# Digifant Cold Start / Hesitation / Idle problems



## Mike Ocksbigg (Apr 16, 2005)

Here's the rundown:
92 Jetta Carat
CSW Chip
270 cam/adjustable gear advanced 4 degrees
TT exhaust
93 octane
New coolant temp sensor 2 weeks ago.(4th one this year!!)
Grounds cleaned yesterday: o2 sensor ground(right rear of the cylinder head), battery->chassis->transmission ground.
Cleaned and dielectric greased the CTS, ISV, and MAF connectors
Mechanical timing checked for accuracy
Ignition timing adjusted and correct per the procedure in the Bentley

*Symptom #1:*
The car has a hell of a hard time starting on cold mornings. And when I say cold, I mean anything less than 75 degrees. It takes repeated tries to get it to "catch" when cranking. Sometimes it will take 5-10 minutes to get it to start. During these hard starts, it's definitely getting fuel - you can smell it. Most of the time, I have to get out, unplug the coolant temp sensor, start the car, let it idle at less than 500rpm, then get out and plug the CTS back in before the car dies. 
Here's the strange part - this only happens the first attempt to start the car that day. After I drive the car to work, I can let it sit there all day long(9 hours), and it starts just fine. This has been occurring for years, and I have ignored it for the past few months because it's been warm. At this point, I need to do something about it.

*Symptom #2:*
At idle, the car will advance the timing on it's own(verified with a timing light), stumble, the idle speed will drop to ~600rpm, then it kicks over to retarded timing(roughly 2 degrees ATDC), the idle speed jumps, and it returns to normal idle. This cycle continues constantly, occurring every 5-10 seconds. It idles perfectly with the CTS disconnected. 
*Symptom #3:*
The car bucks and hesitates. It's a little better with the CTS disconnected, but it still hesitates.
Symptoms #2 and #3 came out of adjustments that I made to the mechanical and ignition timing in an attempt to rectify the cold start issue, and a spark-knock (pinging) issue I have been having with the car. At one point, I managed to get the car to start on the first try in the morning, but the cam and ignition timing were so advanced that the car pinged constantly.
I'd like to get this thing running properly so I can enjoy driving it again. I have a new CTS that I'm going to try out today, but I can't imagine that is causing all of these problems. I'd also like to locate and clean the ECU ground if anyone can direct me to it.
Is there a relay I'm missing? Maybe a bad connection elsewhere? Help!


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## Mike Ocksbigg (Apr 16, 2005)

*Re: Digifant Cold Start / Hesitation / Idle problems (Mike Ocksbigg)*

UPDATE: Installed a new coolant temperature sensor. The car ran a little better for about 5 minutes, then back to all of the same problems.


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## giorgos (Dec 17, 1999)

*Re: Digifant Cold Start / Hesitation / Idle problems (Mike Ocksbigg)*

i am having similar issues.

car will not start at all. 
So i grounded the W side of the thermo time switch which in turn makes the CSV to open and release fuel when the engine is warm or cold. Cold I mean about 30C -35C.
Anyways, it start right aways....but I still have the hecistation when AC and all lights are on....
so far I replaced and insocted cleaned:
-Replaced 4 injectors, new o rings..sleeves...
-Replaced fuel filter
-Inspected both fuel pumps by removing them and jumping the relay to see if fuel goes throu them....ok
-new plugs
-re did timing
-checked all grounds
-checked for cracks...ok
-air filter ok
-air plate....under boot ...moves freely...
-fairly new O2...less than 6 months as well cat and exchaust....
-no leaks....air or fuel...
-Check the aux air valve for the AC...it works...
so after all this work car still will not start unless the CSV is hot wired as described above.....


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## Fat Rabbit (Nov 18, 2001)

*Re: Digifant Cold Start / Hesitation / Idle problems (Mike Ocksbigg)*

The ECU should ground with the O2 sensor -- there should be at least two wires that connect to the cylinder head. There is also usually a heaver braided wire that connects to the cylinderhead that comes from near the coil. 
Sounds like a bad ISV to me. Put you hand on it with the car running -- does it vibrate? That's a "quick check" I'd still try another one just to be sure it is opening/operating properly FR


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## giorgos (Dec 17, 1999)

*Re: Digifant Cold Start / Hesitation / Idle problems (Fat Rabbit)*

what is ISV stand for?


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## epjetta (Sep 19, 2006)

*Re: Digifant Cold Start / Hesitation / Idle problems (giorgos)*

ISV = idle stabilizer valve http://****************.com/smile/emgift.gif


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## Perratzo (Jun 1, 2007)

*Re: Digifant Cold Start / Hesitation / Idle problems (Mike Ocksbigg)*

Hi, 
This topic is a bit old but I want to tell you that I have lived with symptom #2 for most of the life in my 88 jetta 8v.
I keep tinkering with the timing to correct it but I always end up having the same problem. On idle, while hot, morning, afternoon or night. The car idles in accelerated/decelerated cycles. The RPM's go under 1000 and then jump up to 3000 in the worst cases.
I have taken it down to a minimum by adjusting the throttle flap screw back a few turns and adjusting the accelerator position screw in order to leave the car accelerated around 1250 rpms, where the problem is not as bothersome. Still, the engine cycles within 900 to 1450 rpms.
I have replaced the coolant sensor twice trying to ax this glitch. I recently found out that when you replace the white (two-wire) coolant sensor, you have to reset the fault code form the computer by disconnecting the blue oil temp sensor and revving the engine past 3000rpms (allowing the throttle flap to completely close) three times before plugging the blue wire back in.
I just did this yesterday (after replacing the coolant sensor five or six months ago) and experienced no sensible difference in my glitch. 
Like you, if I disconnect the coolant sensor, the car idles smoothly and does not hesitate when the light turns green at intersections. I have run the car like this a couple of times but I sense the gas mileage goes up significantly.
In fact this problem got me rear-ended once because i could not get past this hesitation (doesn't buck, but starts to build power really slowly) in time to avoid the jerk behind me who thought I had started going already.
Now I am in the habit of revving it past 2000 before I let go of the clutch.
My ISV seems to work well. All filters replaced (airbox has a clean K&N). New cables and plugs (platinums after coppers after platinums, and so on). New distributor cap and rotor. Timed it right a light and with the coolant sensor disconnected, as recommended by Haynes manual.
Mornings are always hopeful because the car starts right up and revs steady at 1000 or a bit below, but only for a couple of minutes where it starts to stall after dropping revs. It will keep on doing it if I don't tap the gas to avoid the stall or just push the gas to 2500 rpms for a solid minute or more, where it stabilizes into the cumbersome cycle I described. At this time of the day, the tailpipe smells a little rich and at times it has left some blackish hue on the driveway under it.
Upon listening to the tailpipe for a moment I hear:
rrrrrrrrrrrrrrrrthrrrrrrrrrthrrrrrrthrrrrrrrrrrrrrrrrrrrthrrrrrrrrrrrrrrrrrrrrrth
The "r" being normal firing combustion and the "th" I suspect misfire. It is long-intermittent and not constant. This is greatly reduced everytime I do the plugs and cables/rotor and cap. But not completely gone. I also believe that the "th" are the times where the revs drop in my "problem" cycle.
I am still to trace grounding of the system to the bolt on top of the tranny, but I think I will not be doing anything to make a difference. I also suspect a fuel pressure problem but I fear it in that these are expensive components (two fuel pumps and FPR). Why bother with something I am out of reach of?
I will post this as a new topic as well to get more feedback.


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## moto_33yz80 (Sep 10, 2008)

*Re: Digifant Cold Start / Hesitation / Idle problems (Mike Ocksbigg)*

i did the same thing and had similar problems.
plug in ect.
start car.
unplug ect.
rev to 2000 rpm 3-4 times to reset computer.
plug in ect. turn off and restart and you should be golden.
it fixed my car. what i think happens is if you dont reset then the computer still thinks that the sensor is bad. hope this helps.


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## jrtatonka (Mar 20, 2008)

*Re: Digifant Cold Start / Hesitation / Idle problems (moto_33yz80)*

whats an ect?


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## Gin (Feb 19, 2004)

*Re: Digifant Cold Start / Hesitation / Idle problems (jrtatonka)*

Have you tried a different ECU? Sounds like you've covered most everything else. Even if the o2 and coolant sensor is defunct it should still run better than that unless they are shorted. Are you sure its running rich?
Make sure your idle switch is working as well.
_Modified by Gin at 6:19 PM 10-18-2008_


_Modified by Gin at 6:22 PM 10-18-2008_


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## sholford (May 21, 2007)

*Re: Digifant Cold Start / Hesitation / Idle problems (Gin)*

I had a similar problem and it had me stumped for awhile. I eventually found a broken wire to my throttle switch. It was a big pain trying to start the car with it broken and difficult to keep running at low rpms.


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## LASTCHILD (Jun 29, 2008)

*Re: Digifant Cold Start / Hesitation / Idle problems (sholford)*








having the same problem.i need to check everything i just read on this post on my car. http://****************.com/smile/emthup.gif 
91 jetta coupe 8v


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## 1nsanevwfreak (Sep 10, 2007)

*Re: Digifant Cold Start / Hesitation / Idle problems (LASTCHILD)*

I had same problem several years ago, after giving up and taking the car to several shops unsuccessfully. I found that I had an intermittent ground to the ecu, it attaches to a stud on the coolant flange on end of block, mine was covered in rtv. To fix the problem I simply added another ground from the valve cover.


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