# cis help please



## bobelon (Oct 19, 2010)

We have '90 (federal) Golf that intermitently runs rich, seemingly on 2 cyl. Black smoke exhaust and poor power. Usually it clears up after a few min. It can happen when cold or hot. I suspect the cpu as I had a Mercedes V8 that had similar problem dumping raw fuel on one bank and a new cpu solved the problem. Am I on the right track? Could a bad coolant temp sensor make it run this rich? On two cyl.s? Where can I get a rebuilt cpu reasonably?


----------



## ziddey (Apr 16, 2006)

90 federal would be digifant2, not cis.

digifant2 runs off the cts, o2s, and afm pretty much.

I'm not sure how much digifant2 enrichens based on cts signal, but I do know from personal experience that a bad o2 signal can make the car run extremely rich.

You can try unplugging the o2 sensor and seeing if the problem persists.


Are we talking rich when on the pedal? Rich at idle? Idle switch is also something to check, although I don't believe it could cause the issues you're talking about.


How are your ignition components?


----------



## WaterWheels (Aug 14, 2005)

Just a friendly side note as this is a good example. Many countries have different names or slang terms for different models, federal, regular, clipper, etc. It is most often not known by members from other countries what these models have as far as running gear or options or any other stuff. It would be real helpful, and maybe get more responses, if the car was to be described more in detail. This site does happen to be US/Canada heavy so people from places like the UK or South Africa should think about describing their engine/transmission set-ups in more detail to get more help. Just a thought.

If this does use Digifant then yes, swap in a new coolant temperature sender as it can have effects like this if bad. The CPU (ECU) can also be bad or the air sensor too, but the CTS is cheap and easy to do before going deeper.


----------



## bobelon (Oct 19, 2010)

*golf help*

By "federal" I meant "not California". It was made in Mexico and imported to Hawaii. Anyway I replaced the cts and drove it for a couple hunnert miles w/o any problems. It first started missing after only about 15 min. of in town driving. We stopped for coffee and when we continued on it was fine. Next episode was at fwy. speed after about half an hour. Missing and poor power - continued by using more throttle but not wide open. Suddenly it cleared up and about 45min. later same problem occured. Pulled off fwy and at idyl it seemed to be running on two cyls. and pouring out black smoke. Turned it off and let it sit 1/2 hr., did locate a small fuel leak - someone stripped the screw in the fuel rail for testing fuel pressure. Replaced the cts and that's where we are now. Hope this fixed it. What is the default if I unplug the cts and or o2 sensor? Thanks for the ideas.


----------



## bobelon (Oct 19, 2010)

*more golf/jetta stuff*

The ignition system, cap, rotor, wires, plugs - new. The motor is the plane Jane 8 valve, 1.8 L boring Rabbit thing.


----------



## ziddey (Apr 16, 2006)

have you checked injector spray pattern?


----------



## bobelon (Oct 19, 2010)

That is beyond my capabilities but does not seem it would be an intermitent problem.


----------



## bobelon (Oct 19, 2010)

*problem fixed*

Just completed a 1200 mile trip - the damn thing never skipped a beat. Either the cts or the fuel leak appears to have been the problem.


----------

