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Go Back JeepForum.com > Models > Jeep Cherokee & Comanche Forums > MJ Comanche Technical Forum > Loss of power after overheat

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Unread 09-04-2013, 02:13 PM   #1
ATjeep42
Registered User
1988 MJ Comanche 
 
Join Date: Sep 2013
Location: Sunnyvale, Ca
Posts: 1
Loss of power after overheat

I overheated to the point of engine stall after a bad coolant leak. After replacing lost fluid and field patching the leak engine ran OK and I've put a few thousand miles on it since. But I've noticed a significant loss of power (and it sounds like I have a mild misfire at full throttle as well), and 20% lower gas mileage. Noticed engine is running a little rich (blackish tailpipe as opposed to dark brown before), but plugs are clean. No indication of blow-by (oil clean, no visible smoke from tailpipe). No trouble codes. No fluid losses (beyond what deteriorating gaskets have been causing over the last ten years).

FYI 373,000 on original engine w/ no replacements other than typical maintenance (e.g. TPS, O2, crankshaft position sensors, plugs/wires/cap/rotor in the last two years).

Any idea what the problem might be?

1988 Jeep Comanche
4L, 4x4 5 speed manual

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Unread 09-05-2013, 02:46 PM   #2
TrucksBootsNGun
Registered User
1988 MJ Comanche 
 
Join Date: Aug 2013
Location: Flagstaff, ARIZONA
Posts: 46
Not to stray from the topic but you can scan your '88 MJ? I have the same truck ('88, 4L, manual etc) and I've had the dash apart a couple times messing with the dash lights and new radio and not once have I seen anything that I could use to scan the truck.
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Unread 09-08-2013, 06:37 PM   #3
wgirvine
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1992 XJ Cherokee 
 
Join Date: Oct 2007
Location: Rosamond, CA
Posts: 603
Start with the usual tuneup/sensors/fuel pressure items. Other than those... Hmmm.... I'm just thinking out loud here...

That's a lot of miles. Partially clogged fuel filter will show up as loss of power at heavy loads (high revs, or full throttle.) Or...
Camshaft is wearing out? (not as much lift at the valves.) Or...
The overheat softened the valve springs so now they float at high revs? (misfire)

Start with the easy stuff first...
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