Engine Idle - Help!!

[Footin]

I thought 2 volts at idle was about right?

[JimN]

I thought 2 volts at idle was about right?

That depends on where it's being measured. If it's 2VDC going to the MAP sensor, it's a problem but if it's 2VDC from it, it's not.

[Double D]

As I posted before, the grounds need to be checked. If the MAP sensor voltage reference was to a bad ground that happened to be the one the ECM uses, it should throw a code. Again, all voltage and ground references are to the battery posts, not the cable clamps.

I would also recommend that a voltage drop test be done. There are some shared grounds too, and they should be checked out.

I thought 2 volts at idle was about right?

That depends on where it's being measured. If it's 2VDC going to the MAP sensor, it's a problem but if it's 2VDC from it, it's not.

Thanks guys! I will forward Chris this thread to give him your input.

[captain planet]

DD, sorry to hear about your troubles. That's a bummer. If it makes you feel better, I just spent all day packing at my house, called my footin buddy for tomorrow and told him I wasn't coming in the morning because I have to pack more. I just got back from dropping off a load of crap in storage.

Is Chris losing his edge?

[Double D]

DD, sorry to hear about your troubles. That's a bummer. If it makes you feel better, I just spent all day packing at my house, called my footin buddy for tomorrow and told him I wasn't coming in the morning because I have to pack more. I just got back from dropping off a load of crap in storage.

Is Chris losing his edge?

Yeah that sucks for you!! Didn't pack up the computer yet I see??

No, I cant say Chris has lost his edge, he just hasn't really been involved yet.... Now he is!

Hitting Salt Fork tomorrow with the brother and the family. Just dealing with the idle issue for now.

[Double D]

This sucks! I thank everyone for the advice so far but it figures my problem would happen after Harold left for good, and where the heck have the comments been from the BAWS guys??

My man Chris is waiting to hear back from MasterCraft but I still have a crappy running ship.... Going on almost two months now.....

[JimN]

This sucks! I thank everyone for the advice so far but it figures my problem would happen after Harold left for good, and where the heck have the comments been from the BAWS guys??

My man Chris is waiting to hear back from MasterCraft but I still have a crappy running ship.... Going on almost two months now.....

I just looked at your first post and I see a problem. You stated that the ECT isn't a standard GM part and that's wrong. These motors went to Indmar from the regular GM assembly line and there's no difference between that ECT and one on a regular GM car or truck. Second, the photo shows a tan/black wire going to the sensor on the top of the thermostat housing, with blue tape on it. That's WRONG!. That sensor has two wires on it and they're supposed to be yellow and black. If that sensor has two wires and they were twisted together, then connected to the tan/black wire, that's A) a bad repair and B) going to cause a problem when the ECM sees the voltage. If someone hasn't though to call MC for the correct part number, I have to wonder why.

If the shop wants to tear into the motor, it means they don't know this motor. It's not that hard to get info on it and if the diagnostic computer was actually connected, there's no way in hell it showed the correct temperature.

It's a simple system and any GM mechanic can fix it. Any MC tech should be able to fix it, too. If not, they need to go to training or take it upon themselves to find out how this stuff works. The diagnostic section in the manual is the same as what's in a Haynes or Chilton manual, except for the 02/Cat info and a few other minor things.

If it was actually connected to a diagnostic computer and it has a bad sensor, it would have shown up. If it has a bad ground on the motor, it would be seen as low voltage to the ECM and if that's compared to what is measured at the battery, it should be different.

"Increased the timing a bit"? How? Was it in Diagnostic Mode when this was done? If not, there's no way it's accurate, unless by luck. The timing mark would have been jumping all over the place if it wasn't in Diagnostic mode.

You posted that the compression was "perfect". What were the numbers?

Was the fuel pressure checked? If the people working on it went to any MC training, the first thing drilled into their heads was "80% of all driveability issues are fuel-related". This means pressure, volume and fuel quality. If the pressure hasn't been checked, do that now.

Verify the timing order. If it runs rough at idle, it could be wrong. It happens. It could also be a bad plug or plug wire. If the base of the distributor is dirty and not making good contact with the block, the IC module won't operate correctly.

[coz]

Any MC tech should be able to fix it

Sounds like the MC techs can't so I wonder why you don't go to an Indmar tech? Why are you dealing with a dealer that's incapable of getting you back on the water?....probably an easy fix for someone that knows what the hell their doing.

[JimN]

Sounds like the MC techs can't so I wonder why you don't go to an Indmar tech? Why are you dealing with a dealer that's incapable of getting you back on the water?....probably an easy fix for someone that knows what the hell their doing.

If they are a MC dealer, they need to get with the program.

[Double D]

I just looked at your first post and I see a problem. You stated that the ECT isn't a standard GM part and that's wrong. These motors went to Indmar from the regular GM assembly line and there's no difference between that ECT and one on a regular GM car or truck. Second, the photo shows a tan/black wire going to the sensor on the top of the thermostat housing, with blue tape on it. That's WRONG!. That sensor has two wires on it and they're supposed to be yellow and black. If that sensor has two wires and they were twisted together, then connected to the tan/black wire, that's A) a bad repair and B) going to cause a problem when the ECM sees the voltage. If someone hasn't though to call MC for the correct part number, I have to wonder why.

If the shop wants to tear into the motor, it means they don't know this motor. It's not that hard to get info on it and if the diagnostic computer was actually connected, there's no way in hell it showed the correct temperature.

It's a simple system and any GM mechanic can fix it. Any MC tech should be able to fix it, too. If not, they need to go to training or take it upon themselves to find out how this stuff works. The diagnostic section in the manual is the same as what's in a Haynes or Chilton manual, except for the 02/Cat info and a few other minor things.

If it was actually connected to a diagnostic computer and it has a bad sensor, it would have shown up. If it has a bad ground on the motor, it would be seen as low voltage to the ECM and if that's compared to what is measured at the battery, it should be different.

"Increased the timing a bit"? How? Was it in Diagnostic Mode when this was done? If not, there's no way it's accurate, unless by luck. The timing mark would have been jumping all over the place if it wasn't in Diagnostic mode.

You posted that the compression was "perfect". What were the numbers?

Was the fuel pressure checked? If the people working on it went to any MC training, the first thing drilled into their heads was "80% of all driveability issues are fuel-related". This means pressure, volume and fuel quality. If the pressure hasn't been checked, do that now.

Verify the timing order. If it runs rough at idle, it could be wrong. It happens. It could also be a bad plug or plug wire. If the base of the distributor is dirty and not making good contact with the block, the IC module won't operate correctly.

Sounds like the MC techs can't so I wonder why you don't go to an Indmar tech? Why are you dealing with a dealer that's incapable of getting you back on the water?....probably an easy fix for someone that knows what the hell their doing.

Wow, I didn't mean to start a dealer bashing. I have confidence in my dealer to figure it out. If it was an easy fix we would all have the answer and it would be done. Even by your list of ideas there is not one thing that jumps out and says, "THAT IS THE PROBLEM".

• The timing was done in diagnostic mode. Has it been checked when the problem kicks in, no.
• Read further and you will see the sensor was located on the starboard side of the engine on the head. This is not a normal spot for this sensor and the sensor with the blue tape is for the light on the dash. Hence the confusion.
• The cap & rotor were changed, the plugs are new, the wires have been tested, and it only happens after it gets nice and warm. First starts it runs fine until about 20 minutes...

Picture of the sensor location below: And this sensor has been replaced....

[JimN]

Wow, I didn't mean to start a dealer bashing. I have confidence in my dealer to figure it out. If it was an easy fix we would all have the answer and it would be done. Even by your list of ideas there is not one thing that jumps out and says, "THAT IS THE PROBLEM".

• The timing was done in diagnostic mode. Has it been checked when the problem kicks in, no.
• Read further and you will see the sensor was located on the starboard side of the engine on the head. This is not a normal spot for this sensor and the sensor with the blue tape is for the light on the dash. Hence the confusion.
• The cap & rotor were changed, the plugs are new, the wires have been tested, and it only happens after it gets nice and warm. First starts it runs fine until about 20 minutes...

Picture of the sensor location below: And this sensor has been replaced....

That should have two sensors for temperature- one for the ECM and one for the gauge. If it has a separate temperature light, that would explain the upper one but using tape for the connection is a bad way to do that and I can't think of a reason to not use the other one-wire sensor for the gauge and a separate light. If it has only one check engine light, that's supposed to be connected to the ECM's output.

The ECT IS located on the side. If the harness hasn't been modified, that's where it was from the beginning and it's the same sensor they always used. Again, if they didn't call MC for the correct part number, I have to wonder why. Maybe they haven't been a MC dealer for a long time but they need to at least get a copy of the manual.

Diagnostics takes time when the problem may have a thermal component. It can be a connection, a sensor, wires, a module or the pump. Have you re-checked the oil cooler, cooling hoses and impeller?

If it doesn't idle velvet smooth when it's cold, it has a problem, usually with spark. Whether it's a plug, wire, cap, rotor, IC module or firing order remains to be seen. If everything is right, this motor is extremely smooth at idle. Don't be afraid to suspect parts that were replaced. AC MR43T is the correct plug. Don't go cheap and don't let them force you to use something else- these are made for hard use in marine environments.

We were taught that the first four steps in diagnosing a driveability issue:

1) Verify the complaint.
2) Once the complaint has been verified, do a visual inspection. Do a 'wiggle test' of all connections and wires.
3) Run diagnostics- if anything shows up, address it. This includes ALL fuel, spark, compression, electrical and other mechanical tests.
4) Replace any bad parts and verify that the issue has been eliminated.

Mechanical problems are easy. It's the electrical/electronic ones that give most techs fits. I saw that the first time I went to MC training- guys with great reputations for carbureted motors looked at a relay like they were a dog watching TV. They learned but it was foreign territory for them.

One of the best classes offered was 'On-water, advanced diagnostics. They reinforced the basics and then created "Cranks, but no fire" problems on the various boat models, which we had to solve. We had three people in each group and it was a great way to streamline the process.

Maybe he needs to get together with someone else to get the ideas flowing.

Sorry, but I'm intolerant of dealers who don't send their techs to training. There's no gray area, IMO. If they don't, they're doing a huge disservice to their customers and I don't care what brand is being discussed- ALL dealers should have trained techs. I don't know who this dealer is or how long they have sold MC but if they want to be able to service MC, they should be able to service ALL MC, not just the new ones.

I'm not where the boat is and I can't see what was done to diagnose the issue(s) but if everything I posted is done, the problem will be found. It absolutely MUST be tested when the problem shows up, including timing. If it's not at 10°BTDC base timing, have him set it to that. If it's not advancing to the correct maximum at high RPM or when using the diagnostic computer, it could easily be a bad distributor ground or the IC module. There's still a possibility that it's a bad connection between the ECM and IC module, too. Vibration and heat can cause wires to sag and break their connection.

Have him open and close the IAC. If it doesn't function normally, he needs to check it. This is part of the normal diagnostics when an idle issue is present.

If this problem coincides with any accessory installation, the best place to start is by removing the connections that could be causing this.

[coz]

Have him open and close the IAC. If it doesn't function normally, he needs to check it. This is part of the normal diagnostics when an idle issue is present.

I can't believe this wouldn't be the first thing they check if it's an idle problem....remind your dealer IAC stand for Idle Air Conrol and this might be the problem.

[JimN]

I can't believe this wouldn't be the first thing they check if it's an idle problem....remind your dealer IAC stand for Idle Air Conrol and this might be the problem.

Bad fuel pressure/quality, bad injector(s) and crossfire can cause the same thing. The wires on my truck were causing intermittent idle issues on my truck and I figured it out while I was in a drive-through lane, when I heard an odd snapping sound. If I gunned it, it went away for a while but came back. It idled like crap at the time and it's like new, now.

[captain planet]

Are you boating yet DD?

[Double D]

Are you boating yet DD?

I boated on Sunday with the family and it was a chore. When I was in No-Wake areas I had to hold the R's at 10 (still made a lot of wake), and when I was picking up a skier I kept the idle up and went in circles around them until they were ready. It idled bad most of the time and stalled twice.

Still waiting to hear from Chris on the readings he took last Friday.