FredR

For reasons beyond my comprehension the temp2 sensor when it fails can do so with a fixed resistance at either end of the scale. The numbers you have just advised suggest the temp2 is working just fine given they are modulating with temperature and are of the correct value range. As an FYI the temp2 adjusts the LH and EZK as per temperature value until a temp of 80C is reached and then there are no further corrections added and the thing runs directly off the map settings but then I suspect you probably know that given the tenor of your notes.

The MAF screens can impact the stability of the idle but would not explain your problem. Presumably the screen prevented the plastic from being sucked in completely and causing mechanical damage. The wiring inside the MAF plug can often be age degraded with potential to corrupt the output signal. Short of a MAF calibration check not sure there is much one can rely on- if the unit was rebuilt 5 years ago it should be OK. Given you are NZ based we have a few members probably not too far from you who could perhaps test your MAF in their 928.

That someone was dicking around with your 928 suggests a possible focus area but then if it was running OK previously ...?

Will have to scratch my head a bit more on this one now that we have more info on the table as it were.

matwelli

Thanks Fred,
The plastic bag only went as far as the screeb that it damaged.
I should have a wideband o2 meter turning up on Tuesday (will be happier knowing what the actual fuel mix is doing) and have found someone about 2.5 hours from me who has his 928 in boxes, and may have a maf to try.

Will post up the results of the warm idle tomorrow

FredR

The more you can eliminate the closer you are to solving the issue. Over fuelling [within reason] does not tend to cause pick up issues but under fuelling most certainly does. The trouble with a feedback control loop is that the horse has bolted before the control element is applied- have often wondered why they did not put a sensor on the throttle pedal to apply a correction for acceleration enrichment the split second the right foot gets twitchy.

The WBO2 can only help matters- that hooked up with my ST2 kit gives a valuable insight into what is happening in the motor. If you have not done so already you could try adjusting the CO pot you have such that it is fully rich and see how that impacts matters- it cannot do any harm and might do some good if it is functional. The WBO2 should also help you get a measure of what is happening as you adjust the pot. At idle I look for an AFR of 14. As I understand that gives an optimal CO reading and the best idle. I further understand that the idle stability is effected by reversion pulses and thus why the GT models have a faster idle.

If you did the timing belt are you confident you got the cam timing aligned correctly?

You might also try looking for "dancing fairies" on the HT leads- just run the motor in a coal cellar at night with a new moon! You might also try taking a leak over the HT leads but I really do not recommend that test!

matwelli

Ok, for those still interested
MAF engine off = 1.75 volts
MAF engine at 80 deg C Idling no accessories running = 2.68 volts