Engine dies while coasting
Thread Starter
Drifting
Joined: May 2006
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From: Chewelah Wa
Engine dies while coasting
Anyone want to tackle explaining how to change DFCO in the $1F bin for the '85 870 ecm? I am having "coasting" issues where I can feel and hear the engine dying as I come to a stop. It stays running (restarts as soon as you hit the gas or clutch pedal). Thanks!
Thread Starter
Drifting
Joined: May 2006
Posts: 1,428
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From: Chewelah Wa
Thanks for the response, Brian. Any ideas on what I can change to help? I have been playing with the IAC, to no effect. I changed to fully siamesed runners, I think it has changed the airflow at idle. It idles fine, but the coasting shut down bothers me. If I could just get the injectors to stay on........
Safety Car
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From: Glenbeulah Wi
Well, you could try and raise the TPS voltage at idle to see if you can eliminate the DFCO activation point by exceeding the max throttle allowed for DFCO, and see if the car still idles and drives correctly.
Last edited by bjankuski; Aug 23, 2011 at 02:17 PM.
Thread Starter
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
I have thought of this and will try it out. Does anyone know what that magic number might be? There must be access to this info through other ECM's than mine I would think. I will try to find it the hard way I guess. What other conditions can we manipulate to disable DFCO? VSS? (I am guessing no) Does it look for LV8? May this be adjustable in a MAF table? Thanks again........
Thread Starter
Drifting
Joined: May 2006
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From: Chewelah Wa
I have found the TPS settings on a 87 bin....it is a change percentage set at 0. I think that means whatever the TPS min happens to be, that is the new "zero". I may be screwed and have to live with it.
Race Director
Joined: Apr 2002
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From: Anaheim CA
I had this happen to me. Adjusting minimum idle fixed it.
My theory is that over time the linkage pressing against the idle stop screw became bent from the return spring pressure.
I suggest making sure the throttle body and TPS are adjusted correctly before looking at the ECM.
My theory is that over time the linkage pressing against the idle stop screw became bent from the return spring pressure.
I suggest making sure the throttle body and TPS are adjusted correctly before looking at the ECM.
Safety Car
Joined: Sep 2001
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From: Glenbeulah Wi
The 1987 bin has DFCO constants that can be adjusted to turn off the DFCO. I do not see that option in the $1F tune for the 1985. The TPS on a 1985 through 1989 does not return to zero at the min TPS setting. The zero setting is .54 volts and anything higher then .54 will be some percentage of throttle. The LV8 does effect DFCO and maybe you can set the throttle high enough to eliminate the DFCO?
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Thread Starter
Drifting
Joined: May 2006
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From: Chewelah Wa
I have had the throttle stop high and low, reset the TPS and IAC several times. It's been as high as .67v. I tried a different bin that I had, and set the idle to 650. This has lessened the effect to the point where I can live with it. The off idle characteristics have changed with the addition of my siamesed runners, and since I cannot adjust DFCO in my ancient computer, I may be stuck with it. I will never give up on trying to fool it into disable! My hollowed out cat with resonator tips is not helping. The change in exhaust is very noticeable. I may reinstall a hi flow cat to cut down the noise dif, and to get rid of stinky exhaust smell. So Brian, for grins....what do you think the percentage and/or tps voltage setting should be for enable/disable? Another characteristic....my fuel display only goes to 87 mpg when DFCO kicks on....you think it would be 99? I did change injectors.....
Safety Car
Joined: Sep 2001
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From: Glenbeulah Wi
The stock bins for 1986 an newer use 3.1% throttle to disable the DFCO, my guess is .70 or higher TPS voltage would be <3.1%. You could easily change your car to a 1986 or newer computer with a little rewiring and then you could tune your DFCO issue.
Last edited by bjankuski; Aug 25, 2011 at 07:52 AM.
Thread Starter
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Thanks...I appreciate the help. I will try .7v and see what happens. A 165 ecm may be in my future, it really does not look hard to change over. But I am still having fun trying to find a fix, its my nature. Maybe a throttle stop switch hooked to a dylithium crystal circuit...
