Backstory: (Sorry for the wall of text)

1991 Accord with blown motor. Bought a 1993 pole shot for the motor, front end wasn't pushed into the motor or trans. Motor was left running for 5-10 mins after the shot with a broken Rad.

Dropped the motor in the 91 yesterday. Hooked everything back up and it fired right up. Had to change the motor wire harness and the distributor over.

Now:

After it warmed up, it started with a real erratic idle. 800-4000 rpms. Back and forth. After reading on another forum that the anti-freeze lines need to be bled, that's what I did. The idle calmed down, but now goes between 800-2400 rpms.

I've swapped over the IACV, the Throttle body (with TPS), I've checked all vacuum lines multiple times. I tried swapping ECU's, reset the ECU several times. I switched out the MAP sensor (as well as the other sensor that is in that black cover.) Still have the same problem.

I'm not quite sure at this point what it can be. I have the original motor to cannibalize parts off of, it's where I got the IACV and Throttle Body. I know the other motor runs (one cylinder was bad which is what led to me swapping motors.)

My thinking at this point is the TW sensor near the Anti-Freeze bleeder nut. I know if there is air hitting that sensor that it can cause the erratic idle, so I'm thinking that perhaps the sensor itself is bad.

Any thoughts or ideas are welcome. Alternately, if you can tell me where I can find a guide for checking engine codes, the light doesn't come on, but still wouldn't be a bad idea to check. Not sure where the jump box for it is, and which pins i have to loop.

 

The service connector for the ECU is a blue two pin connector that is behind the passenger side kick panel.

As for the idle problem, the 93 has three idle valves that can cause a leak. You replaced the IAC which is #15. #8 and #9 can also cause an idle problem.

 

Yea, the FITV (#8) I checked and doesn't seem to be leaking. As for the #9, I've already replaced that.

 

Anyone else have any ideas?

 

any ideas, anyone?

 

You can try to replace the TW sensor or see if the wiring got damaged somehow. A bad TW sensor should cause the CEL to turn on and the ECU to store a code.

I don't know what differences exist between the 91 and 93 accords, but I wonder if you need to change out the ECU with one from a 93. Can you also tell us what type of accord the donor engine came from, like LX, AT, etc.. Also tell us more information about your car.

 

Well, the donor car was a 93 LX, the patient car is a 91 EX.

I was told the only differences are the Distributor and possibly the harness. As far as the CEL, it doesn't come on.

I have tried switching to the 93 ECU from the donor car, but to no avail.