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Long story, tricky problem

My '99 Subaru Outback keeps stalling when I slow (like for a left turn or when approaching a stoplight). The CE light comes on. First diagnostics pointed to a need to replace the IAC. We did that and the relay to it as well. Problem persists. After 7 visits to the shop, we put in a ECM from a 2000 model. The CE light stayed on, but no more stalling. So I bought a used ECM that exactly matched mine. Now it stalls again! The mechanic is flummoxed and I’m frustrated. Any ideas about what the problem is? I do not want to buy a new ECM @$700, especially since I don’t think that’s the real problem

Post the codes read from the original computer and from the most recent replacement. Do not post someone’s interpretation of what the codes mean, post the codes themselves. If necessary, have them read again.

No idea from here but at this point is when one has to take a deep breath and with a thorough diagnostics manual in hand and a VOM start following the procedures in the book.

Just because a code may point to a certain part does not mean that part is bad; only that a problem exists within that area. Then it’s replace something and hope or follow the manual and do the diagnostics to verify the problem.

Just because a code may point to a certain part does not mean that part is bad ; only that a problem exists within that area. Then it’s replace something and hope or follow the manual and do the diagnostics to verify the problem.

Well worth repeating.

Does the engine stall when you brake during a right turn, or, only during left turns and straight ahead? If the stall occurs anytime the brakes are applied, suspect a ruptured brake booster.
The codes are DIAGNOSTIC Trouble Codes (DTCs). The emphasis is on DIAGNOSTIC. Diagnosis is the process of finding the cause of a problem. It is NOT a solution; but, the diagnostic code helps one get there (to the solution).

Big snowstorm here, so I’m not going out for new diagnostic check. I do have the first code from my beginning problem DTC PI507. The IAC was replaced after this diagnostic and car began to malfunction again after about 2 weeks. After each part replacement, cleaning, etc. the CE light stays off for 2-3 weeks before the exact same symptoms reappear. The exception was when a ECM from a 2000 Outback was installed. CE light remained on and diagnostic code revealed that it was the incorrect ECM, BUT the car ran like a charm for 2 weeks. I do hear all of you about the codes and I’ll get them and post in a couple of days. Thanks

It’s an issue when we let up on the gas and begin to slow down. Not always, but dangerous anyway.