Idle fluctuation, Rpm between 1000 and 2000 Options

[SWH]

Completed rebuild on 1974 914 2.0 L. All fuel and vacuum lines are also new. Engine idle varies between 1000 and 2000 rpm every few seconds what could cause this?

[saigon71]

A hunting idle can also be caused by a lean idle mixture.

Try rotating the mixture knob on the ECU full clockwise and see if it makes a difference.

[JamesM]

A hunting idle can also be caused by a lean idle mixture.

^^^That

But I suspect it is just part of the problem and there are multiple contributing factors.

D-jet idle can be sort of tricky where you have to chase multiple variables simultaneously to get it just right.

My suspicion is you have a combination of ALL the following happening at the same time to some extent.

1. Intake air leak(s)
2. Lean mixture
3. A worn out distributor. or possibly the wrong distributor or misadjusted timing.


I would start by checking the timing and verifying that your vacuum retard is functioning properly. 74 2.0s absolutely require proper functioning vacuum retard to idle properly. Next check what the timing is doing when it is hunting. If you have weak advance springs a small air leak can be enough to get you up to speed to where a bunch of unintended ignition advance then revs you up even higher, at least until it starves itself and drops back down.

long story short, with d-jet you sort of have to check everything, but start with timing and then air leaks.