# DigiFant II 8V - Cold start idle problem.



## juxched (Jul 20, 2013)

Hello, So i recently got a jetta with a 8v and it has digifant II 
Ive been having idle problems when i plugged in my CTS i went in and adjusted my tension adjustment on my MAF while the car was warm and now can run the car with the CTS in while the car is warm.
I already replaced the sensor for my CTS and it fixed nothing the car is idling fine once its warmed up before it was backfiring and i couldnt drive with the CTS in without it bogging out within like 30 seconds of it being plugged in and dying.
Now the only problem im having is its running like crap when the car is cold.
i start it and the RPMS stay below 1000 where they are set to be when the car is warmed up.
They arent adjusting at all its just staying at the same RPM on idle when the car is cold or warm.
What should i do? can anybody help me? so that i could make it so the car idles accordingly too the temp im lost and don't know what to do anymore.
Im beggining too think its something with the ECU or my Digifant i bought the car from a guy that says he rebuilt the heads and the motor is cammed etc but i think he did a really crappy job at wiring up stuff or had no idea what he was doing and just did a crappy job on the whole car and didnt want to deal with it so he sold it to me.
Thanks for any help.


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## Seax_Smith (Jun 1, 2007)

If you have sketchy wiring, especially grounds, deal with that first.

You really can't even diagnose digi until you confirm near zero resistance in the grounds and have confirmed you have no vac leaks.

The "throw parts at it approach" = grounds, vac leaks, CTS, O2 sensor, clean off the AFM 'plate' and arm contact point with alcohol. It helps to drag a clean piece of brown paper bag between the arm contact point of the arm. It is abrasive enough to remove oxidation but not so aggressive to mess anything up. If this doesn't work, try another new CTS because you can get them bad out of the box. 

If you are having trouble with open loop / cold issues, you probably have CTS issues. The O2 sensor doesn't come into play until you get the engine up to temp and the ECU starts taking signal form the O2 sensor, which is closed looped.

You could try a new ECU, but the ECU's, as primitive as they are, are very resilient and rarely go bad without some human assistance.

Has the timing been set correctly?

Has the AFR been checked recently? (remeber the altitude chart in the Bentley.)


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## juxched (Jul 20, 2013)

Seax_Smith said:


> If you have sketchy wiring, especially grounds, deal with that first.
> 
> You really can't even diagnose digi until you confirm near zero resistance in the grounds and have confirmed you have no vac leaks.
> 
> ...



I've done the throw parts at it method and it's healthier now, but the problem still is there... And sorry for not being very consistent been very busy lately.

I recently had swapped ECU's code 037 906 022m to a 037 906 022pa which I would was told would be fine to use on an RV block.
When I first started the car with that installed, I could hear a valve tick louder than I have ever heard. 
Could my timing be off now from adding a different ECU? Also, the car ran great with the new ecu at first despite the ticking would run with coolant sensor in, but then a few after I drove it for a few blocks and it started having the same symptoms of my last ECU. So I had to unplug the blue CTS once again. Lead me to think the wiring harness is bad and that I already had a fried ECU and I just fried this one?? 

Due to narrowing down the cause for coolant temp sensor being unplugged to run, with it in the car would die.
So I bought a plethora of new parts: cap, rotor, wires, plugs, new afm, isv, o2 sensor, fuel filter, clean grounds. bought it without a air bypass valve to charcoal canister and PCV valve, so I got those and put them in too. All of those things to no avail. 
I've been told it could be the fuse box or the wiring harness, I would rather it not be. But there are some corroded contacts that I've cleaned and melted wires that need tended to.
There are no vacuum leaks, Manifolds are not leaking, no leaks before o2 either.


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## Seax_Smith (Jun 1, 2007)

Take a look in your other thread.

What are the specifics of your car. RD Engine code.

Jetta or golf? What year? Which build - mexi, 'merica or german? CE1, CE2 or the wiring that came out of Westmoreland PA?


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## juxched (Jul 20, 2013)

Seax_Smith said:


> Take a look in your other thread.
> 
> What are the specifics of your car. RD Engine code.
> 
> Jetta or golf? What year? Which build - mexi, 'merica or german? CE1, CE2 or the wiring that came out of Westmoreland PA?


Jetta with an RV engine code. And it's 3VW so it's mexi I believe, and how do I tell if it's CE1 or CE2?


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## Seax_Smith (Jun 1, 2007)

3vw is mexi. CE2 starts somewhere between 87 and 88. 

CEI looks like this:









CE2 looks like this on the back side:









images from:
www.a2resource.com/electrical/systems.html


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## Fat Rabbit (Nov 18, 2001)

Using a multimeter you can test the resistance of the CTS to see that it is working. It is a thermal resistor so the resistance varies with temperature. Most manuals have a resistance curve graph. Basic numbers would be something like 5-6000 Ohms with the engine cold and 150-250 Ohms hot. Depending on the ambient temp the upper number might be lower -- ie. in hotter weather the coolant will be warmer. 

You can also use a multimeter to check the wiring for continuity. Basically from the sensor connection back to the multi prong connector at the ECU (Computer). Back in the day I did a lot of rewiring on Digifant cars usually for breaks near electrical connectors. So check those wires near connectors.

There are usually several ground wires connected to the cylinder head coolant flange stud/bolt at the transmission end of the engine. Remove those and clean them. One of those is an important ground from the ECU to the engine. If that is not in place the ECU will fry as it tries to look for a ground. There is also usually a fat flat braided copper wire from a coil bracket bolt to the cylinder head cover -- attaching at the transmission end rear cover bolt. Lots of times that wire gets left off during engine out rebuilds when it drops down along the firewall.

The CE2 fuse and relay panels are substantial and in my experience cause few issues. However the rear electrical connectors on the CE2 panels sometimes work loose especially if the fuse and relay panel is not securely (properly) mounted in its holder. It is easy to reach around behind the panel and snug those connectors in. 

These days pretty good digital multimeters can be purchased for under $20. You could also borrow or rent one from an auto parts place. The less expensive multimeters require manually setting the resistance range so you will have to make sure that you do that. More expensive multimeters are auto ranging. Lately I have been using a multimeter that I got for free with a coupon at Harbor Freight. It seems to do the job testing for voltage and continuity. If I want great accuracy then I get out my more expensive model. 

I have also seen some issues with the connector at the airflow sensor -- usually because it is loose. 

Oh, I generally have tried to replace ECU's with an identical part number -- meaning the last two letters are the same -- the first numbers are always the same. However, in theory, another Digifant ECU of the same manufacturer should work as long as it has the correct number of connectors. Those letters have to mean something. There were also some ECU updates along the way which have different PN's for the same car. A dealer parts department or someone with ETKA (a VW Parts Program) could probably tell you which letters might signify updated ECUs for your car. 

Just a few thoughts -- hope they help solve the issue(s) with your car. FR


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