Mechanics

POSSIBLE SPARK KNOCK

1999 Dodge Dakota

Noises problem
1999 Dodge Dakota V8 Four Wheel Drive Automatic 150000 miles

I am hearing a sound that is like a spark knock and I suspect that is what it is but I have had the computer udated for spark knock, vacuum leaks checked under the intake at the plenum, and a complete tune-up. I am at my wits end as to what the problem is and now people are telling me to take it to a dealer to have a proffessional fuel cleaning job. There is also a noise that sounds like it is coming from the lower rear portion of the engine and do not have a clue. I am the third owner and the second owner kind of took care of the truck but not sure how well he did at it. Any ideas would be helpful on how to locate and find the source for the engine noises would be greatly appreciated. These noises are louder than they should be but not loud enough to think the engine is going to fall apart though.
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Beef99
July 11, 2009.




Does it knock at idle? On acceleration? Does it quit when you lift off gas?

Docfixit
Jul 11, 2009.
It only does it under acceleration, not at idle. When I am at a cruizing speed, and step on the gas it sounds like spark knock. It is not extrememly loud and I cannot hear it at higher speeds unless the window is down. The vehicle runs superb and is in great condition. The engine idles smoothly too. It is not the timing chain either.
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Tiny
Beef99
Jul 11, 2009.
Your year engine has a common problem with spark knock on accel. Caused by a leaking intake plenum pan gasket. It is internal and only clue to it being problem is knock and a slight rise in oil consumption.

Docfixit
Jul 11, 2009.
And yes, it quits when I take my foot off of the gas, I am pretty good with engines and vehicles and have restored many but this is driving me crazy lol.

Tiny
Beef99
Jul 11, 2009.
The plenum has been looked at and tested, there is no oil consumption, the throttle body is clean as a whistle inside and someone at a reputable shop said they disconnected the hoses that go into the plastic part for the air filter assembly from the valve covers, and checked to see what the engine did when they were plugged and so on, and that test checked out too(supposedly for vacuum leaks).

Tiny
Beef99
Jul 11, 2009.
Check EGR operation should pull off check passage ways clean if needed. If EGR does not recirculate exhaust into combustion chamber then temps rise NoX forms and you get spark knock.

Docfixit
Jul 11, 2009.
Thanks, I haven't heard this one before, I will do that!

Tiny
Beef99
Jul 11, 2009.
It also sounds like a octane ping, which means you need a better grade of fuel. Where the new spark plugs put in the same heat range as the ones you took out? Also the gap on the plugs might not be set right.

Tiny
Cement head
Jul 20, 2009.
It was a combination of a minor exhaust leak and the EGR that needed to be cleaned. Thank you for the advice but I am usually pretty good with mechanical problems but when you are not familier with a vehicle or have a sound that could be a million things it is easy to overlook something. My truck is not stock and always runs on high octane fuel and never anything under 93 octane. It has hot pluds in it, high voltage coil, a performance chip, and other performance additions and the problem existed since before I obtained the vehicle and continued the same even after all the tune-ups were done and performance parts added.

Tiny
Beef99
Jul 20, 2009.

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