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Old 08-11-2019, 05:19 PM
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LTR sluggish and surging.

Hi All,

I thought I had a fuel pump that was going out but it wasn't the case. No big deal though, glad to have replaced that Carter pump as it was original to the boat with 650-700 hours.

The boat is still brutally sluggish when trying to pull a skier. The holeshot is pathetic. In general, the boat will be very sluggish when you drop the throttle, and then anywhere between 20-30 mph it might all of a sudden jump back to life and will hold solid until the end of the run. Or it will be brutally slow in acceleration. It's very distinctive when it "comes back to life", its really just clicks back to normal and you hear the engine rev up to the power level that it should be at that throttle position. Sometimes it will throttle back down, like a "surging" feel. Another thing thing I did noticed is that I'm only getting 3900 or so RPM out of the boat and 39mph top end. I used to be able to get 44 mph with this prop, so something isn't right there...

Engine doesn't misfire, great fuel pressure and temp holds perfectly at 160. The plugs are good and I replaced the ignition wires about 3 years ago, they might have 100 hours on them. I checked the throttle linkage with the PP and that all looks fine. I thought it might have been bad gas but I put in a fresh tank and no changes. As I mentioned in the first paragraph I put in a new E2044 fuel pump this weekend.

I read the thread from Soder and his problem seems similar to mine, correct Soder? From what I gather I should be checking or replacing the following items - 1. TPS, 2. ICM, 3. ECU.
My initial thought is it's the TPS, but to be honest I don't even know how the TPS works. And since the throttle is mechanical could the TPS slow the boat down if it was faulty?

Can you guys give any instruction on testing the TPS or ICM to determine if they are faulty? Boat is in storage so I gotta drive across town to work on it....

Thanks
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Old 08-11-2019, 10:31 PM
37tr3n5k 37tr3n5k is offline
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Your symptoms are very similar to DomXStar. He finally got a hold of a diagnostic computer and it was his MAP sensor. They will cause this symptom. Below is the thread:


https://teamtalk.mastercraft.com//sh...d.php?t=101090

Soder's issue nded up being a coil. The ICM is seperate from the coil in earlier models.

In response to your question, the TPS should have an output voltage between .7 and .8 volts in an MEFI 4 ECM. This value is recognized in scanning software and is easiest diagnosed using it. You can see the value move when moving the throttle.

Testing a MAP sensor is done the same way- it should read "29 - 48 kPa / 1 - 2 Volts (Depends on engine vacuum
and barometric pressure)."

Last edited by 37tr3n5k; 08-12-2019 at 08:21 AM.
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Old 08-12-2019, 10:54 AM
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paintpollz paintpollz is offline
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Quote:
Originally Posted by 37tr3n5k View Post
Your symptoms are very similar to DomXStar. He finally got a hold of a diagnostic computer and it was his MAP sensor. They will cause this symptom. Below is the thread:


https://teamtalk.mastercraft.com//sh...d.php?t=101090

Soder's issue nded up being a coil. The ICM is seperate from the coil in earlier models.

In response to your question, the TPS should have an output voltage between .7 and .8 volts in an MEFI 4 ECM. This value is recognized in scanning software and is easiest diagnosed using it. You can see the value move when moving the throttle.

Testing a MAP sensor is done the same way- it should read "29 - 48 kPa / 1 - 2 Volts (Depends on engine vacuum
and barometric pressure)."
37tr3n5k, much appreciated. So I'm guessing there's two plays to call here. First play would be to get one of these mefi scan things to test the sensors. Based on Doms thread, I think I would need to the following scan tool?

http://mefiburn.com/mefiscan.asp

mefiscan4-u

Then I could always have this in case I need to scan for something in the future.

The second play would be to just start throwing parts at it. Maybe start with the MAP sensor, and then go from there. No way to know what sensor is going if you can't scan.

Am I on the right path here? Thanks
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Last edited by paintpollz; 08-12-2019 at 11:06 AM.
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Old 08-12-2019, 11:06 AM
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.......

Can someone confirm these replacement part numbers?

MAP Sensor - ACDelco 12615136

- OE 09359409

TPS Sensor - AV Delco 17106681


ICM Module - ACDelco D1943A
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Last edited by paintpollz; 08-16-2019 at 03:54 PM.
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Old 08-12-2019, 01:20 PM
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Quote:
Originally Posted by paintpollz View Post
I read the thread from Soder and his problem seems similar to mine, correct Soder? From what I gather I should be checking or replacing the following items - 1. TPS, 2. ICM, 3. ECU.
My initial thought is it's the TPS, but to be honest I don't even know how the TPS works. And since the throttle is mechanical could the TPS slow the boat down if it was faulty?
My first bet would be your ICM. I had this exact same symptom a few years ago:

https://teamtalk.mastercraft.com/showthread.php?t=74673

I believe one job the ICM has is to switch the timing from base timing to ECM timing when the RPMs get above 400-ish. Basically if the starter isn’t spinning the engine, let the ECM control the timing. It seems like it’s not switching soon enough.

As far as testing, I’m not sure sure of a good test. Bob at MEFIburn suggests getting a used one from a junkyard as the new ones are cheap quality. The $55 one I replaced in 2016 from NAPA has already failed. I grabbed a cheap one on at OReily for $35 for a backup.

37tr3n5k Is correct on testing the TPS and MAP sensor. My MEFIburn software shows those voltages coming back. It’s easy to test the ground, 5V reference voltage and the return signal voltage with a volt meter. Both are 3-wire sensors (ground, 5V reference, return signal voltage).
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Last edited by Soder; 09-08-2019 at 10:32 PM.
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Old 08-12-2019, 02:41 PM
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Quote:
Originally Posted by Soder View Post
My first bet would be your ICM. I had this exact same symptom a few years ago:

https://teamtalk.mastercraft.com/showthread.php?t=74673

I believe one job the ICM has is to switch the timing from base timing to ECM timing when the RPMs get above 400-ish. Basically if the starter isnít spinning the engine, let the ECM control the timing. It seems like itís not switching soon enough.

As far as testing, Iím not sure sure of a good test. Bob at MEFIburn suggests getting a used one from a junkyard as the new ones are cheap quality. The $55 one I replaced in 2016 from NAPA has already failed. I grabbed a cheap one on at OReily for $35 for a backup.

37tr3n5k Is correct on testing the TPS and MAP sensor. My MEFIburn software shows those voltages coming back. Itís easy to test the ground, 5V reference voltage and the return signal voltage with a volt meter. Both are 3-wire sensors (ground, 5V reference, return signal voltage).
Hmmmm. what to do. Buy the MEFI software or just shoot from the hip with the ICM....???
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Old 08-12-2019, 04:19 PM
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Grabbed an ICM from Summit during my lunch break. it was $50 with tax. I didn't know you applied thermal paste to this. I work in the lighting industry so I know what happens first hand if you don't have high quality paste,,,your products will fry. Hoping this is the issue. Will report back later this week.
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Old 08-16-2019, 03:51 PM
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Is this not the right part number for an ignition control module on an LTR?

ICM Module - ACDelco D1943A.

I can't find where this thing would go. Looks like this isn't going to work with an LTR since I don't have a cap and rotor.

Is this what I should have bought?

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Old 08-16-2019, 07:27 PM
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Quote:
Originally Posted by paintpollz View Post
Is this not the right part number for an ignition control module on an LTR?

ICM Module - ACDelco D1943A.

I can't find where this thing would go. Looks like this isn't going to work with an LTR since I don't have a cap and rotor.

Is this what I should have bought?

Attachment 189751
I've never seen an ICM that looks like that. I'm not familiar with the LTR ignition system. Can you take a picture of where the spark plug wires are plugged in (opposite the plugs)? The ICM should sit under that "distributor cap."
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Last edited by Soder; 09-08-2019 at 10:33 PM.
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Old 08-16-2019, 08:55 PM
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Quote:
Originally Posted by paintpollz View Post
Is this not the right part number for an ignition control module on an LTR?

ICM Module - ACDelco D1943A.

I can't find where this thing would go. Looks like this isn't going to work with an LTR since I don't have a cap and rotor.

Is this what I should have bought?

Attachment 189751


Take a look at this thread should explain it all. It is a little old but was updated a year ago or so. Should get you on the right track.

The LTR doesn't have a distributor it uses the Cadillac Northstar ignition system.

https://teamtalk.mastercraft.com//sh...ad.php?t=39965
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