Jumpy Cruise Control - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 05-11-2003, 03:16 PM   #1
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Default Jumpy Cruise Control

I have a little over 140k miles on my car, the vast majority of it on the interstate. Everyone in my family who uses the car just puts the cruise at 70mph and sits back, but lately I have noticed that at around that particular spot in the RPM band (about 2100RPM), the engine doesnt stay at a specific RPM. It will rhytmically rev and drop noticably, no matter what the incline is or whatever. Is this just wear from driving constantly at a certain speed and RPM? I drove 75mph home yesterday (you cant slow down of course ) and it didn't give me any trouble, but I an trying to keep my record clean, so I dont want to do this for long.
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Old 05-11-2003, 09:37 PM   #2
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Sounds like the throttle position sensor (my favorite problem). You need to test it. Sounds like the rheostat may have a dead spot in it.
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Old 05-11-2003, 10:27 PM   #3
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How do I go about checking/repairing the TPS?
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Old 05-11-2003, 10:45 PM   #4
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Easiest way to check it is with a Tech 1 or other scan tool that monitors the throttle angle continuously. But if you don't have a scan tool you can probe the variable voltage output (on a 93 it is dark blue, I think it is the same color on yours) to see if there is a continuous voltage increase as you slowly move the throttle from idle to WOT. It should go from about 0.2 to 4.5 smoothly.
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Old 06-05-2003, 10:31 PM   #5
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well, we took it to a shop to get some other stuff done, and we asked the mechanic about the problem. He thought that it is the solenoid that keeps the engine in OD. I have noticed that this problem only happens when I am in overdrive too. Does anyone know how much it would be to go get this fixed??? Another question, how much is a tranny flush? The tranny could probably use one anyway (its the original one), and I might as well do it while the car is in the shop. Any help would be appreciated alot.
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Old 06-06-2003, 12:23 AM   #6
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You can test the TPS (RHEOSTAT) By hooking up an OHM meter to it and run the **** or what ever back and forth until you might hit some very high OHM'* or a 0L. This means you have a break or a bad connection... The next step is to just get a new one... Hope this helps.
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Old 06-06-2003, 12:44 AM   #7
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it only happens when im on OD, wouldnt the TPS be going crazy at any speed? Another thing, it only happens when my car is warmed up (195 deg).
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Old 06-06-2003, 01:06 AM   #8
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Welp then your car is a lemon !!!!!!!!!! Jk hehe that is odd.....
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Old 06-06-2003, 03:01 AM   #9
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I still wouldn't rule out the TPS. How often do you use cruise when you're NOT in OD? If your mechanic suspects the TC Lockup solonoid or something similar, he should get a scanner on there and prove it before he does any work. I think the TPS is still your most likely culprit. If you're not in lockup (using cruise at a lower speed or in another gear).....your throttle would normally be at a different level than if you were in TC lockup on the freeway, right? So if your dead spot is LOWER, the problem would be as you stated. If your dead spot were closer to the WOT end of the sensor, your problem would be the opposite. Make sense? 9 times out of 10, it'* the TPS, and it won't always throw a code for all failure modes.

A tranny flush should cost you between 60-90 bux. Mine was 80. Did wonders.
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Old 06-06-2003, 02:13 PM   #10
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If it was the trans I would think that it happen at a consistent 65, a consistent 75, a consistent 80, etc. From what I read it only happens at 70?
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