loot87

My 91 Turbo is having some troubles starting. It starts fine when warm. When stone cold (temps are usually below freezing at night), it will start but has to turn over a few seconds and needs a little gas.

After I drive it about 30 minutes to work and leave it sitting for 4-8 hours, it has much more diffculty. Daytime temps have been 50s and 60s. I have to let it turn over for 3 or 4 cycles of 5 seconds each, giving it gas. Finally something catches and it slowly fires up.

I have checked the AAV by pinching the hose on the right side of the intercooler. The idle stays the same. It's due for a tune-up. Anything else I can try in the meantime?

Thanks.
Chris

John McM

Mmm, shouldn't need any gas [throttle] to start. It may sound like an obvious question, but how old is the battery? I couldn't believe the starting difference when I replaced my battery, and that was in a temperate climate. Low temps make batteries even less effective.

loot87

It came with the car. I think the alternator and battery we replaced about 35k miles ago. It has no issues turning over and always starts with a little gas when very cold. It's just that in-between time when it's only been sitting a few hours that it just turns and turns.

John McM

I had a new battery in late 2001. 12,000 miles later in 2005, I noticed that it wasn't holding its charge. Put a new battery in and it started first flick cold or hot [had to make sure I didn't hold the key too long, it was that fast].

With a long time between battery changes you forget what a good one's like. Only you can judge whether that may be the issue here. I think it would be worth a go, if it always starts, but is slower in some instances.

PorschePhD

You need to look at the mixture. This will determine how the car runs. Try unplugging the 02 and see if it improves. If it does then the system needs to be fattened up. The engine needs more fuel when cold to fire and run. Once warm the WUR pressure go up leaning the car out and using less fuel. By unplugging the 02 you cause the control to go to a set 42% duty and fatten up.

You may also have a cold start injector going bad or the switch is not working. Try the 02 trick first.

loot87

If the O2 trick works, what do I do then?

PorschePhD

If you have a wide band or CO home tester you can increase the CO or AFR. If you measure before hand and tell me what it is I can tell you what it should/could be set at. Is the car stock?

loot87

Yeah, I think so. What's AFR?
As a further datapoint, it just started after sitting idle for four hours and it's about 60 today. It fired up, but really low idle, like 200. I gave it a little gas it kicked up to about 600. I then gave it a little more gas and the idle hit 900 and stayed there. I shut it off and it fired right back up without any gas.

PorschePhD

Air Fuel Ratio.

loot87

OK, will unplug o2 sensor and let you know.
Thanks!

loot87

I did some reading up on the AAV and think it's my problem (or one of them). The attached picture is what it looks like when cold. Can y'all confirm that this is too far closed and faulty?
Is 930 606 102 00 the correct part number?
Thanks.
Chris

viperbob

That is the correct part #. Man those things are a pain. I have replaced bunches of them. Talk about old technology. And they are stupid expensive. Porsche list these days is $750. They can be had as a Bosch aftermarket part for less though, but still very expensive for a single part Do what Stephen suggested first to make sure everything else is operating properly.

loot87

I think my AAR was OK after all. It moves from half way open when in the freezer to full closed when in the oven.
I'll have to wait for the symptoms to arise again and try the O2 trick. In the meantime, I'm going to do a tune up and buy a fuel pressure tester. I'm due anyway.

diabolos88

hi Stephen,
just any home CO hand held tester will work for adjusting the AFR mixture? I thought the meter needed to be an automotive type with the long wand to go inside the exhaust pipe, am I wrong?

PorschePhD

Gunson gas tester pro is what you want.