Still can't find what causes my problem Options

[andreic]

Well, here we go again. A month or so ago I posted about the troubles I am having with my 1.7L D-Jet engine. I did a lot of testing since, but still can't find the root of the problem. Help!

Here is what has been going on for the past few months; before that the car was running perfectly.

When starting the car cold it runs perfectly for a couple of minutes, idling high as expected. For these few minutes the car drives well. Then the problem starts. The idle drops to the point where the red alternator light comes on in the dash. The engine bogs on transition from idle to power, sometimes backfiring. If driving, it has low power, and it constantly stumbles pretty badly. As it warms up things get better, to the point that after about 15 minutes of driving it is almost ok (you can still feel a bit of stumbling at all powers, but it gets much better than before). The idle comes up to almost where it should be after warming up, but it is never smooth, it hunts and feels as though every once in a while not all cylinders are firing. It is impossible to bring the idle up above 850-900 rpm by unscrewing the bleed air screw; after a certain point it does nothing. Turning the idle mixture screw on the control box has almost no effect on the idle (unless turning mixture very low, when the idle drops further).

Diagnostics performed:

1) Fuel pressure checked 28 psi, very steady. All hoses in the fuel system replaced, new fuel pump before the trouble started (and ran well after).
2) Compressions uniformly 120-125 psi.
3) Valve gap adjusted three months or so ago, a few weeks before problems started.
4) New spark plugs, new points, rotor, and cap. Dwell angle and timing checked several times.
5) MPS checked: holds vacuum well, resistances checked good.
6) CHT sensor measures right where it should be when engine cold; wiring to the harness good.
7) Removed plug from TPS; drivability problems still there, or slightly worse; idle slightly lower.
8) Removed D-Jet harness from the control box (brain), measured resistances between various pins as described in Anders' instructions, all within specs.
9) Replaced coil and spark plug wires with others I had in my garage, no change.
10) All vacuum lines replaced with new.
11) Checked the injection points in the distributor by taking them out (they looked to be very clean) and checking that they do make a contact while turning the distributor cam (I don't have an oscilloscope to test them further).

To me it feels as if the engine either does not always have a spark (but then why would it run consistently well in the beginning, and then be much worse, then improve as it warms up?), or that it is running very lean, for some reason.

Things I could still do:

1) Replace condenser on the distributor.
2) Check that distributor canister holds vacuum on both ports.
3) Check fuel pressure with engine cold, when the problems I mentioned are worse.
4) Send the injectors to be checked and cleaned.
5) Recheck the valve gap.
6) Try to clean up the various places where the harness grounds are.
7) Other things??

I don't know what order to try to do the above things, or what else to try. This problem has driven me nuts! Please help with any suggestions I may not have thought of.

Thanks,
Andrei.