Idle and low rev hesitation problems

A

Anonymous

Guest
I've just had a rebuild but think somehow a couple of pipes must have been put on backwards!

I remember before the rebuild when I came to a stop (from high revs) the revs would fall to around 1200 rpm hold for a few seconds and then drop to 900.

Now after the rebuild they fall to around 400 rpm, and then after a few seconds return to 900!

All pipes seem to be connected to something so I guess something has been switched. Anyone got any ideas?
 
A

Anonymous

Guest
checked my lambda sensor. Am getting 1v continously at 2-3000rpm so I guess its running rich (open loop).
Can anyone confirm if this may be the source of my idle problem? I would have thought on the decel closed loop control is used.

The lambda sensor is quite new (4000 miles) but has suffered a blown engine incident. If it was ok can anyone suggest something else to look at before I pay £80 for a new one. I'm ruling out lambda wiring problems since I am getting a voltage reading.
 
A

Anonymous

Guest
I checked my MAF earth at the weekend and it was massively out (should be less than 9mV, it was 30mV!!) When I earthed it I managed to get down to 8mV. Unfortunately it solved nothing.

I was wandering if an earth point could have been missed on rebuild (hence 30mV, I know that prior to rebuild I had 5mV on the middle pin). Does anyone know where the other end of the MAF earth (standard one, middle wire) should go to?

Engine is still running in open loop during half throttle (lambda sensor reads rich), with a flat spot at 2-3000rpm, once I break 4500rpm then all is ok.

I have an apexi SAFC so I know that the MAF and TPS are being read.

checked pipe runs using manual and all looks ok.

ECU still gives a 55 (no fault)

HELP!
 
Fast Guy

Fast Guy

Moderators
Staff member
The ECU supplies the exhaust gas sensor with approx 1v and then measures the output voltage depending on its resistance. If the output voltage is always 1v that may suggest it's faulty (but I aren't too sure) It might be worth getting hold of another known good one to try before you buy. :wink:

I'd check the maf again as that often gives problems with rich running, which it looks like you have low down in the rev range.

Have a check of this picture too.

http://www.gti-r.com/Reference/BoostControls.gif
 
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