This might be a stupid question to you guys, but to me the only stupid question is the one left not asked.

When I start the 7 up, it shoots up automatically to 3000 rpms. Just like its supposed to with the AWS. But after an alloted time of about 15 seconds, about the time the idle should drop back down, the idle remains at not 3 but 4000 rpms.

I wanted to check my TB but wasn't sure what to check for. Any help would be great!

Car is an 87 turbo with a new rebuild.

 

Does the same thing happen if you start the car in gear (which is actually preferrable)?

-b

 

How is that preferable? If you start it in gear with the clutch in it will skip the fast idle.

 

disconnect the throttle and cruise control cables, try to start it again and see what happens

 

Worth trying I suppose, but illogical.
If this were a cable (either one) or throttle plate issue, would it start at 3k rpm (like it's supposed to) and then bump up to 4k?
Seems like it's start at 4k and stay there.

 

The idle speed increasing is pretty weird, but a similar problem was fixed in this thread: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/high-idle-loping-idle-questions-854949/. The secondary throttle plates were sticking open slightly and allowing engine speed to approach redline on startup. This was on a car without a BAC or AWS valve however, so if you have them, they could be a factor as well.

 

well disconnecting the cables is just the lazy way to check that. What you really need to do is check the TPS voltage. It should be 1 volt max with the engine warmed up or the fast idle cam manually rotated down. If it's higher than that (and your sensor was calibrated correctly) your throttle plates are open too far.

 

Can't hurt to try it. The car now longer has cruise control.

When I turn the car on, it goes straight to 3k rpm like its supposed to. From then on the idle doesn't drop but keeps going to 4k rpm and hovers there.

I'm kind of paranoid about leaving my car on at this point since its a rebuild with no miles on the motor. I suppose another question to ask is, if leaving the car running while the idle is set this high will have ill affects to the engine if I left it running to check the engine?

Car still has the BAC. Just to reference, which way should the screw be rotated?

Thanks for taking the time to help me out guys.

 

bringing the screw on the bac closer to the passenger side should drop idle, spinning it closer to the driver side should raise the idle, also has anyone, icluding u messed with the hard idle screws on the throttle body?

 

That's the screw that's on the back of the UIM correct? If so I tried rotating it both clock wise and counter clockwise, but returned it to its original position when it seemed to solve nothing.

 

The one I believe you turned will adjust the secondary throttle which was my problem. Unscrewing it will let the butterflies close more or open later if they are closed all of the way already. If you screw it in it will open the butterflies a little allowing air in at lower rpm or idle. I had to unscrew mine almost all of the way out but my engine was approaching redline when I started it. My tps was at 1 ohm at idle so that wasn't the problem. You should check that to be sure.

 

Sounds like something I need to look into. Can anyone else verify this for sure?

 

Anyone knowledgeable please?

 

Anyone?

 

just tapping the throttle should take it out of AWS phase also.

if you want to try seeing if the throttle is stuck just be sure both throttle and cruise cables have some small amount of slack then turn the throttle cam back manually by pushing on it in the reverse direction of the cables pulling on it.

i suspect your thermowax is fubar though, i have had a few that had poor or no coolant circulation through the thermowax on the back of the throttle body resulting in a stuck high idle. you didn't do a throttle body mod and leave it installed did you?

 

No TB mod, to my knowledge. I understand that this maybe a noob question, but which one is the thermowax? I know its on the back of the TB, but there's a lot to look at back there.

 

it has a yellowish plastic cap and vent at the end, that's about all that you can see from the back of a T2. directly behind the primary throttle plates.

 

This is absolutely weird. Earlier I had shut the car off and made a post on the forum. Then I went back into the garage about 20 minutes later and turned the car back on, and the idle went from a steady 1400 rpms, to 5000 rpms. Even higher than the original problem had started out as.

The BAC is screwed in all the way and won't lower idle anymore. I'm going to remove the throttle cable tomorrow and see if that reveals anything. Thank you Karack and to everyone else for the help.

 

So I removed the throttle cable off completely and proceeded to start the car, as suggested in an earlier post.

The rpm shot up 5K rpm this time around. Is it safe to say that the thermowax may be fubar?

 

if u manually close the top throttle plates and the idle drops then the thermowax is bad.. i think

 

Should I try to replace the TB?

 

I'm gonna try a different TB and see what happens

 

Could my idle be screwed up with the, what I believe to be, the air bypass solenoid valve removed? Its located on the UIM above the BAC.

The wire connector broke off and I capped off the fitting on the intercooler that it goes to.

 

Are NA and turbo thermowax's the same? Any differences for the S4 and S5s?

 

did you check your TPS? this tends to happen when they go bad.