Slow idle at start 1979 FI

[DJPJMJ]

Been trying to figure this out for 2 weeks, need some new ideas.
I've had this car for about 8 months, always started beautifully, 1 slight turn of the key, good idle. Now when I start it in the morning, it takes a second more to catch, and the idle is about 650-700rpm at first. If you leave it idling it will slowly creep up (15 min) to 875rpm. If you start driving right away with the low idle, it will bog down a bit until fully warm.
When it's fully warm it seems Ok as far as driving. If you start it again thru the day, same low idle until it picks up..
So far, I have:
Checked timing, it's at 5ATDC like it should be.
Dwell @ 47.
Tried starting with the air filter off, same.
Fuel pressure is good.
Spark plugs all look good, greyish white.
Checked valves, good @ .006.
Aux air valve test good, although it's in the 80's here so shouldn't matter.
Decel thing seems ok.
Can't find any vacuum leaks with carb spray method.
I have an extra ECU, switched it out, same. Everything ohms out ok at the ECU connector.
Everything looks to be in good shape, but doesn't run right.
Looking for ideas on what to test next. Could this be a condenser or coil problem, fuel filter, fuel injectors?
No smoke or anyting like that out the exhaust. Thanks in advance.

[VW_Jimbo]

What is battery voltage before you crank it with the key off?

What is the voltage while cranking?

What do the plugs look like?

What do the points look like?

What does the oil smell like?

Did you check the high tension ends for corrosion?

Voltage to coil is? At cranking?

Fuel filter is new, old or?

Last fill up was?

Just off the top! That is what I would check!
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[DJPJMJ]

battery is pretty fresh but I will check that.
Points are good, oil change recently and does not smell like gas, plugs are good, wire are in good shape. In fact,everything looks to be in good shape and well maintained.
Forgot to mention I also changed the temp II sensor, no change.
I'm stumped but I'll keep poking at it, cleaning connectors etc.

[busdaddy]

A big pat on the back for the in depth description of the issue, and what you've done so far, well done!

I'm wondering if you have a vacuum leak that closes up when it gets to operating temp?, much of what you describe sounds like it's lean.

If you push on the flap in the AFM through the rectangular hole under the air filter element when idling cold does the idle improve? Push too much and it'll get worse, but a little bit will fool it into richening the mixture a small amount.

Report back with your findings.
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[DJPJMJ]

Thanks, I did try to do my homework first!
Got home after work and pushed slightly on the flap while it was idling in the 600's.
The idle increased to a high 800's. Like you said, push too much and its worse.
I guess this indicate a lean mixture?

[busdaddy]

[VW_Jimbo]

[DJPJMJ]

Fuel pressure test was about 38 not running, about 34 running. I did not do a volume test. I didn't think volume would be a problem since if it goes down the road ok there would be plenty of gas for idle?
The temp II sensor was changed as hopefully a quick fix for this problem, got that wrong. I did clean up the hole. Both new and old make no change to the problem.
I'll look more in to the fuel now that it seems like a lean problem.
Appreciate the help guys......

[DJPJMJ]

Fuel pressure test was about 38 not running, about 34 running. I did not do a volume test. I didn't think volume would be a problem since if it goes down the road ok there would be plenty of gas for idle?
The temp II sensor was changed as hopefully a quick fix for this problem, got that wrong. I did clean up the hole. Both new and old make no change to the problem.
I'll look more in to the fuel now that it seems like a lean problem.
Appreciate the help guys......

[VW_Jimbo]

[DJPJMJ]

I had meant to do the volume test when I checked pressure, just plain forgot.
I do my share of ass-uming though, I'll say that.
Testing the sensor at the ECU is a good one, try to do that tomorrow.

[MuzzcoVW]

How about the auxiliary air valve? Every one I have in my collection was jammed shut with old coked up oil. If that is stuck closed your idle will be low. I soak them in Berrymans chemdip for several hours and the rinse with carb cleaner. Works great. The idle on my '75 is about 11-1200 right after startup, and slowly settles to 900 ( I don't like my idle lower than that)

[MuzzcoVW]

[DJPJMJ]

After reading this I went out, started the car, and while it had it's cold slow idle going on I sprayed the S boot with carb cleaner. Definite jump in idle. I did check it before visually and with carb cleaner, maybe it was warm at the time?
I took it off, on the bench, I'll look for cracks again tonight after work and try it.

[busdaddy]

While that S boot is out of the way remove and clean the terminals of the white ground wires attached to the top of the alternator close to the shroud, in rare cases a bad ground could possibly add to this issue. The ECU needs it for a reference to judge the TS2 output amongst other things.

Don't drop that screw though.
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

Слава Україні!

[DJPJMJ]

So no joy on the S boot. No cracks that I can find, put it back on.
Hit it with some carb cleaner again and no idle change this time, hmm.
Something else though, there's been some buzzing noise from under the dash lately I Couldn't figure out. Today it got a lot louder and turns out the fuel pump is noisy as all hell. Looks.like that's the next thing I look at. It will have to wait until the weekend though. Fuel filter, bad pump, kinked lines? Guess I'll find out.
May or may not be the problem.

[PuddleRainbow]

I'm going with Muz on:

[busdaddy]

I considered AAV at first, until I read the symptoms, it may be part of the slow idle, but it's still running too lean and that's a bigger issue.

[VW_Jimbo]

[DJPJMJ]

All 4 plugs looked good when I pulled them, all a greyish white and clean, gapped correctly.
The plugs/points/dist. cap all less than a 1000 miles old. I've ordered a new fuel after hearing that noisy pump. Should be here in a few days.