Gmecm [Gmecm] Idle problem

[Robert W Hughes]

Another possibility if you are using a scan tool at all is that the ECU 
when it sees 10K or a short on the sense line of the ALDL connector 
(A&B) moves the idle to 1000rpm.

> Are you guys using a tach to see the RPM, or the ALDL data? Maybe the
> ALDL data actually says 750? I'm far from an expert, but there are
> things that could mess up the perceived RPM by the computer, like #
> cylinders.
> 
>>> On Monday 22 August 2005 12:03, Programmer wrote:
>> 
>>>>> Those IAC numbers are not indicating a vacuum leak. Check the
>>>>> "P/N" signal to the computer. If it's getting an 'ingear' 
>>>>> signal when you're actually in park, you'll have a high idle.
>>>>> Another problem is a false VSS signal (from RFI or EMI) down
>>>>> the signal line to the computer (if it thinks you're on the
>>>>> move, the IAC counts will rise). Drop your commanded RPM
>>>>> values...750 doesn't really equal 750...
>> 
>>> 
>>> How is it that 750!=750? ... I have this problem too: I just did
>>> a swap from a carb to a 7747 ECM + TBI on a Ford 302, and the set
>>> the idles to about 850RPM (a bit bigger than stock cam), and I
>>> get about 1200 RPM no matter what I do too. The IAC speeds the
>>> thing up whenever I do something to lower it.
>>> 
>>> I'm sure the P/N switch signal is in "N", and the ALDL data
>>> doesen't show any VSS pulses.
>>> 
>>> The closed loop also kicks in at a temp much-much higher (about
>>> 85°C) than what the calibration says (35°C). Why these
>>> discrepancies?
>>> 
>>> -- Tomas J. Sokorai Sch. 
>>> _______________________________________________ Gmecm mailing
>>> list Gmecm at diy-efi.org 
>>> http://lists.diy-efi.org/mailman/listinfo/gmecm


-- 
Robert W. Hughes (Bob)
BackYard Engineering
29:40.237N, 95:28.726W or perhaps 30:55.265N, 95:20.590W
Houston, Texas "The city with too much Oxygen"
rwhughe at oplink.net

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