Ok I drove my car after a trans swap for a month or so, and the whole time, the engine would idle high (2500) rpm. I would snap the throttle, and the rpm's would come down slowly (10 seconds or so to go from 2500 to 750 rpm). This was one of a few problems with the swap. I actually swapped back to the auto for the time being. I'm considering swaping the T5 back in, but this idle problem is kinda keeping me from it. The engine idled fine before the swap, and now that the auto is back in. Was I supposed to jump any of the wires on the TCC connector? When I worked for GM, I hooked a tech 1 up to it and all the sensors were working fine. I really want the 5 spd back, so if anyone knows the answer to this question please let me know.

Car is an 86' 305 tpi

 

If I am not mistaken, It is probably your timing. I do not know what it should be at on the top of my head, but the timing is usually different for when you hve a manual or an auto. Not by much, but it could make a difference. Call up autozone and ask for the timing specs for both and they could tell you.

 

I believe your right on the timing being different between auto & manual, but it shouldn't cause the idle to be over 1500 rpm higher. I guess it would be worth a try, but the fact that it will SLOWLY come back down to normal idle makes me think it's something else.
Thanks for your input, this will be the first thing I do after I swap back.

 

Since the idle does come down by itself, that makes me think its the idle air control (IAC). Did you put a manual trans chip into it or keep the stock one? The computer does control the idle differently depending on the transmission. Since TPI and manual trans didnt come from the factory in 1986, you could use a stock manual trans TPI chip from an 87.
This is just a guess, and it'd be a lot of work to put the T5 back in, but that's what I would do.

 

try cleaning your trottle boddy. its possible its not closing all the way if the old spring thats built into it is worn out. its possible that the 700r4's tv cable is acting as a spring and pulling it shut. but when you throw that t5 in thier the tv cable is no longer connected so its staying open a little. happend to me on an old chevy celebrity. i just added a carburator return spring to it and was done with the whole thing.

 

Changing the transmission didn't change the engine's "timing" needs significantly. The "specs" won't be more than a couple of degrees different, regardless; certainly not enough to cause this magnitude of a malfunction. Dinking with the "timing" isn't the universal cure-all that some people would like to think that it is.

Not likely to be the TB or the IAC either, if swapping the 700 back in fixed it.

Might be worth checking to see if the TV cable is still hooked to the TB, and if maybe that's causing anything weird to happen.

One thing that could be an issue however, is that the ECM will react very strangely without VSS pulses. Does the speedo work correctly with the T-5? If not, getting that straightened out, may solve it.

 

thank you for your suggestions, I cleaned the throttle body when I installed an air foil, I did remove the tv cable when I did the swap. I used the stock chip, but the speedo wasn't accurate. I think that the speedo might be the problem now that you mention it, because when I had the car hooked up to a tech 1 in the air I put it in gear and the MPH on the tech 1 did not match the speedometer.
Thanks again for the help