High idle and miss fire with scanner.

[smdk2500]

So my 95 2500 5.7 wouldn't start this morning. It wouid crank but not fire. It acted like i wasn't getting any fuel. When i got off work I tried it again it cranked longer normal but finally fired up. I didn't have SES light but hooked up my scanner just to look at things. After it had warmed up to operating temp while viewing the data stream it would miss badly and was idling from 950 up to 1100 rpm. As soon as i unhooked the scanner the ldle returned to normal and quit missing. Has anyone ever heard of missing and high idle with a scanner hooked up and then stop when removed?

 

[skylark]

I have a snap op mt2500 that idles high with the earlier 7747 tbi ecms. No misfire issues though.

 

[smdk2500]

my scanner is the snapon solus edge. When i first got it i hooked it up and was playing learning how to use it and didn't have this issue. Tried starting the truck this morning and it ran for about 30 seconds and died and wont restart. I wish it would do this in the after noon and not at 630 in the morning when the whole neighbor hood is asleep and i have more time to mess with it.

 

[PlayingWithTBI]

I have a snap op mt2500 that idles high with the earlier 7747 tbi ecms. No misfire issues though.

I don't know if your scanner does this but, when I short pins A & B with a 10K Ohm resistor my 7747 will idle about 1,000RPM and sound like it's missing. In the Scalars this setting adds spark when the pins are shorted with the resistor. You don't need the resistor with this ECU.

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[smdk2500]

Well i messed with it after work and im not getting any spark which i figured was what was happening. Pulled the cap and it has some corrosion on the terminals but not to the wire i was using to check spark. had the ignition module tested and orileys and they said it was ok. I did find that the pick up coil plug has some corrosion build up in it. Im wondering if that is fully causing my problem. I just need to find a easy way to get it cleaned out with out having to remove the distributer.