Labman

Sorry for the long post but this is a tricky one.

I have had an intermittent rough idle problem for about a month now. Its most likely an electrical connection problem as its very on/off fine one day, bad the next.

The OBDII diagnostic states:
P0102 MAFF Sensor Low
P0021 Cam Position Sensor - Bank 2 (this is the one to control VVT at back left of engine, not the main one at the front next to the battery)
P0113 Intake Air temp sensor

I've checked everything back to the ECU and all seems fine, only managed to check the Cam sensor when its working so waiting for fault to reappear and check it again. Checked all connections for corrosion and sprayed contact cleaner for good measure, everything was bright and shiney anyway.
The resistance of the cam sensor is 2200Ohms so its not the sensor thats faulty.

When idling poor the MAF signal output is:
0.7v ignition on engine not running
1.73v idling cold, revs about 1400rpm
0.2v idling hot revs 500-600rpm

When idling normally the MAF signal is:
0.7v ignition on engine not running
1.58v idling cold revs about 1400rpm, voltage rises with throtle blips
1.18v idling hot revs about 700rpm

So my questions are, if the cam sensor connection was lost would this cause the ECU to over compensate sending the MAF voltages screwy?
If the MAF is intermittent (has anyone ever come across an intermittent faulty MAF) would this cause the ECU to false trigger the CAM sensor as faulty?

As I said above, I'm yet to test for the Cam sensor when its idling rough, when it goes again it should give me another small clue as to whats going on. I've been checking the wrong one, thought it was the main sensor at the front. durrh.

FYI, car is a totally standard STi8 type UK, recently serviced, new plugs, filters, oil etc. I'm 99% sure I've eliminated all other causes like Idle control valve for instance.
Any thoughts, ideas greatly appreciated.

Cheers

blacrat00

hi had exact same prob, exact, was a cut in the cam sensor cable.
was intermittent, etc on bends and roundabouts.
JJ

Labman

Cheers mate.
I discovered it was a dodgey connection in the engine bay to the cam sensor.
Have given it a clean and so far so good, been fine for the last 3000 miles or so.

blacrat00

thats the usual, i got a company that sells looms and makes looms,

Jap Performance Parts : Home


JJ