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Post manifold work noise...still

LynchMob

NAXJA Forum User
I replaced the manifold gasket and have since been hearing a kind of "compressor noise"....like a pssht pssht pssht pssht from the engine...it's most noticeable at high rpm at highway speed. It sounds like an air/exhaust leak at one of the cylinders maybe.

I've checked all my bolts, connectors, vac lines...the only thing I did not do as per FSM is replace the manifold to down pipe ring/gasket. I would think a leak there would be constant...this one varies as if it's tied only to one cylinder.

I had thought this was caused by the old injector orings not being seated, allowing air to escape through, but it's still making the noise.

Any other guesses?
 
You don't say what year model. If you are absolutely sure it isn't the gasket, what about the donut where the manifold ties to the exhaust pipe, or the pipe down from the EGR to the exhaust manifold. Use the shade tree stethescope, a length of gas line hose held to your ear and probe around with the other end.
 
Oops! And I'm usually so good at that.

1990 XJ I6 AW4 NP231 AC/Cruise Stock

That donut gasket was what I meant...that and the EGR tube were on my list to check again today (for the third time!)...maybe they got off centre or something. Wouldn't this cause a constant noise...??
 
Use the hose trick or the carb cleaner trick to try and isolate it. If it is a pulsating noise, it most likely is the intake/exhaust gasket.
 
The gasket is new...it's what I was working on. Re-checked the donut gasket, egr tube, manifold bolts/nuts, valve cover bolts/nuts and still have the noise.

What would a clogged injector/failed injector sound like? I don't seem to be lacking any power at all.

My oil is due for a change but I've never had it
sound like this towards the end of a oil cycle.

At least the original high idle problem is gone...I can live with a noise...and this is just a POS beater. My real toy...
x1pGg9EMswqL-_J69nz98Hpqq-iPWmJITpMx5B0va-apFTMQR-bTJ4onpUM_CDwUe0tSGwShgiX81k2dctNPFMhNR_-jif04-m04OoBbQOnxP9mR9AFQE6iCFjjnRCiCwhYnsIk3cCJIcCYqCdtFXTEvw


Thanks for the help!
 
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