Here is some background. The van is a 91 and has 99,000 miles on her. She had been loved and meticulously maintained by a family member since new till his death in 2006. After that, she spent 2 years in a heated garage without beign driven, until I inherited her in 2008. Since then, I have been struggling to keep the old van on the road.

My issue is that the van starts great, but runs rich (much black smoke/ fuel smell.) After warm up, the van will not restart. The plugs are extremely carbon fouled. Wait an hour, and she runs great (albeit rich) till the next shutdown.

On my quest to solve this problem, I discovered a clogged fuel filter with much rust. Traced it back to the tank, and found rust in there too. I have since replaced (with all new parts) the gas tank, fuel lines, fuel filter, fuel pump, and fuel pressure regulator.

Further, I have replaced the O2 sensor, plugs, wires, rotor, temp II sensor, ecu and idle control relay. I have set timing, checked and adjusted the throttle position sensor, and put a meter on all the usual suspects per the bently manual. All check out and are within spec. I even cleaned all connections and replaced corroded ground strap from engine to chassis. Also, the infamous "vanagon syndorome" wiring harness had been replaced several years ago with the factory fix.

After having no success and, on a hunch, I disconnected the temp II connector, thinking it may be telling the ecu that the engine is constantly cold, thus enriching the mixture. She started right up with no black smoke and ran great, with slightly less performance than before and a slightly higher idle. I Have been running her for three weeks like that, with no problems. Pulled the plugs the other day, all carbon is gone (they are the desired light brown in color.)

Today I replaced the Temp II sensor with a new unit, and once connected, she belched black smoke, stalled, and would not restart. As soon as I disconnect the Temp II, she starts right up.

This has become the most expensive "free" vehicle I have ever owned, but I am committed to keeping her on the road. Any suggestions would be greatly appreciated. I am running out of options.
Thanks,
Art G

LOL, thanks Bresha.

If all pin-out tests at the ECM harness plug check out, I
would assume a problem with the ECM.

You haven't mentioned timing...?

What looks like a rich running condition, might not actually
be a rich running condition... I know, sounds weird, but
I had a Jetta one time that fell on it's face & smoked. Ran
good once the temp sensor was disconnected... ended-up
being the intank pump.

So you might have a fuel delivery problem... since you
replaced the pump & regulator, that just leaves the injectors.

Pull the injectors and look at the spray pattern & quantity.

Have you actually checked the fuel pressure? just in case the return line is clogged?

If all you replaced check out good at the ECU plug, I would say that your MAF is bad. Try to adjust it...

Check the connection inside the harness coming from the MAf. In the harness there are the three wires the come together One come from the MAF, one from the Coolant sensor and one from the idle switch. These three wires are connected together in inside the big harness. You have to slice open the plastic wire harness protector to get to it. The wires are brown/white. You will get these exact symptoms if this connection is corroded.