‘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]

Well, now that I have four plugs that fit, the car definitely runs better. I’m still so pissed that a guy who sells himself on being a classic Porsche specialist could miss something so damn basic.

I also replaced the temp II sensor. No change on cold start, but it was pretty warm here today so I didn’t expect the computer to go into cold start mode based on readings from the temp switch anyway.
It does make me think about finding a temp switch that has a much higher temp window. I think modern knowledge of engine wear has taught us that getting the oil pressure up as quickly as you can provides a huge benefit to engine longevity. The reasoning of the 914 era was to overcome cold engine/oil friction so the car would stay running. Thus, it makes sense they would choose a 15C/55F temp switch.

[emerygt350]

getting the oil pressure up as quickly as you can provides a huge benefit to engine longevity. The reasoning of the 914 era was to overcome cold engine/oil friction so the car would stay running. Thus, it makes sense they would choose a 15C/55F temp switch.

Oil pressure while cold should peg to 60 at idle almost immediately.

You are still having low cold idle? Did you pull the aar hose off the plenum yet while it is running low and cold?

[wonkipop]

getting the oil pressure up as quickly as you can provides a huge benefit to engine longevity. The reasoning of the 914 era was to overcome cold engine/oil friction so the car would stay running. Thus, it makes sense they would choose a 15C/55F temp switch.

Oil pressure while cold should peg to 60 at idle almost immediately.

You are still having low cold idle? Did you pull the aar hose off the plenum yet while it is running low and cold?

theoretically a good tip for Van B and me.
but its a bastard of a hose to get off easily that one.
its very short and curved.
to get that off i have to unbolt the AAV and manouvre it to pull the hose.
its because its so short its virtually impossible to push it back far enough off the plenum or AAV connections.

but i tend to think it probably is the AAV.
looks like Van B's CHT test and replacement knocked that sensor out of the equation.
i tested mine in situ 2 years back and it was working so i never bothered to remove and change it.

i'm going to try and take a real close look again at my AAV at christmas and see if i can find out anything concrete about just what rate it should close at.

my mechanic thinks its highly likely it is the AAV as he thinks as they get old they get weaker and close faster as a possibility as well as the other type of failure which is they just don't work at all and are jammed either closed or open.

there is another sensor in the AFM unit. called sensor 1.
it measures the incoming air temp.
i have not gone into it apart from reading that it appears to be non replaceable.
guys who have mucked around with L jet for years would know more about it and what it might do.