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Help Chasing Erratic Idle Please

Old 10-24-2017, 09:30 AM
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Originally Posted by SB View Post
May have missed it...what is your fuel psi when running good vs running bad ?
didn't you calk about the VST in some cases flooding the plenum in another thread.....but I've slept sense then.
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Old 10-25-2017, 07:36 AM
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Originally Posted by SB View Post
May have missed it...what is your fuel psi when running good vs running bad ?
Haven't checked as I verified good fuel pressure prior to this issue. I'll go back and see where it stands now. Thinking fuel pressure regulator?

Originally Posted by F-2 Speedy View Post
didn't you calk about the VST in some cases flooding the plenum in another thread.....but I've slept sense then.
VST was completely rebuilt 15 hrs, ago.

Originally Posted by Warship2k15 View Post
Wiring harness bad?Fuel injectors bad?
I checked the harness at all the sensor connectors earlier in the thread, all came out well. I'll see what the scanner software I have coming nets prior to pulling injectors.

On a lighter note, I've gone from being very frustrated to excited to find the gremlin and solve this very random issue. Wish it wasn't costing me so much time out on the water though and time away from other smaller projects.

Keith

Last edited by Tractionless; 10-25-2017 at 07:39 AM.
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Old 10-25-2017, 11:12 AM
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Originally Posted by F-2 Speedy View Post
didn't you calk about the VST in some cases flooding the plenum in another thread.....but I've slept sense then.
That wouldn't apply to this situation. The VST plenum flooding comes into play after a warm engine has sat for a period of time allowing fuel to percolate out of the aged VST internal diaphragm thru the yellow hose and into the plenum. Having said that its good to bring up and cover all the bases.
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Old 10-25-2017, 11:15 AM
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Originally Posted by Tractionless View Post
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.
Can you replicate the poor idle / normal idle issue by fiddling with the TPS connector or its associated harness? One of the pins might be suspect.
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Old 10-26-2017, 08:32 AM
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Originally Posted by Trash View Post
That wouldn't apply to this situation. The VST plenum flooding comes into play after a warm engine has sat for a period of time allowing fuel to percolate out of the aged VST internal diaphragm thru the yellow hose and into the plenum. Having said that its good to bring up and cover all the bases.
Yep, no issue with hot restarts.

Originally Posted by Trash View Post
Can you replicate the poor idle / normal idle issue by fiddling with the TPS connector or its associated harness? One of the pins might be suspect.
Thought about that after packing it up the other night. I should have the scanning software this weekend and will check the harness (fiddling) as well as fuel pressure and bring up sensor diagnostics etc. all at once.
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Old 10-26-2017, 05:50 PM
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If you`re chasing an erratic idle problem I`d recommend better shoes and/or some endurance training.
It may be tough at first but once you catch that erratic idle, it will be well worth it and you will feel a great sense of accomplishment.
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Old 10-31-2017, 08:10 AM
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Dorman (CTI) P/N-84598, TPS harness has corrected the 1100 rpm and blowing black smoke idle on the hose on cold startup.

I'll have the boat on the water this weekend with a scanner to see if it's still going to idle surge and die on the hose during flushout. Stay tuned!
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Old 10-31-2017, 11:21 PM
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Originally Posted by Tractionless View Post
Dorman (CTI) P/N-84598, TPS harness has corrected the 1100 rpm and blowing black smoke idle on the hose on cold startup.

I'll have the boat on the water this weekend with a scanner to see if it's still going to idle surge and die on the hose during flushout. Stay tuned!
So perhaps the lesson for all is to fiddle with the pins.....
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Old 11-07-2017, 07:33 AM
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As promised the on water update.

Fired and idled at the correct rpm and no surging on the ramp and in the slip prior to getting underway. No issues idling out of the canal nor when bringing the throttles up to 1k rpm on the way out. Two no wake zones taken at 1k rpm and no surging. I anchored for 3.5 hrs. And upon restart it idled high at 900 rpm but no surge when brought up to 1k rpm to no wake past the other boats at anchorage. Got on plane for 1/4 mile and back down to 1k rpm for no wake under the bridge and it was surging at the 1k rpm point. Had the wifey take the helm while I grabbed the scanning gear, I should have steered to the left and kept it surging as by the time were were back up on plane and to the next bridge a few miles away the (idle) surge stopped at the 1k rpm point. Back to the canal and to 1k rpm and no surging all the way to the ramp where it idled fine at the slip prior to loading. On the hose it idled like a champ and I didn't have to continually goose the throttle to keep the engine running for washout.

All in all it seems most of the issue is solved for now but I've been to this point before and prior to authoring the thread. I'll make a dedicated on water datalogging only day in the near future to assess all sensors etc in real time and try to poinpoint what seems to be an inconsistent situation within the engine electronic system.
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Old 01-06-2019, 08:08 PM
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I've been working on this for over the past year with scans etc. Upon the advice of another member today I pulled the vac. line to the fuel pressure regulator while the 1k rpm surging was taking place and it immediately stopped the surging. Even though fuel pressure reads good with the vac line attached at all times, including during surging I may be leaning toward replacing the FPR. I will update the thread with my findings.

Keith
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