Engine swap & now CEL all the time

[kidge007]

Great site, been on the side for some while, but now I need help!

Have a UK spec 1991 Legacy 2.0 Turbo 5 speed, Superchipped and with a 3 inch full turbo back exhaust.

The original engine blew a head gasket, but as a friend had a scrapper, so it was gonna be easier to just swap the engine over rather than do a re-build.

The scrapper was an auto, so hopefully the engine had an easier life.

First problem was that the engine loom connections were not the same, so I just swaped the loom over, although the auto did not have a canister purge solenoid valve, so again that was swapped over, with the pipe work connected to the ends near the carbon canister, rather than in the original position of under the inlet manifold.

When the car had the exhaust fitted (prior to the engine swap) the CEL would occasionally come on, but just by dipping the clutch and letting the car idle for a second the light would go off.

The new engine fired on the button, but the CEL was on. Took the car for a spin and all I was getting was 0.3 bar, but it revved clean through the range.

Checked all the pipes were in the correct place from the excellent diagram (vacuum.png)

No change

Went to local Subaru Dealer and as a favour to a mate a mechanic connected the select monitor. Strangely he could not read the ecu, or even see it!!!!!!!

So I read the "how to read trouble codes" and set about finding the black and green wires. Green no prob...Black NO...mine are white....anyway they work and the light blinked away.

51
24
12
44

Fiddled a bit re-checked connectors, cleared error codes and tried again.

45
51
24
12
35

I wanted to know that the wastgate was working so left off pipe K and low and behold boost and the woosh of the dump, but also a lot of ignition cut/fuel cut. But at lease those components were working.

Put it all back as it should be but this time with a make shift MBC, bit of adjustment, but I was still running 0.5 ish when the fuel/ignition cuts the engine.

The error codes looked as if the problem area was the MAP sensor and the pressure exchange solenoid, so having a spare car, I just swapped them over......No change.

Maybe the problem is the engine to car loom connectors. Took them apart and all looked well.

Cleared the errors again, and tried once again.

44
45
32
35

Fiddled some more, you know the touch test, have a wiggle etc. Then had another go.

32
35
44
45
24

Wonder if its the ECU

Changed the ECU, the original was G7 an the new one from the auto is a E4. No change. Still fuel/ign cut at around 0.5 bar.

Clear codes and try again.

45
51
52
24
35

Guess I should not be worried by 51 & 52 and maybe there is an easy fix.

Will error code 35 affect the engine that much????

So the problem comes down to the MAP sensor which has errored across two units that were fully working priviously and the air control valve that does not always produce an error???

Spoke to Superchips today to find out what there little box does and basically its a FCD with a limit that will allow about 1 bar, so if that is working why am I getting fuel cut at 0.5??

Sorry for the length, but I had hoped to figure it all out for myself.

Suggestions please

[Legacy777]

Did you swap the ECU too, or just the harness?

It sounds like the auto harness you used is pinned differently.

[kidge007]

I swapped the engine harness of the auto over to my 5 speed, so that it would connect with the car loom.

I have also tried the autos ECU, but I am still getting CEL errors. Have just found out that the auto was a grey import. Ie it was a jap spec car.

[Legacy777]

I don't really understand why you had to swap the engine harness over.

And when you're talking about engine harness, you're just talking about the harness that is connected to the engine, and plugs into the connectors behind the battery?

[kidge007]

Absolutely... thats the daddy, the two off white plugs behind the battery. Maybe I should have suspected that it may be an import when the two connectors would not fit.

As in my mega post the only difference between the auto harness and my harness apart from the plug ends is the connector for the Canister purge solenoid valve.

[Legacy777]

If that's the case, go back and swap your MT engine harness back onto the engine.

[kidge007]

Sorry prob not making myself clear.

MT engine out

Auto engine in

Couldnt connect the auto engine to the car cos of the different connectors.

MT inlet manifold off & harness removed

Auto inlet manifold off & harness removed

MT harness attached to auto inlet manifold & re fitted into car.

As an aside yes it may have been easier to just put the MT inlet manifold with wiring onto the auto engine. But that was late at night and we may not have been thinking quite straight.

[kidge007]

Has anybody had a bad earth cause CEL errors like the above?

[Legacy777]

As an aside yes it may have been easier to just put the MT inlet manifold with wiring onto the auto engine. But that was late at night and we may not have been thinking quite straight.

I'd recommend going back and doing this personally.

[THAWA]

It shouldn't matter what manifold is on there. The connectors are going to the right places, and the sensors should all be the same anyway.

It sounds like the boost problem is that it's only giving wastegate pressure. Why? Dunno.

Do you know what codes were being thrown before the swap?

[kidge007]

I dont know for sure, but I would guess that the code was for the lamda sensor, when the exhause was changed.

But that is only a guess, as it would come and go. But when it then stayed on prior to the engine change, all the time....No I did not pull the codes/code.

Saying that it was still on full boost and was performing well.