Need help please. Trying to solve this pinging problem. Stock 87. I know I shouldn't hear pinging if knock sensor is working correctly,(will have to check that) but what should I be looking for as the cause? I run 93 octane, still pings under hard acceleration. What is the ideal timing setting? Just trying to figure this all out.

 

Well - you are correct - stock, with a stock chip shouldn't be pinging. Not with stock compression, stock PROM and 93 octane.

Unless - it Could be "all carbon-ed up" and therefore have a detonation tendency. Or something is causing it to go very Lean, making it more likely to detonate.

Either way the knock sensor should be telling the ECM all about it and the ECM Should be pulling timing out to stop it from happening. BTW - if a knock signal continues for long enough the ECM will set a code and turn on the SES.

Otherwise, the ECM does run a diagnostic to verify operation of the knock sensor. If the Check engine light isn't on then That is presumeably OK. You can test it with a timing light and a hammer - warm the car up, put the light on it, and tap on the passenger side exhaust manifold (or anything else solid and part of the motor) - the timing should jump towards less advance.

The "stock" baseline advance (EST bypass wire disconnected) should be in the 4-8 degree range (advanced, or Before TDC) I don't know Exactly what the '87 should be, but it'll be close to that.

Make absolutely certain that the timing mark on the harmonic damper is Right before you trust it - dampers of this vintage have a nasty habit of having "slipped" - rotated on the hub which moves the timing mark (from the correct location in relation the true TDC of #1 piston) and really messes up trying to set the advance.

 

I checked the timing, 4 degrees, but like you said if the timing mark has slipped.... I guess I could try changing the timing and check for pinging. I did seafoam the engine this summer so hopefully it removed some carbon. Also no SES light and no codes. Also, could lesser quality spark plug wires have any effect? Might have to replace what I think are older cheap wires. Thanks

 

Timing is supposed to be between 6 and 10 degrees BTDC. If yours is 4 degrees ATDC that could be the cause. Remove the driver's side valve cover and compare to the rotor position. I know its not the easiest thing to do and if it looks really off dont hesitate to get a mechanic to help you, its worth it.

Cheap spark plug wires will not cause pinging and they're not a cause for concern unless they're worn out or broken.

 

4 Degress before tdc is retarded, compred to 6-10 degrees btdc.
Do not advance timing (to 6-10 degrees). It will make it ping harder.

Disclaimer:
I normally do not contradict a posters comments, but would hate to see the op break a motor by advancing timing.

 

I have an 87 with no mods and am having the exact same problem... I have it at the Chevy Dealer right now getting looked at. The guy said he was sure it was a ping issue and said it was probably related to the EGR or a timing issue. I sure hope they figure it out, because it is very annoying once the engine is good and warm. Under heavy acceleration it pings in different spots through out the rpm range and you can notice the slight drop in power because of retardation...

 

The harmonic balancers are known to spin the outer portion when the get old. If anyone suspects this, change it immediately.
They make a mess when they let go.

 

I'll be sure to mention that to the tech on monday when they open up and get back to me! Thanks!

 

I am only slightly familiar with the balancer. Is it difficult to replace and easy to find a new one?

 

You will need to buy or rent a harmonic balance puller from ur local auto parts store. Other than that its fairly easy to take off.

 

Whats the engine temp at?
This might have nothing to do with anything but on my mazda was recently over heating, I pulled the therostat and it runs soo much cooler as a matter of fact it has never ran better! It used to ping when it warmed up under load Not anymore with cooler temps.
Just a interesting thoght

 

Usually will run at 198 degrees or less at cruising, lately even less now that the temperatures have dropped outside. But the temp will climb pretty fast at idle in traffic

 

I'm sorry, maybe I wasnt clear in my explanation. I wasnt telling the OP to advance the timing, but simply saying thats where its supposed to be. I was trying to say that he should check the valvetrain geometry to make sure its really at 4 degrees.

 

The chevy dealer ran some tests and said it was the EGR. They wanted $700 to replace the EGR, Selinoid, and Gasket... **** that, I will change it my self!

 

Rat bastards!