Running rough
03-09-2017, 06:04 PM
#1
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Location: Belle Vernon PA
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Year: 1966
Model: Cherokee
Engine: 4.0 H.O.
Running rough
96 Jeep Cherokee 4.0L
replaced:
CPS
NSS
ASD relay
Distributor
Starter
O2 sensors
Cleaned IACV
Jeep starts and runs fine till it warms up, after it's warm it acts like it has a misfire. I had my friend who owns a shop plug it into a scan tool and no codes other than too cold for too long P1281 I think, he said it could be the thermostat is stuck or the sensor is bad. Has anyone ran into this issue.
Also all these parts have been replaced brand new in the last 2 weeks.
replaced:
CPS
NSS
ASD relay
Distributor
Starter
O2 sensors
Cleaned IACV
Jeep starts and runs fine till it warms up, after it's warm it acts like it has a misfire. I had my friend who owns a shop plug it into a scan tool and no codes other than too cold for too long P1281 I think, he said it could be the thermostat is stuck or the sensor is bad. Has anyone ran into this issue.
Also all these parts have been replaced brand new in the last 2 weeks.
03-09-2017, 06:16 PM
#2
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Year: 1999
Model: Cherokee
Engine: 4.0
Gotta chase that code and the primary suspect would be the thermostat. I'd pop in a new quality stat (dealer or Stant SuperStat) in and see if that resolves the code. Be sure it's a 195 degree stat!
If a new stat resolves the code but NOT the symptom (which may be possible here), the one engine management sensor I would either test or replace would be the coolant temperature sensor. If that sensor goes south, it sends incorrect temp data to the computer and the computer gets confused on what the actual temperature of the coolant really is, which can send an incorrect fuel/air mixture into the engine. And that can lead to an engine that isn't running well.
I'd start with the stat, especially if it's been a while since replacement, but because of your symptom of rough running.....could be that CTS. Good luck and keep us updated!
If a new stat resolves the code but NOT the symptom (which may be possible here), the one engine management sensor I would either test or replace would be the coolant temperature sensor. If that sensor goes south, it sends incorrect temp data to the computer and the computer gets confused on what the actual temperature of the coolant really is, which can send an incorrect fuel/air mixture into the engine. And that can lead to an engine that isn't running well.
I'd start with the stat, especially if it's been a while since replacement, but because of your symptom of rough running.....could be that CTS. Good luck and keep us updated!
Last edited by tjwalker; 03-09-2017 at 06:32 PM.
03-09-2017, 07:44 PM
#3
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Year: 1966
Model: Cherokee
Engine: 4.0 H.O.
Well I bought new plugs, stat and a new CTS today, I'll install them this weekend and see if that helps, I'll keep you posted 👍
03-12-2017, 09:43 AM
#4
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Year: 1966
Model: Cherokee
Engine: 4.0 H.O.
Put the new stat in and new CTS in and now it won't even start cold anymore, it acts like it wants to start but all it does is sputter and won't start. All the cranking and no starting is starting to kill my battery as well.
03-12-2017, 11:51 PM
#5
CF Veteran
That stat definitely won't keep it from starting. So rule that out for a moment. The CTS is definitely read by the computer during startup while it determines a fuel delivery strategy, and if the old one was producing a wildly different value, that can sometimes lead to some starting weirdness until the computer adjusts (which usually doesn't take long).
Your number one priority right now is to get the battery fully charged up, before attempting to start again. A low voltage start, can cause problems just like you are seeing. So you need to make sure that isn't a variable.
Your number one priority right now is to get the battery fully charged up, before attempting to start again. A low voltage start, can cause problems just like you are seeing. So you need to make sure that isn't a variable.
03-13-2017, 03:17 PM
#6
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Year: 1966
Model: Cherokee
Engine: 4.0 H.O.
Well I replaced the stat anyways cause it was bad, but I replaced the CTS as well and nothing changed. I have seen mention of xjs having an issue with the injectors getting too hot and it vaporizes the fuel in them before they can ever spray which can cause a misfire that is inconsistent. It would make sense being that the issues don't happen till after the Jeep is hot, I wouldn't begin to know how to keep them from getting hot though.
03-13-2017, 03:32 PM
#7
What kind of plugs do you have? I went through the same thing replacing a bunch of stuff. I had replaced the plugs with brand new autolite's. Figured that couldn't be the problem. Changed back tot eh cheap Champion Coppers and the warm idle problems went away completely. I didn't see plugs on your list so worth a shop and $15.