Press clutch, RPMs surge, lift accelerator pedal

[HawkPilot]

2006 TJ, 4.0L, 6 spd.

When I’m decelerating, to slow to a stop, I press the clutch and engine RPMs increase to 2500-3000. If I slide my toe under the accelerator pedal and lift the RPM decreases to normal.

When letting feet off all pedals and simply stepping on the brake to slow, no RPM issues, when I touch the clutch, the RPMs increase. For under accelerator, lift, RPMs reduce to normal.


Near history:

-Checked carpet around accelerator pedal, lubed the accelerator cable both at the pedal and near the throttle body with white lithium grease.

-New IAC: In the past year, was getting codes for IAC with accompanying RPM fluctuations. I cleaned it twice, in ~6 month intervals, codes ceased/normal, then replaced it with a new Mopar about a month ago. No more issues since.

-New TPS: Yesterday I replaced the TPS, battery disconnected while performing swap. During a short drive, thought it was fixed…nope, starting doing the revving thing again. Lifting the accelerator pedal caused RPMs to return to normal.

I’ve got no codes and the Jeep runs great otherwise. I’m leaning towards replacing the throttle cable next. Any suggestions?


Rich

 

[Chris]

2006 TJ, 4.0L, 6 spd.

When I’m decelerating, to slow to a stop, I press the clutch the and engine RPMs increase to 2500-3000. If I slide my toe under the accelerator pedal and lift the RPM decreases to normal.

When letting feet off all pedals and simply stepping on the brake to slow, no RPM issues, when I touch the clutch, the RPMs increase. For under accelerator, lift, RPMs reduce to normal.


Near history:

-Checked carpet around accelerator pedal, lubed the accelerator cable both at the pedal and near the throttle body with white lithium grease.

-New IAC: In the past year, was getting codes for IAC with accompanying RPM fluctuations. I cleaned it twice, in ~6 month intervals, codes ceased/normal, then replaced it with a new Mopar about a month ago. No more issues since.

-New TPS: Yesterday I replaced the TPS, battery disconnected while performing swap. During a short drive, thought it was fixed…nope, starting doing the revving thing again. Lifting the accelerator pedal caused RPMs to return to normal.

I’ve got no codes and the Jeep runs great otherwise. I’m leaning towards replacing the throttle cable next. Any suggestions?


Rich

Since you've replaced both the IAC and TPS recently, the next logical step might be to look at the throttle cable and its routing. Even if it seems fine, it's worth inspecting for any binding or odd wear that could cause the throttle to not return to its resting position as it should. This is where I would start.

In addition, have you checked for any vacuum leaks or any issues with the intake air system? Sometimes even small leaks can cause weird idle behavior and RPM fluctuations. You might also want to verify that the throttle body itself is clean and not sticking in any way.

Another thought is that there could be an issue with the clutch itself, particularly if it’s not disengaging fully, causing the engine to rev higher unexpectedly.

Given that there are no codes, if it persists after checking these areas, you could also consider running diagnostics with a scanner that monitors live data. This might give you insight into how the various sensors are working while you’re experiencing the issue.

Keep us posted on what you find! Good luck!

 

[KennethS]

Manually lifting the pedal and reducing the engine RPM indicates the throttle is not closing fully by itself. Check the throttle return spring first to ensure it’s there and connected to the proper points. If that’s OK, check the operation of the throttle body to see if it’s binding, then check the cable itself for smooth movement.

 

[HawkPilot]

Thanks, guys. I’ll check those things.

Rich

 

[HawkPilot]

I went to the local auto parts store and grabbed a pack of generic throttle return springs. I attached one, as seen on the ‘04 and prior TJs. The TJ is running like a champ, no RPM surges. I suspect the organic TB return spring is tired…it has 172,000 miles on it.

Thanks for the assists,


Rich

 

[KennethS]

Good job, and thanks for following up with the resolution to the problem. This really helps others who have a similar issue and search the forum.

 

[HawkPilot]