Can a failing ICV prevent cold starts only?

[loki475]

I'm having trouble getting my engine started when cold. I have to hold the throttle open for 20-30 seconds and then it idles perfect. Its like the cold start function is not giving enough air, but once its a little warmed up it runs perfect. I've tried opening the idle screw a bunch and that will let it start cold, barely, but then it idles high.

I've replaced almost everything on the engine except my rusty old ICV. I have gone through the digifant protraining manual with no luck. But my sensors are all new anyways. Temp II, throttle switch, AFM, idle control unit and ECU have all been replaced along with fuel pump, water pump and all hoses.

Has anyone had a failing ICV keep from getting that extra air during cold start? It seems like its just missing that bit of extra air. After testing the new Temp II sensor I'm also wondering if a new ECU has given anyone problems?

Summer is here and I spend my days working on my syncro van instead of camping in it. If I need a new ICV so be it, but I can't keep throwing money at this van. Its getting depressing.

[loki475]

I should also add I replaced the hydraulic lifters and valve screws. I thought maybe a dead lifter(s) could cause the cold start issue. They're new and I pre-bled them but the van has been in my barn for several months. I've been test running it around the barn but that's about it. There is no lifter noise at start up.

[pablum]

There're continuity/resistance tests in the digifant manual taken incorporating the harness where the connector joins it to the computer...

If you have any problems with your wiring that might suss it out.
_________________
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. -- bluebus86

[loki475]

I checked over all connections and wires and grounds. But I don't think that could cause my cold start issue. It runs really good once its a bit warm. I originally thought it had to be the temp II sensor but it corresponds with the graphs in the digifant manual. I did the tests per the manual, at the ECU harness connector.

This is why I'm worried my new ECU is acting up. More ECU ghosts... The temp II sensor wiring at the ECU shows proper values, but still no cold start.

Could someone clarify what is in control during cold start function? Does the ICV give air during cold start? The digifant manual doesn't give many tests for cold start problems. I'm sooo close to driving this van everywhere this summer.

[pablum]

Then maybe it's a sticky ICV? Try cleaning that out with carb cleaner.
_________________
The wise man learns from history, the fool from experience.
-
I see [a cat] in the street and i aim for the pest with my car. -- bluebus86

[loki475]

Ok ill give that a try. When I originally had my fried idle control module give me problems I cleaned the ICV while looking for the issue. But I'll clean it again.
I was just unsure whether or not the ICV gives extra air during start up or is it just additional fuel?
I also have a new AFM so I'll test that also. Maybe throw the old one back on. Could a stiff AFM valve cause this cold start issue? Maybe it needs some break in time?

[pablum]

[jocoman]

You could also remove the ICV but have it plugged in. Have someone turn the key on (but do not start) and watch the valve. It should pull back just a little ways. If it does nothing or slams all the way then you have an issue.

[pablum]

[loki475]

ok so the ICV does operate during cold start, I'll look into it more. I'm checking the temp 2 sensor one more time.
I also replaced the hall sensor during the motor overhaul so I just recently adjusted the timing (35* @ 3000rpm) when I finally got it running. It needed a slight tweak and now I'm wondering if this played a part. If the engine wasn't quite warm enough when I did the timing, what affect does that have on the setting.

[loki475]

Temp 2 sensor is definitely ok. I just turned the key and the ICV doesn't seem to be doing anything with just key on. Does it operate for a short moment or stay on? I don't have anyone to help me so I'm running back to look at it once I turn the key.

I remember when I was diagnosing the failed idle control unit I had felt the ICV buzzing with key on. I hope the new idle control unit isn't causing this. I'm starting to feel like these vanagon parts vendors saw me coming a mile away. What do you think? $300 for a new ICV? I have to get it local if I want it for this long weekend coming up.

[pablum]

[loki475]

The ICV is not operating. I'm going to bench test it. I haven't touched the AFM screw yet or looked into it. I installed a new AFM and assumed it was ready to go. I can also re-install the original AFM to test since it had not failed, I just replaced it with a new unit that has the 'hesitation fix' inside.

[loki475]

Bench test shows the ICV is toast. With 12v applied it tries to snap but only makes it about 1mm then closes. If I keep trying it doesn't even do that anymore.

I couldn't understand why it ran so good once it was warmed up. Then I remembered that I had to keep opening the idle speed screw every other time I started the engine because the idle speed had dropped. That's when the ICV must have been slowly failing. Once it finally stopped working I was idling through the throttle valve at that point. The screw is out pretty far.

I'll know for sure later this week once my ICV arrives.

[Wildthings]

[loki475]

So it was definitely the ICV. Runs great now. Strange how it failed slowly though. That made troubleshooting tricky

[erikgundy98]

[erikgundy98]

[loki475]

I got it from frank condelli. But now the new idle control valve is not working either. I had similar problems tuning again but not quite as bad. When I checked to see what the idle control valve was doing, it was doing nothing. Bench tested it and it does not operate with 12V. So that's a $300 part that doesn't work. It was some aftermarket company. I need to start searching junk yards.

[loki475]

So it wasn't the idle control valve after all, but an intermittent connection to the idle control unit. It caused the ICV to come on and off. Now I think that has fried the idle control unit. It wont idle below 950rpm with the screw all the way in and the milliamp reading is 620 and not fluctuating.