1990 jeep engine issues
03-23-2019, 08:41 AM
#1
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Model: Cherokee(XJ)
1990 jeep engine issues
hello i have a 1990 jeep cherokee. 4.0, the issue i am having is it starts up, it idles fine, you get it up to about 2000rpm and it starts misfireing, runs rough. My friend was trying to find a scan tool but because its so old he is having a hard time locating one. Does any one have any thoughts on this?
03-23-2019, 10:07 AM
#2
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Year: 1992
Model: Cherokee
Engine: 4.0L L6 PowerTech (stock)
I'm not sure whether 1990 is the older style Renix (Renault Bendix) engine without a scanning port or whether it is a newer engine with an older style of scanning port. If there is a port, then it exists in the engine's bay on the driver's side near the body. If it takes obd, then it requires d.c. power from the cigarette lighter while connected to function. At least that is how the model at O'Reilly's works.
What is the fuel pressure at the rail? It is free to "rent" a gauge at a parts store.
What is the fuel pressure at the rail? It is free to "rent" a gauge at a parts store.
03-23-2019, 11:49 AM
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Year: 1989
Model: Comanche (MJ)
Engine: 4.0
It's Renix. I'd start by check fuel pressure. Check or eliminate the ballast resistor on the drivers fender. The connections tend to get corroded or the ceramic resistor gets broken. You can just remove the resistor and splice the two wires together,
04-17-2019, 07:39 PM
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Model: Cherokee(XJ)
More found issues
Been doing some research and I found out that that this cherokee was a california jeep and the engine was replaced with a regular 4.0. So with that being found out would this play into it idling rough and misfiring? Maybe with the california emissions? Maybe a timing issue? I am still at a loss as to what to do next.
04-17-2019, 07:54 PM
#5
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Could be a number of things. However, an XJ that starts and idles fine, but gets problematic over 2000 rpm is a common symptom of cheap aftermarket replacement crankshaft position sensors. Is this a possibility?
Bad O2 sensors resulting in rich/lean mixtures can also cause these types of problems, but this class of problem will usually present itself at idle rpm as well - after the vehicle has warmed up for a few minutes and has started using the O2 sensors for air fuel mixture calculations.
Bad O2 sensors resulting in rich/lean mixtures can also cause these types of problems, but this class of problem will usually present itself at idle rpm as well - after the vehicle has warmed up for a few minutes and has started using the O2 sensors for air fuel mixture calculations.
04-17-2019, 09:00 PM
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Year: 1989
Model: Comanche (MJ)
Engine: 4.0
I think the only difference for a 1990 was the tuning in the engine computer. Have you checked the fuel pressure yet? Have you done the usual tune-up type stuff like plugs and wires? Pull the ignition module off and clean the connectors underneath as well.
04-18-2019, 01:19 PM
#7
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Been doing some research and I found out that that this cherokee was a california jeep and the engine was replaced with a regular 4.0. So with that being found out would this play into it idling rough and misfiring? Maybe with the california emissions? Maybe a timing issue? I am still at a loss as to what to do next.
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04-19-2019, 08:05 AM
#8
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
1 would go to www.ctuiser54.com and complete Tips 1,3,4, and 5 before doing anything else.
great idea to check the fuel pressure and make sure your intake manifold bolts are not loose.
great idea to check the fuel pressure and make sure your intake manifold bolts are not loose.
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