Pulled my car out of the garage to do a few odd jobs to it and when I fired it back up to put it away the idle was very lumpy. It's always been prone to stalling when cold since I got a mafsim for the apexi pfc but this was different.

Normally it'll rev fine and drive ok and after a minute or so all is well but even when warmed up now it's still the same. When you apply throttle the revs will rise to just over 1k and if you continue to add throttle it gets progressively rough and then stalls.

The commander is showing between 45 and 80 mV for airflow, does that sound about right?

Oh yes, the odd jobs were nothing to do with the engine. I just had to hardwire in a gps camera detector.

Any advice would be greatly appreciated.

Cheers

 

I initially tried a simple multiplication of RPM and MAP to give the MAFSIM output. However, the MAF response to a jab of the throttle was too slow and the PFC lacked the enrichment sensitivity to sort it out.

So there is second calculation that takes TPS reading at high vacuum levels and clips the minimum airflow output according to a lookup table.

The calibration of this lookup table catches the jabs of the throttle as well as the opening of the idle speed control valve on returning to idle. The calibration is a compromise for varying air and coolant temperatures, and compensating for these would make an already complex setup trickier still.

What Andy, Andrew and I found was that despite these difficulties the manners are usually acceptable for the highly tuned cars it is used on, certainly I've seen worse on posh standalones.

If there is a new problem where it is behaving differently then the TPS wiring could be suspect. You can test this by having the ignition on II without starting the engine and seeing if the MAF voltage varies with movements of the throttle. Andy could advise you further knowing the calibration on your car what values you should see.

 

Cheers JB, have replied on 22B.