cmeuzelaar
NAXJA Forum User
- Location
- Madison, WI
OK, first things first, YES, I have searched the forum and can't find anything that matches this.
The specs: '89 Cherokee Laredo, 4.0L, NP231, AW4, stock everything
The problem: high idle (1500-2000 rpm out of gear) when warm (500-750 when cold). If I start the jeep when cold and let warm up, the idle climbs up to around 1500-1750 and stays there. This takes several minutes. If I then kill it, wait several minutes, and restart it, the idle starts at about 500 rpm and eventually climbs to 1000 rpm (fine by me). If I then drive it, the idle will climb to 1500-2000 rpm and stay there until I repeat the sequence.
What I've checked:
What I know I need to check:
Jeep starts and runs fine (just high idle). I just want my fuel economy and braking to be better (high idle causes surges in braking). I can give exact values for most of the sensors if people want/need them to help me figure this out.
Thanks,
Chris
The specs: '89 Cherokee Laredo, 4.0L, NP231, AW4, stock everything
The problem: high idle (1500-2000 rpm out of gear) when warm (500-750 when cold). If I start the jeep when cold and let warm up, the idle climbs up to around 1500-1750 and stays there. This takes several minutes. If I then kill it, wait several minutes, and restart it, the idle starts at about 500 rpm and eventually climbs to 1000 rpm (fine by me). If I then drive it, the idle will climb to 1500-2000 rpm and stay there until I repeat the sequence.
What I've checked:
- TPS--not replaced, but smooth and even across range and properly adjusted
- MAT--resistance is in spec as the engine warms up
- MAP--source is within spec, output is low once engine is warm (per Mitchell OnDemand specs--spec is 1.5V to 2.1V, reading is 1.35V)
- IAS (IAC, ISS, whatever--the Idle Air Servo)--replaced--not sure how to verify operation
- EGR control solenoid--appears to be working correctly, need a guage to verify
- Intake Manifold bolts--tight
- Blocking off IAS input hole--no change in idle
What I know I need to check:
- O2 sensor (a little hard with no jack in a cold garage)
- CTS (same story--going to try getting readings at the ECU)
- Fuel pressure (specifically the regulator--need to rent/borrow guage)
Jeep starts and runs fine (just high idle). I just want my fuel economy and braking to be better (high idle causes surges in braking). I can give exact values for most of the sensors if people want/need them to help me figure this out.
Thanks,
Chris