Hi
I get an occaisonal fault with flat spot on take off - loads of people have reported it, and consensus seems to be Idle Control Valve playing up. I tested mine yesterday using the Haynes (!) figues. They say check the resistance of the valve, mine checks out ok. i.e. outer terminals c. 40 ohms, centre to outside terminal 20.4 and 19.6 (roughly 20 each). Haynes says check for voltage on ICV wiring with ignition on - I have battery voltage to centre terminal, 9.8 volts to one outside terminal, but only 5.6 volts to the other outside terminal (book says both should be around 10 volts). check was with engine cold. does this mean my ECU is faulty?
I'm not an auto electrician, so any advice very gratefully received. I have spare ECU, came from 1989 320i like mine, has same Bosch number. Can I just fit this in, or will the 'memory' values in the new ECU chip cause problems?
Thanks folks (Especially Brian Moore if you're watching, cos I know you know your stuff!!!)
Idle Control Valve - electrical values? HELP!!!
Moderator: martauto
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Treeman612
- E30 Zone Newbie
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- Location: Newbury, Berks
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Brianmoooore
- E30 Zone Team Member
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I've got the resistance measurements I took off an 89 325 recorded in my E30 folder. 1-2 20.4ohms, and 2-3 18.9 ohms.
You really need to get your hands on a known good idle valve to check by substitution.
You can swap the ECUs over if you like, but ECU problems are rare. It will take about 50 miles or so of driving for the new ECU to settle down.
I think I would suspect the air flow meter before the ICV though.
Check the throttle position switch as well.
Problem with occasional faults like this, is you can test the faulty part and it may check out OK, if it's behaving itself at that particular moment.
You really need to get your hands on a known good idle valve to check by substitution.
You can swap the ECUs over if you like, but ECU problems are rare. It will take about 50 miles or so of driving for the new ECU to settle down.
I think I would suspect the air flow meter before the ICV though.
Check the throttle position switch as well.
Problem with occasional faults like this, is you can test the faulty part and it may check out OK, if it's behaving itself at that particular moment.
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Treeman612
- E30 Zone Newbie
- Posts: 238
- Joined: Thu Jan 20, 2005 11:00 pm
- Location: Newbury, Berks
Thanks, Brian - looks like my readings are ok on the ICV, but you didn't comment about the low current to one side of the electrical connector, as tested with ignition on - that's why I queried if ECU was faulty. I have Air Valve off known good runner to substitute, so I'll try that. I'll also follow the Haynes instructions to check the TPS (Throttle Position Sensor). As you say, the problem with intermittent faults is exactly that - they never play up when you get an expert to look at it!