Very high idle (A/C removed)

loki475 · Posted: Wed Mar 22, 2017 2:23 pm Post subject: Very high idle (A/C removed)

Ok so after 6 months of restoring my Syncro, and bending 2 pushrods as well as breaking some lifters, I've finally got it running. Unfortunately instead of idling it immediately climbs to 2000-2500 rpm. I removed the AC compressor while working on the engine and I did not see a point in re-installing AC (for the winter).

My question is does having the AC wiring disconnected send the wrong signal to the idle control unit? Should I re-install the AC compressor? I'm just about to go put the original Temp sensor back in, as I replaced this also and I want to rule it out as well. The TPS clicks and I will also test it today with my multimeter.

Red Beard · Posted: Wed Mar 22, 2017 2:46 pm Post subject: Re: Very high idle (AC removed)

I disconnected my AC wiring and removed the belt on my system with no ill effects on idle. I think it has to be something else.

pablum · Samba Member Joined: December 17, 2015 Posts: 562

Don't forget to give the idle air bypass hose a pinch while it's idling!
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I see [a cat] in the street and i aim for the pest with my car. -- Evil or Very Mad

bluebus86

loki475 · Posted: Wed Mar 22, 2017 3:45 pm Post subject: Re: Very high idle (AC removed)

Ok I'll go pinch the hose. Temp sensor change did nothing. I only have 12-13" manifold vacuum currently. And when I shut the engine off I hear a hissing sound as it comes to a stop. I was sure it was a vacuum leak but I've sealed up everything twice. I thought I fixed it earlier today but I had just forgot to plug the AFM back in, somehow that made it run fine.

0to60in6min · Posted: Wed Mar 22, 2017 3:57 pm Post subject: Re: Very high idle (AC removed)

- disconnect the plug on the ICV (Idle Control Valve) to see if there's any change

- make sure that he ICU (Idle Control Unit) is connected

- does the throttle body switch give a proper click?

pablum · Samba Member Joined: December 17, 2015 Posts: 562

Also, it's almost certain that these suggestions all presuppose that your idle is correctly set (throttle bypass and afm bypass).
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The wise man learns from history, the fool from experience.
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I see [a cat] in the street and i aim for the pest with my car. -- Evil or Very Mad

bluebus86

loki475 · Posted: Wed Mar 22, 2017 5:11 pm Post subject: Re: Very high idle (AC removed)

Ok Pablum, I pinched the idle control valve hose and it idled perfect! Thank you! So that means it's either the control valve or idle control unit? Or could it be any one of the input sensors to the idle control unit? I thought I had tested the control valve earlier, with the key on it vibrates. Is that not an accurate test? Also, when I disconnect the control valve it kills the engine.

I also noticed when fixing up the engine bay the idle control unit was sitting on its side, not up on its perch, so I mounted it on the perch. Maybe moving it around finally killed it? The terminals also look corroded, so maybe new terminals might make the difference. The engine ran good before I started restoring the van, so I was focusing on things I had changed/replaced.

pablum · Samba Member Joined: December 17, 2015 Posts: 562

It sticks when it opens, allowing too much air to pass... clean it well and it should be fine.

I guess there could be some kinda short in the ICU that made it stick open, but probably you have a sticky valve.
_________________
The wise man learns from history, the fool from experience.
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I see [a cat] in the street and i aim for the pest with my car. -- Evil or Very Mad

bluebus86

0to60in6min · Posted: Wed Mar 22, 2017 5:33 pm Post subject: Re: Very high idle (AC removed)

@ loki475

you got a PM

loki475 · Posted: Thu Mar 23, 2017 8:19 am Post subject: Re: Very high idle (AC removed)

I cleaned the control valve for the second time but it wasn't really dirty anyways. The valve moves freely, no sticking at all, and it hums strong with the key on. I'm guessing the idle control unit is toast?

DometicLover · Posted: Thu Mar 23, 2017 9:07 am Post subject: Re: Very high idle (AC removed)

If the valve hums, it means the ICU is not "toasted". From personal experience the valve always allows a small amount of air thru, therefore clamping the hose will give you false reading.

Do you have a locker on your van? Check for vacuum leak and make sure all wiring are ok. If the coil signal to the ICU is disconnected the RPM will jump to that RPM range. If the A/C connector is getting 12V, the idle will jump as well, but not the 2000RPM

I once had a similar issue on my van, idle was perfect before I did extensive work on the engine during the winter and on first start-up idle jumped to around 2000RPM, Testing for vacuum leak using "quick-start" and propane revealed nothing. I ended making a smoke tester and found the seals on the Throttle Body were leaking.

loki475 · Posted: Thu Mar 23, 2017 9:54 am Post subject: Re: Very high idle (AC removed)

The throttle shaft doesn't feel like it has play but it does look kinda rough. I'll try to find a leak there this afternoon.

When I replaced the coil I had to replace some wire ends at the same time. Maybe I should double check the ICU coil wire.

DometicLover · Posted: Thu Mar 23, 2017 10:24 am Post subject: Re: Very high idle (AC removed)

If the TB is rough then wear might be the issue. See post below

https://www.thesamba.com/vw//forum/viewtopic.php?p=5172845

The signal for the RPM to the ICU comes from the Hall sender not the coil. Check for continuity.

T3 Pilot · Posted: Thu Mar 23, 2017 10:54 am Post subject: Re: Very high idle (AC removed)

Another Classic brought to you by VW with some relevance to the topic at hand.....

https://www.youtube.com/watch?v=0cyvKi4V4CI
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The most important part in every vehicle is the nut behind the wheel......

loki475 · Posted: Thu Mar 23, 2017 1:05 pm Post subject: Re: Very high idle (AC removed)

So I went to do some tests for throttle shaft wear and when I started the engine it shot right up to 2500 rpm and kept climbing to 3000 rpm before I shut it down. This makes it hard to look for problems so I pinched the ICV hose just enough to make it idle around 1000 rpm. But as soon as I release the hose it jumps to between 2000-3000 rpm.

loki475 · Posted: Thu Mar 23, 2017 1:11 pm Post subject: Re: Very high idle (AC removed)

Over the winter I replaced the fuel pressure regulator and all fuel hoses so now I'm wondering if excessive fuel pressure would cause this.

DometicLover · Posted: Thu Mar 23, 2017 2:25 pm Post subject: Re: Very high idle (AC removed)

What's the RPM when you un-plug the Idle Control Valve?

loki475 · Posted: Thu Mar 23, 2017 2:31 pm Post subject: Re: Very high idle (AC removed)

When I unplug the idle control valve the engine dies. I think the valve isn't working properly. Every part I could throw at it is in the 300 dollar range. Idle control valve, idle control unit or throttle body. I'm forced to figure this one out but I'm running out of time before the surf season begins. I need my surfmobile!

DometicLover · Posted: Thu Mar 23, 2017 3:17 pm Post subject: Re: Very high idle (AC removed)

It dies, good! I doubt it's the trottle body wear or a vacuum leak then.

Do the idle test and adjustment mentioned here (p121)

http://www.vanagonauts.com/files/Vanagon%20Digifant%20Fuel%20Injection%20System.pdf

loki475 · Posted: Thu Mar 23, 2017 3:53 pm Post subject: Re: Very high idle (AC removed)

Ok I'll do those tests in the morning. I didn't think it was a vacuum leak. At almost 3000 rpm that would be an obvious vacuum leak. Plus its a steady increase to that rpm. Can a failing control valve raise the idle that high? I couldn't find the #1 input to the idle control unit but I think I did now. Its a white wire?


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