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Discussion Starter #1
I just bought a 1990 Jetta GLI with a CIS-E Motronic system. The guy I bought it from had the coolant temp sensor unplugged because he said it was bad. When it's unplugged the idle lopes like it's got a hot cam and it runs rich, other than that it runs beautiful...FAST.
I tested the sensor that was in it and it was at about 600 ohms near operating temp, which tells me it was ok, but I went ahead and replaced it anyway. The first time I started it with the new sensor plugged in it barely ran at all. I then decided to disconnect the negative battery cable (with the ignition off) and let it sit for about 10 minutes. I reconnected the - cable and it started right up and ran PERFECT for about two days...idle and all. Then out of the blue it just dogged out on me on the highway. I repeated the process about three times and finally decided to leave it unplugged until I can properly correct the problem

Anyone have any helpful suggestions as to where to start with this?
 

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Re: 2.0 16V headache... (gtiguy_113)

The other question I have is;
Am I going to damage my engine by running it with the sensor unplugged?
 

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Re: 2.0 16V headache... (gtiguy_113)

you shouldn't drive your car when it's running pig rich like that, you can wear out your piston rings, its not good for the cat, and it thins the motor oil out.
I had a similar problem with my 16v and the CTS, but keep in mind my car is CIS-E Jetronic. I had to keep the CTS unplugged to run, but like your car, it would run super rich and the idle was all over the place. It turned out to be my fuel mixture was way off. It was too lean to run with the CTS plugged in, but when unplugged it would just run way rich because the computer thinks the motor is dead cold, so it enriches the mixture. If you leave it unplugged the computer will think the engine is cold all the time. I don't know much about motronic engine managment, so I dont know if any of this will help you. Good luck though http://****************.com/smile/emthup.gif
 

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Re: 2.0 16V headache... (KraftwerkMk1Jetta)

Any input helps a lot, thank you. I am new to motronics myself...more of a early 8v guy.
I was headed in that direction because I noticed that someone had drilled out the tamper proof plug in the fuel dist. The only thing I hesitated about was that it ran beautifully for 2 days after I pulled the ground wire. Started to think I had a bad ground or another bad sensor maybe......Oxy sensor?
 

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Re: 2.0 16V headache... (gtiguy_113)

I've heard that pullinig the neg battery cable on can clear the ECU of any faults but I'm not sure if that's Motronic or Digifant. I would def check all those grounds though for sure http://****************.com/smile/emthup.gif Good luck man, and don't let it get you down http://****************.com/smile/emthup.gif
 

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i bet it is your fuel mixture. the PO prolly was messing w/ the mixture screw in the fuel dizzy to get the car to run w/ the sensor out. then when you put the sensor in the base mixture is way off causing it to act up.
if you do a little research on this site im sure you can get step by step directions on how to adjust your fuel mixture correctly.
good luck
Matt
 

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Re: (littledevil34)

Thanks. I have been tweeking the timing and mixture and I've got it pretty close. I will take it to a local VW mechanic to have it dyno'ed.
Last night I went to put a timing light on it and I was walking by, on my way to shut the car off, and I heard something in the engine bay so I leaned over to listen and a radiator hose burst in my face! It knocked my over and blinded me for about 10 seconds. Once I could see again I took off into a dead run for the kitchen sink to flush my eyes and had my wife take me to emergency.
Turns out I scalded my face and ear area and the WHITES of my eye. I lucked out big time.
WEAR SAFTEY GLASSES!!!!!!!!
 

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Re: (littledevil34)

Good luck with the injury - and good tip on the glasses. Saw a great quote in Autoweek, written by one of their columnists who was blowing brake-caliper pistons out with an air gun. He had suited up in work clothes, heavy gloves, safety glasses AND a motorcycle helmet - to guard against the piston blowing out too fast. His opinion?
"There's always a last time"
Good luck and get well quick.
 

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Discussion Starter #11
Thanks everyone.
My eye is nearly healed...fastest healing organ in the body the doc says. I do have some ugly burns around my eyelid and nose area though.
The hose that broke was a T shaped hose that was connected to the waterpump, oil cooler, and the flange on the front of the block. It burst at the side and shot straight up into my face. The fan is cycling fine...after-run works good too.
I am replacing the whole works this weekend so I can get on with the air/fuel mixture tweekin'.
"There's always a last time" -WORDS TO LIVE BY
 
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