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914World.com _ 914World Garage _ Idle problems

Posted by: BahnBrenner914 Jul 27 2005, 10:00 PM

So the ongoing project has been restarted after a 3 month break... no comment... and i fired the car up again and it starts and runs and isnt hunting much... the problem is that it idles at 1500 when i fire it up and then it slowly (really SLOWLY, like 30 seconds) climbs up to 2000 and i dont know if it will climb higher (i'll post a comment when i let it run longer tonight). I know 99% of you all have dealt with this, so help me go from to

Posted by: Bleyseng Jul 27 2005, 11:10 PM

check to make sure the vacuum hoses are connected correctly and check for vacuum leaks.
If the AAR valve is working it will start out with a 1500-1800 idle then after 5 minutes drop down to whatever you idle is set to.

To check to vacuum leaks plug the AAR valve hose so it can't leak and then you can look for other leaks.

Posted by: Rand Jul 27 2005, 11:49 PM

Mine also idles faster after warmed up, and it's been a hair-pulling battle.

If the AAR valve is NOT working, it should fail closed, right? Meaning opposite behavior of what we are experiencing... It should open when cold, then close down as it warms up. It should feed extra air into the intake when it's cold, and therefor idle faster when cold and slow down as it warms up. So a bad AAR would mean when cold it might idle slower or need some gas pedal feathering until it warms up, but not idle faster when warm.

Fast idle usually means vacuum leak (or improperly connected vacuum hoses) or too-advanced timing. But I still haven't figured out how temperature plays into this yet, especially when it idles faster after warm.

Posted by: Dave_Darling Jul 28 2005, 12:39 AM

The AAR typically fails open, though I have heard people say that theirs failed closed. The valve sits open most of the time (because we can only drive the car so many hours per day, right?). So when it freezes up, it tends to freeze open.

That could cause this sort of behavior.

--DD

Posted by: Rand Jul 28 2005, 12:52 AM

Ok, good to know. But in my particular case, the behavior didn't change if I plugged the hose after the AAR valve. So I know I'm not getting faster idle after warm because of the AAR valve staying open. Still searching...

Posted by: Bleyseng Jul 28 2005, 07:28 AM

I vote this is the number one complaint, bad idle.

Usually the AAR is rusted stuck open, the idle is adjusted wrong and there are vacuum leaks. Its like chasing your tail!

Test the AAR to see if it opens and closes first. Then check the hoses to see if they are connected properly. Then test for vacuum leaks ie injector seals, hoses, TB gasket, worn out dizzy etc...

Posted by: BahnBrenner914 Jul 28 2005, 12:28 PM

yeah, i started it up last night and it started running about 1500 to 2000 but after a minute and some revving, it calmed down to a 1100 idle. I also noticed that when i revved it, it went up quick and then came back down really slow. I've replaced all the vacuum hoses so i know they are all good... and where is this AAR valve?

Posted by: Bleyseng Jul 28 2005, 02:20 PM

see pic

Attached image(s)

Posted by: smooth_eddy Jul 28 2005, 04:30 PM

The AAR is easy to remove and bench test with aligators and a battery charger. I had similar problems, 20 minute Geoff found incorrectly connected vac hoses and a bad AAR on my car. Eddy

Posted by: redshift Jul 28 2005, 04:36 PM

QUOTE (Bleyseng @ Jul 28 2005, 04:20 PM)
see pic

Nice pic, Geoff! Where'd you get that one? I don't think I've see it before...

M

Posted by: Bleyseng Jul 28 2005, 04:48 PM

here is how Miles fixes his AAR valve...by doing the AAR Valve Dance!

Attached thumbnail(s)

Posted by: Dave_Darling Jul 28 2005, 05:52 PM

Also check the Decel Valve. It could be sticking open.

--DD

Posted by: DNHunt Jul 28 2005, 06:31 PM

Damn Miles that's one tall sheep.

Posted by: fatlando Jul 28 2005, 07:49 PM

my car is doing the same up and down thing too. I have a fuel injected stock 75 2.0 engine. that photo that was pictured, can i use that as a refrence?

thanx

fat lando

Posted by: BahnBrenner914 Jul 28 2005, 09:06 PM

QUOTE (Dave_Darling @ Jul 28 2005, 03:52 PM)
Also check the Decel Valve.

Where is that? i dont see it in the wonderfully labeled pic

Posted by: Rand Jul 28 2005, 10:44 PM

On my '75 2.0 it was right next to the MPS. Fastened by the same clamp in fact. Now it's gone.

Spilled Spot remover on my dog. Now he's gone.

I digress.

Posted by: Bleyseng Jul 28 2005, 10:58 PM

The MPS and decel valve are mounted under the battery tray. Chuck the decel valve and plug the hoses....

Use the 73 2.0l pic for hose layout as its a real Factory pic!

Posted by: Dave_Darling Jul 29 2005, 10:30 AM

A real factory pic, with only a few things moved around and in the wrong place....

--DD

Posted by: fatlando Jul 29 2005, 12:44 PM

QUOTE (Dave_Darling @ Jul 29 2005, 08:30 AM)
A real factory pic, with only a few things moved around and in the wrong place....

--DD

Dave,

Do you have the whereabouts of a "real" factory picture of all the vaccum hoses for a stock fuel injected 75 2.0?

i gotta fix my kerplunk this weekend.

Posted by: Dave_Darling Jul 29 2005, 01:03 PM

Nope!

I do, however, know where there are some line-drawings (which can occasionally show things clearer than photos) that have the 73-74 2.0 hose locations. The fuel hose routing is slightly different on the 75-76 cars, of course... You could use the 75 1.8 diagram for the fuel hose routing, I suppose.

--DD

Posted by: fatlando Jul 29 2005, 01:27 PM

dave,

just went to the bird site and got what i was looking for. thanx. and your'e the author...you sneaky little guy!

Posted by: smooth_eddy Jul 29 2005, 04:43 PM

Lando...

post it on the board here so we can all see it. Eddy

Posted by: Dave_Darling Jul 29 2005, 04:59 PM

Just go to the Bird site. On the main page (OK, the main Porsche page), over on the left side, is a section of links for 914 stuff. One of those links is "EFI Hose Diagrams". Click on it.

--DD

Posted by: smooth_eddy Jul 29 2005, 07:35 PM

Oh here it is: http://www.pelicanparts.com/914/technical_specs/914_20FI_diag.htm

Thanks Dave.