Solved!!!!!!!

After replacing the cold start valve, fuel pressure regulator and coolant tem sensor.....no change, still surged.

So I put the old coolant temp sensor, as the motor was still hot and called it a night. It hit me in the middle of the night. "What if the 'loaner' coolant temp sensor was bad also?" Its a big temperature varying resistor. I had some resistors in my tool box, what the hell? I threw in a 720 resistor in and made contact from the sensor wire and coolant temp sensor. Immediately the surging stopped and held idle at about 1200 RPM. No stalling from WOT with all accessories turned on. I then dropped in a 220 resistor and bam.......rock solid at 1,000RPM. No hunting for idle. At 80 on the temp gauge the 'inline resistor' puts the total OMH in the 350 range, IE within specs. So I fabricated a little water proof adapter to get me by until a new sensor comes in.

But today, she runs like new for the first time under my ownership.

Liquid, I have a special box on loan to me from a old school German tech. It hooks up to the car battery and then clips on to the black 02 sensor wire (inline IE bare). It has about 13 LED's in a row. The center 3 lights are green. Adjusting the idle illuminates the lights. The goal is to get the lights bouncing in the green area. Think of the center eye on the old Knight Rider 'Kitt' nose. You can see the 02 sensor working as it micro adjusts. So the little lights on the unit sway back and forth in the green arc.

Thanks for all the input guys. I was hoping it was going to be something simple and not costly. But more importantly, I get to keep my man card!!!!

Christian

Congrats! It's always a treat to dodge the shop.

You've inspired me to pick up a Beru coolant temp sensor. Mine reads about 100 ohms out of spec at 80°C. It looks old and falling apart, and is such a basic piece of the puzzle on these cars.

Liquid,

My sensor was new via Ebay. The resistance was just way off. The thing that sucks is, has the same part number as MB! On the outside it has the same markings as the Bosch unit. In the future, Ill pay the premium to buy from a reputable dealer like Peachparts, MB or AutohouseAZ.

I've been through the eBay wringer on car parts. I also got a non-oe (FAE) oil pressure sensor from a reputable site. It is out of spec. It reads 1 bar with koeo and always reads 1 bar too high. I know the oil pressure is OK because I've tested with a pressure gauge on that port.

The pisser is, it has the Bosch markings on it! WTF! I have another one en route from Pelican Parts. The MB part number is the same as the Bosch but $40 higher. But yea, no more Ebay parts for me.

Side note, I did drop it of to an Indy and they had it for 2 weeks. They couldnt fix it but didnt charge me either.