Rough idle/stalling easily

[Paul Fraser]

Symptoms as above on a '97 996 with 58000 miles. Have already cleaned the ICV and throttle body as per a couple of posts on here. What is next? Could the ICV be needing replaced? At £250 a pop it's not something I'd like to try on spec, but I presume they eventually wear out to the point that you can't sort them by cleaning them?

PS Had a look for leaks while the throttle body/air filter housing rubber was off.

PPS The car is also occasionally throwing P300/301/302/303 codes at idle (once a month or so) which I presume is a grumbling variocam solenoid, or is this maybe related?

MAS recently changed on due to previous check lights (a non-consistent mixture of the above and some P304/306 codes but the latter seem to have stopped post MAS change).

[Loren]

The ICV should turn freely and not be all gummed up. It is a solenoid so you can put 12 volts to it and see/hear if it actuates.

I have seen them so sticky they won't move and I have also seen bad solenoids.

[Paul Fraser]

Thanks for that. I'll whip it out and put 12V on it -- does it open quickly/completely?

[Loren]

It is like a little rotating cylinder (inside).

[Paul Fraser]

OK, 12V applied one way closed the metal shutter completely and the other way opened it completely so I presume this is working ok? In the unpowered position it is like in the photo attached.

Started the car (first time in a couple of days) and the idle/revs seemed normal, slightly higher than usual, 1000-1100ish.

After a very short run the idle was back to where it normally was in terms of revs 800-850ish and quality, lumpy.

Can I rule the ICV out and, if so, what's next?

[Loren]

Sounds, like it is working. I hope the paper gasket is not damaged (sorry, forgot to warn you about that).

How does the inside of the throttle butterfly look?

[Paul Fraser]

It had a new paper gasket as I had it off before and broke it the last time :)

The throttle butterfly has been cleaned and sits slightly cracked open. I'll get the hose off and photograph that tomorrow.

I presume if it was an ignition coil problem this would throw a check light?

[Loren]

It had a new paper gasket as I had it off before and broke it the last time :)

The throttle butterfly has been cleaned and sits slightly cracked open. I'll get the hose off and photograph that tomorrow.

I presume if it was an ignition coil problem this would throw a check light?

Yes, a bad coil would give misfires and fault codes.

Have you had the car fault codes read recently?

[Paul Fraser]

I have been doing the upper level ones myself with a OBD2 reader (as above the occasional P300-303 and the less occaisonal P304/6, which always come up when it is idling -- probably on average this comes up once every three-six weeks for the last few months); are there deeper codes I would need a Durametric or somesuch to get?

[Loren]

If you have a bad coil or spark plug it usually shows up at all speeds and even more so at high RPM.

[Paul Fraser]

OK, more on this (I moved house a year or so ago so the car has been mostly sitting in the garage).

Got a durametric reader (good piece of kit) and pulled the following codes:

P1531

Unknown DTC: 1531

I've edited this as when I cleared them this was the only one that kept coming back. It indicates a timing chain problem, how could this have happened, if indeed it is that?

Anyone care to hazard a diagnosis and what do I do next? TIA

Edited July 21, 2009 by Paul Fraser

[Richard Hamilton]

P1531 is "Camshaft Adjustment Bank 1". I would suspect the Variocam Actuator on Bank 1.

[Paul Fraser]

I assume this is the variocam solenoid valve then? There is another chap on the board who replaced his in situ, but the manual states (15 37 19) that the variocam tensioning element has to be vertical or correct seating of the compression spring is no longer ensured. Anyone know anything about this?