Fix rough idle on DME car without an exhaust analyzer?

[oly]

I want to fix a rough idle problem on my stock 3.2 using the factory procedure for setting the idle mixture control and idle speed (Allan Caldwell article in this September's Panorama). The procedure says to use an exhaust analyzer. My questions are:

1. Is there anyway to do this job without the analyzer? I've seen posts here for non-analyzer procedures on CIS cars so it seems like somebody might have a similar work around for DME cars.

2. If the answer to 1. is “no”, does anybody have any recommendations for an analyzer that costs less than $100? Can I just rent an analyzer from a car parts store? Or is it better to wait until spring here in VT and bring the car to a Porsche shop for their analyzer?

If it matters, the problem is that the idle speed oscillates and over the last few years the engine has stalled once or twice when it was cold.

[ben parrish]

Oly,
do a search...there is a few posts that describe the process using your O2 sensor and an ohm meter.

good luck,
Ben

[oly]

Thanks Ben!

[dad911]

Are you sure that there isn't a vacuum leak?

[oly]

dad911,

No I am not sure; a vacuum COULD be the source.

[NutmegCarrera]

Sounds real familiar...
I'm midstream in a similar situation. I have an '85 with a questionable past, so have been working at it as I have time, money, etc...

O2 sensor is only part of it. I went thru fuel filter, air filter, and looked at O2 w/ meter.
Then, the fun stuff started...

There's an article floating around on "adjustment" of the flapper box wiper. Mine was leaving quite a trail in the "resistance?" strip. After adjustment, much improvement.
Then, took a look at the wide open throttle switch. Also not working. A matter of "rapping" on it got this improved. Then looked at adjustment of the throttle linkage. Not anywhere near using full range. Adjustment there yielded further improvement.

Replaced plugs, and found that new ones installed by PO looked good. Went from platinum +4 to standard electrode. No difference.

At this point, I still have roughness at idle. Next stop is new plug wires, cap & rotor, as well as a new cylinder head temp sensor.

I'm betting that this next step will be a large improvement - based on results found in myriad hours here on this board.

Your milage may vary, but your level of enthusiasm and interest is likely paralleled by many here.

Next spring is likely update from me. Forecast calls for wet/cold/snow here in WI. Likely done driving for the year. Subaru earns it's keep...

[stlrj]

Originally Posted by oly

dad911,

No I am not sure; a vacuum COULD be the source.

I would concentrate on the possibility of a vacuum leak before anything else. Intake gasket leaks are a common source and are easy to verify with carb cleaner sprayed at the intake manifold bases at idle.

Cheers,

Joe