Engine Knock Pinging

THEBOOGIEMAN

MEMBER
PONTIAC BONNEVILLE

I have an 85 Bonneville 8 cyl 5.0 with only 39,000 Original miles on it. Engine knocks when at temp with a load on it. (Going up a hill ) Or when at temp at or over 55mph. When shes cold not a problem at all.
When I 1st start the car I can get it to 85 mph without any noise at all. Once it hits temp if I drop under 55 and then give it gas to get back to 55.
It rattles like I have metal bottle caps in the engine.
So far.
Changed oil pressure sensor and checked pressure.
Changed EGR valve.
Changed radiator.
I thought oil pressure first but that was fine.
Maybe heat so I changed radiator. EGR was my last thought. Changed and no change.
Actually took it to a dealership by me to look at it.
They said carbon build up. They used Top Engine Cleaner. Didn't work either.
Since then I've Seafoamed engine. Use 93 oct gas.
And she still knocks. Dealership mentioned it could be mechanical. I can't figure out how that could be, if it runs like it does when its cold.
Thanks for your time. The Boogieman

3 Replies

RASMATAZ

MECHANIC
75,992 POSTS

You need to double check the passages on the intake and exhaust manifold where the EGR at. Is the engine getting hotter than usual. Might also be a lean mixture, sparkplug with wrong heat range, overly advanced or the knock sensor itself.

Spark knock/Pinging/Detonation is normally caused by the EGR-there's no mixture dilution to reduce combustion chamber temperature tp prevent oxides of nitrogen formation. NOX

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Sunday, September 9th, 2007 AT 7:54 PM

THEBOOGIEMAN

MEMBER
2 POSTS

Thanks for getting back to me so soon.
My fault I should have mentioned it. Timing is dead on. Knock sensor is working. I changed the radiator because maybe heat was the cause of the knocking.
Temp is fine. So heat not the problem.
Checked the EGR passages like you said. There WAS a carbon build up when I first changed it. Cleared it. Looked fine this time. Unless I'm not getting deep enough? Should I throw some Carbon Cleaner down the passages?
I hope you agree with me, that if its not knocking when cold. That it not mechanical.
I could drop a new engine in it. BUT hate to do that if its just something stupid and not mechanical.
Carbon build up sounds right to me. They only put on 2,000 miles on it in the last 6 years. So engine never got hot enough to burn off carbon.
But the dealership used Top Engine Cleaner in it.
I've used Seafoam twice on it. Now use 93 oct. Gas with Chevron Techron Concentrate in it. At least 4 tanks full so far. Could carbon still be the problem after all that? I'm not sure.
Thanks again, The Boogieman

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Monday, September 10th, 2007 AT 12:31 PM

RASMATAZ

MECHANIC
75,992 POSTS

Pinging occurs during acceleration or WOT and sounds like a bunch of marbles being thrown into an empty can-try to get deep on the passages

Also check the ignition timing I know its being controlled by the PCM. You have done everything that I will do to eliminate spark knock/pinging/detonation

How about the knock sensor, if the computer don't see the KS signal while pinging is happening it will not retard the timing

Preignition occurs before the sparkplug fires because of hot spots in the combustion chamber-meaning carbon accumulation. And Detonation is the 2nd explosion after the initial spark.

If you're getting the knock while engine is still cold sounds more like engine bearings.

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Monday, September 10th, 2007 AT 4:53 PM