Cold Idle surging

[wtdash]

This is my newly created '90 Legacy w/a '93 EJ22T swapped in - 130K miles. Has had a high idle (1800+) til fully warm since the swap - I've check vacuum lines. Cleaned the IAC and it got a little better.

I swapped the front Coolant sensor out a week ago, which made no difference.

This a.m. on a 0 degrees day (-20 wind chill) started it up and it idled high but started to surge 500-700+ RPM - to 2500 RPM - for just a second then would return to the 1800 RPM...also, the cooling fans would cycle on/off @ the same time.

After 5 mins it the surging ceased and after 10 mins the idle returned to normal - 700 ish RPM once it was warm.

The heater was on HEAT only- neither the Heat/Def nor the Def were on.


Any feedback is appreciated.

[Legacy777]

I'd suspect the AT/MT pin is not wired correctly.

I'd suggest double checking the wiring. Did you do anything with that wire? I don't believe you should have had to.

[wtdash]

If you're referring to an ECU pin I only swapped the cam/crank sensors, and added the turbo sensors wiring.

Since the EJ22T came out of an AT car, my car had a turbo 4EAT and I put in the turbo TCU when finished w/the swap, and since the ECU for the 5spd and AT are the same, I thought I was golden..

Is this the one you're referring to (from the ECU Pinout)?
B48.20 Transmission ID

or these:
B58.9 Park switch
B58.10 Neutral switch

Thanks,
Todd

[wtdash]

I briefly (maybe 2 secs) got a CEL this am.....likely was there yesterday, too, but today I was looking for it.

However, the RPMs did not surge like yesterday.

I'll pull the codes tonite.

There was also a clicking noise coming from the front dash - w/the defroster on and off.

What relays sit under there?


At the risk of being focused on the wrong thing, I think this is due to the super cold weather.

We're to stay well before freezing, w/overnite temps below 0, for the next week!

[Legacy777]

Yeah I'm referring to the transmission ID. Everything "should" be the same for the transmission type, however there were some changes that the factory manuals didn't pick up in the 92+ MY's. I don't think they affected the turbo ECU's, but I can't say for sure. The only way to tell for sure is to read the output from the select monitor. You can use Vikash's scan tool to do that.

[wtdash]

Re: V's scan tool - I just bought the wiring/connectors to do that....sitting on the work bench.

Thanks,
Td

[wtdash]

Codes are:
45: Pressure sensor and pressure exchange solenoid valve (I have Vikash's FCD installed)
and
49: Air flow sensor - Left over from when I temporarily had the JECs MAF installed.

Both should have been cleared, since I removed the Neg. batt. cable for over an hour after putting the Hitachi MAF back in, and finished the FCD installed.


Car runs fine once warmed up!

[Legacy777]

Use the green & black connectors together to clear the codes.