hally

Hi,

Its was a cold and misty morning, say 3 Degrees C. (The coldest conditions I have recently driven the car in)
Initially the car starts and is running fine. After about 10mins cruising on the highway in 5th gear the car stumbles, the digital readout on the o2 sensor has changed to show a consistent rich condition, high 0.8's. (usually once warmed up it justs jumps around when in closed loop, as it was doing prior to stumbling)
I pull over, switch off and restart the car, everything is OK for a while then it happens again.
This time I cruise in 4th gear at a higher rpm and I experience no problems for the rest of trip, had a good day including setting a PB at the club sprint event that I was heading to and pulling on my Boxter S nemisis down the straights (thanks to the guru chip upgrade!).
Interestingly I've adjusted my manual boost controller so that peak boost was 15psi, however on this cold morning I was seeing 17psi.

I don't seem to have any significant vaccum or boost leaks, cold at ~900rpm my autometer gauge reads 17psi vacuum, and on boost as I said I'm seeing 17psi tapering off above 5000rpm as typical with a stock turbo & intake etc.

I wish I had thought to look at my temperature gauge, as I am now thinking that maybe the thermostat is malfunctioning in the cold conditions causing the cold engine fuel enrichment to be triggered.

The o2 sensor seems to be working as it was displaying a voltage consistent with the rich condition that caused the stumbling.

Maybe the air temp sensor in the AFM could be faulty also, but as I understand it, this is not refered to unless the enrichment fuel maps are triggered by a cold engine temperature.

I will go for another drive on a cold night and see if I can reproduce the problem.

any ideas on my problem?
cheers

Jaak Lepson

Hally ... test the AFM by placing jumpers between terminals 3 + DC and terminal 4 - ground (earth) from the AFM and the terminal plug. Remove the air filter and with the ignition on (car not running) slowly push the flapper valve open with something plastic. The voltage should rise with no abrupt voltage spikes to read +4.5 VDC from around 0.245 VDC.

There should be no abrupt voltage spikes. If there are, then the AFM is faulty and should be changed.

Hope this helps,
Jaak Lepson

hally

Thanks Jaak,

I'll test out my AFM as you suggested. Hopefully its faulty that would give me a good excuse to upgrade to a MAP or MAF. (-: