Can somebody ID this new idle quirk?, starts & runs well -- until warm Options

[Prospectfarms]

(IMG:style_emoticons/default/beer3.gif) (IMG:style_emoticons/default/beer3.gif) (IMG:style_emoticons/default/beer3.gif)

O.K., I'm better now... D-jet is driving me to drink.

The 1.7 starts and runs well until it warms up. After 10 min. idling smoothly @ 900 it hesitates two or three times and stops idling at all, which means I can't keep it running long enough to set the timing. I can keep it going by feathering the throttle, but my nice smooth idle is gone. I reproduced the symptom three times in a row today.

By clamping off the Vac hoses one-by-one it appears the FI components seem to be doing what they're supposed to. No other vacuum or capacitance probs. found so far. Haven't checked the injectors.

This started after I repaired the ground strap on my distributor -- must have bumped something else. CHT?

I have the FI diagnostic checklists and am working on them. If this was a carburetor I'd say it was running with a clogged idle jet (IMG:style_emoticons/default/wacko.gif) . These symptoms seem specific and uncommon. At least I've not seen others posts that describe the same thing. Did I miss one?

[r_towle]

Unplug and cap all vacuum lines at the plenum.
the only line that should be plugged into the plenum is the MPS vacuum.

How is the idle then?
Set valves, dwell, and timing.
How is the idle?

If its still bad, and it still shows signs of dropping off after its hot...check your CHT for the proper Ohm readings for your ECU.
Anders site has the correct readings for your ECU and your CHT...
Each year is a bit different.

If that fails...there is are three more things that affect idle.
Failed MPS...runs to rich and stalls
Failed Cold Start Injector , always open, runs rich and stalls
Poorly adjusted TPS...runs rich and stalls.

You really need to ensure your ignition system is set properly before any FI diagnostics...you will chase your tail if the valves are adjusted wrong, or your dwell and timing are off....even just a little bit.

Djet is very sensitive to proper dwell and timing for the idle speed.

Djet and Ljet are both early systems and are both a guess at best for the proper A/F settings.
Both systems suck.

When the LH jet was introduced...that has the O2 sensor and the feedback made the system self adjust...then they had a decent system.

Rich

[Prospectfarms]

Unplug and cap all vacuum lines at the plenum.
the only line that should be plugged into the plenum is the MPS vacuum.

How is the idle then?
Set valves, dwell, and timing.
How is the idle?

If its still bad, and it still shows signs of dropping off after its hot...check your CHT for the proper Ohm readings for your ECU.
Anders site has the correct readings for your ECU and your CHT...
Each year is a bit different.

If that fails...there is are three more things that affect idle.
Failed MPS...runs to rich and stalls
Failed Cold Start Injector , always open, runs rich and stalls
Poorly adjusted TPS...runs rich and stalls.

You really need to ensure your ignition system is set properly before any FI diagnostics...you will chase your tail if the valves are adjusted wrong, or your dwell and timing are off....even just a little bit.

Djet is very sensitive to proper dwell and timing for the idle speed.

Djet and Ljet are both early systems and are both a guess at best for the proper A/F settings.
Both systems suck.

When the LH jet was introduced...that has the O2 sensor and the feedback made the system self adjust...then they had a decent system.

Rich

Rich, I appreciate your thoughtfully honest comments, that info is gold, e.g., now I'll be able to set the timing.

"When the LH jet was introduced...that has the O2 sensor and the feedback made the system self adjust...then they had a decent system."

Does that describe what some call an "open loop" system?

Have you used this information to customize fuel delivery on your car(s)?

Despite the continuos frustrations, I really enjoyed learning carburetor theory a few years ago, now I'm loving "Fi 101."

[r_towle]

Unplug and cap all vacuum lines at the plenum.
the only line that should be plugged into the plenum is the MPS vacuum.

How is the idle then?
Set valves, dwell, and timing.
How is the idle?

If its still bad, and it still shows signs of dropping off after its hot...check your CHT for the proper Ohm readings for your ECU.
Anders site has the correct readings for your ECU and your CHT...
Each year is a bit different.

If that fails...there is are three more things that affect idle.
Failed MPS...runs to rich and stalls
Failed Cold Start Injector , always open, runs rich and stalls
Poorly adjusted TPS...runs rich and stalls.

You really need to ensure your ignition system is set properly before any FI diagnostics...you will chase your tail if the valves are adjusted wrong, or your dwell and timing are off....even just a little bit.

Djet is very sensitive to proper dwell and timing for the idle speed.

Djet and Ljet are both early systems and are both a guess at best for the proper A/F settings.
Both systems suck.

When the LH jet was introduced...that has the O2 sensor and the feedback made the system self adjust...then they had a decent system.

Rich

Rich, I appreciate your thoughtfully honest comments, that info is gold, e.g., now I'll be able to set the timing.

"When the LH jet was introduced...that has the O2 sensor and the feedback made the system self adjust...then they had a decent system."

Does that describe what some call an "open loop" system?

Have you used this information to customize fuel delivery on your car(s)?

Despite the continuos frustrations, I really enjoyed learning carburetor theory a few years ago, now I'm loving "Fi 101."

FI is simple.
You are still measuring air flow.
ALL EFI systems measure air flow.
Based upon air flow, fuel is metered out to match the airflow.

There are two schools of thought on measuring air flow
Manifold pressure, and air flow volume.
Both measure air.
Both still exist in one form or another.

With the introduction of an O2 sensor, the computer can see if it guessed properly and do slight tuning based upon the exhaust gas mixture...

Heat sensors, specifically head temp sensors, tell the computer if the car is to hot, and it adds fuel to cool the motor.

The rest of the sensors are for even more fine tuning.

Rich