Idle Help Needed

[scuba steve]

After completing a motor swap, my 92 N/A doesn't want to idle properly all the time. It will sit at 700 and then drop down to 650, back up to 700, then down to 550, up to 700, down below 500, and then it kicks back up above 1200, settles back to 700 and starts the process all over again. But it doesn't do it all the time. Only about 20% of the time while idling. The rest of the time it will bounce mildly between 700 and 650.

Can this be caused by codes 51 and 52. This car started as an AT but it now has a 5 spd in it. But I drove 10K like that without problems before I put my frankenmotor in. But those codes do refer to the inhibitor and neutral switch. They came on briefly, but haven't come back.

The engine is a 98 EJ25D with 94 EJ22E heads and wiring. It has the Delta Cams 220 grind, WRX exhaust and 3" intake off of an 01 Legacy. It hauls ass right off the line and pulls to redline. Not a racecar, but torque on-demand is always welcomed. And sounds awesome. Just wish it would idle correctly before I get the lightened flywheel. I tried swapping out the knock sensor and water temp sensor off my other motor to no avail. The motor had this problem to much lesser extent before I swapped it into this car. And this car ran perfectly before the swap. Any ideas???

Steve

[Legacy777]

Steve,

Can you elaborate a little more on what you did when you did the AT to MT swap? There is a pin on the ECU that tells it whether the car is a MT or AT. Also, if the neutral switch was not hooked up when the manual trans was swapped in, that could be another problem.

Have you read my AWD & 5spd swap write up? It has a lot of the details on what needs to be done to make the electronics/ECU happy.

www.surrealmirage.com/subaru/swap

[scuba steve]

Oh yes Josh, I've been reading your swap writeup for 4 or 5 years now. It is very much appreciated having that info in a neat lpackage like that. I've done 5 or 6 swaps. I don't think I've ever cut the ecu wire to "select" manual. But i've never had a problem until now. Until after I made the motor swap. After my tranny swap, everything was fine for 10K. Then I did the motor swap, and now it has the warbling idle. I will definately go and cut that wire and see what happens. This motor did have this problem to a significantly less extent in my sedan before the swap. But that was auto, and I bet the TCU just masked it some. I'm using the intake manifold that was in the car, and not the one from the motor. Note that the same problem was present to a lesser extent berore, even though it had a different manifold and connected sensors. The only sensors that came over in the swap on the motor are the knock sensor, water temp sensor, and cam sensor. I swapped the knock and temp sensors with believed good units with no effect. I'm not sure the cam sensor could affect idle like that. But I'll double check all the swap wiring. It's possible something's come apart from that.

I just noticed this last trip that when the AC is on with the compressor is engaged the idle stays pegged at 800rpm just like it's supposed to.

I may have a manual ECU laying around. Think that might help? Thank.s

Steve

[scuba steve]

Well, I cut no 20 on B48 and no change. It dawned on me that the car is behaving similar to having no MAF signal. So I disconnect the MAF connector and it starts up and is pretty much the same. I changed the MAF twice with known good ones and no change. I traced the wires back to the firewall and the appear fine. There aren't very many more signals the ECU uses at idle. I guess I'll try the O2 sensor next.

Note: I have double checked all vacuum hoses as well.

[Legacy777]

Did you leave the TCU in when you did your swap? If so, it really should be removed.

Regarding the idle with AC on, that is normal.

I'm assuming the ECU in your car is a JECS ecu, and the one that came in the 92 Legacy, is that correct? What color are the injectors? Are you using the plastic black JECS MAF sensor?

[scuba steve]

I pulled the TCU and I have tried I think 4 different MAFs now.

I have to put this issue away for awhile. I just picked up a 91 Loyale wgon with blown HGs. Once I get that going, I'll be parking my Legacy wagon with the idle issue. I'll be pulling the motor and putting it back in my sedan with the AT. Then I'll see what issues I have with it when its back where it came from. Thanks for the hlep Josh.