# CIS-E & Wideband Fluctuation



## racingti (Jul 10, 2003)

I recently installed a AEM wide band on my 2.0 16v w/ Scirocco CIS-E (exhaust cam for intake and ignition timing set to ~8 degrees BTDC). I am bouncing all over the place on the gauge, never steady even when driving steady. Typically sitting around 15 to 18 on the highway, down to around 12 to 13 when wide open throttle. I do have a TT fuel enrichment module on the car to help the top end and my WOT switch does work. I have my DPR set to about 5 mA. I haven't adjusted anything air meter plate since the install and have never adjusted the DPR.

My buddy's VR6 Turbo was pretty steady on the wideband, but his was OBD1 with a C2 chip.

Couple of questions:
1. Is the CIS-E different, should I expect the gauge to be bouncing all over (kinda like the DPR mA readings)? Or should it be steady?

2. Do you think the TT Fuel enrichment module is hiding a lean issue through the entire range? (I know that all 16v's lean out on the top end without help.)

3. Vacuum leak?


If this normal for CIS-E, let me know, but I feel like the bouncing is not typical. 

Any ideas or suggests are welcome. Thanks.


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## Butcher (Jan 31, 2001)

Unplug the lambda sensor and see if it stables out. 

It is possible that the reaction time for a CIS-e system is much slower and therefore have a bigger cycle than a newer EFI system.


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## kwak (Apr 7, 2005)

When the CIS ECU reads the oxygen sensor the computer sends the mixture to the other side of stoichiometric (14.7). When the mixture is above the ECU sends the mixture to the low side. When it is low it sends it to the high side. This is called closed loop. So yes, it is supposed to be bouncing. 

The issue is how much swing. I never ran a gauge but I used to run one of those DIY LED bar graphs and always saw the "bouncing" but do not know what a mixture gauge might read. But the Bentley manual does have a way to check how much fluctuation there should be. See the DPR current values at idle in the CIS Idle Specification section. Notice that the 8V has a wider range than the 16V.

At WOT the ECU switches out of closed loop and goes with a fixed enrichment value. The signal does not bounce. Is you mixture bouncing at WOT? If so then you have a problem somewhere. It could be as simple as the ECU is not seeing the WOT. Which pins to test on the ECU connector is given in the Electrical Tests (CIS-E) - Control Unit Inputs section of the Bentley.

As an aside, it is worth checking if you fuel enrichment trigger wire is connected to the correct wire of the WOT switch. The Bentley wiring diagram has the wrong color wire for the 87 GTI 16V. I only discovered this back when I had an Autotech fuel enrichment module and was trying to check it was working.

The fuel enrichment module is only supposed to work a WOT and gives a bit higher mixture than the factory ECU -- a higher fixed DPR value.


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## racingti (Jul 10, 2003)

Butcher - I will try unplugging the O2 sensor tonight and let y'all know the results.

kwak - I am expecting the bounce but seems to be a little to much. Tonight I will test the WOT switch with the multi-meter connected to the DPR, that way it runs the signal through the ECU. I would have to say that the TT Fuel Enrichment Module is hooked up correctly because of the substantial added performance felt at higher RPMs. I will also pay attention to the wideband on WOT to see if it is static. 

Thanks guys for the ideas. I will report back.


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## Butcher (Jan 31, 2001)

A weak O2 sensor will cycle slower. 

Again, with a mechanical fuel injection system, it will react slower. That is why CIS-e can no longer pass today's strict emissions tests. Even EFI is not the top of the food chain any more. Now it's direct injection and a wide band sensor, much quicker to make changes.


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## racingti (Jul 10, 2003)

With my wife watching our kids and I got to the Rabbit last between the rain showers. (I am tired of the rain this summer.)

- Used fuel injection cleaner to check for vacuum leaks - no leaks!! 
- Unplugged the O2 sensor and no change at all. (At this point I am kinda expecting a weak O2 sensor, because it is about 10+ yrs old but has probably less then 5,00 miles. Maybe??)

After warming the car up I connect my multi-meter to the DPR, but evidently my connector has gone bad in the last 1-2 yrs. It won't idle when the connector is in place. After 3x times of taking it on and off, I said forget it. :banghead: (I suspect that I should of used some electrical cleaner, but it was late, I was tired and I didn't think of that until this morning.) If doesn't work after cleaning I order another.

I said to myself, let's try to tune with the Wideband Sensor. So went for a drive and adjusted the plate height multiple times. I did all my measurements staying out of WOT and did the same thing every time (cruising and accelerating w/o WOT). 
When ever I would floor it and kick in the WOT the gauge would peg around Rich at 10-11 steady. So WOT switch is working.

1st Drive - No Adjustment - Cruising: bouncing around 15 to 18 and off the scale lean on using the motor to slow down. Acceleration: bouncing around 12 to 13.
2nd Drive - 1/4 turn CCW/Lean - Cruising: bouncing around 16 to 18 and off the scale lean on decelerating.  Acceleration: Bouncing around 12.5 to 14. (felt like it took the pull out of the bottom end, kind of flat.)
3rd Drive - 1/4 turn CW/Rich (from starting point) - Cruising: Bouncing around 14 to 16 with less fluctuation.  Acceleration: Bouncing around 12 to 13 with less fluctuation.
4th Drive - 1/2 turn CW/Rich (from starting point) - Cruising: bouncing around 14 to 15 with *Much* less fluctuation.  Acceleration: Bouncing around 11 to 13 with *Much* less fluctuation.

By the 3rd & 4th drive the Wideband gauge was behaving like I would expect it should, much steadier as I drive and through out the range. So I guess I was running it lean which caused the large range of bouncing. Once I get a new connector or figure out what's going on with mine, I will post up my DPR mA. For now I will continue to tune with the Wideband. :thumbup:


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## kwak (Apr 7, 2005)

It is good to know that the swing is wider when the "idle mixture" is off. Thanks for posting that.

Mixture going very lean with closed throttle and RPM above 1500 is normal. A negative current value is sent to the DPR effectively shutting the fuel off.


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## racingti (Jul 10, 2003)

Well, a little confused here. I was tired the other night and didn't hook up my DPR harness correct. (Plugged in backwards, that is why it wouldn't idle or rev) It ran normal afterward I plugged it back together, though.
Tonight I hooked up the harness and got the multi-meter out. Bing, it worked. A solid 8.1. Yep, no bounce, no hunt, no searching, solid. 



I check my O2 sensor. The picture doesn't show because of the flash. Started the car and the sensor starts climbing. But never above .35v and eventually settles to a solid .01v all at idle and with revs. :thumbdown:



I am figuring my CIS-E O2 sensor is toast.  I am going to buy one tomorrow, hopefully. If it isn't my O2, I am thinking grounds or I fried my DPR in the plug reversal. 
So now I am not sure what normal is on my wideband gauge bouncing. 

Thoughts? Comments? Suggestions? Questions?

Thanks


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## kwak (Apr 7, 2005)

This site http://www.scirocco.org/tech/misc/afgauge/af.html has the DIY mixture meter I made for my car years ago. It reads the O2 signal while it is still plugged in. At the bottom of that page are the values of the O2 sensor.

Back up a bit to get a better understanding of what is happening when.

Previously without the DPR test harness your wideband was showing the mixture was oscillating. This is only possible if the O2 sensor is working correctly. Is the wideband still oscillating?

Was either your DPR test or O2 sensor test done with the O2 sensor unplugged? If so then it makes perfect sense that CIS-E defaults to a lean condition since a positive DPR value like 8ma means to richen the mixture.

If the O2 sensor is still plugged in then check two things.

1) What is the value on the wideband when the stock O2 sensor reads 0.01 volts?
2) The Bentley manual in the CIS-E section under "CIS-E Electrical Tests" tells how to check the O2 sensor wiring.


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## racingti (Jul 10, 2003)

_Is the wideband still oscillating?_ -> Yes but not nearly a much.

_Was either your DPR test or O2 sensor test done with the O2 sensor unplugged?_ -> The DPR was tested with the O2 plugged in. The O2 sensor test was done unplugged.

_What is the value on the wideband when the stock O2 sensor reads 0.01 volts?_ -> The wide band was a pretty steady around 14.7. I got this because of the earlier adjustments on the air plate.

Thanks for the help.


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## kwak (Apr 7, 2005)

racingti said:


> The DPR was tested with the O2 plugged in. The O2 sensor test was done unplugged.


OK, this makes sense. When the O2 sensor is plugged in you are getting a small oscillation (good), and a DPR value of 8 (good), and a mixture of 14.7 (good). Back when the idle mixture was off and you had a big oscillation it showed that your ECU, O2 sensor, and DPR are definitely working correctly.

With the O2 sensor unplugged the ECU is not going to know what to do so it makes sense that it removes the fuel enrichment from the DPR and leaves you with the mechanical mixture setting by itself (lean). If you really want to see what the O2 sensor check the value with it plugged in.

So it looks like you have answered #1 in your original post. Now about #2.



racingti said:


> 2. Do you think the TT Fuel enrichment module is hiding a lean issue through the entire range? (I know that all 16v's lean out on the top end without help.)


I believe "lean" here is a relative term and in reality you will find that the mixture is leaner than optimum enrichment for maximum power but not "lean". For example, it you run at just under WOT so the ECU is still running closed loop you have already seen that there is some enrichment going on, but this is not the mixture ideal for maximum power. At WOT when the WOT switch is depressed the ECU goes open loop and sends a fixed (non varying) enrichment value to the DPR. And it uses the same DPR value throughout the RPM range. The TT module just sends a higher fixed DPR value at WOT than the stock value.

To check WOT mixture disable the TT module and run through the RPM range while you keep track of the values on your mixture meter. Then run again with the TT module enabled. This will show you exactly what is going on.


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## racingti (Jul 10, 2003)

*CIS-E &amp; Wideband Fluctuation*

I don't think I am explaining it very well. The DPR reading is a Solid 8.1, with no hunting like normal (7,8,9...7,8,9...). And I can't change the 8.1 mA whether I lean or enrich the mixture at the air plate, it only stays at 8.1 mA. It should change the DPR reading. Thoughts?

I will test my WOT switch with the fuel enrichment module disconnected and connected. See where I am on this. 





Sent from my iPhone using Tapatalk


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## racingti (Jul 10, 2003)

I disconnected my TT Fuel Enrichment Module for the following testing. After 20 min warm-up:

DPR reading still constant 8.1 mA
The plug that attaches to the DPR is reading a constant 8.1 mA
WOT switch makes no change on Multi-meter when triggered still a 8.1 mA
Plugged the DPR back into the fuel distributor while running and idle went from smooth to slowly rising and lowering about 200 RPM.

With O2 plugged in the wideband reads about 14.6 to 14.8.
With O2 unplugged 12 to 13.

Bought, but haven't changed O2 sensor yet. 

I am confused. Thoughts


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## kwak (Apr 7, 2005)

It sounds like you are testing the DPR value with the DPR unplugged. Is that what you are doing? You cannot test the DPR value that way. See CIS-E > Differential Pressure Regulator in the Bentley manual. Most folks get hold of a DPR test harness so they don't have to cut a wire in the factory harness.

If you activate the WOT switch by hand make sure the idle switch is not activated at the same time. Closed throttle mode probably overrides WOT mode. You may also have to add some RPM. I know the Autotech fuel module only activates above 2500 RPM. Don't know if the factory ECU has a certain RPM it needs to be above.

I wonder if the mixture going rich with the O2 sensor unplugged is a safety feature?

[edit: saw your post in the other forum section...] If you are using a DPR harness, test its continuity to make sure the wiring is good. Plugging the DPR connector back in and the idle now fluctuates a little tells me the O2 sensor and DPR are working. But having the fluctuating go away when the test harness is in place tells me something about the DRP test setup is not working.


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## Butcher (Jan 31, 2001)

Its hard to see, but I believe you are testing volts, not amps.


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## racingti (Jul 10, 2003)

Butcher - I think you are right. It's what happens when you are tired after work, kids and can only get out to the car test in the dark with the mosquitos. Hahaha :facepalm:

I still wonder if my O2 sensor was working correctly because of the volts it did show. I pulled the O2 sensor last night to replace it. Going to clean grounds and connectors while in the process. 

Will let y'all know the progress.


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## racingti (Jul 10, 2003)

Update: New 02 sensor. Used the correct multi-meter measurement of mA this time. Set my DPR to about 4 mA. Idling smooth with a 14.7 on the wideband. 

Even if my old O2 sensor was good I didn't mind changing it, 40 bucks later (using a '89 Mustang 5.0 O2 sensor and my old wiring). It was 12-14 years old and the rubber boot around the wires was cracked and half gone. 

Now to the drag strip tomorrow to test, if it doesn't rain!!


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