[Mk2] [Turbo] Rev1 Turbo High Idle

[MartinF]

So i'm nearing the end of fitting the Rev1 turbo engine in to my JDM Rev3 NA and for some reason the engine seems to be suffering from a high idle of 1250rpm.

When it's cold it seems to idle around 1500rpm and then drop to 1250 as it warms.

Things i've done so far to try and ensure all is well:

Set timing, albeit at higher revs. Was already spot on, and had to use the plug lead no.1 as my timing light would not pick up the Ignitor signal from diagnostics port. Assume this is OK.

Checked error codes - none.

Checked THW signal to ECU and voltage drops as the coolant warms as you'd expect and in line with Toyota manual.

Checked IDLE switch signal to ECU, All OK.

Checked for vacuum leaks, none and a good vacuum in plenum.

When I disconnected the ISC valve revs climbed a little, which I assume means it is at least doing something.

Throttle cable is slack enough.

The PSC and the PSCT signals along with the AC magentic clutch are all connected to the ECU.

I'm probably at the stage where I need to start measuring all the main signals going to the ECU to try and find out if one of them is amiss, but before I start that time consuming process has anybody got any previous experience of a high idle and found the cure to be something I have overlooked so far.

Not forgetting that this is a conversion.

[Mike 2]

you may have answered this yourself, throttle cable not slack enough!

Try unhooking the throttle cable and see if the revs drop. If it does you may have to check routing of cable or adjust mounting bracket.

[MartinF]

Doh!

That was actually a typo, I've edited now to say it is slack enough. Thanks

[bobhatton]

So i'm nearing the end of fitting the Rev1 turbo engine in to my JDM Rev3 NA and for some reason the engine seems to be suffering from a high idle of 1250rpm.

When it's cold it seems to idle around 1500rpm and then drop to 1250 as it warms.

Things i've done so far to try and ensure all is well:

Set timing, albeit at higher revs. Was already spot on, and had to use the plug lead no.1 as my timing light would not pick up the Ignitor signal from diagnostics port. Assume this is OK.

Checked error codes - none.

Checked THW signal to ECU and voltage drops as the coolant warms as you'd expect and in line with Toyota manual.

Checked IDLE switch signal to ECU, All OK.

Checked for vacuum leaks, none and a good vacuum in plenum.

When I disconnected the ISC valve revs climbed a little, which I assume means it is at least doing something.

Throttle cable is slack enough.

The PSC and the PSCT signals along with the AC magentic clutch are all connected to the ECU.

I'm probably at the stage where I need to start measuring all the main signals going to the ECU to try and find out if one of them is amiss, but before I start that time consuming process has anybody got any previous experience of a high idle and found the cure to be something I have overlooked so far.

Not forgetting that this is a conversion.

Remove and plug the AC idle up valve pipe to manifold.

[PW@Woodsport]

Also clamp the ISCV pipe that runs to the intake pipe at the turbo to get a 900rpm idle, then start/stop the engine letting it run for a second or so 10 times in a row.

Unclamp the ISCV pipe and see if that works.

[MartinF]

Thanks guys, i'll give these a go when I next get chance to spend some time on it and let you know how I get on.

[Peter Gidden]

Just to clarify - you set timing to 10 degrees BTDC with E1 and TE1 linked?

[MartinF]

Yep, but the idle was still high at the time. When I disconnected the link timing dropped back to about 15degs IIRC

[MartinF]

Well looks like i'm still struggling with this issue.

Car is all back on the road now and performed fine at North Weald the other week, it's just I still seem to be suffering from this high idle.

I've managed to get it down to about 1100rpm now with slight rotation of the ISCV.

The only way I can get it to idle right (about 750rpm) is by clamping the air pipe to the ISCV. I tried switching the car on and off 10 times, throttling slightly a couple of times and letting it settle back to 750rpm, but as soon as the clamp is removed it goes up to about 1300rpm and slowly settles back to 1100rpm. Based on the above behaviour (settling back to 1100rpm) and also the fact that the idle increases if I disconnect the ISCV I assume it is working OK.

Plugging the AC idle up lines by themselves doesn't seem to change anything.

Open to any other ideas people may have.

[Peter Gidden]

Basic question, but you have checked cam timing?

[MartinF]

Yep, fitted a new cam belt with tensioners etc. before fitting the engine and checked it a fair few times then and have checked it again since the idle issue.

Assume if the cam timing was out then I wouldn't be able to get my ignition timing correct ?