Roush RPM Spike

[mkkrs1]

Have any of you Fox body owners encountered this problem. When I shift gears the rpm spikes up a sticks when driving normal. If I shift around 1800 the rpm will climb to 2200-2400. Need to get fixed before mustang week.



mike 89-718

 

[SGOODRIC50]

Yes, I have experienced that problem. It was something on the actual transmission that was causing it. I am not sure exactly what it's called, but if you go to your local autoparts store they can look up everything related to the tranny and find it very easily. Good luck

 

[marcus95]

Have any of you Fox body owners encountered this problem. When I shift gears the rpm spikes up a sticks when driving normal. If I shift around 1800 the rpm will climb to 2200-2400. Need to get fixed before mustang week.



mike 89-718

Sounds like your IAC ( idle air control ) to me. It's that small cylinder unit bolted to the front of your throttle body. Just a shot in the dark but wrap on that with the end of a screwdriver or something that wont damage the outside and see it that clears it up. How many miles? Occasionally, they need to be replaced. Hopefully Casey from Haney Motorsports will chime in and verify what the probelm is. Sounds like something in that area of idle control.

 

[FASN8N]

Could also be a throttle position sensor out of range (TPS). You can check the voltage and it shoud be set as close to 1.0 volt w/o going over. .96, .97. 98 etc.....

 

[HMSPORT]

That is what I would say is the problem. Take the IAC valve off and try cleaning it out with some brake clean. They do get gummed up inside after awhile. It also can be a possible TPS voltage/thottle blade set idle adjustment. Sometimes when the TPS volts a low, the processor sees that and activates the IAC. Then you start having a hung up idle. Ford has an adaptor plate that goes between the t.b and the IAC. It has a couple of set screws that allow more or less
airflow (bypassing the IAC). This is a good idle tuning peice especially if you have a big duration cam. I think the p/n is
F2PZ-9F929-A

 

[mkkrs1]

I have cleaned the IAC but I have not checked the TPS voltage. This is a stock 89 saleen with 93k. Does any one know if you replace the TPS or IAC do they have to be calibrated or is it a remove and replace that simple.

 

[FASN8N]

If you remove/replace the TPS it has to be calibrated.