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Rrrockhound's Avatar
 
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D-jet throttle switch

On my 2.0 with D-jet, turning the mixture knob has no impact on CO, which according to Brad means the throttle switch is out of adjustment. When I try to adjust it, the resistance doesn't go to zero, but bottoms out at 0.4 ohms (and yes, I zeroed out the meter first). But besides that, no matter how I adjust the throttle switch, it doesn't re-activate the mixture knob anyway. Meanwhile, my CO is really high, about 5.3%, and I assume my a/f is pretty rich, so I have to do something.

I'd just buy a new throttle switch in a heartbeat if they weren't NLA. But since I'm stuck with the one I have, anyone have any ideas?
Old 03-28-2007, 05:21 PM
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The switch really is a switch; the contacts get shorted to each other when it is closed. It's on or off, not "more resistance" and "less resistance". Pop the plastic cover off and look.

0.4 ohms isn't bad--it's a simple on/off, so that should be enough to tell the ECU that the thing is at idle.

Does shorting the two pins in question together (in the plug on the wiring harness) allow the knob to do anything? If not, you've ruled out the TPS.

--DD
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Old 03-28-2007, 07:32 PM
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For a new TPS, try calling Otto at Otto's of Venice Beach - look him up on Google.

As DD says, I don't think your problem is your TPS. If the ECU knob has no effect on idle mixture when you short the pins, then your problem is either with the ECU itself or some other component that is causing a rich mixture. I would check the fuel pressure, the CHT (right part number, correct resistance hot and cold, verified at the ECU plug) and the MPS (right part number, not tampered with, primary and secondary resistances verified at the ECU plug, holds a vacuum) before I would be sure that it was the ECU. If it's the ECU, the best way to verify is by swapping with a known good ECU. You can usually find an ECU on Ebay for a reasonable price.
Old 03-29-2007, 07:48 AM
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Thanks for the ideas. Good call on jumping the pins together. Still no effect on the mixture knob from what I can tell (I didn't hook up the CO meter but I couldn't detect any change in the idle). I happen to have a couple of spare ECUs on hand so I'll try one of those next. I went ahead and sourced a new TPS anyway because I plan to keep the little money pit for a few more years.
Old 03-29-2007, 05:17 PM
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Update: I swapped in a spare ECU and it made a difference right away. I could adjust the idle and without even hooking up my CO meter I could see a difference at the tailpipe (no soot). While I had the side of the old ECU open, I checked the underside of the mixture knob and could see little parts rattling around inside the clear housing, so no wonder it didn't work. I'm really glad I stocked up on spare ECUs. Dave and Brad: thanks!
Old 03-30-2007, 04:22 PM
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I've seen a few other ECU's with broken idle mixture pots, so it's not unheard of. Glad it's fixed!
Old 04-02-2007, 07:45 AM
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