# CIS-E suddenly runs pig rich



## chois (May 12, 2000)

OK so after our race on Sunday our car was running fine. Finished 2nd, turned the fastest race lap, ran great. It was running fine as we idled over to impound, ran fine as we pulled it off the scales to the impound area, started fine when we were released 15min later and died 10 ft later.
Then it was damn hard to get restarted and would not idle, requried constant throttle feathering to keep it going, and was spitting and popping. I was able to coax it over to, and on to our trailer, but it just ain't a happy motor.
My first thought is potential failure in coolant temp circuit, which could cause the DPR to go very rich (open circuit = cold). I pulled the WOT connector and cold start injector to make sure it would not get more fuel when I was trying to restart it.
Any other suggestions?
Current Setup:
CIS-E
There is no O2 sensor
There is no knock box
Coolant temp sensor based fuel enrichment (potentiometer in line with sensor, triggered by WOT switch)
The car has run fine like this for several years, so no it is not the lack of either that caused the problem.
It ran fine on the dyno a week earlier with AFR climbing from 12.6-13.6 through the power band (3500-6700rpm)
We have 4 weeks to make it right, any suggestions are appreciated.


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## rorin8v (Oct 15, 2007)

first thought i got was vacuum leak. 
or a sensor going bad.


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## chois (May 12, 2000)

Vacuum leak is one to check, but it seems that would give lean, rather than rich results.
I agree on the sensor - if the CTS fails 'open' it could mess things up. There are not any other sensors (other than the MAF potentiometer) talking to the ecu to worry about.


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## WackyWabbitRacer (Apr 24, 2001)

*Re: CIS-E suddenly runs pig rich (chois)*


_Quote, originally posted by *chois* »_Then it was damn hard to get restarted and would not idle, requried constant throttle feathering to keep it going, and was spitting and popping. I was able to coax it over to, and on to our trailer, but it just ain't a happy motor. 

The symptom sounds very much like a significant vacuum leak causing a lean fuel condition. 
Are you running CIS? If so, the reason that I said a lean condition is because "constant throttle feathering" would cause the Air Sensor Plate to raise. If a CIS engine will not idle, the normal reason is a vacuum leak after the Air Sensor Plate. Spitting & popping are typical indications of a lean mixture.
On the MK1 throttle body, the Air Idle Screw was infamous for becoming loose and dropping out the TB. This causes a condition similar to your symptom. I mention this as I don't know the generation of VW that you are racing.
Cheers, WWR.


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## chois (May 12, 2000)

I did a quick feel around the intake when it first happened and didn't find anything, but I agree with the logic.
Should pull the car off the trailer and look at it tonight or tomorrow night. I will report back what we find.


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## Kanoa9321 (Jun 20, 2002)

*Re: (chois)*

On my Rabbit this exact same thing happened, was fine on track then at idle it was weird but if you gave it alot of gas it was fine. Turned out to be a vacuum leak


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## chois (May 12, 2000)

I will have time to check it out today.


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## chois (May 12, 2000)

Well - that was really weird.
It was not a vacuum leak - I checked in detail, looked, felt, squeezed, pulled every possible connection (I did find that I should replace the brake booster piping very soon). 
Then started it up - same situation - running very rich, and hardly idling.
Pulled the cold start injector connector off, and pulled the CTS plug and jumpered it with a wire.
Sprayed potential leak points with carb cleaner, no difference.
Pulled each plug wire individually - no difference.
It was so rich, I decided to just give the flow plate adjustment a tweak. I started with 1/4 turn ccw, and it seemed to smooth out a bit. So I kept going. I ended up going a full 1-3/8 turns ccw, and it is idling and revving as cleanly as ever.
Next up - I will trigger the enrichment system to see if it is working. All I can think of right now are two possibilities.
1. There was some sort of flow restriction in the system from when I changed injector lines and injectors last month.
2. The fuel enrichment is 'stuck on' making it run with the added fuel I want at WOT when idling.
I will let you know what I find.
Unfortunately this means that all my dyno time 2 weeks ago will need to be repeated to get the fueling right after messing with every part of the system. I realy like the guys at GRD, and Tuan is a great help in tuning the car, but it's a shame to have to invest another day at their shop because of somethign that I let fail on the car...


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## chois (May 12, 2000)

Just ran out and restated fine. Manually switched the fuel enrichment, and got no change - so that is where I will start.


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## WackyWabbitRacer (Apr 24, 2001)

*Re: (chois)*


_Quote, originally posted by *chois* »_It was so rich, I decided to just give the flow plate adjustment a tweak. I started with 1/4 turn ccw, and it seemed to smooth out a bit. So I kept going. I ended up going a full 1-3/8 turns ccw, and it is idling and revving as cleanly as ever.

The idle mixture screw on the fuel distributor should have not changed that much after one race weekend. I believe something else is wrong and the adjustment of the idle mixture screw is compensating for that.
Good luck, WWR.


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## chois (May 12, 2000)

Absolutely, and what we know now is that the problem is in fact running rich, not a vacuum leak.
I am going through the enrichemnt circuit now, and have already found a questionable connection. I will let you know when I find the smoking gun.


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## chois (May 12, 2000)

*Re: (chois)*

OK so here is the full post mortem.
As is so often is the case, this was a self inflicted problem. We used our qualifying session last Sunday to scrub in a fresh set of Hoosiers, for use at a later event. The process is pretty simple, start easy, do progressively faster laps, run one very hard lap, then cool the tires back down, and put them away for a while. I made sure to have an open track for the hot lap - but a miata came out of the pits as I started it and balked me in turn 1. I considered running another hot lap to make up for it, but decided to just get the tires off the car and try to make it up in the race (I didn't - had a great race, ran the fastest laps, made a nice pass on the leader, but gave it back with a dumb mistake). Anyhow when we checked the car over after qualifying the battery was laying on the starter solenoid, and leaning against the brand new radiator







. Yep, I did not propery secure the battery when I put the front end back together weeks earlier. I was super glad that I didn't go for an extra hot lap. All was working OK and we didn't see any pulled wires, so we tightened the battery down and went racing.
The fuel enrichment worked fine during the race, I could feel it kick in every time I tripped the WOT switch under the yellow, but the wire running from the coolant temperature sensor to my potentiometer (and switch, and relay) was pulled enough to break...right as we pulled out of impound (its like the car likes me, could not have happened at a better time







)
Looking at the system, and how I use it, I have decided to remove the CTS from the system all together, and simply run the ECU signal through my potentiometer to ground. The water temp is always up when I use this car and the CTS serves no purpose. I can manually trigger the fuel enrichment during warmup (just like I manually switch the cold start injector now) to fatten things up, and I end up with half the potential failure points in the sysetm - heck only one wire passes through the firewall now http://****************.com/smile/emthup.gif .
So to verify the theory on what went wrong, and to verify how I plan to rewire the car - I took the dash side of the broken connection, and jumpered it to ground. I took my 3mm allen wrench and cranked 1-3/8 turn clockwise, and started the car. It runs great! Just to be sure, I cranked the potentiometer up to a very high resistance and it ran like crap. So yeah it was just a broken CTS signal wire







, and we are ready to go racing again this month. http://****************.com/smile/emthup.gif 
Thanks for the input guys.










_Modified by chois at 5:48 PM 5-3-2008_


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## WackyWabbitRacer (Apr 24, 2001)

*Re: (chois)*

Glad you found the problem http://****************.com/smile/emthup.gif Sometimes the solution is retracing "your steps" after a situation occurs.
Cheers, WWR.


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## Stephen16V (Nov 7, 2006)

Can someone give me a break down on where the wires from the CTS go? Im assuming one goes to the ECU (terminal?) and other to ground?
this is for a 16V with basic CIS from a scirocco. 
I also am suspecting a wire issue, and would love to run the wires directly to they're proper destinations. Seems my car is getting re-wired peice by peice, except Im not making it look pretty at all, just enough to limp home.


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## Longitudinal (Nov 13, 2004)

*Re: (Stephen16V)*


_Quote, originally posted by *Stephen16V* »_this is for a 16V with basic CIS from a scirocco. 


If it is CIS-Basic, there is no CTS. If it is CIS-Lambda from a MKII Scirocco, then there is.
To the OP, why are you deleting the O2S and CTS? Properly adjusted, CIS-E will run great and supply as much fuel as you desire, especially on a naturally aspirated 8V.


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## chois (May 12, 2000)

This is for a race only application, so really driveability is of no concern - I just need it to run right in the conditions we see on track.
I deleted the CTS because I NEVER run the engine at anything other than full operating temperature - thus it never has any impact on what the ecu is doing. I prefer to simplify the wiring path and minimize failure points, while having very direct control of mixture.
I have no O2 because I run the thing open loop all the time anyhow, AND I have at times tested with leaded race fuel.


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## chois (May 12, 2000)

The new setup worked great at Road America on Saturday - we finished 2nd and set a new personal best of 2:52.1.
It failed again on Sunday - cable from potentiometer to ECU got tangled in the steering column coming off track from qualifying and broke. Did a quick fix, but the car was down on power for the race and lost 3 seconds/lap...
Time to get the dash out and tie down all the wires, rewire the fuel enrichment, and go back to the dyno (again....) to set the resistance.


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