Dreaded Bucking Throttle Issue

1998 Cherokee XJ Classic

Okay, so I have scoured forums high and low. There's many threads on the matter, but most are several hundred posts long with no solutions found. And since I'm starting to get desperate I figured I would take a shot at a new thread to see if a solution can be found.

The issue for those unfamiliar with it, is a random "bucking" under acceleration. It feels like the throttle is cutting out and coming back in quick succession. It's an intermittent issue, and seems to start about 5 mins into driving (from cold), though not always. Some days it drives great and others not so much. When it happens, no matter how much throttle is given it simply bogs down and continues to sputter and buck. Shutting the ignition off and back on will sometimes cure the issue. Other times it picks back up where it left off, or may take a few mins to start again. Shutting it off and letting it cool seems to "reset" the issue.

I have already replaced the PCM with no luck. IAC was replaced as well.

Any thoughts on the issue would be greatly appreciated!

Posts from other forums have suggested everything from O2 sensor, fuel pump and filters, battery terminals, TPS, IAC, PCM, TCM, PCM Connector... Virtually every sensor and electronic, transmission or fuel related device has been suspected as the culprit. All have been tried by one poster or another without any luck. Seems as if it's ghost gremlin that doesn't want to be found.

Just out of curiousity have you checked fuel pressure? You can have fuel but maybe not enough pressure when under load. Driveability gremlins can be a bitch unfortunatly. Full tuneup has been done? Just asking because Id make sure all basic maintenance was done first before I toss a bunch of electronucs at it.

aka cavfighter

I haven't checked fuel pressure but I'll check it this weekend. I don't think it's fuel since it typically drives fine with no issue. It's truly a random intermittent issue. It tends to start a few minutes after I leave the driveway, but not always and doesn't seem to be triggered by anything like bumps turns or hills.


Sent from my SM-G935P using WAYALIFE mobile app

I haven't had a tune up recently and one needs to be done. However, I'm leaning toward doing an LS1 swap so I'm really just wanting to keep it running until the spring without sinking a ton of money into a motor that will be coming out.

Sent from my SM-G935P using WAYALIFE mobile app

Almost wonder if heat is causing a resistance issue somewhere like in a plug wire, coil pack, or something causing it to misfire? If it was mine I would still start by at least pulling plugs and wires and checking the condition (wiggle test). Id also still check fuel pressure to rule that out. I know my BT obd scanner and Torque pro will let me look at PID's (02 sensor, fuel trim, etc). Hope you figure it out.

aka cavfighter

This is going to be a ‘pin the tail on the real issue’ scenario without a scan for codes and a look at engine data when the problem is happening.


Sent from my iPhone using WAYALIFE mobile app

I had a similar problem, it would cut out just enough to make the jeep buck. Some days it would do it multiple times yet other times it would go several days without it happening. Different from what you described it never sputtered and ran poorly. In the 6 weeks the problem was going on it went to the dealership 4 times. Also, no codes. Long story short an old friend recommended a crankshaft sensor. In many cases it can cause the symptoms you stated. It's a 20 dollar part so worth a try. That took care of the problem.

MrEmmDubya said:

I had a similar problem, it would cut out just enough to make the jeep buck. Some days it would do it multiple times yet other times it would go several days without it happening. Different from what you described it never sputtered and ran poorly. In the 6 weeks the problem was going on it went to the dealership 4 times. Also, no codes. Long story short an old friend recommended a crankshaft sensor. In many cases it can cause the symptoms you stated. It's a 20 dollar part so worth a try. That took care of the problem.

Click to expand...

I'll go ahead and order one. Thank you! I'm also going to order an O2 sensor and catalytic converter (it probably needs them anyway) plugs and wires, and clean up all of the connectors and fill them with dielectric grease. I'll also check fuel pressure this weekend. I may go ahead and get an OBD reader as well to run tests. No codes showing but maybe checking values might indicate further issues.

I appreciate the responses! Ill report back once the parts come in.