# CIS-E leaning out in high RPMs.



## O 16581 72452 5 (Sep 15, 2006)

This is a 2.0 swapped Rabbit, originally carb'd so there's some things not factory intended with the swap. I've unhooked the O2 sensor and drove the car around with a multimeter hooked up to try to diagnose my car losing power in higher RPMs.

I don't have a tach, so i can't say the exact RPMs, but i'd say above 4,500-5,000 the volts start dropping off until somewhere near redline when it hits 0 volts.

Idle and part throttle is rich, even if i have it running at .5 volts for idle, it'll be in the .8s while driving. I now have it at .8 idle and in the 8s and 9s in part throttle to compensate for it leaning at high RPMs, but it still leans out before redline. Until mid-high RPMs, the A/F never leaves the 8s.

What's going on here? Is there a way to enrich high RPMs only?


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## ps2375 (Aug 13, 2003)

You might have better luck seeing actual AFR's with a wide-band sensor and controller and gauge. I think CIS-e is known to do this, this is why the enrichment add-on was brought about. We didn't have this issue with CIS Basic, but we had a stock motor and only went to about 6500rpm at the most.


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## O 16581 72452 5 (Sep 15, 2006)

I don't really see a point in a wideband (yes, i've tuned with them). I can tell exactly what's going on with a multimeter hooked up to my narrowband. When it starts sputtering at under .2 volts, i know it's lean.


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## ps2375 (Aug 13, 2003)

If you have tuned with a WB, then you must know a NB can only tell you 2 things, (1) it's rich and (2)it's lean. Not how rich or how lean, by a lot or by a little. Almost useless.


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## WaterWheels (Aug 14, 2005)

Not real sure about what you are doing here so maybe you can expand a little on just how you are doing things. CIS-e if you remove the O2 sensor from the picture the fuel computer sends a fixed signal, ~10mA, to the diferential pressure regulator. This will allow you to drive the car until you "get it fixed". Even if you adjust the idle mixture, it works kind of like basic CIS with no O2 sensor, to a richer idle the system is not adjusting the mixture as the engine conditions change and will go lean.

On another hand, I hope it is not at the DPR that you are taking this reading?


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## O 16581 72452 5 (Sep 15, 2006)

It basically runs the same with or without an O2, i removed the O2 signal wire and put my voltage probe in it for my readings. Figured i could get a good base reading from doing this and tune to make it run near what it should without an O2 to "fine tune" itself.

Atleast this is what i've done in the past when tuning turbo cars with wideband, but maybe i'm on the wrong page trying to do this with CIS.

Regardless if i have the O2 hooked up or not, it's wanting to lean out in high RPMs. I've measured voltage with the O2 hooked up at idle and i have to tune the fuel screw rich for the high RPMs to even want to think about not sputtering.


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## O 16581 72452 5 (Sep 15, 2006)

And i used to think narrowbands were useless too until i hooked up a multimeter to mine and measured the voltage on pulls/idle. Anything under .2 sputters lean and anything above about .9 starts to sputter rich. I read ideal tuning on a narrowband was .5, anything above or below is rich/lean. Car idles the best when it's doing a .5 volt idle. I can't say narrowband is inaccurate any more after this experience.


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## redGTInj (Jul 6, 2003)

fuel enrichment module from TT or autotech


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## ps2375 (Aug 13, 2003)

O 16581 72452 5 said:


> I can't say narrowband is inaccurate any more after this experience.


It may not be inaccurate, but it is not very good at telling you how rich or how lean the motor is, the slope of the output from "X1" AFR to "X2" AFR is steep and thus the actual difference in voltage is very small or "narrow", hence the name.


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## nbvwfan (Aug 15, 2007)

With it unhooked the computer maps to a fixed input of .58V.
Your car is leaning out due to the mechanical parameters of the metering cone, fuel distributor, the the negation of a O2 voltage signal.
If you have a 2.0 16V running off an 1.8 8V fuel meter, you will have this exact scenario, you are running out of sensor plate lift, slit opening, or plunger travel.
Plug the O2 back in, and let us know more details of the setup.
I think you could get more fuel if you tune the DPR, but it is not recommended unless you know the ma signal and relationship to lean/rich in CIS-E
If you have worked with a WB, then put one in.
The signal of the NB is not telling you more than rich/ideal and lean.


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## nbvwfan (Aug 15, 2007)

redGTInj said:


> fuel enrichment module from TT or autotech


^ Just get this


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## O 16581 72452 5 (Sep 15, 2006)

Yeah, i'm thinking fuel enrichment module.


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## redGTInj (Jul 6, 2003)

its proven... i made 181 to the wheels on Jetronic it works :thumbup:


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## O 16581 72452 5 (Sep 15, 2006)

Jesus, that's impressive.

But for now i moved to Colorado and the elevation fixed the problem...well, until the car just completely died. Now i have new worries.


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