LTR sluggish and surging.

[paintpollz]

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

[37tr3n5k]

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//showthread.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)."

[paintpollz]

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//showthread.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

[paintpollz]

.......

Can someone confirm these replacement part numbers?

MAP Sensor - ACDelco 12615136

- OE 09359409

TPS Sensor - AV Delco 17106681


ICM Module - ACDelco D1943A

[Soder]

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).

[paintpollz]

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).

Hmmmm. what to do. Buy the MEFI software or just shoot from the hip with the ICM....???

[paintpollz]

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.

[paintpollz]

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?

[Soder]

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?

[ATTACH]189751[/ATTACH]

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."

[mtajpa]

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?

[ATTACH]189751[/ATTACH]

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//showthread.php?t=39965

[paintpollz]

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

Yep just found it. I wish I could actually diagnose what's wrong before spending $900 on new coil packs and an ICM. I'd rather avoid the classic case of throwing parts at it until it fixes it. Will the MEFI burn software be able to tell me if I'm having ignition issues? Or, will the sensor readings help me diagnose an ignition issue?? I hate to beat a dead horse with this but I want to spend $$$ in the right places. If you tell me to just get it and post up the readings I will

I took the MAP sensor out and it was filled with crap, so I cleaned it but same symptoms are occurring.

[mtajpa]

First thing to look at would be fuel pressure during the sluggish performance. If it is not a steady pressure then check the connections to the pump for signs of corrosion or heat. You did use the Oetiker clamps if I recall. Does your fuel pressure remain when the pump is turned off?
If it goes to zero then it indicates a leak. Probably internal to the pump.

My next place to look if you suspect an electrical issue would be to dissemble the coil packs and check the coils visually and clean ALL connections.

In my opinion 90% of the issues found on the LTR/LT1's have probably been connection issues in which people have replaced parts only to have the issues flare up again.

This is the area I would be focusing on first.

Hope this helps

[paintpollz]

First thing to look at would be fuel pressure during the sluggish performance. If it is not a steady pressure then check the connections to the pump for signs of corrosion or heat. You did use the Oetiker clamps if I recall. Does your fuel pressure remain when the pump is turned off?
If it goes to zero then it indicates a leak. Probably internal to the pump.

My next place to look if you suspect an electrical issue would be to dissemble the coil packs and check the coils visually and clean ALL connections.

In my opinion 90% of the issues found on the LTR/LT1's have probably been connection issues in which people have replaced parts only to have the issues flare up again.

This is the area I would be focusing on first.

Hope this helps

This does help and thank you.

I ordered Oetiker lamps however they were too large, so I used the hose clamps that came with the pump kit. I know that's not preferable, however the same exact symptoms were present before I replaced the original fuel pump, so I would not think I have a leak or this these issues were due to the fuel pump going out. I do plan on going back and replacing those hose clamps with Oetiker clamps once I can figure out the correct ones to use with the replacement submersible fuel line. maybe jharmon can help with that ,I think he replaced the hard fuel line on his boat with the same one I have.

I have not put a pressure gauge on the fuel rail yet.

I did double check the connection to the pump and its OK. It's not loose/wiggling/corroded.

I'm watching the kiddo right now,,,once wifey gets home I'm pulling off the coil packs and inspecting those and the ICM.

[paintpollz]

Took off the coil packs and ICM. The connections look perfect, they show no signs of corrosion at all.

One question though, should there be thermal paste on the back of the ICM that attaches to the plate on the engine? Because there is nothing there but looks like there might have been a paste on it previously.

[mtajpa]

Not sure about the paste. Be sure the tower parts of the coil packs do not have any cracks as this could be a path to short out. The #6 tower looks like a vertical crack in the picture. The bolt holes need to be cleaned as well as I think this is the negative connection to coils not 100% on that one.