Cutting out at higher speeds

JeepTherapy · Oct 7, 2005

I have noticed a new problem with my Cherokee the past 2-3 weeks. It seems that once it is warmed up and I am driving at highway speeds (50ish and above) the engine seems like it is cutting out. The RPM's stay constant and when I hit the gas the pickup is fine and the engine does not rev up higher thus making me believe that this is not a possible transmission problem.

It is a 1992 XJ, any ideas on where I can start with the troubleshooting :repair: ?

Thanks,

Kevin

xj trenton · Oct 7, 2005

1 st thing check fuel pressure mine did the same thing when I hooked up a pressure guage it was very low about 15psi should be around 35-40 check pressure regulator but it would most likely fuel pump. The other thing that stood out was it got great fuel economy before the new pump (running lean) after the fuel economy dropped back to normal. The other culperate could be the crank position sensor.

JeepTherapy · Oct 7, 2005

xj trenton said:
1 st thing check fuel pressure mine did the same thing when I hooked up a pressure guage it was very low about 15psi should be around 35-40 check pressure regulator but it would most likely fuel pump. The other thing that stood out was it got great fuel economy before the new pump (running lean) after the fuel economy dropped back to normal. The other culperate could be the crank position sensor.

I'll look into the fuel problem. It was getting average MPG last time I filled up. It does have almost 149,000 miles on it and I have not replaced the CPS yet, although some people told me to do it 40,000 miles ago.

Thanks for your help,

Kevin

Matthew Currie · Oct 7, 2005

Does it seem as if the whole engine is stumbling, or is it missing, as if one cylinder is going out? Does it make a difference whether it's under load?

I'd start with some of the conventional tuneup items if you haven't already. Plugs and wires, fuel filter, air cleaner, maybe a dose of Techron and a general cleanup of connections. Check vacuum lines very carefully too, especially the crankcase vent line which tends to rot and crack, and the line to the map sensor.

If it feels as if one cylinder is cutting out when it gets warm, a fault in the fuel injector harness might be a suspect.

JeepTherapy · Oct 7, 2005

Matthew Currie said:
Does it seem as if the whole engine is stumbling, or is it missing, as if one cylinder is going out? Does it make a difference whether it's under load?

I'd start with some of the conventional tuneup items if you haven't already. Plugs and wires, fuel filter, air cleaner, maybe a dose of Techron and a general cleanup of connections. Check vacuum lines very carefully too, especially the crankcase vent line which tends to rot and crack, and the line to the map sensor.

If it feels as if one cylinder is cutting out when it gets warm, a fault in the fuel injector harness might be a suspect.

I would describe it as more of a "hiccup" like it is missing on one cylinder. This only seems to happen, or is only noticeable at higher speeds.

Thanks for your reply.

Kevin

piperRonnie · Oct 7, 2005

I had similar symptoms with my XJ, but since it was OBDII, I found out rather quickly that is was the TPS.
Yours being OBDI, you might want to check the TPS. I don't know if the check engine light would illuminate on your year for a TPS problem.

Cutting out at higher speeds

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