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Old 03-01-2013, 04:06 PM
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Noob with question on throttle pedal response

1st time OBS owner here, just picked up my truck this week and slowly getting a few bugs worked out of it, hope you guys don't flame me too bad, I tried searching this a few times without much luck on an answer.

If I hook my Snap-On scanner to the truck with the engine running, slowly apply ~10% throttle, the throttle pedal voltage rises up to a little over 1 volt before the duty cycle on the injectors responds...basically the truck has a pretty bad dead spot to the throttle. Being a manual it is really noticable, and I am sure there could be several things contributing to the issue...so here is the short list of things I have done so far

Baldwin fuel filter

Fresh fuel

Checked and corrected fuel pressure (the regulator was stuck, giving me only 15-20 psi, now I have 45-50 at idle and almost 70-75 @ 2500 rpm)

Cleaned the electrical connector at the throttle pedal

Like I mentioned, the voltage does increase with the throttle...just the engine does respond until I get close to 1.2V. The best I recall it idles around .58V

The truck has a stock ECU (no chip or tune) and is an original part...the IDM is not original, cannot see any sticker or ID tags on it, but it is all black. Back in the day NAPA's line of replacement ECU's were black (Echlin brand??).

I am going to pull the IDM and see if I can identify it.

Any other thoughts or information you guys may need to know?

Thank you in advance!!

Last edited by Reed P; 03-01-2013 at 04:13 PM.
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Old 03-01-2013, 06:27 PM
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Set your scanner up to look at the idle validation switch. I'll bet it doesn't switch from zero to one until right about the time you see the duty cycle ramp up. Classic "dead pedal" phenomenon. There's a place where you can adjust the stop so the idle switch closes "earlier" in the pedal travel, but you'd have to search here and on the other PSD sites for a thread with the exact procedure.
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Old 03-02-2013, 06:17 AM
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I will check that and do some research, thank you for the idea!
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Old 03-02-2013, 06:23 AM
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Good call I read about that also
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Old 03-02-2013, 10:12 AM
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Checked the switch with a digital volt meter because my old Snap on scanner does not show the IVS data on the screen. The switch was full of dirt and crud from all the years and was a little sticky but still closed the circuit right before the rpm raised. I cleaned it out and the truck seems to be a little more responsive so I am going to take the time to pull out the the whole assembly and clean it all up...maybe a little tlc will do it good!

The injector pulse width hangs around 1.26-1.27ms at idle, and now I start to give the truck a little throttle and it raises to 1.30-1.31 pretty much instantly, so I think I am on the right track.
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Old 03-02-2013, 12:41 PM
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Does it take a lot of pedal movement to close the IVS?
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Old 03-02-2013, 01:46 PM
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The switch closes around .90 volts on the throttle position sensor, then the truck will respond to throttle input around the 1.15-1.20V range currently.

Another dumb question, the IVS is doing what for the tune in the truck? I am used to vehicles that the idle is determined by the minimum TPS threshold...so I am taking it my truck only knows it is at idle position by the IVS?

What are you guys seeing for injector pulse width at idle? I guess that would tell me a little more about my settings/throttle behavior

Thanks again for all the input!
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