up. It trips the knock and retards the timing. I took it to a shop and they said it was timing. I have fooled around with the base timing and it doesn't make a difference other than how fast it feels. At 6* it feels faster than 0.

I have injector cleaner in the premium fuel, good plugs, wires, cap, the distributor is good and solid everything is stock but the cam. The cam is mild and supposed to be computer friendly. not sure what size it is cause I didn't build the motor. I started to check the compression when I had all the plugs out. All the smog crap is still there so I gave up on #5 cylinder but the first 4 were between 170 and 180 on a cold motor so I didn't bother with the other 4.

Fuel pressure is around 38 so that seems fine. How do I make the timing right? It seems that its an advancing of the timing issue. Or is it something else?

Oh and all the vacuum lines look good. Can't find a bad vacuum line at all.

UPDATE: It was a defective knock sensor. I did some research on how the knock sensor functions and realized the ecm was retarding the timing because it had no signal from the knock.