Runs great but has a stumble at half throttle

Smiling_JIm

New Member
Joined
Jul 9, 2022
Messages
12
Location
Menifee, CA
89 YJ Wrangler 2.5L - 19k miles on new engine. Runs great and has good power, except a slight stumble between 2k to 3k rpm. All vacuum leaks fixed. All sensors + TPS and Fuel Press Reg, and CPS replaced. Seems to run lean at mid range and part throttle. ECU rebuilt to new spec. Any ideas?
 

ytradio

YJ Enthusiast
Joined
Aug 24, 2021
Messages
221
Location
WV
Be patient my friend, sometimes it may take a while for the person with the correct knowledge to see your post. The weekend always seem to be a little slower to me.
 
OP
S

Smiling_JIm

New Member
Joined
Jul 9, 2022
Messages
12
Location
Menifee, CA
Cleaned and re-crimped the 2 pin sockets on the Crank Position Sensor (it's new). Seems to run a little better, still getting a mild stumble at 2k to 3k rpm. The last sensor i can swap out is the coolant temp sensor (the front one which goes to the ECU). Got parts this week. I know the ECU wants good sensor signals for temp, and throttle position, or it will 'Hunt' (can't find the correct Fuel/Air Ratio)... Any thoughts?
 

Thrasher4219

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Supporting Member
Joined
Feb 8, 2022
Messages
9
Location
USA
I've had a similar problem with the wiring harness to my CPS. After replacing the CPS I finally tracked it to the wiring harness. I could kill the engine with a wiggle of the connector. Poor jeep would stutter and buck like a bronco before I found the problem. Good luck, hope this helps.