So I've been having issues with my 1992 f150 with a 302 and manual transmission. Whenever I accelerate and shift, the rpm does not drop, so it automatically speeds up to get back to the rpm I accelerated to. I have recently replaced the coolant temp sender, IAT sensor, distributor, IAC new from Napa (no change), and a full top end engine rebuild from the heads up. Currently, I can drive it with the IAC unplugged, and it drives fine, no rpm issues and throttle screw is set to idle at around 800 so it is drivable. The timing is set at 8 degrees if I remember right because 10 caused idle to be too high. I don't think it has to do with the cruise control, but from research, it might be the MAP sensor? I also read that the TB could be worn out and I was thinking of getting a new BBK throttle body because I don't really know if I can trust used or reman units, but the $400 price tag is kinda hard to swallow haha. Also, the TPS is tested, in range, and adjusted correctly.

 

My personal experience with the bbk throttle body was a return. I could never get to idle below 1200. Its design allowed too much air to bypass the butterflies. I exchanged it and new one did the same thing. Again, my experience! I got a remanned and it worked perfect. Have you checked all vacuum lines for a leak?

 

Haven't checked for a vacuum leak, because I don't think I have the equipment to do so. Would I be able to use an air compressor at low PSI to hear for leaks, or something else? I don't have a smoke machine like some have used.

 

Where did you buy your reman throttle body?

 

rockauto


start by inspecting every inch for cracks. Another option is to buy vacuum caps, remove a line and cap it at the tree. See if any of those correct the issue.

 

You can also pull each line, suck on one end and put your finger in the other, options!

 

ok, I will try that and report back.

 

Checked today and I didn't see any cracks in the vacuum lines anywhere

 

Test the map sensor. Also, With truck running, intake hoses off, can you choke the motor completely by covering the throttle bores?

 

How do I go about testing the MAP?