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90 Cherokee Exhaust Question

M

megabyte5689

NAXJA Forum User
Location
Kansas
I have a 90 XJ 4.0 engine, and recently I've had some problems. When I've driven the car around and let it idle and it gets up to a constant 210 degrees it starts idling real rough, and it has died a couple of times. I pop the hood and I smell what I think smells like a lawn mower exhaust smell. It smells like this in the engine bay on cold starts too. My question is could this be a exhaust manifold problem?
 
The thing is, is that I just changed out the EGR valve so that can't be it. Whenever I first start the car up it sounds like an 60's chevy pick up
 
That year, and those around it, are known for manifold breaks (not brakes).
Ikn what you mean by 60' PU sound. If you hear a ticking like sound under the hood it is likely a failed exhaust manifold. Solution? Header.
 
You can weld the OEM header but that won't last forever. Headers are expensive for Renix Jeeps. Alsd check that the manifold bolts are tight where they bolt to the head. (smell) and I would change the O2 sensor as well. (rough idle when at operating temp) Cat replacement would be my last thing if the first things don't cure the problem.
 
Ya there is a ticking noise also to when it is cold. The o2 sensor should be fine, I just changed that out last fall. not many miles on the sensor then. That might also explain why my jeep sounds like a school bus too. Great! do I have to weld headers on?
 
megabyte5689 said:
Ya there is a ticking noise also to when it is cold. The o2 sensor should be fine, I just changed that out last fall. not many miles on the sensor then. That might also explain why my jeep sounds like a school bus too. Great! do I have to weld headers on?
Click to expand...
Much easier to weld it off the Jeep. Unbolt the stock header from the Jeep and search for the crack. Weld it and re-install. If you can get to it then of course you can weld it while it is still on the vehicle.
REMEMBER TO DISCONECT THE NEG BATTERY LEAD if you plan to weld while still installed on the Jeep. Good Luck. Let us know if that solves your problems.
 
megabyte5689 said:
Ya there is a ticking noise also to when it is cold. The o2 sensor should be fine, I just changed that out last fall. not many miles on the sensor then. That might also explain why my jeep sounds like a school bus too. Great! do I have to weld headers on?
Click to expand...
No, first check and make sure the intake/exhaust manifold bolts are tightend to spec. Then check for cracks in the exhaust manifold, usually around the area where the runners meet near the collecter. There will usually be some white residue around the crack. If they need welding most times it is just easier to pull the manifold and weld it where you can get to all of the crack easier.

94exhaustky1.jpg
 
This concerns me whenever I start the car because it makes that noise like the oil needs to be changed or something. I'm pretty sure it's that manifold now. Last night I drove the Jeep and when I started it, it made that noise and then when I started driving it made a ticking noise, when I accelerated and then it went away when I started driving the car. More than likely from what you guys have said it's the exhaust manifold.
 
90cherokeeexhaustmanifozm8.th.jpg
Upon getting under the 90 XJ today I noticed this crack. I figure this is my problem. I put my finger right on it and it is definitely a crack. It's not terribly bad but still enough to effect running performance.
 
megabyte5689 said:
http://cgi.ebay.com/ebaymotors/JEEP-CHEROKEE-COMANCHE-4-0-87-90-EXHAUST-MANIFOLD-NEW_W0QQitemZ140230046507QQcmdZViewItem?hash=item140230046507&
Could someone please tell me if this would be a good brand new exhaust manifold to get so I can replace my cracked one. I'm trying to avoid shelling out $200 at the stealership and spending that much at an Autozone or Oreilly's. Is stainless steal all right?
Click to expand...

I'm no exhaust manifold expert, but I would not buy that one if it was me. The welds do not look very promising.

In my own experience, changing the exhaust manifold is a Pain In The A$$ so you might as well spend a little more money(if possible...) to get a better quality header. The last thing you want is to have to go back and redo the whole task of putting a new header in.
 
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