‘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.

[wonkipop]

@Van B & @StarBear .

full cold start test this morning for you.
car hasn't been started for a week so fuel system has bled down to lowest pressure.

temp = 13C (55-56F).
yep its a miserable spring day in melbourne.
arctic roaring 40s cold front coming through.

no touch nothing. car on its own.

two cranks. err err bam fires.

5-6 seconds strong start at 1000 rpm.
(i figure thats the cold start injector working - so much for 50 and below).

then idle drops to bottom of tach. don't even know if its making 750 rpm.
doesn't sound like it. but its keeping itself going steady.
this lasts for 2 minutes.

at 2 minute to 3 minute mark is the interesting bit.
this is the weakest phase.
it stumbles, barely keeps itself going but L jet just won't let it die.
comes back, stumbles again comes back, does this 3 times.

at 3 minute mark it begins getting stronger. but still not there to set idle.
stops stumbling. gets even at 800 rpm.

up to 4 minute mark stays at even 800 rpm.
can feel warm air puffing out from underneath at my ankles.

at 5 minute mark hits even 850 rpm and is strong and steady.

at 6 minute mark it hits the idle we set it to back at last service which was 950 rpm.
like StarBear we found it sat there nice and even last time we tuned it so that is where we have it.

its a full 6 minutes.

-----

i did not do the emorygt test of pulling hose off decel valve line.
like you only get one full cold chance a day (more like a week really have to shift other french things out of the way).

awful weather coming in down here.
so i probably won't get a chance for a drive today. (IMG:style_emoticons/default/sad.gif)
but i'll let it sit while i potter about doing some other stuff and try a "cool" start later to see what it does after you leave it for most of the day.

[emerygt350]

You have to do the aar tests. They cost nothing and until you do I think next steps are really hard to guess. A low idle is always retarded timing and or a rich mix on a fuel injected engine. The aar is really key for that craptastic half warm period on these engines.