Rough idle, bucking, and backfiring through intake.
03-03-2017, 05:04 PM
#1
Newbie
Thread Starter
Join Date: Mar 2017
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
Rough idle, bucking, and backfiring through intake.
I have an 87 Jeep Cherokee Laredo 4.0 4x4 with automatic transmission. All of a sudden it started missing with hesitation and now when you put it in gear it won't take fuel. However it will take fuel when in park but has a very bad miss. Ive put a new distributer, cap and rotor button on as well as new plugs and wires. New throttle position sensor, idle position sensor and a crankshaft position sensor. Checked all wiring and vacuum lines everything is good there. Any help would be greatly appreciated.
03-05-2017, 12:21 PM
#2
Seasoned Member
My first inclination would be something having to do with the manifold absolute pressure sensor, its wiring/grounding or the vacuum line associated with it. Check the connector to verify that you have 4.5-5.0VDC AND a ground in 2 of the 3 terminals. Remove the plastic line that runs from it to the manifold, plug one end and check with a hand-held vacuum pump/gauge. Some cracks don't show up so easily to the eye. Then, using the pump/gauge and a volt meter, check that the output voltage changes based on applied vacuum.
Once you've done that, let me know.
Once you've done that, let me know.