XJ loses power at 50mph
06-20-2013, 12:29 AM
#1
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Year: 1988
Model: Cherokee
Engine: 4.0
XJ loses power at 50mph
I have an 88 XJ 4.0, 5 speed that is stumbling around 45-50 mph. It only does this when it is 65 degrees and warmer. When I down shift and floor the throttle it hesitates then smooths out, but once you level off on the throttle it will start to stumble. I have tested and changed the TPS and the AIC, next is the MAP. Does anyone have a suggestion or solution?
06-20-2013, 01:05 AM
#2
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Year: 90,84
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Engine: 4.0,2.5
I might check the fuel filter and fuel pressure. Also Plugs, cap, rotor. I'd clean and gap the plugs, (.035), clean the cap in the sink. Others would can them and buy new.
Pressure is checked at the schrader, (tire type) valve on the fuel rail. 31 lbs with the vac line on the regulator, 39 with it off.
Cruiser will be along in the AM most likely. There is a bunch of info in the link in my signature...there is plenty to check and go through. I'm a big fan of checking the cps...anytime, even if the radio won't work! (takes less than 3 minutes, and it seems it can do almost anything.)
Those wires under the manifolds to your sensors get messed up, especially the ones to the 02 sensor. With an 87-90 renix Jeep, you need a Digital volt meter to really do anything. The $5 Harbor Freight one actually works, at least for a while.
See "sensor ground test" in the link, also a place to start. Welcome!
Pressure is checked at the schrader, (tire type) valve on the fuel rail. 31 lbs with the vac line on the regulator, 39 with it off.
Cruiser will be along in the AM most likely. There is a bunch of info in the link in my signature...there is plenty to check and go through. I'm a big fan of checking the cps...anytime, even if the radio won't work! (takes less than 3 minutes, and it seems it can do almost anything.)
Those wires under the manifolds to your sensors get messed up, especially the ones to the 02 sensor. With an 87-90 renix Jeep, you need a Digital volt meter to really do anything. The $5 Harbor Freight one actually works, at least for a while.
See "sensor ground test" in the link, also a place to start. Welcome!
Last edited by DFlintstone; 06-20-2013 at 01:07 AM.
06-20-2013, 03:52 AM
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Year: 1989 xj sport 2dr
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Engine: 12 hole bosch Injectors
Agreed start basic don't start throwing every sensor it uses on .Figureing out a problems a lot cheaper than getting lucky with replacing part after part.
06-20-2013, 08:02 AM
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06-20-2013, 08:03 AM
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I have an 88 XJ 4.0, 5 speed that is stumbling around 45-50 mph. It only does this when it is 65 degrees and warmer. When I down shift and floor the throttle it hesitates then smooths out, but once you level off on the throttle it will start to stumble. I have tested and changed the TPS and the AIC, next is the MAP. Does anyone have a suggestion or solution?
06-20-2013, 08:05 AM
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Year: 1990
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You could also have a clogged catalytic converter. It can be checked using the simple test below.
CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION
Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.
CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION
Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.
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06-20-2013, 04:22 PM
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Look at it this way. One guys has a similar symptom and someone responds that a CPS fixed his. Another guy says a TPS fixed his. Another guy says an O2 sensor fixed his. Another claims it was his CTS. Yet another his IAT. They may all be correct but that does nothing for the OP!!!!
06-20-2013, 06:57 PM
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06-20-2013, 07:14 PM
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Smoke is kickin my ***.
06-20-2013, 07:23 PM
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"global cooling", should help that. 
Sorry to hear that. I'm keeping free ("deli buckets) here with water. The thermals from the fire can send embers a long ways. I'd feel pretty stupid if my hose didn't reach, and all I needed was a bucket of water.
Messed up, didn't intent to delete ALL that^
Sorry to hear that. I'm keeping free ("deli buckets) here with water. The thermals from the fire can send embers a long ways. I'd feel pretty stupid if my hose didn't reach, and all I needed was a bucket of water.
Messed up, didn't intent to delete ALL that^
Last edited by DFlintstone; 06-20-2013 at 07:27 PM.
06-20-2013, 08:54 PM
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XJ loses power at 50mph
First off thanks for the replies.
Cruiser, I've already done what you wrote in posts 1-3 a couple of months ago. I'm going to see if I can check the CPS and the fuel pressure on Saturday. There is no cat to check and I just put a new muffler and tail pipe on from the four bolt flange back.
Today on the way home it started acting up again so I accelerated up to 65 and then pushed the clutch in and coasted I watched the Tach, it was jumping back and forth until I reach until I reached 45 mph and it settled down. Once I reached 50 it started acting up again.
Cruiser, I've already done what you wrote in posts 1-3 a couple of months ago. I'm going to see if I can check the CPS and the fuel pressure on Saturday. There is no cat to check and I just put a new muffler and tail pipe on from the four bolt flange back.
Today on the way home it started acting up again so I accelerated up to 65 and then pushed the clutch in and coasted I watched the Tach, it was jumping back and forth until I reach until I reached 45 mph and it settled down. Once I reached 50 it started acting up again.