Pinging under acceleration
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,327
Likes: 5
From: 2010 C6 Grand Sport Convertible
Pinging under acceleration
A quick question or two.....The gas is fresh, the engine and air temps are cool, and my LT1 pings bad under load in higher gears. I'm using 93 Octane. Should'nt the knock sensor disarm the pre-ignition? It feels like its working, at least partially, because the torque thats felt, drops off in higher gears(like spark was being retarded) when slowly accelerating before the pinging begins. Could the infamous opti be on its last leg, or the plug wires play culprit? There are no codes being thrown.
Mike
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
Could be several things. You might try:
1) Fuel from another source
2) Look for a vacuum leak (can cause lean-out)
3) Maybe a cooler spark plug
4) Injector cleaner (deposits in the combustion chamber can cause pinging)
Does she run any hotter than usual?
Thinking out loud.
1) Fuel from another source
2) Look for a vacuum leak (can cause lean-out)
3) Maybe a cooler spark plug
4) Injector cleaner (deposits in the combustion chamber can cause pinging)
Does she run any hotter than usual?
Thinking out loud.
Tech Contributor
Joined: Jun 2004
Posts: 20,936
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Just a couple of thoughts. With cooler weather, the absolute humidity (not relative humidity) is almost always lower. This enhances the conditions for knock/detonation (preignition is not related to ignition timing, and generally occurs prior to ignition. It is a dieseling type situation caused by hot spots in the chamber). Additional knock occurances would be expected in the weather you are describing.
You mentioned that the engine is cool. Is it in the normal range, or do you have a lower temp thermostat in it? Lower coolant temps generally allow/cause the ECM to advance the timing a bit, which may be increasing the quantity of knock.
If you are detecting a loss of torque, that seems to indicate that the ESC is hearing the knock, and the ECM is pulling out spark timing to eliminate the knock. Do you have any internal engine modifications that increase the noise signature of the engine? Additional internal noise (from modifications or just a stock engine with wide tolerances) sets up a higher threshold level in the ESC electronics that then require that the knock level be higher to hear (via the knock sensor) above the normal mechanical background noise.
Sorry, more questions than answers, but I'm just trying to understand more of what you're dealing with here.
You mentioned that the engine is cool. Is it in the normal range, or do you have a lower temp thermostat in it? Lower coolant temps generally allow/cause the ECM to advance the timing a bit, which may be increasing the quantity of knock.
If you are detecting a loss of torque, that seems to indicate that the ESC is hearing the knock, and the ECM is pulling out spark timing to eliminate the knock. Do you have any internal engine modifications that increase the noise signature of the engine? Additional internal noise (from modifications or just a stock engine with wide tolerances) sets up a higher threshold level in the ESC electronics that then require that the knock level be higher to hear (via the knock sensor) above the normal mechanical background noise.
Sorry, more questions than answers, but I'm just trying to understand more of what you're dealing with here.
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,327
Likes: 5
From: 2010 C6 Grand Sport Convertible
The motor is all stock. The operating temp was fine....approx 175-180deg -vs- 200 plus or minus in the summer months. It's a pain in the **** to hear it knock like hell when even my kids 4.0L jeep doesn't do that. If it were a 25 yr older car, I'd simply retard the ignition timing a tad. Thanks for the feedback. It gives me great starting points instead of tossing expensive parts at it until fixed.
Mike
Mike
Advanced
Joined: Oct 2007
Posts: 82
Likes: 0
From: Brownsville Texas
I don't know if this will help but I have a new L98 with less than 1500 miles on it which has been running perfectly. Recently, I found a crack in the connector which goes to the Idle Air Control (IAC) Valve. It was throwing a Code 15 and I starting getting the "pinging" on acceleration even though I'm using Hi Octane Shell gas. I'm positive the two are related. I've ordered a new IAC connector. If I replace it and the pinging goes away, I'll post it here in a couple of days. 
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Instructor
Joined: Nov 2006
Posts: 103
Likes: 0
From: Ft Liquordale Florida
I don't know if this will help but I have a new L98 with less than 1500 miles on it which has been running perfectly. Recently, I found a crack in the connector which goes to the Idle Air Control (IAC) Valve. It was throwing a Code 15 and I starting getting the "pinging" on acceleration even though I'm using Hi Octane Shell gas. I'm positive the two are related. I've ordered a new IAC connector. If I replace it and the pinging goes away, I'll post it here in a couple of days.
Instructor
Joined: Nov 2006
Posts: 103
Likes: 0
From: Ft Liquordale Florida
A quick question or two.....The gas is fresh, the engine and air temps are cool, and my LT1 pings bad under load in higher gears. I'm using 93 Octane. Should'nt the knock sensor disarm the pre-ignition? It feels like its working, at least partially, because the torque thats felt, drops off in higher gears(like spark was being retarded) when slowly accelerating before the pinging begins. Could the infamous opti be on its last leg, or the plug wires play culprit? There are no codes being thrown.
Mike
Citgo 93 octane is probably really 91, make sure you are using a GOOD gas station like Mobil, Bp, Shell, Chevron