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-   -   Help Chasing Erratic Idle Please (https://www.offshoreonly.com/forums/general-q/349163-help-chasing-erratic-idle-please.html)

Tractionless 10-22-2017 07:38 AM

Installed a teflon lubbed new IAC motor yesterday, TPS still set at 0.58v, fired up on the hose and it ran rough (like a dead hole(s)) blowing black smoke and idling at 1100 RPM.

From previous info. given above; with the old IAC and TPS at 0.58v it ran fine on the water, no black smoke but wouldn't stay running on the hose and idle surged on the water. Additionally when the TPS was set at 0.7v (manual value) it ran exactly how it did in my opening sentence when I fired it for the first time on the water; however, ran fine on the hose. When I brought the TPS value down to 0.58v on the water it didn't smoke, idled at 600 and purred like a kitten, now back to rough running, high idle and blowing black smoke.

ECU's get swapped next.

Warship2k15 10-22-2017 09:53 AM

Did you check your meter for acurracy or try a different meter.
You could also hook up the the other rod and see what it's reading now.
It could definitely be the ecu.
But you don't want to be chasing your tail because you have a meter that started acting up.

Tractionless 10-22-2017 10:45 AM


Originally Posted by Warship2k15 (Post 4589334)
Did you check your meter for acurracy or try a different meter.
You could also hook up the the other rod and see what it's reading now.
It could definitely be the ecu.
But you don't want to be chasing your tail because you have a meter that started acting up.

Oh yea, 3 multi-meters all reading the same thing. Being I get the same (idling) results with multiple IAC's, TPS' (at varying voltages), water temp. sensors, MAP sensors and after verifying all connectors are receiving and providing the correct "info"; I'm going to see what I get from swapping ECU's today.

On car platforms I've seen issues with ECU's on the fritz causing intermittent issues.

Tractionless 10-22-2017 06:35 PM

I first confirmed the good running engine TPS is the same voltage as the erratic running unit 0.57V. I prefer to compare apples to apples but read on.....................

As promised, ATTEMPTED to swap the ECU's today and happened upon MEFI 1's with two different Model numbers. The erratic idling #16234539 and #16189069 on the other engine that has zero issue. See attached picture, they are different sizes. I stopped right there as I'm not sure whether or not they are swap-able. The #162 (erratic engine) was used by Mercruiser the #161 was not and seems to be a GM car/truck ECU (see attached picture from MEFI Burn). So now I have more questions than answers.

Should the Non-Mercruiser unit (#161) even be on a boat? Did modifications to sensors, harness, tune etc. need to be made to use in on my engine? I was afraid of swapping them and potentially cause more harm than good.

https://uniim1.shutterfly.com/ng/ser...714842/enhance

https://uniim1.shutterfly.com/ng/ser...714862/enhance

Keith

AllDodge 10-22-2017 07:14 PM

Don't know right now but might have found the issue so long as the ECU was not re-flashed. Need to look more indepth

Trash 10-22-2017 10:28 PM

See my reply in your other post...

Tractionless 10-23-2017 01:33 PM

I called MEFI Burn today with the issue. They stated any of the model numbers of MEFI 1 will work but must have the correct tune installed. MB also stated the MEFI's were used in other platforms other than the marine industry. If I have to purchase another unit I'll need to ensure its loaded with the proper mapping for my engine, no matter what the model number.

Atleast I now know I can swap side to side and see if my issue goes away. Hopefully the weather will hold up to do it after work tonight. Then I'll know if I need an ECU or the problem is somewhere else in the harness in which case I'm buying a scanner.

Tractionless 10-24-2017 07:27 AM

Swapped ECu's and no change, still idling at 1100 rpm, blowing black smoke and running rough.

Switched back to original ECU, unplugged the TPS harness to tape the exposed insulation (used during testing) plugged it back into the TPS, decided to start the engine again and VIOLA; idles at 750 rpm, no smoking and not running rough! Then I blipped the throttle and right back to running rough, blowing black smoke and idling at 1100 rpm?!!?

Normally I'd assume TPS going bad; however, I've already experimented with a new TPS, set at the same base voltage as the OE unit and it had the same rough running, blowing black smoked and idling at 1100 rpm issue. See post #14. The harness side at the TPS has been tested as well, see post #13.

I feel I'm out of options and I ordered scanning software from MEFI Burn before writing this post.

Warship2k15 10-24-2017 07:54 AM

Wiring harness bad?Fuel injectors bad?

SB 10-24-2017 08:58 AM

May have missed it...what is your fuel psi when running good vs running bad ?


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