high idle after stall - 747 $42.

[mp305]

Hi guys, this is my first post, I have been reading this forum since 3 years ago and I really appreciate all the info that you post here.!!!

Maybe you can help me with a direct question regarding the only final issue that I have with a continuous high idle after engines goes under the " stall saver RPM"


Normally the engine runs good and smooth during warm, hot and cold driving. Engines runs in close loop, no Malfunctions Flags... everything is OK!!!! From cold during warming, RPM reach 675-700 RPMs idle as tables data, Idle ALDS info: IAC count: 25, open loop and Idle / Cool Flag on.


But the issue starts when, due to manual transmission load, RPMs drops very low about 300 to 450. After this particular driving conditions (under stall saver RPM") , engines RPMs recovers as per tables, but the new idle speed becomes 850-875. Idle ALDS info IAC count: 60, Close loop, BLM, Idle / Cool Flags on. This condition keeps in time "forever" until I restart the engine.


Some background


Engine 305 L03 attached to a MT 4speed. (engine formed AT transmission version from a junk yard), ECM 747 with Moates EX remote switch, $42-1227747-5.9.3.xdf.
Engine harness, injectors, heated O2 sensor, sensor thermostat etc etc ...all new with the right specs. Fuel Pressure at TBI OK, IAC learning.
ASDN stock BIN (Engine L03 Disp 5.0, Trans Manual MG5,) downloaded from this forum (thanks!!) manual transmission option check, no EGR patch check, BPW small adjustment by me.... and the rest parameters are "untouched" by me.
No VSS


I am not a tuner guy, but after reading the whole XDF descriptions and checking the data retrieved with ALDL before and after the issue.. I have many suspects.... all the " stall saver parameters".

Any hint about to config a faster go back to normal idle after goes to stall will be appreciated. Thanks in advance.

[steveo]

there's probably some kind of VSS issue related to the stall saver, perhaps it requires a certain gain in vehicle speed to exit stall saver, and since there's no vss, it never exits.

lots of weird things happen to idle without a vss. what if you just disable the stall saver entirely?

[mp305]

there's probably some kind of VSS issue related to the stall saver, perhaps it requires a certain gain in vehicle speed to exit stall saver, and since there's no vss, it never exits.

lots of weird things happen to idle without a vss. what if you just disable the stall saver entirely?


Thanks for the advice.


After that I connected a VSS manually in order to simulate some speed (I still don't have a proper transmission hookup adapter for the VSS) but issues remains. Also I reduced the stall RPM almost 0 in order to skip it, but noup...


But while I was doing that.... I realize that my ECM has the park/neutral cable grounded and Park/Neutral flags is always on.


Therefore "IAC - Desired C/L Idle Speed " table will never work. ( and that is my issue.... C/L iddle...)


In general terms, for a manual transmission bin, which is the normal wiring Park/Neutral ECM signal condition grounded or free ?


I am running the ECM with Park/Neutral flags is always on, but seems to run good.

Thanks in advance.

[fastacton]

All of the manual transmission harnesses I've pulled don't even have the park/neutral wire installed. I've never checked to see is installing one and grounding it makes any difference.

[350yj]

there's probably some kind of VSS issue related to the stall saver, perhaps it requires a certain gain in vehicle speed to exit stall saver, and since there's no vss, it never exits.

lots of weird things happen to idle without a vss. what if you just disable the stall saver entirely?

What cells should be edited where to disable VSS? I am having this same issue.

--
Kris

[1project2many]

VSS really can't be "disabled." Stall saver enable rpm could be brought to a minimum value but the ecm would still be looking for VSS input.

[mp305]

Thanks for the feedbacks.

Finally I had some time to check the park/Neutral cable grounded condition. I already know that the cable was grounded since the wiring harness installation , and also I always saw the park neutral flags ON but never consider as a issue.

Well.... seems that is very important because after un-grounding the cable (i.e cut...), ECMs went to DRIVE mode and now everything works as tables (RPMs, iddle & IAC steps v/s temp, stall saver, Close loop... etc etc). RPMs goes to my table setting after stall recovering. Issue solved.

Of course now the VSS malfunction is ON (check light always ON), but I just deleted this warning flag meanwhile I look for a proper VSS for my transmission.


Thanks again
Mario.