‘74 1.8L L-Jetronic Cold Start Low Idle, Mystery solved! Options

[Van B]

Ok fellas, here’s the run down Aux Air Regulator (AAR) and Cold Start Valve (CSV)/injector both work fine. Many of you have also been keeping up with my high idle issue that we figured out.

But yet, when the car is cold, i.e. room temp, I don’t get the high idle I should on start-up. Instead she cranks a bit and then lumbers to life. Idle lopes around 700-800rpm and then smooths out as it warms.

In all other aspects of operation, the engine seems to be pretty happy.

Thoughts? Experience? (IMG:style_emoticons/default/confused24.gif)

-Van

See post #419 on page 14 for a synopsis of the outcome.

[Van B]

Lots of science going on down under today lol!
My car has a similar pattern but no stumbles.

Here’s what I’ve concluded:
- My CSV aka 5th injector only works while cranking the engine
— This is where the initial gusto on startup comes from

-2min is the average time for the heating element to close the AAR from 15C
— This is the same time my car spends at 700rpm before it starts to climb

- Even a slight vacuum leak on the manifold will negatively impact idle
— Vacuum advance is essentially inoperative at idle but retard is directly impacted via air screw
— I had to re-time again today as I found that the short tube from AAR to manifold wasn’t sealing completely
—- changed the tube and timing was off by 1 degree
—- Since the procedure on our car requires air screw adjustment prior to timing, you must retime whenever you do work that affects manifold pressure


Now, about the AAR, I’m 100% mine is fully functional. I can’t say it works as well as it should or could, but it’s working. Also, and most confusing, when it starts to close, is when the car starts to pick up rpm. Too much air and too little fuel? Should the CSV continue to add fuel after start up?
These are the things I’m wondering right now.

Van