tailpipe

Four out of my five cars have had to have the WUR adjusted richer after they were brought back to life after sitting for years. I had taken them apart and they were all very clean inside didn't make a difference in the function after cleaning. I have had lots of experiance with VW rabbit CIS they are notorious for cloging the fliter screen with crud I have yet to see that in a 928. Your symptoms sound exactly the same as all four of mine although yours could be something completely different.

Erik N

OK I got the stuff to make the WUR adjustable...

I took the car out this morning to get it nice and hot, and to double-check the A/F mixture. It's adjusted back down (CCW) from the rich "begin to stagger" point to the "totally smooth" point. So I feel that's a good starting point.

One thing that I forgot to mention is that when the car is HOT, after a heat-soaking a while, she reluctantly fires while cranking and then nurses its idle back to steady for a bit. It feels exactly like my old carbureted cars used to when hot flooded. The issue sorts itself out after a bit of idling.

Anyway, I'm gonna stop being a ***** about it and start drilling and tapping this afternoon.

Erik N

So I drilled and tapped the center of the aluminum plug. I also tried to drill a anti-rotation "keeper" hole... but that was not as clean as I would have liked. I believe the pin and the housing have different hardnesses. I don't think a locator pin will work with the result. See pic #1.

So instead I Locktighted in the allen bolt and I kerfed both the allen bolt and the housing in-line w/ each other w/ a hacksaw so I can ensure they stay aligned. Then added some paint. Pic #2.

I will adjust the height of the pin tomorrow. I'm thinking raise it ~1mm to start... any feedback from the experts is welcome

rjm65

Make sure you unplug the electrical connector on top of the WUR, it will slow down the heating up of the lever inside the WUR, and allow you more time to make adjustments. Remember the heat from the engine also effects the WUR, so once the engine starts to warm up you practically have to wait overnight to do any further cold system pressure adjustments. Make the adjustments as small as possible, a little goes a long ways.

Bad fuel accumulator could be the culprit of your heat soak rough idle issue. You can check the the bleed down rate of the accumulator with a CIS Fuel Pressure Gauge kit, and of course also confirm all your other fuel pressures. :-)

marlinspike

In my experience, while unplugging the connector gives you longer to make your adjustments, it also means that even with a proper tune after a few minutes the engine will die because the WUR didn't warm up fast enough.

I think 1mm would be a lot. I've never thought of it in mm terms, but backing it up even 1/8 of a turn of a normal-threaded screw (coarse? non-fine?) makes a big difference in the cold start mixture.
You might want to seal up where you drilled with RTV. Any leaks in the WUR will mess it up.

SMTCapeCod

That's some interesting stuff. I think the unwiredtools.com regulator never really got off the ground, but I haven't checked in a while.

Isn't the 930 guy begging for some differential metal corrosion using stainless in these components?

marlinspike

Uh...they're on like the 3rd revision and have shipped quite a few of them. Previous revisions had a tendency to break, and it takes many months for them to get you a replacement. On the other hand, the latest revision seems much more robust and is modular (so they could just send you a replacement part, rather than an entire unit, hopefully making it quicker), but I haven't installed my latest revision yet to give any feedback.

On the 930 guy, 1-not all components are stainless, some are aluminum. 2 - I haven't had any seizing issues. Granted I've only had mine for ~6 months.

SMTCapeCod

Thanks, I followed them for a while when it was first offered. I checked back in a year or more ago and they were in-between versions. I'll see if there is a good application thread in other RL areas.

Erik N

So I messed w/ the pin height. I first tapped it down ~1mm, to break it loose. That made the car barely idle... about 400RPM. I then raised the pin to ~1mm above it's original height, thus leaning out the WUR, and the idle (still cold) evened out quite a bit. It was still surging a tiny bit, but no big deal.

Took the car out and got it nice and hot, then re-adjusted the A/F screw. It took about 1/4-1/3 turn CW, thus richening it till I found it's new "sweet spot".

Will see how it starts tomorrow morning, when it's cold again.

marlinspike

I still think you're compensating for some other problem. You have a Wideband O2 and a spare O2 bung in your exhaust? I'd hate for you to be making the idle mixture, which is very noticeable, good while ruining the mixture under speed. Does the CIS on this year of 928 have an O2 sensor for correction?

Erik N

No O2 bungs or sensors anywhere.

After I get it sorted I will do some hot laps and then check the color of the plugs.

marlinspike

Ah, ok, in that case that mixture screw will only adjust idle mixture (well, very slightly under throttle but not worth mentioning).

Color of the plugs...what year is this? They make wideband O2 sensors you know.

Erik N

It's still 2010, but the car was made over 30 years ago...

Gotta go- TURKEY TIME!

marlinspike

Well, heck, if you'll put down a deposit (i.e. in case it breaks), and promise to not run the car with it installed unless it has given you the green-light after warming up, I could send you my LM-2 to borrow for tuning purposes and just ship it back when you're done.

Dennis Wilson

The A/F mixture screw affects the ratio through ALL rpm's, not just idle.

Dennis