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Discussion Starter · #1 ·
I've been fighting a very bad CIS-E hesitation in my 89 GTI 16valve for about a year. I use the car for Rallycross and the problem has recently gotten a lot worse.
First, so you know I'm not cheating on this test, I do have the Bentley and I did perform all the electrical tests - they passed. I've replaced all vacuum lines that are still on the car and checked the intake tube and boots for cracks. It's got an entirely new fuel system from the lift pump all the way through to new injectors and o-rings. I've removed, disassembled and cleaned the fuel distributor twice, I've aligned the intake plate. The problem was not affected by anything I did.
I recently purchased the VW Harness that allows me to monitor the current at the DPR on the fuel distributor. I read up on what I should see on the ammeter during operation and how to adjust it. As expected, it read 0.00ma and didn't change when I revved the engine. That meant it was too rich. So I started adjusting the 3mm allen head adjuster behind the fuel distributor a little at a time to see if I could get the ammeter to change. At apprx 3 turns counterclockwise I suddenly got a response on the ammeter. Instead of the 5ma I was looking for I got 20ma. It seemed to "bottom out" around 12ma and increase when I adjusted either way. But the motor was running great. No hesitation at all. I'm like all patting myself on the back and giving myself air high fives, when I disconnected the ammeter and the engine died. Uh, wtf? Tried to start the car and could barely get it to run. I hooked up the ammeter to see what the DPR was reading, jumped in and it started right up and ran smooth. Just to test, I turned off the ammeter and the car died.
I've had this problem long enough that I'm willing to buy a cheap ammeter and duct tape it in the rain tray if that's what it takes to make the car run right, but I'd like some other opinions on what the problem might be. Any ideas?
 

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I have a 30 year old meter that is rated at +- 1.5% accuracy of the displayed value. So at 10mA it is at worst case only 0.2mA off. My meter did not cause me problems like you are having. So my guess is that your meter has too much resistance and that it is throwing off the current draw of the circuit. Try a different meter.

Strapping a cheap meter in the car might fix the partial throttle "E" portion of CIS-E but your full throttle CIS mixture might end up being way off. If you don't already know, at full throttle the ECU ignores the oxygen sensor function and relies solely on that 3mm screw being set to the correct mixture, called "idle mixture" in the Bentley. At non-full throttle the ECU uses the oxygen sensor to adjust the DPR current until the oxygen sensor is hovering around stoichiometric. If the oxygen sensor reads lean the current is increased, if rich the current is decreased. The test/adjustment you are doing assumes the oxygen sensor signal (and CTS) are working correctly. If so then that adjustment just happens to also dial in the CIS "idle mixture" (full throttle mechanical mixture).
 

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I had a problem with my 16V engine as it would go very lean when you opened the throttle. Even going full throttle would not help.
I used a wideband O2 meter to determine this.
I removed the DPR and made small adjustments to it. About 1 /4 turn at a time, sometimes less!

I think I ended up turning the screw a total of 1 full turn CW to get the A/F ratio correct for power.
I see something between 12 and 13 to 1 under hard acceleration.

I would suggest that you get a wideband O2 meter installed.
Then you won't need the amp meter but will be able to see the results of any adjustments to the DPR via the meter.

Making changes as large as you have to the DPR will have to be undone.
You engine ran OK before but with a slight hiccup.
You should only have required a small change to the DPR to correct this.
 

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Discussion Starter · #4 ·
It isn't running okay and it is way more than a hiccup. When it takes 30 seconds or more to get the engine to rev high enough to leave a stop sign there's a real problem. I worked around it by revving high enough to launch and limiting time not at full throttle. That translates in to going through corners double clutching to keep the revs up so I wouldn't just bog down and roll sputtering across the finish line 20 seconds after everyone else. The wideband O2 sensor is a great idea but I don't want to throw a couple hundred dollars at troubleshooting if I don't have to.
I know 3 turns in any direction is not right but the point I was trying to make was that adding an ammeter to the DPR circuit allowed me to adjust the engine to run normally. Without the ammeter in the circuit no amount of adjustment made it run right. Can anyone tell me theoretically why that is happening? I'm suspecting a bad OXS computer because everything else I've checked statically is good.
 

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I thought of something else besides what I said earlier. If there is resistance in your test harness that could throw things off. Use your meter to test it.
 

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An ammeter simply runs inline with whatever circuit, measuring current. If you still have it connected, but now turn the meter off, it will not be a closed circuit anymore (ie no power to the dpr and you run lean to the point of possibly stalling out).

I'm not exactly following with what you ended up seeing when you adjusted your mixture. It should oscillate around 10ma, pretty quickly and smoothly, and not more than 1.5-2ma in either direction. Vacuum/intake leaks and o2 sensor are generally suspect
 

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Did you set everything according to the Bentley manual?

I put a rebuilt Fuel Distributor in my Scirocco and couldn't get it to run at the specified settings. I ended up cranking the CO adjustment 2 or 3 full turns. I think it was clockwise. Anyhow, I needed to get it running to get it out of my Mom's garage. I got it running, just at a Differential Regulator Current of 0.

Last year, I figured out I needed to purge or bleed the fuel system to get it running right. I suddenly had an epiphany while reading somewhere how to bleed off fuel pressure before opening the system.

The steps I came up with are not in the Bentley or any other manual that I know of. I think you are just "supposed to know you have to bleed it", but I sure didn't. Maybe in a perfect world the system would bleed the air out by itself within a few minutes. Of course, you have to get it running first for that to happen.

I set everything BACK to the default settings. Purged the air and it worked like a champ. Even passed emissions testing with flying colors.

The OP of the following thread said he didn't mess with the settings, but did replace his Fuel Filter, so I didn't suggest he normalize the settings.

Set the Control Plunger basic adjustment, the Sensor Plate position and the Air Flow Sensor basic adjustment.

I put the steps I came up with to bleed the system in post 4 of the following thread. Start at step 1:

http://forums.vwvortex.com/showthread.php?7194077-88-Scirocco-16v-idling-and-fuel-issues


There is also a simple way to bleed off fuel pressure for safety, but you might want to make a harness. (It's easier with a purpose-built harness.) I can post that next time if you want.


Good luck.

Sincerely,

Eric
 

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There is no bleeding sequence for CIS or CIS-e. I have never read in any factory manual that indicates there is one. Knowing how this system works, it is self bleeding. There is only a bleeding sequence where air can be 'trapped' in a circuit where there is no way to get out. Such as a brake lines or clutch lines.

Releasing the fuel pressure before you work on the car is just a good thing to do to prevent fuel mist catching fire or get in your eye. If we all read and followed the safety requirements in everything we did in life, we would never get anything done. Can you imagine kids on a play ground? Take the normal precautions that you would normally take while doing anything.
 

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I thought I stumbled on it, but found the reference when I was looking up something else just now.

On page 93 of Volkswagen Water-cooled, Frond-Drive performance Handbook by Greg Raven, it says:

"One technique that might save you a few hours of time is bleeding the air from your fuel injection system. If you have any of the fuel lines apart for any reason, the sytem might not be able to prime itself once you get everything back together. To purge the air from the system you will need to bridge the fuel pump relay using a jumper wire. With the fuel pump running, reach underneath the airflow housing (you will need to unclip the air filter housing to do this) and push up on the air sensor plate until you hear gasoline squeaking from the injectors.

Do not get too carried away with this, as you can flood the motor. You need to do it only long enough to get the fuel into the injector lines. After that, the fuel injection should be able to clear itself. In a pinch, you can even use this to get your car running again if it vapor locks in the heat." *


* Volkswagen Water-Cooled, Front-Drive Performance Handbook. pg 93. © Greg Raven, 1987
 

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There is always someone that will right something, but I still stand by that there I have never seen a 'Factory' bleeding statement with CIS or CISe. It is self bleeding. When the air flow plate is opened [up or down depending on the manufacturer], the fuel will be pushed out to the fuel injectors. Either you open the plate or the engine does, both accomplish the same thing.

I would definitely heed the comment about flooding the engine. Do it too much and your hydro lock the engine.
 

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Discussion Starter · #13 ·
I forgot to update this thread when I found and fixed the problem(s).

Fix #1: Bad connector. I forget which person said there might be resistance in the wire but they were right. The connector on the side of the fuel distributor had some resistance. It still passed a continuity test, but had a few ohms and resistance would fluctuate when the wire was moved around. It always had continuity, but it also had some resistance. Using the ammeter bypassed the problem. Fixed that.

Fix #2: Blown resistor on input of computer. This was the real problem all along. I opened the computer and tested components. A low ohm high wattage resistor was open. The timing wouldn't electronically advance because the computer wasn't responding to the inputs it was getting. I suspect it was blown when the coil was removed/replaced. The Bentley diagram is opposite the polarity of the coil I have.

The car runs great now. I picked up a couple of seconds per run and it's actually pretty competitive.
 
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