Boat Engine
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Cargo Master
Joined: Aug 2002
Posts: 2,117
Likes: 8
From: Over Yonder, MN
Boat Engine
Figured it fits best in this forum as there is no general gas engine forum. Anyways my brothers boat has got us scratching are heads. It idles up then nearly stalls out, then idles up and again nearly stalls out, it continues this cycle endlessly… When you give it gas it runs along fine. After some poking we found that if you disconnect the TPS it idles fine, little high but otherwise smooth, but as expected giving it gas results in stalling out. So we replaced the TPS with one from the auto store… does the same thing, accept now it stalls out if you give it gas when the TPS is plugged in. Near as we can tell it’s just a plane ol’ Chevy 350 with TBI, about what you’d find in a 96ish pickup. Would the wrong TPS cause this? Or something else we’re not seeing?
Elder User
Joined: Sep 2006
Posts: 798
Likes: 1
From: Alma Arkansas
Did you adjust the new TPS sensor to read the proper voltage range idle and WOT or did you just screw it on and plug it up? These things have to be adjusted properly. Also remove the IAC motor and clean it and the aera where it seats?
Here is a link with some good how to info.
http://s-series.org/component/option...m,1/task,item/
Here is a link with some good how to info.
http://s-series.org/component/option...m,1/task,item/
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Cargo Master
Joined: Aug 2002
Posts: 2,117
Likes: 8
From: Over Yonder, MN
I dont think there was any type of adjustment on the TPS, but i'll look again.
Edit: it has no adjustment, it screws on in a fixed position.
Edit: it has no adjustment, it screws on in a fixed position.
Last edited by screwy; Oct 3, 2006 at 09:30 AM.
Posting Guru
Joined: Jul 2004
Posts: 1,627
Likes: 0
From: West Valley Utah
Does it have an idle air control? If so, that could be the problem.
You might try cleaning the throttle body and electrical connections also. Put dielectric grease on electrical connections to keep them from corrosion.
You might try cleaning the throttle body and electrical connections also. Put dielectric grease on electrical connections to keep them from corrosion.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 421
From: Long Island USA
Put the original TPS back on and see if it goes back to it's original symptoms.
Check whatever sets the idle, IAC, or whatever.
Check this out, from a quick Google:
http://www.rinda.com/acro/EFI_Articl...uiser%20efi%22
TPS voltage at idle is important. It sounds like it goes into some pre-set mode when the TPS is unplugged.
Check whatever sets the idle, IAC, or whatever.
Check this out, from a quick Google:
http://www.rinda.com/acro/EFI_Articl...uiser%20efi%22
TPS voltage at idle is important. It sounds like it goes into some pre-set mode when the TPS is unplugged.
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Cargo Master
Joined: Aug 2002
Posts: 2,117
Likes: 8
From: Over Yonder, MN
Well after looking at it myself, I found when it’s supposed to be in idle the TPS is actually turned quite a bit. If I have the TPS connected but not mounted it idles nice and if I try (as best I can) to turn the sensor while increasing the throttle I can get it to run good as well. It would seem the problem is that the TPS is turned too much while the butterflies are in idle, but I thought the computer was supposed to be smart enough to adapt to the sensor. Anyways, the simple fix would be to turn the sensor so it was aligned right, but there are no adjustments for it, the only way would be to get out the dremel and make some big modifications to it and hope for the best. Any Ideas?
It’ll be awhile before I get back to this, he’s storing the boat for the winter and come summer we need to pull the motor to replace a bad oil pump. Shame a 4yr old boat is having these problems.
It’ll be awhile before I get back to this, he’s storing the boat for the winter and come summer we need to pull the motor to replace a bad oil pump. Shame a 4yr old boat is having these problems.
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Elder User
Joined: Sep 2006
Posts: 798
Likes: 1
From: Alma Arkansas
You can bend the little metal tab on the inside of the TPS to gain some adjustment. But from what you describe it sounds like sombody has monkeyed with the baseline throttle opening screw and or a bad or sticky IAC. I would clean the IAC and then go through the procedure to establish minimum air, the idle speed. And then see what happens
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Cargo Master
Joined: Aug 2002
Posts: 2,117
Likes: 8
From: Over Yonder, MN
Originally Posted by jake00
uhhh,,, pull that motor during the off season...
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