Check engine light

88' Audi 90. Getting C/E light al the timeafter just a few minutes of travel. Mitchell CDs no help and I don't have the big manual. 5 Cyc/5 speed 234K miles. Seems to have lost it's power too, must drop down a
gear lower on hills then in the past. Otherwise runs fine. Any ideas where to start? I can fix GMs and Chryslers but new to Audi.
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Le Mans is keeping me up real late tonight / this morning so thought I would respond now.
SMJ is a great reference: http://www.sjmautotechnik.com /
You should be able to find what you need there.
the first thing to look for is how to pull the codes from the ECU to know what the CEL is complaining about. Could be many things. Knock sensor might be worrying the ECU into retarding the timing. Temperature sensor is a common failure. Could be fuel pressure due to a dirty filter. ....
TonyJ previous 4 T44s N/A 5spd q current 98.5 1.8TQM
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Thanks for the link, I'll look there ASAP. The problem is finding out HOW to obtain the codes, that's what I need. If I knew what type error it is I can fix it OK. I've had car about a year and was running find, then started running bad on wet days, WD40 proved it was the plug wires so I changed them and not got 34.1 MPG instead of 32.3 and pep was back. I later replaced the speedo as the odometer was not advancing and found many bad bulbs in the cluster. After replacing them I noticed the CEL was coming on. I think that was probably one of the bad bulbs, and this problem was there before. Still runs great, 34.1 MPG but SOMETIMES I have to drop at least 1 gear on the same hill I ran in 5th yesterday. Also anyone know which temp sensor is what? There are several and I can't find documentation as to which is exactly for guage, ECU, fan low and high, etc. This is a 88' model 90 5 cyc with 5 speed. Thanks.
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The thermo sensor for the radiator fan is located on the bottom, back of the radiator, just below the lower radiator hose.
The MFTS (Multi function temperature sensor) supplies information to the ECU is typically located just below the place where the upper radiator hose is connected to the block. Above the same location is the temperature sensor for the gage (if I remember correctly).
Some of the I5s had the MFTS located on the rear of the head if you do not find it by the upper radiator hose.
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Codes are retrieved by putting a fuse in the top of the fuel pump relay with the key on for a few seconds, then pull it out. The codes will blink out on the check engine light. You need a manual to identify the codes. Bentley's is a great manual. My "88 90 did the same thing. Knock sensor. Just take it off, clean the surfaces good and put it back on. Be sure not to overtighten it. Torque sensitive. Should work for a while.
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