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Old 12-19-2014, 10:34 PM
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Power surge at off idle

I am experiencing an interesting problem on a 2005 WK 5.7. After the vehicle is warm (driving 20 minutes at freeway speeds), then coming to a stop such as a stop light, when touching the throttle, the lurches forward with a less than 1 second significant power on (like stabbing the throttle very quickly). Over the last few months, it has been getting more frequent and more violent (not really the right word). It seems to mellow out with 92 octane.

Then today, I get a P0520 code. Now I am wondering if this is causing the issue since bad oil pressure readings can mess with the MDS. Though, I am not sure why this would be the case coming off idle.

Is it possible that there is a issue with the TPS?

This is very unnerving when the jeep wants to lunge.

Can you imagine what the sheriff deputy next to you at the light must think with the light changes and the vehicle stabs the throttle on its own?

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Old 12-20-2014, 10:50 AM
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Re: Power surge at off idle

What kind/weight oil are you using and is the level full? Do you have a way to check the oil pressure? That's the first thing I'd check AFTER I cleared the code to see if it comes back within a day or two. If it does, I'd change the oil pressure sensor. I am not so sure that this problem is related to your surging though. I once got this code, cleared it, and it never came back. I still have a new sensor sitting on the shelf just in case though.

It could be a TPS problem, but I think I'd check the transmission fluid level and condition first. When is the last time it was serviced? Does it up/down shift properly? Any hesitation when going into gear, especially the first time after its sat for a while? Does it slam or "ooze" into gear when shifting from reverse to drive or drive to reverse?

Bottom line, eliminate the easy, inexpensive stuff first, and then go from there.
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Old 12-20-2014, 06:25 PM
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Re: Power surge at off idle

Oil: 5-20wt Mobil 1. Oil level well within the safe zone. About 1,000 to 1,500 mile on the current change.

The only issue with the transmission is it will bleed down after sitting a while and not very often. Had it in under warranty and dealer replaced check valve. Transmission is solid shifting. I have about 84k on the vehicle.

When I checked the DTC, it showed the P0520 code as frozen and pending.

I have an oil pressure sensor being delivered. Will probably change it out next weekend.

I am assuming the WK is throttle by wire. As I said before, the car is acting like I am stabbing (stomping on) the throttle. Kind of like the PCM commanding fuel into the intake with the MDS active. When the MDS is deactivated, there is extra fuel and I get the power surge. Or, the TPS could be sending the wrong voltage to the PCM suggesting I have stabbed the throttle.

I am going to start with the OPS and see what that does for the power surge. Its been my experience that getting a code will only require attention later. Since the factory manual states the MDS could be affected by false readings from the OPS, might as well remove that possibility.

Anyone have experience with the Standard Products oil pressure sensor. They generally make good quality replacement parts. It's on Amazon for $26.
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Old 12-20-2014, 07:18 PM
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Re: Power surge at off idle

I don't have the problem you are experiencing but I am getting a surge idling after its warmed up. Only happens when the roads are wet after its rained. Still haven't figured it out....
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Old 01-11-2015, 06:57 PM
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Re: Power surge at off idle

Reporting Back on the power surge issue at just off idle.

I had a real issue trying to disconnect the electrical connector's locking tab as it was on the upper side of the sensor. The sensor is angled towards the back of the car. With your head point to the rear of the car, and looking up at the sensor, the tab was in the 12:00 position. In order to slide the tab to the right, I had to take a #1 flat bit and file the blunt end to a point. Then slipping that in a short driver, I was able to reach up (barely) and slip the bit in between the tab and its housing, then wiggling the bit and pushing it to the right.

As for the power surge, after I replaced the Oil Pressure Sensor, I only notice one slight power surge within a day or two. After that, I have not experienced the power surge. The car seems to run smoother at all throttle positions and I am definitely getting better mileage. As much as 2 MPG better.
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