Thread: '91 SE-R - Engine Wants To Take Off

how is the motor new? is it a JDM one or rebuilt? Have someone fire it up with your hand under the intake mani and see if you can feel a leak, try on top as well...

Update:

Yesterday I had a fellow racer stop by which was a major help! We were able to confirm that while the car is idling extremely high, it isn't taching out. However, I don't know just how high as the tachometer is either not getting signal or is broken? Does anyone here know a good way to troubleshoot the tachometer or where it's electrical connectors are?

As it turns out, disconnecting the MAF sensor actually causes the car to drop back and sputter, and then reconnecting it causes it to return to an extremely high idle. While it may not be THE definitive fix, definitely seems like a replacement MAF sensor is in order. I will get that replaced and report back with the results.

Edit: To answer the above question, it is a 30k mile JDM unit.

Sounds very similar to what happened to me when I did injectors on a low port 94 SE-R. I hung a five pound plumbing wrench on the throttle at the throttle body to make sure it wouldn't pull open. Still went straight to redline. Hmmmm. Unhooked the cruise and throttle cables and it idled fine....... Hmmmmm. Turns out the sheath of the throttle cable had pulled out of it's fitting at the firewall and had pre-tensioned and opened the throttle. I put the heavy wrench on an already open throttle. I would check to make sure that the throttle and cruise cables are not pulling the throttle plate open, even at "rest." I had a thread on it about a year ago. Good luck, Chuck

Does anyone know where to find / test the signal circuit for the tachometer? I would really like to get it working, I don't know if it's a missed connector, circuit fault or a failed tachometer.

My new MAF sensor is coming in on Tuesday and we'll see what that does. Currently:
MAF sensor plugged in - idles really high
Disconnect MAF sensor - sputters down to a lumpy "idle" and dies if left alone
Reconnect MAF sensor while doing above - returns to a really high - but smooth - RPM

It'll do the exact same thing.


Because the MAF is telling the ECU to put send the correct amount of fuel to the motor based on how much air is going through it.


Because now the ECU has no idea of how much fuel to add because it doesn't see any air going into the motor.

Have you even tried to adjust the idle using the screw over by the oil filter?

I appreciate the confirmation, your advice makes sense. Excuse my inexperience as this is my first time installing an engine into a car, outside of my college automotive classes (which was the same exact engine in-and-out on clean, unused shop cars).

The unit I swapped over came off the old engine, regarding the AAC and that idle screw. If I want to try and adjust it, I need to get a long pair of pliers to try moving it because the plastic screw has already been stripped from the looks of it. Could the sensor on that AAC unit also be a potential issue?

If that new MAF sensor isn't going to make a difference, I'll go ahead and cancel that order. Perhaps it is that idle screw or an issue with the AAC unit itself. Since the throttle plate is completely closed while the engine revs up, I assume it is something along those lines. I just need to sort out what is telling the car to deliver the extra fuel it needs to idle that high.

It's not a sensor on the AAC as it's movement is commanded by the ECU; the problem would be that it has gotten stuck wide open. That, and/or your stripped idle set screw is set way open, and/or the IACV is stuck open.
It's not a question of extra fuel, your problem is that the engine is sucking in extra air. The ECU just doing its job and delivering the correct amount of fuel so that it doesn't idle lean or rich.

Have you read this?
http://www.sr20-forum.com/general-maintenance/20375-how-cold-idle-fix.html

Thank you so much for the information! This my first time having to do a serious troubleshoot on an engine-install so every bit of information is much needed and appreciated! This has been a learning process for sure.

I will read up on the cold idle fix you just linked. Next time I have time to work on the car (tomorrow or Tuesday at the latest), I will first attempt to adjust the idle set screw and see what affect I can have with that adjustment. I will report back ASAP with my findings.

I also have the IACV I removed from the other engine I can try swapping over, but I will start with the simplest thing first.

Thanks again for your input, I will update soon.

The new IACV I installed did absolutely nothing for the car. The one I installed from the old engine is in terrible condition and the idle set screw was stripped and stuck, so I thought it was worth a try.

Idle set screw in - no difference. Idle set screw out - no difference. Looks like I need to think a little deeper once again.