# Cold start issue



## haymakerxxx (Mar 23, 2010)

Question #1- I have replaced all vacuum leak sources that everyone says to check, ISV is deleted, however, at idle, for the first 10 min. or so on a cold start the car won't idle (mostly it will die). Then, when it gets warm, the idle returns to 1k and idles like a dream (very steady and smooth). When the car is warm it will happen briefly on start up (until the O2 sensor gets a signal I assume). The car is an 85 Jetta 1.8 8v, however many things have been swapped/hacked/cut/removed/shat upon by one of the PO's. Any ideas?? I'm really stumped, I've poured over as much info as I can and I've got nothing. Any help would be great, love you long time. 

Question #2- Does anyone know what kind of CIS doesn't have a WOT or Idle switch, doesn't have a WUR, and has the 2-wire ISV?

Also, I have checked that the CSV is in working order, however, I was not able to check the TTS yet but if the CSV is working I would assume that system is all working correctly.


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## WaterWheels (Aug 14, 2005)

haymakerxxx said:


> Question #1- ISV is deleted, however, at idle, for the first 10 min. or so on a cold start the car won't idle (mostly it will die). Then, when it gets warm, the idle returns to 1k
> 
> Question #2- Does anyone know what kind of CIS doesn't have a WOT or Idle switch, doesn't have a WUR, and has the 2-wire ISV?
> 
> Also, I have checked that the CSV is in working order, however, I was not able to check the TTS yet but if the CSV is working I would assume that system is all working correctly.


#1 - That is what the ISV helps with. A cold engine needs more fuel and with it more air to stay running. Once warm this enrichment is no longer needed and is cut back, so no ISV = poor cold start/idle until warm. You could install an AAV to maybe help things when cold.

#2 - Old (original) basic CIS has no switches. Only CIS-e and Motronic do not use a warm up ragulator. Only engine I can think of with a 2 pin ISV is a European 16v engine with the code KR.

TTS may or may not be working correctly if the CSV is working. It could still be bad in a way that does not effect things or at least it does not right now. The CSV is designed only to function during cranking with a cold engine so it is not the source of your bad cold engine idle.


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## ziddey (Apr 16, 2006)

This is an 85 jetta gl, I'm imagining? I've seen that year's gls come with a more basic form of cis-e, like seen in the fox1's. There'd be no knock box, no idle wot switches, and the ISV is replaced with the older style AAR + idle boost valve(s).

If this is so, then yes, the idle boost valve can usually be deleted without issue if the system is in good shape. However, the AAR is pretty vital for cold running. I've got 3 of these that are either too restricted to begin with, or heat up and close far too quickly.

So, since this is cis-e, you should be looking into your engine coolant temp sensor. This governs enrichment while cold. A new bosch unit is around $30. 

If you want to play around with the mixture, either build a dpr test harness (read the stickies), or when the car is warmed up, unplug the o2 sensor and measure the voltage against a ground of your choice. You'll want to set it to approximately 0.75v at idle. The idea is to establish your baseline properly, so that while you're in open loop, your mixture is still close enough.


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## haymakerxxx (Mar 23, 2010)

ziddey said:


> This is an 85 jetta gl, I'm imagining? I've seen that year's gls come with a more basic form of cis-e, like seen in the fox1's. There'd be no knock box, no idle wot switches, and the ISV is replaced with the older style AAR + idle boost valve(s).
> 
> If this is so, then yes, the idle boost valve can usually be deleted without issue if the system is in good shape. However, the AAR is pretty vital for cold running. I've got 3 of these that are either too restricted to begin with, or heat up and close far too quickly.
> 
> ...



This is awesome info. Thank you. I'm going to try all of this and I'll be back to update.


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## haymakerxxx (Mar 23, 2010)

Update: I replaced the TTS with a brand new unit, didnt help. Replaced this unit







which changed very little. Then after warming the car up I disconnected my single wire O2 sensor and ran a multimeter to IT and a ground. This yielded a reading of .22v @ idle. Then I adjusted the mixture screw clockwise (about 1/16 of a turn at a time + a hearty blip of the of the throttle), however the voltage began to drop into the teens (I think it ended up at about .13v @ an idle speed of 1k in open loop). I know this voltage is far different than what ZIDDEY had said to expect, maybe my 02 sensor is bunk, but doing this has allowed me to start my car from a cold state with a 1k idle (by itself) then transitions seamlessly to a 1k idle in closed loop mode once the 02 produces a signal. One thing I also want to point out is that I inspected every intake boot, replaced almost all vacuum hoses, new intake manifold gasket, and replaced the injector O-rings. I believe all of those things were necessary to my success at fixing the problem I was having. Thank you guys for your help as well. :thumbup: /thread


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