Car stalls

[Paul Fraser]

My 996 has largely been in my garage for the last three months while I got the aircon sorted out. Only been started a few times and on one very short trip. Battery replaced during this furlough as previous one losing charge.

Drove to Aberdeen (2.5 hours) and enroute car stalled when slowing down at Dundee (after 1.4 hours driving) and repeatedly at end of trip.

These all happened due to the revs collapsing when slowing down or stopped.

No CEL.

MAF problem or do I need to look at something else?

1997 996 C2

TIA.

[0586slb]

Paul,

I'm making an asumption the car does not have egas, being a 97. However, it will still have some form of Idle Air Control. On Audis of a similar year, when the throttle cable is relaxed, the butterfly is moved in a small range to control the idle - a bit like egas for the first 8 degrees of movement. Or it may be an IAC valve (Idle Air Control) which allows a controlled amount of air to bypass the closed throttle. Either way, the trottle body or IAC can become clogged with oily carbon depostits and not work as designed. Try looking for what type of system your car utilises and post back so we can help some more.

[Richard Hamilton]

Paul

I'd try cleaning the ICV as 058slb suggests. There is a thread on here somewhere, and Loren posted a picture of the location of the valve, which is attached to the throttle body.

Refresh my memory - is yours a tiptronic? I have a friend with a similar problem. It ticks over smoothly, but the revs drop and it stalls when he engages drive or reverse. Only when hot. He has cleaned the ICV with carb cleaner, but no improvement. I'll let you know what happens.

Edited July 28, 2006 by Richard Hamilton

[Paul Fraser]

Manual non-egas. I'll try what you have suggested when I get back home, thanks.

PS Mine started from cold and idled fine too.

[djantlive]

is it possible that the battery needs to be charged?

[Paul Fraser]

It had a new battery fitted just before this, started ok and the problem then manifested itself after quite a long run. Also started ok the day after and idled fine (while cold), so I doubt this is the problem.

[1999Porsche911]

It had a new battery fitted just before this, started ok and the problem then manifested itself after quite a long run. Also started ok the day after and idled fine (while cold), so I doubt this is the problem.

What may be happening, as mentioned above. is that at closed throttle the ICV is stuck in a position that does not allow enough air to get into the intake. Remove the valve by removing the 2 screws and gasket and spray liberally with carb cleaner. Reassemble using same gasket. When you clean it, move the actuator manually to be sure it is not jambed.

Jim

[Paul Fraser]

I'm going to have a look at this on Tuesday and have been looking around the forum for other threads that might shine a little more light on the location and procedure for removing the ICV. Jim's post helps a little and I've found the part on the PET but can anyone post a photo showing where the part is on the engine please (probably obvious when you look at the engine but I'm away from home at the moment)? Thanks.

[Loren]

It is hard to miss. The ICV is a solenoid just on the left of the throttle body. It is held on by two allen head screws and has a delicate paper gasket (don't lose or damage the gasket) between the solenoid and the throttle body.

Cleaning works sometimes - but if it is too gummed up then it will need to be replaced.

[Paul Fraser]

Thanks, Loren, I'm clearer on what I need to do now. For anyone else coming after me with the same problem, this link might help:

https://techinfo.porsche.com/techinfo/pdf/e...996_KATALOG.pdf

Illustration 107-00

[Richard Hamilton]

Knew I'd seen one somewhere:

http://www.renntech.org/forums/index.php?s...ost&p=40668

or http://www.renntech.org/forums/index.php?s...ost&p=45536

[GaryAZ]

....car stalled when slowing down at Dundee (after 1.4 hours driving) and repeatedly at end of trip.

This sounds all too much like what happened when my MAF failed. Car stalled when approaching a stop light. Put the clutch in - dead. Starter motor would turn but engine wouldn't start. After the car cooled off it would start and run just fine until hot again. For me the conclusive test was this: When the engine was hot, unplugged the MAF ie: just undo the connector on the top of the sensor. The car would start and run. So you might try this. If you conclude it's MAF I know some people clean them off. In my case it was replaced and the car runs great.

[Paul Fraser]

I've still got my doubts about the MAF but I'm getting ahead of myself...

Got the ICV out (pig of a job getting the rear screw because of the two pipes at the back. If my Dad hadn't been there with another set of hands I would have had to take off the throttle housing... and probaby break that gasket too, but that's another story). Cleaned off the the ICV with carb cleaner and the silver hatch inside it seemed to be moving freely. Car idled when hot and didn't stall this time, but idle revs are only around 650 and it seems to be running roughly, and I'm talking more than the usual. With the aircon in it seems to be a bit happier, idling around 800-850.

Where do I go next? I have a spare MAF I got off of Ebay so I'm thinking about dropping that in, and sorting the exhaust shields which are probably causing the rattling sound at idle -- I hope that isn't the engine!

PS Thanks for the links Richard, they helped.

[Paul Fraser]

Well so much for the spare MAF off of Ebay, it's a complete lemon. Car idles at 800-850 and then stalls when any throttle given. Couldn't rev above 1500-2000 rpm. Knew I should have tested it when I got it.

Put the old one in (after cleaning the wrong part) and it idled at 800-850 but sounded slightly rough. The right hand exhaust seems to be putting out a different frequency of exhaust to the left. Is the sports exhaust handed, i.e. right hand exhaust for right hand manifold and left for left or is it all mixed? If it is separate I think I might have a problem on one cylinder, but surely that would generate a check light?

[Loren]

Remember when you replace an MAF the DME needs to be reset (either with a PST2/PIWIS or with a battery disconnect for 5 minutes). The DME needs to learn the new MAF and it is normal to have the car run rough for the first several miles until the DME adapts to the new part(s).

[Paul Fraser]

Thanks Loren. I guess I'll be doing that again tomorrow then... :)