Whistle & now Smacking

Hi Fellow XJer's,

First off - here are my Jeep Details:
2001, 122k miles, AW4, 4.0, 6" lift on 35's with 4:56 gears

Over the past 6 or 8 months I have been getting a high whistling sound from the motor. It used to go away when the motor warmed up and now it is pretty constant. Check engine light is on with an EVAP leak code (don't have the exact code). I did a visual and even used a can of carb cleaner to see if I could find the evap leak and nothing. I have done this twice. Did some reading and I am tempted to change the AVAP Sensor and Filter but I don't think that's what caused today's issue.

About 5 months ago I took it in and had the Spark Plugs and Coil Pack Replaced (Mis fired pretty bad and found out # 5 & 6 on the rail were bad). My mechanic said they found an evap line at the gas tank that was dis connected. Errod code went away for about a week and well - needless to say that wasn't the issue.

This morning when I went to start the Jeep, I got a loud slapping sound that was consistant with the motor speed, i.e. I would hit the gas and it would increase. As the motor warmed up it went away but the whistle is still there. Got on the freeway and it started to hesitate so I pulled over and then it was driving "OK".

So - with my experiences in the XJ world this sounds like either a cracked exhaust manifold or exhaust manifold gasket.

Any and all input would be greatly appreciated.

Have a good one,
Mark

FWIW, I had a a whistling sound in another vehicle between idle and 4000rpm. Turned out to be a hole in the rubber intake bellows/tube. However, in that vehicle, the hole was between the MAF and the intake. Never had any driveability issues.

Slapping sound - well, my lifters will make noise for a while.

I have a 2001, 135k miles, AW4.

BMXGuy - Thank you for hte info. I forgot to mention that my whistling sound is when I am not accelerating. Really odd.

The slapping sound is LOUD and defintiely sounds like the manifold - any word on that?

No experience with a Jeep manifold. But we had a loose exhaust manifold bolt on a racecar and we could hear it and it definitely affected performance. Technically, it could be a cracked or leaking manifold. Don't know what would cause it to crack though. For intake manifolds we used to spray WD-40 to look for leaks (idle smooths out). Not sure you want to go spraying WD-40 around a hot exhaust manifold. Not sure what you could use but the technique is the same. Just can't evaporate before it hits the manifold and definitely not combustible!

Piston slap is a well known issue with worn engines but, it goes away (mostly) once the Heep is up to temp. Banging either under acceleration (main bearings) or during deceleration (rod bearings) is another story. Those noises do not go away with temperature.

Throttle Bodies are known to cause a whistling noise. The Idle Air Controller port gets full of junk, restricts the passage which increases the velocity (the air mass being the same) and you get a whistle.

Just a thought...

Good call on the Air Controller Port.....

Took it to my mechanic this morning for the Exhaust Manifold. As soon as I drove up he came out and we both said "exhaust Manifold" - it was quite funny. We'll see how deep it gets - could just be the gasket or it could need a whole new manifold. No idea if the whistling has anything to do with the Manifold issue.

I could do the owrk myself but a mechanic can go through and find things I probably couldn't and with the amount of driving I am doing now (80 miles a day) I need it running top-top until I can get a commuter.

Tool my mechanic a day but he found the problem.

Turns out my oil pump is takin a dump and because the oil pressure is so high it was causing the lifters to stay open there ofre causing the slapping sound. They are replacing the oil pump and a soncer I have no idea what it's called - haha Then an engine flush and new valve cover gasket. Waiting on one last part and should be good to go.

We'll see. I and the mechanic initially thought it was either the exhaust manifold or manifold gasket. No idea it could have been the oil pump.