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Engine pinging


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Eric of Pa.
Novice

Nov 16, 2006, 1:31 PM

Post #1 of 3 (2268 views)
Engine pinging Sign In

My 95 Surburban likes to ping when under load at certain rpms.Whats the cause and cure for that? Thanks


DanD
Veteran / Moderator
DanD profile image

Nov 16, 2006, 7:15 PM

Post #2 of 3 (2259 views)
Re: Engine pinging Sign In

The first thing I would check is whether the base ignition timing was set to spec? Next would be to check that the EGR were functioning properly. The EGR (exhaust gas recirculation) valve when functioning cools the combustion temperatures and was designed to reduced NOx emissions but a side benefit was a reduction in engine pinging.
If those were adjusted and doing what was intended I would try having the engine decarbonized ; sometimes carbon build up will raise compression ratios and cause detonation that audibly sounds just like a ping.
What grade of fuel is recommended for this truck and what fuel are you using?
The last thing would be engine mechanical as in a loose timing chain. A loose timing chain will retard valve timing and if someone unknowingly adjusted ignition timing to spec with a loose chain that would cause a ping. The distributor is driven by the camshaft and the cam is driven by the timing chain so it’s kind of a domino affect.
Just a bunch of things that can cause an engine ping; who’s doing what to who is at times a process of elimination.
Dan.

Canadian "EH"






steve01832
Veteran
steve01832 profile image

Nov 19, 2006, 3:59 AM

Post #3 of 3 (2250 views)
Re: Engine pinging Sign In

I would like to ad one more thing. Remove the EGR Valve and look at the underside. You will see the pintle and probably see blackish carbon around it. If you take a small piece of coat hanger, you can try to push the pintle in. You shouldn't feel any resistance as the pintle is forced off of its seat. If you do, hold the pintle in and spray carb. cleaner inside and clean all of the carbon out until the movement is smooth. You can even insert the correct size torx bit and turn the pintle back and forth to remove the carbon as you clean it. This can cause the EGR to hang closed as the PCM commands it open. This usually kicks the MIL and stores a DTC but not always. I have found this buildup to be common on these vehicles and this cleaning procedure has proven to be effective when I retrieve an incorrect EGR position code. But like I said, this doesn't always kick the MIL and store a code.
Also, check the spark plugs for carbon buildup, proper gap, and most important, proper heat range. Running too hot of a spark plug or too wide of a plug gap will also increase combustion temps.

Steve






 
 
 






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