On the road again (or the taste of success is never too sweet)

[charlesbahn]

Well, my wonderful car (1985 turbo look, 3.2 with Protomotive Turbo and intercooler) began to run like crap early last summer. Would start right up and then idle rough and not fire on all cylinders, but was inconsistent as to which cylinder was off.

Over the summer I spent hours working on it - here is a list (not in chronological order):

1. changed the spark plug wires, spark plugs, cap, and rotor, even swapped in a spare distributor.

2. checked all the vacuum hoses and ran sea foam through the intake. Took the intake apart, cleaned mating surfaces and replaced all the gaskets, torqued and retorqued the bolts.

3. Took apart the fuel rail and replaced the injectors with known good ones.

4. checked all the ground points, cleaned and remounted all

5. Inspected and cleaned the engine harness connections at the rear and front of the engine

6. changed the chip from performance to stock, had the DME tested and pronounced healthy, even tried a known good spare DME replacement. Replaced the notorious fuel pump relay

7. Swapped in a known good idle control valve

8. Tested all of the electrical connections to ICV, AFM, and the Speed and Reference sensors per the Bently manual.

9. Replaced the oil cap gasket (Thx Trog, I thought maybe that was going to be it).

10. Tapped each injector with small hammer.

11. Adjusted the valves

After each of these attempts, the car continued to run like crap and seemed to be getting worse with each effort.

Winter came and I just put the car up to wait for Spring. So I recently renewed the quest.

Well here's the answer. It was the reference and/or speed sensor. I don't know which because I changed them both. I didn't think this was the answer before because they tested O.K. by the simple Bently test- but I didn't oscillocope them which probably would have given me the solution sooner.

Anyway after I replaced them, the car fired right and purred like a kitten! Then went for a good 100 mile "Italian" tune up which she loved.

I actually enjoyed the exercise- I knew I'd solve it sooner or later, and I learned a lot about the car. Fortunately it's not a daily driver and I had the luxury of time.

Hope this is helpful to others who might encounter this problem.

Charles

[CharlesJones]

Fantastic! Yeah, these little problems are a pain when they happen, but indeed the positive thing is that you gain so much knowledge in the diagnostic process, plus you now have many of the potentially troublesome things in your car either replaced or checked. I imagine your car will now be much less likely to give you any other problems for quite a while.

Is the speed sensor the one that reads off the flywheel?

[charlesbahn]

Both the speed and reference sensors sit in a little bracket and read from the flywheel. The speed sensor reads from the teeth and is set at 0.8 mm gap. It is the one that I think was causing the problem since the car would start. The reference sensor reads from a little bolt protruding from the fly wheel and if not functioning will cause the car not to start. I was going to change them one at a time to find which was off, but they were both frozen in the bracket and I had to remove the bracket and decided to just change them both since I had the whole assembly out of the car.

Charles

P.S. If you have to remove the bracket be careful not to damage it getting the sensors out. The top or reference sensor has a sleeve which is easily damaged. The bottom, or speed sensor, doesn't have a sleeve. If you grab the top sensor with pliers, or hit it with a hammer, you will damage the sleeve of the bracket and really fu*k it up.