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Bad idle, rich, wrong fault codes... Bad ECU? 700 1989

posted by  someone claiming to be andrew on  Mon Jan 27 17:55 CST 2003 [RELATED]

740GL 1989 (B230F, LH 2.4)
1. Running very rich (smelly, but no smoke), uneven idle - from 350 (almost dying) to 1000RPM, engine shakes alot at idle.

2. As soon as it starts, the ECU sets 2 wrong fault codes:

- 312 Signal missing for knock-related fuel enrichment, Wiring break between EZK terminal 4 and FI #28 - checked wiring - OK, measured 0.7V at terminal 28 at ECU (unplugged) - so the fault code is wrong!

- 213 Throttle switch full load setting faulty or grounding short, Wiring fault to TPS or TPS failure - checked TPS - OK, checked wiring - OK, so thats wrong too!

So far I replaced O2 sensor and FPR, temp sensor checks OK, cleaned throttle body. From cold the car starts nice and idles at about 1000rpm in neutral or 800 in drive. After 2-3 min. the idle drops down and starts moving fast between 3500-700rpm. If I disconnect the fuel pump (from the connector next to the fuses), the idle goes right back to 1000rpm and the car runs for about 5-6 sec. before dying. If I reconnect the pump before the car dies - the idle starts jumping around again.

After driving for about 10 min. the check engine light comes on and there is a new code - 231 Fuel trim (lambda control) too lean or too rich at part load.

Another thing I noticed (may be unrelated) - if I drive slowly (20-25mph) the speedo doesnt move at all. I have to go over 30 for it to start showing the speed.

Does all this sound as bad ECU (I hope not...)? I have one of "those" #561s.






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