No idle - '74 2.0l FI Options

[watsonrx13]

Since I've rebuilt my '74 2.0l FI engine I've had problems with the car not idling. After it warms up it dies. I've set the timing to 27 and the dwell is at 46. I tried adjusting the ECU knob and the air idle screw but neither appear to have any effect on the idle. When I adjust the knob I can feel it click. I counted 21 total clicks. The engine runs great above idle. The injectors have been rebuilt, new AA vacuum hoses replaced, all gaskets are new.

Can the ECU be taken apart and cleaned?

Does anyone have a pic of the ECU opened up showing the knob area?

Any recommendations on how to fix the idle problem I'm having?

-- Rob

[detoxcowboy]

From the link I posted further up this post..


The longer I drive, and the hotter the engine gets, the more the idle drops until it wants to stall (fully warmed-up)

Rich idle mixture: This seems to be fairly common on 914's where the idle mixture is set "by ear". When you have carburetors, you learn to set idle mixture by looking for the setting where you get the highest engine speed with closed throttle. This doesn't work for D-Jetronic cars! Set your idle CO to spec by having a shop use a quality CO meter. Trust me on this one, I chased this condition for at least 5+ years!! Note that when I say "rich", I'm talking about idle mixtures of 5% CO or greater. I've seen as much as 8%

and...

Engine bogs from idle (poor idle to part-load transition), or idle drops down well below 1000 rpm after the car is fully warmed up or is hot from running hard

Idle mixture too rich
Retarded timing
Check that timing is set to spec. Set the CO level to factory specs by using a quality gas analyzer. If a gas analyzer is not available, use the "trial-and-error" method of adjusting the ECU knob one click counter-clockwise at a time, re-adjust the air bleed screw to set the idle and repeat if necessary. Usually, if the idle is too rich, the idle speed is very responsive to adjustments to the air bleed screw.

and..



Cold resistance of the cylinder head temperature sensor is too low.
This problem seems to get worse on older cars as the engine wears. There are a couple of solutions. You can "cherry pick" a cylinder head temperature sensor with the highest value you can find, or you can add ballast resistance to the sensor - however,
and...

"My car runs rich and I don't know why!!"

Cylinder Head Temperature Sensor - open in either the sensor or in the wiring harness or connector, failed sensor (stuck at high resistance value), wrong sensor for application.