Hello,
I have a 1974 2.0.

It is running OK.
but I have a high idle, with the air screw all the way closed.
I move the timing around, it is high when on spot 27 degrees, (dynamic)
so, I retard it a little by ear.

cold the car is about 850 900 rpm, warm and hot at about 1100 or 1000. (probably 1200 with 27 degree timing)
but I can only bring it lower with timing, retarding distributor.

i have unplugged that one heat sensor, in and out to see what it does.

I killed my CPU brain, so I have a 1973 version. (I have the knob on CPU all the way counter clockwise, i have tried everywhere inbetween)
(i once saw a chart about the differences between 73 and 74 CPU. but cannot find it)

I was wondering if one of my sensors was worn...causing high idle.
all hoses are attached, and new, and the things they are connected to seem fine. like decel valve.
I haven't checked the one just near the throttle body. aux air regulator.

all my electronic stuff is new, wires, coil, cap, rotor, points, etc.
my rings are new, valves adjusted, and i have about 140 psi on all cylinders.

the car acts a little like it is missing when cold. but once I am 175 degrees, it is pretty smooth. sometimes when i smash the gas...it will hesitate. (too much air, too much gas?)
i think the point-sensor things inside the distributor are o.k. but maybe they need some oil? and i could put some oil on the felt inside there.

I rebuilt my throttle body, to try to reduce air leaks...

I need a new or better throttle plate, the brass disc, a previous owner drilled extra holes in it. (which are now plugged) But, I would like a better one.
anyone have one?

Ouch ouch ouch. So many things.
First, the 73 computer is a one year deal and you need a specific cht sensor and resistor for it.
Second, the mps you have probably isn't built for the 73 ECU either.
Third, if your idle cold is that low, I doubt the aar is working.
Fourth, all of the odd behavior sounds a bit like a lean mixture

Have you checked your plugs?

Set timing to factory spec and leave there

The knob on the ECU only works if you have the TPS calibrated (see link)
https://www.pelicanparts.com/techarticles/9...alibrate_20.jpg

Perform a smoke test or remove each item that connects to the throttle body (AAR, Decel PCV) one by one until the idle lowers

Check if the MPS holds vacuum solid or at least takes time to bleed off

Did you replace the throttle body gasket?

Are there any unused vacuum ports? If so are they properly capped

Thanks every point in the comments is helping.
1. Problem 1 figured out.
I painted my sheet metal, and had no ground going to the Aux air Reg.
So the little guy wasn’t heating up inside, (now it’s very hot) and does a pretty good job closing the AAR.
So that’s that.
It was staying open.

Now I’ll go look at the other things you’all mentioned.

Yes, it has new gaskets around the intake box.
And when I looked at plugs, they were a slight tan/brown.

If it's stuck open your car cold should be at 1300 rpm. Warm it would be even higher....

I was going to say decelerator valve but I see you mentioned it was fine. It was a source of my high idle. I had to tighten the spring a bit to keep it closed at idle.

Vacuum leak

Those shiny wheels look good!

This is the most chaotic help thread I have ever seen. PM me if you want help trouble shooting.

https://members.rennlist.com/pbanders/DJetParts.htm

Rich gave you all the answers.

Use the link he gave you to Anders' site. Read it, learn it, live it.
Your MPS and ECU and CHT should match. You can make the non-matching stuff work, but it's not necessarily straight forward. All the info is on Anders' site.

After that, fix your vacuum leaks.

It sounds like you are on the right track as far as narrowing down the problem.

Is the vacuum retard hooked up and working on your distributor?
Are your distributor advance springs still intact and working properly?
Is your crank case vent valve intact and working properly?


I think i have had more running issues cause by distributors than any other component on d-jet cars. Investing in a 123dizzy saves a lot of headaches.

Also, as stated that 73 ECU wont work properly with your setup

You are correct. When I purchased my '74 LE, it had the 73 mps and 73 ECU but with a 74 CHT and the resistor had been removed but a '73 CHT with the correct resister and wiring were in a box. Not sure when a prior owner had swapped Djet part as the motor was numbers matching to the car. Perhaps the PO had access to a 73 2.0L Djet setup but had not read Paul Anders' excellent research on these systems. See it on Rennlist or search pbanders.

My car started and ran but had quirky drivability issues, including idle problems until I switched all the components to match the 1974 system.