D-Jet ECU Idle Mixture screw CCW to idle Options

[Morrie]

Let me start with saying I need to go through the system in more detail soon. I am collecting vacuum hoses, will get injectors tested, and so on.

Meanwhile, the car runs very fast and strong. The two symptoms I have are odd, and seem contradictory to me.

First, the car wants to idle high when warm. I can adjust that out mostly with the idle speed screw on the throttle body, but there is a tipping point there where the idle speed becomes very sensitive, up to that point large changes in screw setting do little to nothing.

Second, the ECU idle mixture screw needs to be full CCW to idle. If I move the setting off of full CCW it starts to stall and die.

Third, maybe unrelated, is a puff of blackish smoke on decel. (is that over run?). Not sure if this is related, or just some wear showing.

The car runs smooth and strong under throttle, will smoke the tires off the line if asked, and starts easily both cold and warm. It actually does run pretty well with the above considered, but it doesn't seem like these conditions are normal.

Still a learner on D-Jet here, reading and understanding as I go... Having fun, not frustrated.

Thanks guys!
Morrie

[BeatNavy]

So...I agree that these things potentially seem to be contradictory, at least the way you've described them. Likely more than one thing going on.

I do think you're running too rich. That would explain the idle knob having to be full CCW on ECU, the "puff of smoke" on decal, and very sensitive idle bypass screw. Verify if this is the case: pull the plugs and check to see if they are dark and sooty. (I assume you don't have a wideband sensor?)

The following are some possible causes of running too rich:

-Fuel pressure too high (should be approx 28-29 psi)
-MPS not holding vacuum
-Leaking CSV (disconnect fuel line to see if that makes a difference)
-Failing CHT (check resistance both warm and cold)
-Leaking injectors

The fact that you have a high idle even though I think you're running rich would suggest you may have vacuum leak and/or timing too far advanced. The latter is easy to check. The former takes some real hunting.

If you haven't already, read this a few times and give us some more info: https://members.rennlist.com/pbanders/djetp...tm#troubleshoot