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Thread: RPM Surge

  1. #1
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    Default RPM Surge

    Is there anything other than a bad TPS that would cause RPM surge while cruising? My Jeep just started doing this again within the last 10-12 days, and it's somewhat sporadic at the moment. It seems to only do it after I've been driving for awhile. My Jeep doesn't currently exhibit erratic idle, which is another symptom of a bad TPS, but the RPM surge is pretty much identical to what it was doing when my original TPS went bad. When the original TPS failed, I also had an erratic idle. I took it to a dealer today, and their diagnostics found nothing wrong. Can a TPS fail gradually? I would assume that it could due to the mechanical/electrical nature of the part.
    '01 4.7 Limited Up Country, Front & Rear Addco Sway Bars, Pro Comp MX-6 Shocks, K&N FIPK With 9" AEM Dry Flow Filter, Akebono Front Calipers, Stillen Rotors & Pads, Goodridge Stainless Steel Brake Lines, Kolak 3" Stainless Steel Exhaust With Magnaflow 12589 Muffler

  2. #2

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    Quote Originally Posted by BTC View Post
    Is there anything other than a bad TPS that would cause RPM surge while cruising? My Jeep just started doing this again within the last 10-12 days, and it's somewhat sporadic at the moment. It seems to only do it after I've been driving for awhile. My Jeep doesn't currently exhibit erratic idle, which is another symptom of a bad TPS, but the RPM surge is pretty much identical to what it was doing when my original TPS went bad. When the original TPS failed, I also had an erratic idle. I took it to a dealer today, and their diagnostics found nothing wrong. Can a TPS fail gradually? I would assume that it could due to the mechanical/electrical nature of the part.
    Brake light switch could unlock TCC and RPMs could surge 200-300 RPM then settle back down. One way to check is if the cruise control intermittently shuts down.

    Could be TPS for sure though, inside the TPS is a conductive wiper touching a resistive disc, when the wiper contacts the same part of the disc consistently like at cruising highway speed, it can wear part of it down intermittently lose contact.

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    Quote Originally Posted by twojeeps View Post
    Brake light switch could unlock TCC and RPMs could surge 200-300 RPM then settle back down. One way to check is if the cruise control intermittently shuts down.

    Could be TPS for sure though, inside the TPS is a conductive wiper touching a resistive disc, when the wiper contacts the same part of the disc consistently like at cruising highway speed, it can wear part of it down intermittently lose contact.
    It really just started doing it the last 50 miles of a trip from Michigan to Kentucky. It's done it a couple times since I've been down here, but I haven't really been anywhere that would allow setting the cruise control for sustained periods of time.

    The cruise has never disengaged, so I don't think it's the first thing you mentioned. It's acts pretty much like it did the first time the TPS went bad, with the exception that the idle still seems stable. I guess I'll just give it some more time and see what transpires. I'm kinda pissed that I took it to the dealer, but I didn't really want to drive back to Michigan and have the rpm's fluctuating like that, and hoped having the TPS replaced before heading back would resolve the issue. It would have been more fun to just set 100 bucks on fire. Oh well.
    '01 4.7 Limited Up Country, Front & Rear Addco Sway Bars, Pro Comp MX-6 Shocks, K&N FIPK With 9" AEM Dry Flow Filter, Akebono Front Calipers, Stillen Rotors & Pads, Goodridge Stainless Steel Brake Lines, Kolak 3" Stainless Steel Exhaust With Magnaflow 12589 Muffler

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    New TPS at Advance Auto for about $35.00, if the torx screws come loose easily, its a five minute fix.

    My 01 first had the fluctuating idle, that stopped for awhile then it started with the rpm changes while driving. Replaced the TPS two weeks ago, alls well.


    05 WK Limited 5.7L
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    I also think it's the TPS(I've had this problem before and it was the TPS), but the shop found nothing wrong, which meant they wouldn't call it in to my warranty company, so I had to pay for the diagnostics. I have no idea what kind of tests they ran. For all I know, they could have eaten a Snickers and said all's good. I do know they drove it, and couldn't reproduce the problem, which I did not find surprising. I was just curious if it could potentially be something other than the TPS.
    '01 4.7 Limited Up Country, Front & Rear Addco Sway Bars, Pro Comp MX-6 Shocks, K&N FIPK With 9" AEM Dry Flow Filter, Akebono Front Calipers, Stillen Rotors & Pads, Goodridge Stainless Steel Brake Lines, Kolak 3" Stainless Steel Exhaust With Magnaflow 12589 Muffler

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    Quote Originally Posted by BTC View Post
    I also think it's the TPS(I've had this problem before and it was the TPS), but the shop found nothing wrong, which meant they wouldn't call it in to my warranty company, so I had to pay for the diagnostics. I have no idea what kind of tests they ran. For all I know, they could have eaten a Snickers and said all's good. I do know they drove it, and couldn't reproduce the problem, which I did not find surprising. I was just curious if it could potentially be something other than the TPS.
    I had the codes checked twice at Advance when the TPS was flipping out, and neither time did it regisiter any codes. I did check the old TPS with my ohm meter after replacing it. You can see an inconsistent readings in a small area when sweeping thru the sensors range. Also recalled when the IAC bit the dust a few years back, it also didn't drop any codes. I guess maybe either of the sensors have to completely fail (it will throw a CEL if disconnected) before any codes are dumped.

    If you do change it and then sweep the old sensor with a ohm meter and it shows inconsistent readings in a certain spot. I'd take it the dealer, show them and demand your diagnostic fee be refunded.

    Good luck with your repair.

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    Have you checked for a vacuum leak? Did this occur when you were on a two mile upgrade?
    -br

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    muchacho largo longboy's Avatar
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    Mine is doing the same thing, most of the threads I've read pointed me towards TPS. I guess we'll see, I have a new Mopar one on order that should be here this week.
    2006 WK 5.7 Hemi

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    Quote Originally Posted by Billy Ray View Post
    Have you checked for a vacuum leak? Did this occur when you were on a two mile upgrade?
    Honestly, I wouldn't know how to check for a vacuum leak. It didn't happen on a long upgrade. It just kind of started happening when I was cruising along at 70-75. The rpm's started surging a few hundred rpm's, and then falling back.

    I'm assuming the dealer's diagnostic procedures consisted of more than simply pulling codes, but who knows. They knew beforehand that it wasn't throwing a code, or at least my check engine light was not on. When my original TPS failed, the check engine light also never came on.
    '01 4.7 Limited Up Country, Front & Rear Addco Sway Bars, Pro Comp MX-6 Shocks, K&N FIPK With 9" AEM Dry Flow Filter, Akebono Front Calipers, Stillen Rotors & Pads, Goodridge Stainless Steel Brake Lines, Kolak 3" Stainless Steel Exhaust With Magnaflow 12589 Muffler

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    I experienced the surge a few times while driving back to Michigan from Kentucky. It honestly doesn't seem to happen as often as it did when the TPS was bad. I'm wondering if this could potentially be a torque converter issue. I've also got kind of a whining noise going on that seems to be more prevalent under engine acceleration, even when the vehichle is in park.

    Anyone ever had a torque converter fail? Do they ever make a high pitched whining noise, kind of like a turbine? I've probably noticed this noise for a few weeks now.
    '01 4.7 Limited Up Country, Front & Rear Addco Sway Bars, Pro Comp MX-6 Shocks, K&N FIPK With 9" AEM Dry Flow Filter, Akebono Front Calipers, Stillen Rotors & Pads, Goodridge Stainless Steel Brake Lines, Kolak 3" Stainless Steel Exhaust With Magnaflow 12589 Muffler

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    Mnay people have reported problems with the aftermarket TPS, I went and got an OEM one and its been fine for atleast 2 years now.

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    I'm trying to figure out what could be causing this other than the TPS. According to a dealer's diagnostics, there is nothing wrong with my current TPS. I definitely think I have a whine that's relatively new. At first I thought it might be coming from the transmission, but the noise is present even when the vehicle is in park. The pitch of the whine rises and falls with engine speed, and seems much more prevalent when the engine is under acceleration.
    '01 4.7 Limited Up Country, Front & Rear Addco Sway Bars, Pro Comp MX-6 Shocks, K&N FIPK With 9" AEM Dry Flow Filter, Akebono Front Calipers, Stillen Rotors & Pads, Goodridge Stainless Steel Brake Lines, Kolak 3" Stainless Steel Exhaust With Magnaflow 12589 Muffler

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    muchacho largo longboy's Avatar
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    So, I replaced my aftermarket TPS on Saturday with a Mopar one. I only have 30 miles on it since replacing it, but no RPM surging like I had previously. Guess we'll keep an eye on it and see what happens-

    So far, so good.
    2006 WK 5.7 Hemi

  14. #14

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    Quote Originally Posted by BTC View Post
    I experienced the surge a few times while driving back to Michigan from Kentucky. It honestly doesn't seem to happen as often as it did when the TPS was bad. I'm wondering if this could potentially be a torque converter issue. I've also got kind of a whining noise going on that seems to be more prevalent under engine acceleration, even when the vehichle is in park.

    Anyone ever had a torque converter fail? Do they ever make a high pitched whining noise, kind of like a turbine? I've probably noticed this noise for a few weeks now.
    If it's a torque converter failing, you need to figure it out ASAP before the particles from the failing converter destroy your transmission.

    Drop the pan, if your converter is failing it's probably filling your pan with debris, if you catch it soon it could save the trans. If the pan is clean, at least you have new fluid and know it's something else.

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    Had the same problem with our 2001. The torque conv is locking and unlocking. My friend at the dealership updated the program on the computer and the problem went away. The tranny seems to shift better also.

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    muchacho largo longboy's Avatar
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    Quote Originally Posted by longboy View Post
    So, I replaced my aftermarket TPS on Saturday with a Mopar one. I only have 30 miles on it since replacing it, but no RPM surging like I had previously. Guess we'll keep an eye on it and see what happens-

    So far, so good.
    So, one year later and the WJ's RPMs are surging once again on my WJ. If it's the TPS again, this will be the 3rd one I've had in the Jeep in the 5+ years I've owned it.

    This is pretty ridiculous to be replacing these yearly. Guess I'll do the TPS/IAC/Throttle Body cleaning this weekend and see if I have any vacuum leaks. Friggin' Jeeps.
    2006 WK 5.7 Hemi

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    My initial problem gradually got worse, and I replaced the TPS a few weeks ago, which resolved the issue. Taking it to the dealer turned out to be a waste of both time & money, even after I told them what I believed to be the problem. The whine I had mentioned turned out to be the idler pulley.
    '01 4.7 Limited Up Country, Front & Rear Addco Sway Bars, Pro Comp MX-6 Shocks, K&N FIPK With 9" AEM Dry Flow Filter, Akebono Front Calipers, Stillen Rotors & Pads, Goodridge Stainless Steel Brake Lines, Kolak 3" Stainless Steel Exhaust With Magnaflow 12589 Muffler

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    Quote Originally Posted by longboy View Post
    So, one year later and the WJ's RPMs are surging once again on my WJ. If it's the TPS again, this will be the 3rd one I've had in the Jeep in the 5+ years I've owned it.

    This is pretty ridiculous to be replacing these yearly. Guess I'll do the TPS/IAC/Throttle Body cleaning this weekend and see if I have any vacuum leaks. Friggin' Jeeps.
    Did you replace it with an aftermarket one?

    I replaced mine back in June with an aftermarket one...and just found out that it is acting up again...I seldom get to drive the ZJ...the wife does...of course it is lifted and lockers are going in soon....and I get the mini van...mind you it is not so bad...when I don't have all 3 kids or if it is still nice out we all pile into the TJ...but will have to put the top on soon.
    Ian McCutchon
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  19. #19
    muchacho largo longboy's Avatar
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    First one I bought (2 years ago) was an aftermarket one, Niehoff brand I believe. Lasted 13 months until I was getting the surging RPMs.

    Second one I bought (1 year ago) was a Mopar one. The engine would hint at RPMs surging while on the highway, but nothing horrible until earlier this week. Usually the RPM surges would be 100-200 RPMs total, but on Monday it was fluctuating a good 600 RPMs up and down on my way home from work. I drove it to work on Tuesday and Wednesday and it hasn't done it again.

    I'm going to check some vacuum lines this weekend if I get a chance, but not sure about the TPS just yet. IAC motor is relatively new (also Mopar) and throttle body was cleaned last summer when I replaced the TPS the last time.
    2006 WK 5.7 Hemi

  20. #20
    wine taster kjk's Avatar
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    The first one I bought (Mopar) lasted a few years.

    The 2nd one (Mopar) was bad out of the box and no they don't take returns on electrical parts at the dealer. I'm out $75.

    Went to Autozone and got one for $35 with a 2 year warranty. It's been great.
    5.9 ZJ SCT tuned PCM/ KJK CAI/ Thorley headers with 3" Magnaflow cat and muffler/ Modded kegger/ TransGo shift kit/ Vanco brake kit/ Braided steel brake lines/ Mopar cupholder insert!

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