3sge SW20 MR2 Diag Code 31

[Stu-]

A friends Dad has an auto 3sge SW20 MR2 that's he's been having an issue with the engine struggling to idle and blowing clouds of black smoke. I gave him a hand today and in diagnostic mode code 31 came up. So I tested the wiring from the map sensor back to the ecu and that's all fine with good continuity/little to no difference in resistance. Checked the 3 wires at the map sensor plug and there was earth, 5v and the output which was changing with amounts of vac as expected. Apparently the map sensor is new from Toyota too just recently. I also checked the water temp sensor (also new) and wiring back to the ecu which is all fine.

Anyone got any ideas as to what the issue might be? I'm thinking its potentially the ecu itself.
Apparently it started out as a sporadic problem that gradually got worse and now the car is undrivable.
Most of the sensors have been replaced - all bar the idle up solenoid under the throttle body which interestingly causes the engine to stall when unplugged.

Does anyone on the North Shore (or greater Auckland for that matter) have a spare SW20 3sge auto ecu we could test?

Cheers
Stu

[Lloyd]

How often is it faulting? If it's only ever throwing 31 and faults often enough then it couldn't hurt to get a scope on the 3 wires and see what's actually playing when it faults.

[Grrrrrrr!]

Pop the lid off the ECU and see if a capacitor has spewed its guts everywhere. Piss easy to do on a sw20, and they are of about the right age to have failing cap issues which in my experience usually show as intermittent and just keep getting worse like you have described.

[Stu-]

Ive had the lid off and nothing seems amiss bit it was only a quick look. The fault is always there, although it did seem to be slightly better when the engine was hot. Its just 31 thats showing.
Anyone got an ecu I can try?

[matt dunn]

I had a celica with a 3sge that had a similar problem.

we found it to be oil and crap blocking the map sensor line.

maybe clean it out or replace the vacuum tube.

check it for leaks etc too.

[Lloyd]

Just to add to Matts post, if it has a little filter in the line to the MAP sensor then try it without that there too.

[Stu-]

I've checked the line and infact replaced it and ran it from another location and its still had the issue
At one stage I had it running and took the line off from the map sensor and there was plenty of vac there