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Old 11-08-2015, 05:16 PM
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Bucking! Narrowed it down a bit.

98 Wrangler, 2.5l automatic transmission.

I've been searching and trying for months already to find the cause of the bucking und sputtering. Still no success.
After reading this forum a lot I've replaced:
- Spark plugs and cables
- air filter
- upstream O2 sensor
- throttle position sensor

What I noticed is that the bucking usually starts when I drive through potholes or over speed bumps etc., so basically when the vehicle takes some kind of shaking.

Has anybody ever experienced this and can point me in a direction that might help finding the cause of the bucking?

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Old 11-09-2015, 09:13 AM   #2
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Quote:
Originally Posted by Wrangler-98 View Post
98 Wrangler, 2.5l automatic transmission.

I've been searching and trying for months already to find the cause of the bucking und sputtering. Still no success.
After reading this forum a lot I've replaced:
- Spark plugs and cables
- air filter
- upstream O2 sensor
- throttle position sensor

What I noticed is that the bucking usually starts when I drive through potholes or over speed bumps etc., so basically when the vehicle takes some kind of shaking.

Has anybody ever experienced this and can point me in a direction that might help finding the cause of the bucking?
I had the same problem and I refered to the kind people of this forum. They had suggested several options. One of them was unheard of to me, unplugging the clock spring.

I did that, and my 2.5L stopped bucking, spitting and spuddering. Bought a new clockspring and installed. No issues since.

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Old 11-09-2015, 10:04 AM   #3
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Distributor cap and rotor?
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Old 11-09-2015, 12:39 PM
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Distributor cap and rotor?
We'll replace it today, thanks.
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Old 11-09-2015, 12:43 PM
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Originally Posted by EightyFour View Post
I had the same problem and I refered to the kind people of this forum. They had suggested several options. One of them was unheard of to me, unplugging the clock spring.

I did that, and my 2.5L stopped bucking, spitting and spuddering. Bought a new clockspring and installed. No issues since.
Thanks. The clock spring - du you think it had anything to do with bucking while driving with cruise control? Because I usually don't use cruise control. Just trying to understand what role the clock spring might play.
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Old 11-09-2015, 01:26 PM   #6
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Originally Posted by Wrangler-98 View Post
Thanks. The clock spring - du you think it had anything to do with bucking while driving with cruise control? Because I usually don't use cruise control. Just trying to understand what role the clock spring might play.
Not sure, but it very well could be.

My symptoms was intermittent high idle while stopped, bucking, and spitting and spuddering under load with a chaser of a low idle / stalling coming to a stop.

Its an easy diagnosis, just unplug the clock spring. if symptoms continue to occurr, then I'm wrong and it wasn't the clock spring. Just my experience with this overly priced part.
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Old 11-09-2015, 02:21 PM   #7
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Quote:
Originally Posted by Wrangler-98 View Post
Thanks. The clock spring - du you think it had anything to do with bucking while driving with cruise control? Because I usually don't use cruise control. Just trying to understand what role the clock spring might play.
The clockspring is a multi-wire connector module inside the steering wheel where the wires are coiled up like a clockspring. They connect the horn, cruise control, radio, etc. to the buttons located inside the steering wheel, the wiring is coiled so it won't break when the steering wheel is turned.

When worn, the clockspring can cause various problems by sending erratic voltages out which, depending on the model year TJ, can also get onto the data bus. It can also by a circuitous route cause problems with the Throttle Position Sensor (aka TPS) which can also cause bucking. Or the TPS itself could have gone bad which can cause erratic idle, erratic acceleration, etc.

Whatever you do, if you replace any sensor or the clockspring, I'd try to stay with Mopar replacements. The likelihood of more problems are higher with aftermarket parts like those.
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Old 11-09-2015, 02:34 PM
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Thanks for all the explanations, guys. Much appreciated.
Since I live in Mexico, I can't be too picky which brand replacement part I use. We do have Autozone but they don't carry as many options as in the US.

We removed the distributor cap and the rotor today and noticed that the distributor pin was wobbling inside the distributor so we're trying to replace the entire distributor now.
Will keep you posted.
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Old 11-23-2015, 02:55 PM
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Still having problems. The engine seems to shut off for a second (instrument cluster is still on) while driving, then coming back on, most of the time with a lack of performance.

We've replaced so far:
- Distributor + cap
- Spark plugs and wires
- Ignition coil
- Upstream O2 sensor
- Throttle position sensor
- Fuel pump

Does anybody have any more ideas?
BTW, I don't have any instruments except the horn integrated in the steering wheel so I guess the clock spring should not be the issue here.

The PCM seems not to record any error codes.
Any help would be appreciated. I'm running out of options.
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Old 11-25-2015, 08:34 PM   #10
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Had a similar issue awhile back. Ended up being bad battery connections.
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Old 11-25-2015, 09:08 PM   #11
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Check block to firewall ground

It goes from Back of block to a bolt on firewall then another ground strap from the same bolt on firewall goes up to base of hood
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Old 11-25-2015, 09:33 PM   #12
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Quote:
Originally Posted by Wrangler-98 View Post
Still having problems. The engine seems to shut off for a second (instrument cluster is still on) while driving, then coming back on, most of the time with a lack of performance.

We've replaced so far:
- Distributor + cap
- Spark plugs and wires
- Ignition coil
- Upstream O2 sensor
- Throttle position sensor
- Fuel pump

Does anybody have any more ideas?
BTW, I don't have any instruments except the horn integrated in the steering wheel so I guess the clock spring should not be the issue here.
Re-read the second paragraph in post # 7 above, a defective clockspring can send voltage spikes which can make their way to the throttle position sensor and cause idle/acceleration issues.
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Old 11-26-2015, 12:12 PM
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Thank y'all, amigos.
The problem seems to be gone after we found a not so good looking contact pin at the connector to the crank shaft position sensor. Cleaned it thoroughly and the vehicle is running well now. Keeping my fingers crossed.

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