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4.0 L spark knock

I have a 00 TJ - 4.0. I am getting what I call spark knock at lower RPMs under light acceleration. This is a fairly recent development and I have gotten little help in identifying the cause of the problem. The engine is stock except for the following: Avenger Supercharger with associated larger than stock injectors. A 700R4 AT which has the crank position sensor relocated to the front crankshaft pulley. I burn hi-octane fuel exclusively. I cannot see how the supercharger install would produce this effect, as the engine is not showing boost when the knocking appears. In my old car days I would suspect the timing to be at fault but this computer ignition system is way beyond me. Does anyone have experience with this or suggestion where I might direct my search? tia dw

Reply to
Dalewhite
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Reply to
Kevin in San Diego

'91 and later wranglers do not have a knock sensor. Knock comes about from running too lean, too advanced, or too hot, or not enough octane. Dino's adjustable map sensor:

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allow you to play with your mix under different throttle conditions,which when combined with adjustments to fuel rail pressure, should allow youto dial it in pretty well. Since the blend of additives in gasoline changesbased on the season, you may need to have a different calibration for summerand winter, especially given your extensive modifications.

Reply to
jeff

Reply to
L.W.(ßill) Hughes III

Thanks all for the feedback.dw

Reply to
Dalewhite

I have an '03 with an I6 and I get it too (though it's not at all severe). Not all the time, so I just write it off to "bad" gas.... It started at about 20K miles and I now have 55K miles. I get my gas at the same place usually, so I'm not sure if it is vendor specific. Do you run the hi-octane because of the supercharger? If not, why? Higher octane gas is less volitile than regular- it takes more heat to "explode"- and I've been advised NOT to run it in the Jeep.

Reply to
John R

Dalewhite did pass the time by typing:

For me it's usually bad gas and a bottle of the NOS brand gas drier does wonders. There are others out there, just make sure they are safe for the O2 sensor. A local 7-11 gave the ZJ a real classic "blown head gasket" white cloud one time.

Did they give you a heat range cooler spark plug? You should probably be running at least one heat range cooler. For the I6 that's an RC9YC4 or Autolite 3924. Hot plugs can be a source of preignition problems.

There are various sensors that can also do this but you would have lots more problems than just a little spark knock and I don't believe your 00 has an external fuel filter to mess with, think yours is in the tank.

Good luck. Hope you find the problem.

Reply to
DougW

Isn't a butterfly valve part of a carburator? Don't know engines well enough to know for sure....

Reply to
SteveBrady

Reply to
L.W.(ßill) Hughes III

Reply to
L.W.(ßill) Hughes III

Dale: I would like to here more about your Avenger Supercharger. I have a 2k tj and plan on a supercharger. I am increasing cooling (griffin radiator) - if quadrtec will ever send it. Then header and exhaust. Then the supercharger. Why did your pick Avenger? Did you install yourself? Any problems? What's it like to drive? Thanks - Allen

Reply to
bushman

Reply to
L.W.(ßill) Hughes III

been there bill. they only had the best to say about their product. i'm sure it was a balanced view.

supercharger.

Reply to
bushman

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