cold start problem - 85' cq

andya · 26-02-17, 07:55 PM

Hi all. From cold only, it starts fine, but the revs jump to 2500 rpm, then flucuates, then when it warms up (can be a few minutes waiting), the revs go back to normal and all is good again.

Any ideas? Its an 1985 KV coupe quattro

Andy

Hanuman · 26-02-17, 08:55 PM

Does it have an idle stabilisation a la later cars, or an auxiliary air valve like a WR?
I believe it should have the usual cold start injector, too, although this may be irrelevant at this point.

If it's revving high, but otherwise everything is working as it should; idle control/auxilliary air?

Probably of absolutely no help. Sorry.

Hoyle · 27-02-17, 01:24 PM

KVs have aux air valve.

Try starting it with the AAV disconnected, you'll probably find it's going to idle low until the oil viscosity changes.

I had the opposite. With the AAV connected, it'd run at 2+k rpm even after warming. So I've disconnected mine and set my idle manually by the screw, when warm.

Chris

andya · 27-02-17, 07:16 PM

Cheers Hoyle and Hanuman! Something to go on......

Thanks again
Andy

andya · 21-03-17, 08:12 AM

Well to give you an update,

Mine has the idle control valve, not an AAV. I've swapped it over with others, no difference. Other things I've tried

1. Refurbished the Bosch warm up regulator - got it done professionally, made no difference

2. Replaced various hoses - especially the ones that carry oil - that one behind the isv had turned to a floppy mess! Luckily I've just recently broken a kv GT for parts and I've been swapping bits over. As I have no idea on the state of the vacuum pipes to do with the intake (nylon sheath protection, probably 30 years old), I have just ordered some replacement pipe to replace.

3. After taking the air intake box off yesterday, I could suddenly see the overrun solenoid, and the wire had broken off its clip and was overhanging the exhaust manifold - the result was a melted mess and a connection close to breaking. Like I say, ive just broken a GT, so it was a nice easy swap over. Optimistically I thought this might solve it. Nah!

So I am fast running out of ideas. I have 2 more things to explore - changing those vacuum pipes, you never know, there may be a leak.

And secondly what about a fuel pressure problem? The system relies on the pressure in the system until the pump starts. It could be if the pressure is initially too low, it causes an over revving problem. I'm taking the cq down to Cornwall for a week (i can live with this for now!), but will look to pressure test it on my return, I'll also change those vacuum pipes at the same time.

What do people think? Is there anything else I should be looking at?

Many thanks
Andy

missfire · 22-03-17, 08:54 AM

Manky throttle body full of oil and rubber.

26-02-17, 08:55 PM	#2
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	Does it have an idle stabilisation a la later cars, or an auxiliary air valve like a WR? I believe it should have the usual cold start injector, too, although this may be irrelevant at this point. If it's revving high, but otherwise everything is working as it should; idle control/auxilliary air? Probably of absolutely no help. Sorry. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

27-02-17, 01:24 PM	#3
Hoyle 80q addict Classic Audi Club Member Join Date: Nov 2010 Location: North Wales Posts: 840	KVs have aux air valve. Try starting it with the AAV disconnected, you'll probably find it's going to idle low until the oil viscosity changes. I had the opposite. With the AAV connected, it'd run at 2+k rpm even after warming. So I've disconnected mine and set my idle manually by the screw, when warm. Chris __________________ My 80 Quattro thread

27-02-17, 07:16 PM	#4
andya Senior Member Classic Audi Club Member Join Date: Aug 2010 Location: Hampshire Posts: 1,149	Cheers Hoyle and Hanuman! Something to go on...... Thanks again Andy __________________ 1985 Coupe Quattro 1986 Coupe 1.8 weber carb 1987 Coupe 2.2 GT

21-03-17, 08:12 AM	#5
andya Senior Member Classic Audi Club Member Join Date: Aug 2010 Location: Hampshire Posts: 1,149	Well to give you an update, Mine has the idle control valve, not an AAV. I've swapped it over with others, no difference. Other things I've tried 1. Refurbished the Bosch warm up regulator - got it done professionally, made no difference 2. Replaced various hoses - especially the ones that carry oil - that one behind the isv had turned to a floppy mess! Luckily I've just recently broken a kv GT for parts and I've been swapping bits over. As I have no idea on the state of the vacuum pipes to do with the intake (nylon sheath protection, probably 30 years old), I have just ordered some replacement pipe to replace. 3. After taking the air intake box off yesterday, I could suddenly see the overrun solenoid, and the wire had broken off its clip and was overhanging the exhaust manifold - the result was a melted mess and a connection close to breaking. Like I say, ive just broken a GT, so it was a nice easy swap over. Optimistically I thought this might solve it. Nah! So I am fast running out of ideas. I have 2 more things to explore - changing those vacuum pipes, you never know, there may be a leak. And secondly what about a fuel pressure problem? The system relies on the pressure in the system until the pump starts. It could be if the pressure is initially too low, it causes an over revving problem. I'm taking the cq down to Cornwall for a week (i can live with this for now!), but will look to pressure test it on my return, I'll also change those vacuum pipes at the same time. What do people think? Is there anything else I should be looking at? Many thanks Andy __________________ 1985 Coupe Quattro 1986 Coupe 1.8 weber carb 1987 Coupe 2.2 GT

22-03-17, 08:54 AM	#6
missfire making wooden things Classic Audi Club Member Join Date: Dec 2009 Location: cow land Posts: 8,154	Manky throttle body full of oil and rubber.