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What causes a cold engine to ping on acceleration?

Ecomike

NAXJA# 2091
NAXJA Member
Location
MilkyWay Galaxy
Any one ever had an engine ping (pre ignition) when accelerating on a cold first start engine for 3 minutes or so, that stops after the engine gets warmed up?

If yes, what caused it?
 
I have a similar issue in that warm or cold, under heavy load (up a steep incline) in 4th. Can't figure it out for the life of me. Been doing it since I put the engine in

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My guess is an o2? In going to see if my obd2 reader will read the voltages. Mines constant so could be a bad cad. You should check your o2s though

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NO.


Even if the knock sensor was bad, it should not ping, ONLY on a cold start up at WOT, and vanish completely in 3 minutes when it is hot.

I have never seen any vehicles do this in my life, on a cold start up. Only when they were over heating and about to blow up the radiator, or already had.

Non of the logical known possible items I am aware of can cause it do this on just a cold start up.

I can't make it ping no matter how hard I try once the block temp is up over about 160-180 F.

IAT and CTS are good, O2 sensor good. Fuel pressure good.

It reminds me of using cheap, low octane gas on high compression 70s car. But I don't recall that being an issue on a cold engine at 70-100% WOT either.

RPMs/trans gear is normal. If it was carbon it would still do it hot.

If it was mechanical wear timing (chain), I doubt it would be just a cold start issue? I have found others with the problem that have it had it for ages, but none of them have solved it either.

Thought someone in the crew here might have run across it.

If it was a cold O2 sensor, it should be running rich in open loop, and have no chance to ping? Unless the spark is way too early, but why would the spark be way too early only when cold in those first few minutes?


Only does it cold, under load in gear at >50% of WOT. It should be ignoring the O2 sensor at high throttles anyway?

Renix?

Hate to be Captain Obvious here, but maybe the knock sensor?
 
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Pre-ignition has been known to be initiated in heavily carboned-up engines when the excess fuel (normal rich fuel mixture in startup) hits the hot carbon-buildup in the engine combustion chamber. It doesn't take long for the high flame temperatures and the heat of compression to heat the carbon-buildup hot enough to cause fuel pre-ignition, especially with rich fuel mixture entering the engine. After warm-up, the A/F ratio drops back to normal and there is no excess fuel to support pre-ignition. That may be what's happening in your engine. Likewise, after warmup, you may still have some slight pre-ignition that you're not hearing.

Best regards,

CJR
 
Thanks, that is what I am/was looking for. I was not aware that it was possible with a rich cold mix. But it does have a ton of carbon issues. I guess at wot, and higher RPMs it would get and stay hotter, the carbon.

And glowing carbon can not be controlled by spark timing even with a working knock sensor and working spark electronics, so it fits.

Pre-ignition has been known to be initiated in heavily carboned-up engines when the excess fuel (normal rich fuel mixture in startup) hits the hot carbon-buildup in the engine combustion chamber. It doesn't take long for the high flame temperatures and the heat of compression to heat the carbon-buildup hot enough to cause fuel pre-ignition, especially with rich fuel mixture entering the engine. After warm-up, the A/F ratio drops back to normal and there is no excess fuel to support pre-ignition. That may be what's happening in your engine. Likewise, after warmup, you may still have some slight pre-ignition that you're not hearing.

Best regards,

CJR
 
Thanks, that is what I am/was looking for. I was not aware that it was possible with a rich cold mix. But it does have a ton of carbon issues. I guess at wot, and higher RPMs it would get and stay hotter, the carbon.

And glowing carbon can not be controlled by spark timing even with a working knock sensor and working spark electronics, so it fits.


give it a drink to remove the carbon.

https://www.youtube.com/watch?v=eZDISp2pdSo
 
Run a can of BG44K through it.
 
Are you sure it is just piston slap/rattle? That goes away as things heat up most times.

It is not uncommon with the 4.0L.
 
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