Flint

Hi all, I've been trying to resolve an issue that I've been seeing these past few months and so far have no answers. Nor could I find anything on these pages where anyone had had the exact problem.

When my car is cold, I have real issues when rolling off the line. Any more than just the minimum amount of throttle to get the car moving causes sometimes severe surging, causing the car to lurch forward repeatedly. After the car warms up (above the second white line on the temp guage, below the middle), the car runs perfectly normally (or normally for this one, in its state of tune).

Recently I've repaired the known (operative word "known") leaks in the vacuum system and I cleaned the MAF with that MAF cleaner, but those didn't seem to help much (though the car is more responsive when it's fully warmed up!).

The only potential issue I know if is that I lost some ATF when I replaced my radiator, and right before that I had the transmission fully checked and serviced. I think as a result of the low fluid the car sometimes refuses to change up out of first (or whatever gear the Euro automatics start off in), but again, that's after it's warmed up.

I've read up on MAF issues on the JDF Porsche website and it doesn't seem to exhibit those exact problems (though it does have over 150k!)

So, I'm looking for new ideas or anything I may have missed. Thanks for any suggestions!

John Speake

Hi Devin
While the water temperature on the engine is below 60degC or so, the LH operates in open loop mode, because it thinks the O2 sensor isn't hot enough to give good readings. During this warm up time, the fuelling is critically dependant on MAF calibration. If the MAF is badly aged then the mixture will be much too weak. This could cause the symptoms you have.

When water temp gets to 60degC, the O2 loop comes into play, and this hides the MAf errors to some dgree. Euro 16v LH cars are particularly sensitive to MAF ageing. 3% aged and you will have problems....

Flint

Ahhh, thanks John (And I meant JDSPorsche, not JDF!)

I did confirm that the importer did not actually connect the O2 sensor to anything when they federalized it. Is it even possible to attach that or would it make a difference?

Either way, I see an MAF serviceing in my future. (possibly distant unfortunately).

John Speake

Ah ! Well, there is no way to connect an O2 sensor to a Euro 16 LH ECU. (the components for the O2 loop aren't fitted to the Euro LH pcb).

So the scenario I described seems not to apply in your case.

Does the car run properly when hot ? No hesitation, flat spots, sluggish throttle response ? I guess you haven't driven a good Euro to compare - always a problem.

I would suggest you check out temp 2 resistances, hot and cold, as per the W/S manual.

Flint

Well, I guess I haven't compared to a "good" euro, so I'm not sure, it doesn't at the moment seem to hesitate or have flat spots, but I'll have to pay more attention as I drive.

I'll check out the temp II though. Maybe I'll just replace it though... Thanks!

John Speake

The classic MAf aged symptom is a much worse than typical reduction in urge the hotter the engine water temperature and air temperature are.

Do you think the surging when cold is due to a weak mixture, or over rich ? Any clues ?

Suggest you try to adjust idle CO up to 1%. If too weak, turn MAF 3mm adjuter several turns clockwise. If you can't get up to 1% then the MAF needs replacement.

Mrmerlin

Check and add trans fluid before you get to far working your other problems, no need to damage something else