# CIS-E running lean!



## jimbbski (Jun 3, 2007)

I can't seem to figure out what to do here.
I have a 1988 16V Scriocco that will idle OK but when you try to drive it the A:F ratio goes way lean!
At idle the A/F is at 14.5 with some drift up and down.

I am using a AEM wide band O2 & meter to track the A/F ratio and using a narrow band output from the AEM unit to feed the ECU.
Any throttle input causes the A/F to go way lean. Full throttle or nearly so results in a 18:1 or higher A/F ratio! The AEM meter only goes up to 18:1.

Additional info on the engine:
Just rebuilt with 10.5:1 pistons and a Euro spec intake cam, the exhaust is stock.
The engine is not the issue, something is messed up with the fuel injection system.
I keep looking at the DPR. Would the cam change cause that much of a problem here and require an adjustment there?
The full throttle switch was just replaced so I know that is working.

Any suggestions?

Most people post here about an engine running to rich, I wish!


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## nbvwfan (Aug 15, 2007)

Sounds like the DPR is not working.
Do you have the ~5ma at the DPR via a test harness. If oyu have not current even when tripping the idle switch and WOT, then you need to track down the wiring or replace the DPR.
It sounds like the system is running purely mechanically in which case the A/F you describe is what I have seen.


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## jimbbski (Jun 3, 2007)

I made a test harness but when I placed it in line the car wouldn't even start.
I have to go back to see if I messed up and crossed the wires when I made the harness.

It would seem to me that a fault in a wire is more likely then a bad DPR.
I had a alt. "exciter" wire fault that caused the alt. to not charge the battery. 


I do have another DPR from an old fuel dist. that I picked up some years ago.
I may try it out if the one I have ends up being no good.
What I'm most likely to do though is try to get the best price on a new one which is expensive no matter who sells them.

I have read that Bosch has stopped making them, not sure about that but it wouldn't surprise me.

I'm open to any other suggestions.
I just don't "get" CIS. To some people it's comes easy.
I have worked on late 80's through early 00's Fords and I have no problems with fixing their fuel injection systems.


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## nbvwfan (Aug 15, 2007)

It seems like you have a pretty good handle on it.
My guess is you have something horked up in the wiring and/or your WOT switch is faulty.
I have a few DPR's and they all have been in working condition, as they are just a coil that controls a flow orifice plate.
Maybe yours is not set right but the tiny screw inside is tricky to get perfect.
Considering you have a wideband you can dial it in with some trial and error.
I cannot remember the number of turns "out" from seated they are calibrated to, maybe 2 turns CCW, but with your WB you could get a reference.
Inside the DPR, CW richens the base electrical metering and CCW leans it, it does have an effect on mechanical base mixture as well since it effects the upper/lower chamber pressure delta.
I'd try tracking down if you have a faulty electrical connection first though.
Good luck.


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## jimbbski (Jun 3, 2007)

Well I did have time to go back and check my test harness and found that I messed up and crossed the wires.
So I will have to cut the wires and re-solder them correctly. 
Then maybe I can test the DPR.


I'll keep posting here as I work on it.


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## kwak (Apr 7, 2005)

jimbbski said:


> I just don't "get" CIS. To some people it's comes easy.


CIS is mechanical fuel injection. As the airflow plate lifts up, it lifts a plunger inside of the fuel distributor to add more fuel. That part of it is simple. CIS-E adds electronic mixture adjustment which is controlled by the computer. The electronic part looks at engine temp, idle switch, WOT (wide open throttle) switch, oxygen sensor, etc. The computer then adjust the signal to the DPR to either add or reduce fuel for that condition.

The mechanical part of the mixture adjustment is called "idle mixture" by the Bentley manual. It seems to be called this because the setup procedure is done at idle. But this mechanical adjustment is used through the whole RPM range.

Excluding startup, the ECU has 3 modes: idle, normal running, and WOT. In idle mode, not only is the computer controlling the fuel adjustment, it also controls the idle air stabilizer valve (ISV).

It is really best to look in the Bentley manual and walk through the test procedures for CIS-E.

At idle, check the signal to the DPR and make sure it is in range. Check the ISV and make sure it is in range.

At idle, open the throttle blade just enough to deactivate the idle switch. When you do this the engine should not change - mixture should not change. Check if the DPR is still within range.

At full throttle the computer stops electronically adjusting the mixture and instead goes to a fixed DPR enrichment value. That means the injection is running as mechanical injection only. If the AFR is off at this point the only adjustment is mechanical (the "idle mixture" screw).

If the idle mixture screw is off, the computer in idle mode and normal running is trying to electronically correct the mixture value. It cannot do any correction at WOT.


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## jimbbski (Jun 3, 2007)

I finally got around to fooling with the car today.
I tried a few things that raised more questions and answered a few others.

First: The idle and full throttle switches are functional. I tested them with an OHM meter and they both work.
I tested the circuit at the plug and the center wire is providing power and when I measure current flow I get it at both of the outer leads.
That is center lead to either outer through the volt meter.

Now with the engine running and warmed up I opened the throttle a bit, enough to open the idle switch and then manually closed the full throttle switch.
I did this to test if the DPR was doing anything. I got no change in the engine.

I changed the DPR to one that I had off a spare fuel distributor and again no change in how the engine ran. 

I will be making up a DPR test harness tonight and then test the current through the DPR.
This should tell me if the original DPR and/or the spare are any good.

The engine starts fine. 
Upon startup the idle comes up to "fast idle" after a few seconds.
And the A/F ratio drops into the rich range until the engine warms up.

I have set the A/F idle ratio on the rich side (14-13:1) .
Now as soon as I open the throttle the engine goes way lean.
This happens if the car is being driven or sitting in the garage.
If I hold the throttle at some point steady the A/F ratio drops from way high to something reasonable, like 16-15:1.

At this point baring finding something weird I am going to assume that the DPR is the problem.
A closed full throttle switch is supposed to cause the ECU to send a preset signal to the DPR to go full rich.
This is not happening which is the main reason for my feelings on the DPR at fault. 
I will test the current to the DPR as soon as I can but I can see no other reason for the very LEAN condition of the fuel injection.


Any comments or advise are welcomed.


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## kwak (Apr 7, 2005)

I would assume the "idle mixture" is out of adjustment before assuming a bad DPR. Measuring the signal sent to the DPR is the first thing to check.

Your airflow measuring box might also have a potentiometer mounted on the side of it. It is used to add additional fuel when the throttle is opened (when the airflow plate lifts quickly). If you don't have a Bentley manual yet check this link: *Cold Acceleration Enrichment*.


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## jimbbski (Jun 3, 2007)

Now my problem is not Cold Acceleration Enrichment.
The engine is fully warmed up when the lean condition occurs.

Now an update.

I was checking out the DPR and a spare one taken off a fuel dizzy that I picked up some years ago while parting out a Scriocco.

The Bentley said that the OHM reading on these units should be between 17-20 OHMs.
Both of mine came to 19.7-19.9, so their in the correct range.
I tired to read the amps -/+ going to the DPR but for some reason my meter/s wouldn't show anything.

The fuel pressure was within spec. 
I was left with the answer that both of my DPRs are OK but out of range for the state of the engine as it now exists.

That left me with the need to remove the DPR, remove the cover screw on the adjustment set screw.
I did this and using a 2 MM allen wrench I turned the screw about 1/4 turn. 
I re-installed the DPR, started the engine and then re-adjusted the A/F ratio as it was way rich at idle now.
The engine sounded and acted way better then before.
Before when I open the throttle quickly the engine hesitated and sounded choked with the A/F meter showing off scale lean.
Now the engine revved up and sounded like it wanted to rev.

I let the engine cool and removed the DPR and made a further adjustment, this time 1/8 turn.

The engine sounded even better. Now when I cracked open the throttle it sounded like the race engine that is supposed to be.

This evening, after dark I took the car out for a quick test drive.
While it needs a bit more tuning and further check overs the engine much better!
Running through the first 3 gears using full throttle the engine revs quickly, the car feels faster then before, and sounds good doing it.

I don't expect to see good weather here in the Chicago area to do any tests with it other then a quick blast up and down a nearby highway frontage road.

The thing is I have now confirmed that all of the CIS-E systems are working correctly, except for perhaps the idle bypass valve.
The DPR just needed to be adjusted to add the fuel the engine needed.
I had been just adjusting the fuel distributor but was never able to achieve the A/F ratio I felt the engine required for road racing. 
Now with the higher compression and bigger cam, along with other minor mods more fuel was needed than what the system could provide as set.


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## nbvwfan (Aug 15, 2007)

_The DPR just needed to be adjusted to add the fuel the engine needed._

This was the key and what I found I had to fool with on mine but in the opposite end due to the "Air Pump" of the G-Lader.
From what I remember ~1/4 CW ends up dropping A/F about a point. So it seems you have found the margin the big breathing cams and intake needed by setting the internal gate inside the DPR and unlocked one more of the secrets of CIS-E.

Glad to hear you got things in better shape.
:thumbup:


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