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check engine light after engine change


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i took an engine from a 91 legacy L manual trans and put it in a 91 legacy LSI automatic trans. i now have check engine light on. i didnt see any difference between the two engines other than the throttle body of the A/T engine has what looks like a idle air mixture screw on top of the throttle body (big flush mount brass screw). the M/T engine didnt have this screw. any ideas?

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in the engine computer. It may be looking for a signal it is not getting. On some models you could do a jumper wire if I recall. I think Legacy 777 had to deal with that issue on his manual conversion. You might do a search here if he does not jump in.

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i didnt replace the MAF i used the whole air filter/ MAF unit from the A/T legacy. so now its got a new problem...when engine is cold it wont start unless i hold down accelerator pedal. once the engine warms up it runs fine though. lots of power and really smooth ride. also starts without pressing pedal when warm. Still have CEL too.

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The 90-91 AT & MT legacies had different sensors. The ignitor, coil pack, injectors, IAC valve, MAF sensor, and ECU are different.

 

The ignitor & coil pack won't really matter. The injectors are timed slightly different, so your mixture will not be right on. I'd suggest swapping the AT injectors in. Also, the IAC valve on the AT's is a rotary type valve, compared to the MT's recipricating valve. The MAF sensor is also different.

 

Swap the IAC valve & injectors from the AT car.

 

Also, sounds like your coolant temp sensor is bad.

 

Did you check the codes? Do that before you do anything else. The computer is telling you what it doesn't like....

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Look under the driver's kick panel, and find the two sets of single pole connectors (one green and one black). Connect the black ones and turn the ignition on (without starting the engine). The CEL will flash the codes at you. count the long flashes for the tens, and the short ones for the ones.

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i looked for the connectors under the kick panel and everything that was there was already connected to something else. i have a couple that arent connected to anything above the accelerator pedal.

 

One set of green, and one set of black? If so, those are the connectors you want. The largish one that is not connected to anything is for the Select Monitor. . .

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I'm in the same boat as kzcafe. 91 manual FWD transplanted into a 91 auto AWD. Mine also won't start cold unless the accelator is held down but still doesn't run right even when warmed up. Idles on the stop screw thats not intended for that use. My codes are 24, 32, 49.

49 is the air flow sensor and I swapped the one out of the donor car but it promply overheated for the first time ever. Swapped that back and no overheating problems.

32 is the oxygen sensor. Can't remember if I switch that on this car or a friends. Will have to check into that one.

24 is air control valve but can't find that in the manual. Is that just the butterfly in the throtle body? I see it has several sensors associated with it.

 

I will have to check into the injector swap and IAC as suggested by Legacy777.

Thanks to Gnuman advise I found the connectors after quite a search. They were located right next to the ECM moduel. Wires so short I had a hard time getting them connected. Thanks All

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stumpy, i swapped out the IAC and the throttle body and it starts normal again. problem was that i reused the gaskets for the weekend while dealer was closed and theyre shot already. my setup is as follows now and it runs great. no check engine light and the POWER light is starting to chill out too. again i took an engine from a manual tranny and put it into a auto car.

 

MAF = A/T engine

IAC= A/T engine

throttle body and TPS= A/T engine

knock sensor= MT engine

cam sensors= MT engine

crank sensor= MT engine

injectors will soon be swapped out to= A/T engine

 

it runs great now. thanks everybody i would have never figured this stuff out on my own.

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OH HAPPY DAY,

 

Did the throttle and IAC swap today and for the first time in this car the engine started normal. Swapped out the O2 sensor also and going to run over to Multnomah Falls for a test run.

Thank you all for the information that put me on the right track!!!!

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OH YEA,

 

Test drive turned out better than I had expected. The auto trans has been shifting oddly and the engine performance very poor. Runs great now!! :) Like the one I test drove that got me interested in a Legacy in the first place.

Now all that is left to do is get the AWD kicking in.:-\ Will look for threads on that issue next.

Thanks again for all your help, this forum is great!!!!

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