RPM's getting stuck while driving

turp23 · 02-06-2012, 06:40 AM

I have read about the RPM's hanging, and not coming down fast enough. Problem is, mine won't come down at all. If I am shifting or coasting, the rpm will come down to 1500 and bounce between 1400 and 1600. The only time the rpm will return to normal @750 is when the car comes to a stop. I have already ruled out the linkage. I plan on doing Cliff's copper cap today, but I don't think this will fix my problem. Any suggestions on what else I can check?

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02WhiteGTVert · 02-06-2012, 07:42 AM

Quote:

Originally Posted by turp23

I have read about the RPM's hanging, and not coming down fast enough. Problem is, mine won't come down at all. If I am shifting or coasting, the rpm will come down to 1500 and bounce between 1400 and 1600. The only time the rpm will return to normal @750 is when the car comes to a stop. I have already ruled out the linkage. I plan on doing Cliff's copper cap today, but I don't think this will fix my problem. Any suggestions on what else I can check?

clean MAF, IAC valve, TB, perform a base idle reset. Those are good places to start!

!KLeech! · 02-06-2012, 08:07 AM

check your tps (throttle position sensor) on the side of the throttle body as well!

turp23 · 02-06-2012, 12:59 PM

I did the pipe cap with a 1/4 inch hole. Hanging during shifts are gone, with a short drive. Still hung up between 1100-1300 while coasting, but reading other threads I searched shows that is to keep the fluids up. Pulled the IAC anyway, PO used a tube of gasket maker to make a gasket. Its all but gone, so I will fix that tomorrow. Will see how the drive to work tonight goes.

Tired of fixing PO problems, but its a learning curve. I can pinpoint obvious things, but the little things are what I am becoming educated about. I will know what to look for in purchases to come.

turp23 · 02-07-2012, 02:09 AM

Much better between shifts, but still hanging 1400-1500 while coasting, or if I tap the gas while stopped.

oxfordgt · 02-07-2012, 03:06 AM

Your TPS is going out. It will keep getting worse until the car no longer starts. Go buy the $14 sensor and swap it out. I have had the exact same thing happen.

turp23 · 02-07-2012, 11:22 AM

I bought a new IAC, but the TPS wasnt in stock so I ordered it. The IAC did not fix the problem. Does the TPS have to be installed like the one on the fox bodies? I remember it had to be adjusted with a meter.

oxfordgt · 02-07-2012, 12:00 PM

No they only go on one way. Sometimes with garbage TBs like BBK the casting is bad and you have to mess with it a bit.

When the key is turned on the computer reads the TPS at what ever level it is at and that is what is uses as closed position. No need to adjust it.

turp23 · 02-09-2012, 10:19 AM

Installed the new TPS and it did not help. Now the RPM will shoot up anywhere from 1400-1800 and hold until I come to a complete stop. What else can I check? The one thing that I am uneasy about is the AZ Spectre cai the PO installed. It just bothers me, and does a lot of whistling when I accelerate. There has to be a way to trace this down without having to keep throwing money at it.

turp23 · 02-09-2012, 01:25 PM

Some new findings today.

a) The a/c sends the rpm's into a tizzy. The compressor is kicking on and off anywhere from every 8 to 20 seconds, but its ice cold. It is also putting a strain on the motor that I did not expect from a V8.

b) I noticed for the first time today, when I let off the gas and let the engine slow me down, well it doesnt. It holds a steady speed for several seconds and then the rpm begins to jump up and down. After a few seconds the rpm's start to drop slowly and return to normal.

C) I dont hear the popping in the exhaust from the copper pipe cap I installed in the IAC tube. Why? Because when I let off the gas and coast on the engine the rpm's dont drop, they jump in between 1400-1600.

D) Im aggrivated, but I wont stop. I am determined to fix this. Problem is, I test drove the car hard. Short of beating on it, I really put it through the paces. Did something short out from the engoine getting wet because of the "functional hood scoop"(see other thread)? I will prove this car a wothy purchase. My WIFE will accept nothing less, or I will be sleeping in the FX4!