93 ecu on a 90 swap. Options

[lagos]

I installed a 93 mr2 ecu in my 90 3sgte. I repined the harness plugs to work with the new ecu. The car drives perfectly but wont idle correctly. It will sit at 650 rpm and want to stall out. Then after a few min of driving it will bump itself up to 950rpm for the rest of the drive. If I put the car in diagnostic mode, it will stall right out.

I was thinking maybe it has something to do with the IAC valve, but wannabe confirmed they should be the same. I know 93s have a slightly different throttle body, so maybe that has something to do with it.

Anyone here use a 93 ecu on their 90-92 motor?

[DEATH]

I have the same problem - I bumped the idle to 1k and it idles fine but still acts a little funny on startup. It's nothing major but I'd sure like to get this straightened out - this is my one little gremlin left with all of that. I had started to think about cleaning the IAC valve but hadn't found any useful info on how to do it yet.
Was yours working perfectly before the ECU swap and just popped up immediately after?
I'm staying tuned so I too can work this out.

[lagos]

Yeah, mine was perfect. Only change was the ecu, so its not a cleaning issue.

[DEATH]

Mine was too before the engine came out to be rebuilt but I've been all over the vacuum lines and everything so I'm pretty sure it's not that. Like I said - mines just a slight flutter at warmup but it's annoying when everything else on the car works so well now. I know it's nothing with the engine itself - I suspect it was some minor difference with something between the gt4 engine and my friend's experience with only SW20's. IDK - It's like 99% there but that extra 1% makes the completist in me angry.
If you need anything, pics, me to try various BS with mine, w/e - LMK. I'll be more than happy to help you experiment in fixing your problem.

[lagos]

So your running the 93 motor and the 93 ecu?
One way to check the IAC is to unplug it while the car is running. If its working correctly the idle should go up when you unplug. I haven't gotten around to checking mine yet.

This post has been edited by lagos: Aug 26, 2008 - 1:07 PM

[DEATH]

Cool - I'll try that. But not to distract from your problem - I'm just trying to offer some of my experiences so that if any of them sound like yours we can use mine to maybe help you.
As I said - If there is anything I can do to aid you LMK.

[lagos]

I unplugged the IAC valve. Car idle went up. Plugged it back in, idle went down. So the IAC should be working fine.. heh.
I ended up adjusting the flat head idle screw on the throttle body to bump the idle up from 650 to 800. At least it doesn't idle to the point of almost stalling out now, but after a few min of driving it still settles on 950, and doesn't like to idle correctly when in diagnostic mode.

There must be something different about the 93 throttle body.... or maybe some other issue going on.
Besides that the car drives smoother and better then its ever been on the new 93 ecu (sard rom tune! ).

[lagos]

I did some research and found out that 93s got a different igniter. I wonder if this is whats causing my high idle on this ecu.

[Dr_Tweak]

Sure does sound like a timing issue, remember that when you are in diagnostic mode the timing is locked, since it's stalling out it seems like it's timing related.

No offense but you're 100% sure you got the pin changes right?

Check your ignition timing yet?

-Doc

[lagos]

Yes, I checked the pins twice to make sure that they were pinned and seated correctly.
Car drives 110% better then it did on the stock ecu with no codes. Only issue is that it idles at 950rpm.

Timing was set to 10tdc prior to the ecu swap.
If I try to put the car into diagnostic mode now, it wants to stall out badly (sometimes it does). Then after a few seconds it will recover and bump the idle up to about 1200rpm. If I try to set the timing at that rpm, it will probably read incorrectly since the engine is revving that much higher. Even if this was a timing issue, I dont understand why the car would want to stall out so badly when being put into diagnostic mode. If the timing on this ecu was off, it would only be by a small amount, and shouldn't cause an issue like that.

93's did get a different igniter. Im thinking that my old one is probably reporting the wrong rpm to the ecu. I'll have to track one down to try it.