After replacing the Electronic Spark Control Module, the Knock Sensor, lowering engine timing from 6 to 2 degrees BTDC, and using premium gas (octane 91), I still hear a ping when climbing even a small hill. It seems to be more pronounced when the outside air temperature is in the upper 80s or 90s. I'm using a stock 195 degree thermostat. Would replacing it with a 180 degree thermostat eliminate my problem?

 

The golden rule for posting on the Forum is to always tell us what year of car you have. The C4 generation covers the 84 crossfire....L98 with various changes....LT1 and then the LT4. How we approach your problem will be different based on the year of the car. That said....

Do you know if you are running the stock GM chip?

I had problems with the aftermarket Hypertech chip advancing the timing while it was reducing the fuel to the engine = PING.

When you changed the timing did you unplug the single brown wire?

You might be moving the timing the wrong direction. I solved my PING temporarily by moving the timing. I would adjust it and then run the car. Then adjust it some more and run the car. I kept doing this until the PING problem was close to being solved.

 

getting the general tune correct and using real DELCO parts helps...I had the same problem and bought ALL FORM of part for the ignition...ended up being the fancy wires that were causing the knocking. EGR may be part of it, air leaks...general maint.

Its got a problem if it knocks at 195 degrees with premium fuel.....a big problem. It should be able to run at 235 and not knock

 

Thanks for the info. I have an 87 running with a stock GM chip. The single brown wire is always unplugged when changing the timing and the error code that is created when unplugged is cleared. I'm definitely moving the timing in the correct direction - ping is worse when I move it towards 6 degrees BTDC. When you mentioned that you repeatedly adjusted the the timing after running the car, I'm assuming that you started at 6 degrees and gradually lowered it to a point to where the ping would cease. Is that correct? If so, at what setting did you end up at?

 

The car probably doesn't start to ping until it reaches 215 degrees. Is that typical for this car?

 

As a general thought, it sounds like once it has reach operating temp and starts to run off the sensors the fuel levels are being reduced.

How many miles on the engine?

Do you have the ability to data log the engine?

Perhaps the O2 sensors need to be replaced? I would data log first before throwing parts at the problem. Although O2 sensors are about 18-20 dollars.

 

You really need to scan this engine to see whats really going on...

keep in mind that IF all the ign is in good shape, and the fuel system is right, that you still have some differences between what you see in eng temp and what the ecm can see. Each have a different sensor located at different places, so when you see 215 its very possible for the eng coolant to be at 240, with a tired sensor.

Still, even at that temp, eng knock is the sign of poor or incomplete combustion. Ping (pre-ign) comes from excessive carbon build up on pistons/valves and/or the wrong heat range spark plugs or worn or damaged plugs. Knock is poor combustion, ping is early combustion. The problem needs to be ID'd before the cause can be fixed.

 

OP's timing procedure seems to be correct. Could he have a damper coming apart?

 

What's a good way to remove the carbon that builds up on the pistons and valves, other than a major overhaul? I suspect that is my problem.

 

You could try a product like "Sea Foam" ...read the back of the bottle for instructions or watch some Youtube videos.

With what your describing I suspect your car is super "lean" for whatever reason or you have clogged/partially blocked exaust system. If the car pings excessively don't drive it or if you must go super easy on it until you resolve the issue.

 

You can also bump the octane to 93 and see if that helps.

 

I lost an 87 L98 due to engine knock....it was my fault for the way I was driving it, but the bottom line is that these cast iso/alum pistons do NOT take stress laterally....as in banging around in the cyl,, they work fine up & down. Rattle them around and they come apart like cheap glass-ware.

Do what you can to keep it cooler, retard the timing for now, (rotate dist clockwise) and keep your air jordans light....until this is resolved.

Shattering a piston was a mixed blessing for me...I totally destroyed a good motor and spent a fortune rebuilding and was forced to bore it to the max to save the block....deep deep scars in that broken hole. BUT<-- I got the opportunity to build a little better motor thats served me very well. The lesson is that I'll never step in it again IF I suspect there could be a knock...of ANY type for ANY reason. I'm so gun-shy now that I won;t go out and run it hard without planning to do so...with a quick ck of the timing, fuel and temps. Never again do I want to see a piston in the oil pan from street driving.

Sea Foam or some of the other Hi-end valve/intake cleaners might help. What they do is burn so hot that it causes the carbon buildup to flake off the aluminum pistons dome or crown...or valve relief...where ever the carbon is caked on. When the motor is up to norm temps,. and seems to be running well, floor it and cause some instant hi combustion temps from the sudden jump in fuel/air and combustion. Doing this with the chemical product will help loosen the crud and blow it out. Don;t abuse it, just gently stomp it and wind it up a few times as long as there is no knocking or pinging.

This is assuming that you are 100% sure that your wires are good and all the ign system is good. I spent several months trying to isolate a knock issue like that and found the so called "nice" after market wires caused it all.....although pretty yellow with some nice boots they had so much resistance that the plugs were weak firing and knock was horrible under a load. Slow spark or weak spark is where alot of this comes from.
HEI needs to be fast & hot.
You might want to check the knock sensor as well...when that is functioning as it should, 90% of the knock should be eliminated the instant that it happens. The sensor should hear the 1st maybe 2nd knock vibration and instantly retard the timing enough to stop it and gradually allow timing increase if no more knocking is heard....this is all in milliseconds so the word gradually does'nt get anyone freaked out...
The knock sensor is also VERY sensitive to the torque to screw it in place. IF its been removed, it must NOT be over tightened otherwise that will effect its ability to hear knock. I believe its only 14 ft/lbs to tighten.

Good luck..hope something here helps in some way....at least some things to look at.