These recent cold mornings have made my 98 WRX a bit reluctant to idle properly. It never used to have a problem and would start and hold a rock solid idle whatever the conditions. It usually starts and runs fine, but then after a few seconds it'll hunt up and down a little and sometimes will go down to 500-600 rpm at which point it'll either pick up again or just die. If I'm manouevering out of my drive, if I let off the accelerator suddenly it'll stall, and for the first couple of minutes it'll stall when I stop for a junction.

I tried adjusting the idle speed on my Power FC, but that seems to only make a difference when the engine's warm, and that's not when the problem happens. Once it's been running a while, it's back to normal on idle, apart from it's a little up and down and shaky at times, which it wasn't before. But at least it never stalls when it's warm.

So before I start pulling stuff apart, which sensors can I check on the Commander readout and what sort of voltage values am I looking for? Do I need to change the water temp correction values? At the moment, there are settings for -10 and 10 which are the nearest temp values to what we've had lately. However, it still has these 'cold' start problems at 15-20 degrees during the day when it's been left a while.

Help appreciated.

 

Try cleaning the ICSV - the idle control solenoid valve, it gets gunked up with oil fumes and sticks.
It is the lump on the back of the manifold on the passenger side with a plastic top on and an electrical connector.

 

my idle load water temp corrections...
1.000@80degC
1.125@ 50
1.188@ 30
1.297@ 10
1.391@-10
...no probs with cold-starts/idle so far.

 

OK I'll give those a try. I had cleaned out the idle valve before, but since then my IC had got oil filmed so maybe it's dirtied it up again.

The other thing with the values, there seem to be two columns of values IIRC. What's the difference between them? A bit like the boost settings, there are two columns of numbers there as well?

 

Well I pulled off the pipe feeding the idle control valve and squirted some carb cleaner down it but it doesn't seem to have made a great deal of difference. It still doesn't recover its revs properly after a bit of throttle, dipping down to 500 rpm on the verge of stalling before coming back up again.

Any other ideas apart from the idle valve (I will take that apart and fix it properly though)?

 

You could also clean the crankshaft and camshaft position sensors. That improved mine last year.

 

That's an idea. Didn't think of that. I'll get to it tomorrow morning then.

 

Any updates?

 

In Australia a lot of people have had concerns with the '99-'00 model AFM, if you can borrow one and test it.

 

Well after a rebuild and clean out of the inlet manifold and most of the other engine bay ancillaries, it's running a LOT better, but it still struggles to cold idle. I no for fact I've no vacuum leaks and all the gaskets are brand new. The TB and ISCV are both clean as a whistle.

Once it's warm it runs perfectly. It's just when it's cold that it misbehaves.