Nothing flammable. It is right next to the exhaust, after all.

 

After reading that some people had installed their TPS improperly and had similar issues, I popped off the TPS, cleaned it, and was REAL careful re-installing it...making sure that the slot was lined up in such a way that it would catch the TPS notches correctly. Then, crossing my fingers, I fired her up.

It revved at around 1200 rpm! A helluva lot better than the 2000 it had been doing. But after it warmed up, it started climbing back up to the 2000-2300 mark. I went ahead and disconnected the battery and for the next few hours, the battery cables are being held together. I did the whole turn on the lights, attempt to start the engine, step on the brakes...whatever I could do to drain any electrical storage. Basically, I'm hoping that the ECU had learned that 2000 rpms was "normal" and that by resetting it, it'll bring the rpms back down. If not, I guess it'll be back to the drawing board by probably changing out the TPS and looking for a gasket leak...the only thing left that it could possibly be.

 

you should be checking for a gasket leak first. throwing parts at it won't fix it.

 

What did you use to tighten the bottom bolts on the header? They're a real pita and the only way I could get them real tight was a 14mm ratcheting wrench.

 

the only proper way to do it without alot of cussing and swearing is to use a 3/8 6" and 3" extension, 6pt shallow 9/16 , 3/8 ratchet, and a cheater bar to slide over the handle. Then follow the proper tightening sequence.

 

Well, here's a new wrinkle that should get you scratching your head...no vacuum leaks! Had a mechanic friend try all the tricks in the book, even a smoker/mist thing. He thinks it's possibly a defective throttle body. It IS a bored 63mm TB I got off eBay from a guy who has near 100% satisfaction. Could it be possible? I can also try to borrow a meter to test the TPS. I took it off and cleaned it, but didn't electrically test it.

With no vacuum leaks confirmed and a new IAC installed, what else could it be? If the TPS checks out tonight, I'll write to the TB guy and see about doing an exchange. After that...I dunno. It might become an electrical problem.

 

The tb if flawed would have very obvious defects. I've never seen a tb that failed. There's almost no way it could fail unless the plate didn't match the bore

 

The TB looked fine to me prior to install. So yeah, I'm open to suggestions.

 

sounds like you need a multi meter and adjust the tps. made a world of difference in my '89. had same issue as you. sometimes mine would idle at 1500, then next time 2000, then 3000rpm.

 

H.o. Tps are not adjustable. Only the idle set screw.

Speaking of which, do me a favor and remove the throttle body, snap a pic of the bottom of it. Specifically, the set screw head depth, then how high it sits on the top side

 

Sure. It might have to wait until next week. I go out of town this weekend.

 

Np. I'm wondering if it's set wrong

 

And just to make it official, the TPS checks out okay.

Okay, so to do the process of elimination:

1. Header: I'm pretty sure the new header (with confirmed NO leaks) isn't an issue.

2. 99+ intake manifold: Confirmed NO leaks. I believe all the vacuum hoses are run properly. Any chance a blocked hose or a dead IAT could be causing this problem?

3. 703 injectors: Could malfunctioning injectors cause high RPM? Do I need a fuel regulator? (I know, I know, the answer is no, but maybe just I don't know something.)

4. 63mm-bored TB: This is the only place I can think of where there could be an issue. The IAC valve and TPS are good. I haven't checked the MAP sensor. Could a malfunctioning MAP sensor cause consistent high RPM? I'm going to ask the guy who sold me the TB if I can exchange for a different one. Unfortunately, I already sent him my old one for a core refund. Wish I hadn't had done that so I could throw it back on and see if the new TB *IS* the problem.

 

Could be. Unfortunately, I wouldn't be able to tell either way. I'll post a pic as soon as I get a chance to uninstall the TB, which I'll have to do anyway if I can get the guy to exchange it.

 

you're not likely to even need an exchange. I can tell you where to set it at.