Engine Idle - Help!!

[captain planet]

I passed you on Wales in front of Shady Holloy tonight and you were towing the boat. So.......did it go well?

[Double D]

I passed you on Wales in front of Shady Holloy tonight and you were towing the boat. So.......did it go well?

Was this at 4:30 PM or at 9 PM??

It went OK. My first purchase will be the IAC which was having some real strange readings. They are doing what they can to diagnose it without having me spend and spend on parts.

I did learn that West Branch is a cleaner lake, but it doesn't have the channel. Still prefer Berlin.

[captain planet]

Was this at 4:30 PM or at 9 PM??

It went OK. My first purchase will be the IAC which was having some real strange readings. They are doing what they can to diagnose it without having me spend and spend on parts.

I did learn that West Branch is a cleaner lake, but it doesn't have the channel. Still prefer Berlin.

It was at 9. I was taking another load of stuff from the house.

Did you get the photos of big moe?

[Footin]

Family boating = West Branch

Footin and skiing = Berlin


I would still replace the plug wires even though they tested good, are they original?

[Double D]

It was at 9. I was taking another load of stuff from the house.

Did you get the photos of big moe?

You notice I had no lights on?? The running lights on the darn trailer are now on the fritz. Brakes and signals work... More to work on...

Got the photo's, found it on Google maps, and responded to your mail. Thats just crazy having large objects under water out there..

[Double D]

Family boating = West Branch

Footin and skiing = Berlin


I would still replace the plug wires even though they tested good, are they original?

Agreed on all three comments!

[Footin]

Any updates?

[Double D]

Any updates?

Yep! It's not the coil and its not the IAC!!

[Footin]

Did you try new plug wires? I only ask because they may check ok when cold, but build resistance when the get hot.

Just a guess....

[Double D]

Did you try new plug wires? I only ask because they may check ok when cold, but build resistance when the get hot.

Just a guess....

Put on new wires yesterday and tried it on the lake this morning. Didn't work! Next is to remove the intake and replace the gasket. Leaning towards doing it myself to get it done quickly.

[JimN]

Needs some help guys. I will try to make this short and precise so you don't lose track.

Equipment:
1994 ProStar 205
350 CI Indmar, 275 HP
Throttle Body Fuel Injection

History:
July 2009 filled up with gas at Marina. Started running rough at idle so I thought I got bad gas.

My Fixes:
- Put in treatment in Gas.
- Ran tank empty
- Changed Gas/Water Separator
- Changed Thermostat
- Changed Plugs
- Changed Fuel Filter
- Tested Plug Wires

Result:
Still runs very rough at low idle. Stumbles when engaging to forward.

Next Step:
Took it to the local dealer where they did the following:
- Compression Tested the engine.
- Change Rotor and Cap
- Re-gapped the Plugs
- Replaced the timing control module
- Increased idle a bit
- Water tested it and said it was ready.

Result:
It started better and for the first 25 minutes of speeding and no wake it ran fine. We stopped to gear up to ski and the idle began surging, or should I say dropping. The range of idle on the RPM dial would be from 9 to 8, 9 to 8, 9 to 8 and it wouldn't stop. If you tried to put it in gear, half the time it would stall. So now it is running worse!

Next Step:
Returned it to the dealer where they did the following:
- Replaced two carburetor gaskets that were cracked and sucking air.
- replaced a clear yellow rubber vacuum hose for the map sensor
- Changed PVC Valve
- Did another compression check (Perfect)
- Ran the engine in the shop. (no water test)

Result:
Picked it up last night and ran through the same scenario. 25 minutes of speed areas and no wake zones. Speed to the area to gear up and stop and guess what, it still does it. It wasn't as bad at first but it got worse and back to what it was doing the first time. 9 to 8, 9 to 8 on the tack.

I tried to pull my son on the wakeboard with the Perfect Pass and the engine problem is even messing with that now. Everytime he pulls to make his cut it slows the boat down and the engine cant react quick enough and he hits the wake at 3 mph less than he should. I had to pull him manually.

Additional Information:
- Obviously the dealer didn't water test it long enough to get it hot enough
- Running it in the shop wont get it hot enough
- temp gauge shows a hair below 160 when warm and around 140 when cooled.
- I spoke to the dealer while on the lake and they think it might be the Coolant Temperature Sensor. The wire was lose so I fixed that but it did not correct it.
- It did seem to run better after it sat for 15 minutes while I was fixing that wire, but it didn't last. To me that says temperature....

Next Steps:
The dealer is hoping to order a new Coolant Temperature Sensor (not a standard GM part) because they think there may be a conflict between what the gauge is saying and the sensor is saying which is messing with the computer control.

The dealer is perplexed and if this sensor doesn't fix the problem then they said they might start tearing into the engine, and I don't really want that cost.

On a side note:
- It now runs worse then it did when I first took it in
- The dealer has not charged me for the labor during the second visit
- The compression checks show an almost perfect engine.

So here I am asking for some serious assistance from all you. Hopefully someone has been through this problem.

I see that you have a '94 Indmar motor, then you mention that it had two cracked carb gaskets. If you mean Throttle Body gaskets, I understand. The thing that bothers me is, you indicate that the idle was increased. THIS ISN'T ADJUSTABLE!!!!!!!!!!! This motor uses the IAC to set/maintain idle speed and that screw, which I hope wasn't altered, is only a throttle level rest.

I have some major problems with what has been done so far.

I have a worksheet for EFI diagnostics that we got at the first training session- I'll post it later.

Here's a tip for them- drizzle some gas into the throttle body when it bogs- I use an old mustard bottle with the adjustable tip. If it runs better, it's a fuel issue. If it runs worse, it may be a control issue. Either way, what they're doing to diagnose it isn't logical, systematic, or working. Just deciding to remove the intake manifold so the gasket can be replaced makes no sense. Unless it overheated incredibly badly, that gasket is fine. If it overheated badly enough to toast the intake gasket, the head gaskets are toast, too.

OBJECTIVE TESTING is needed, not guessing by the tech. Has a substitute fuel source (tank) been used? If not, why not? Your fuel pickup tube should have been checked at the very beginning of this ordeal. The fuel line attaches to this via an anti-siphon valve. That should have been checked, too. Also, the fuel line from the tank to the pump should have been checked. If it runs OK at first and not after 15 minutes or more, the gas tank vent should have been checked.

I have a TBI fuel pressure test block that can be connected in line, before the throttle body. Let me know if they need it. Otherwise, they should get a section of fuel line and put a Shrader valve on it so they can test the pressure, which I suspect is low.

A motor needs three things to run- compression, spark (preferably, at the right time in the cycle) and fuel/air mixed correctly. Period. This TBI system isn't that complex that it should cause this much grief. If they don't have a shop manual from MC, they need to get one.

[Double D]

I see that you have a '94 Indmar motor, then you mention that it had two cracked carb gaskets. If you mean Throttle Body gaskets, I understand. The thing that bothers me is, you indicate that the idle was increased. THIS ISN'T ADJUSTABLE!!!!!!!!!!! This motor uses the IAC to set/maintain idle speed and that screw, which I hope wasn't altered, is only a throttle level rest.

I have some major problems with what has been done so far.

I have a worksheet for EFI diagnostics that we got at the first training session- I'll post it later.

Here's a tip for them- drizzle some gas into the throttle body when it bogs- I use an old mustard bottle with the adjustable tip. If it runs better, it's a fuel issue. If it runs worse, it may be a control issue. Either way, what they're doing to diagnose it isn't logical, systematic, or working. Just deciding to remove the intake manifold so the gasket can be replaced makes no sense. Unless it overheated incredibly badly, that gasket is fine. If it overheated badly enough to toast the intake gasket, the head gaskets are toast, too.

OBJECTIVE TESTING is needed, not guessing by the tech. Has a substitute fuel source (tank) been used? If not, why not? Your fuel pickup tube should have been checked at the very beginning of this ordeal. The fuel line attaches to this via an anti-siphon valve. That should have been checked, too. Also, the fuel line from the tank to the pump should have been checked. If it runs OK at first and not after 15 minutes or more, the gas tank vent should have been checked.

I have a TBI fuel pressure test block that can be connected in line, before the throttle body. Let me know if they need it. Otherwise, they should get a section of fuel line and put a Shrader valve on it so they can test the pressure, which I suspect is low.

A motor needs three things to run- compression, spark (preferably, at the right time in the cycle) and fuel/air mixed correctly. Period. This TBI system isn't that complex that it should cause this much grief. If they don't have a shop manual from MC, they need to get one.

JimN,

Idle increase. I only stated what the first guy told me. In later tests when the idle is fine, its hanging around 600.

To my knowledge, none of the fuel stuff you mention has been done. I don't understand how a fuel issue pops up with heat. Can you help me understand that?

So your opinion is to NOT tear into the intake yet?? What is my next test while its sitting in my garage?

Thanks!

[JimN]

JimN,

Idle increase. I only stated what the first guy told me. In later tests when the idle is fine, its hanging around 600.

To my knowledge, none of the fuel stuff you mention has been done. I don't understand how a fuel issue pops up with heat. Can you help me understand that?

So your opinion is to NOT tear into the intake yet?? What is my next test while its sitting in my garage?

Thanks!

Look at the fuel system, from back to front. check the fuel pressure. Make sure the plugs are the right ones (I don't remember seeing the brand or number, but they should be AC MR43TS). Make sure the flame arrestor is clean. If you feel like it, spray the outside of the injectors with carb cleaner. I do this and it smooths the idle on my truck. Verify the firing order again. Make sure the plug wires are pushed all the way onto the distributor cap and the plugs. Run it at night and watch for sparks- if you see any, the wires are bad, even though you posted that they were replaced.

[Double D]

Look at the fuel system, from back to front. check the fuel pressure. Make sure the plugs are the right ones (I don't remember seeing the brand or number, but they should be AC MR43TS). Make sure the flame arrestor is clean. If you feel like it, spray the outside of the injectors with carb cleaner. I do this and it smooths the idle on my truck. Verify the firing order again. Make sure the plug wires are pushed all the way onto the distributor cap and the plugs. Run it at night and watch for sparks- if you see any, the wires are bad, even though you posted that they were replaced.

Still need to understand how heat effects fuel problem.
Front to back. Check what in the tank? How do I know there is a problem? I replaced the fuel filter. How do I test fuel pressure?

Plug wires on pushed on tight since I just replaced them.

Trying to accomplish things on my own so I don't lose any more time. Thanks!

[Double D]

OK, I talked with my neighbor who is a great car mechanic and his step father owns a boat shop. He is going to get me a fuel pressure gauge to test the fuel pressure. He does not think the cast iron intake would be cracked but cant rule out the gasket, or the centering O-Ring. When I was talking to him I did remind myself that I did run so low on gas that it wouldn't start so I could have effected the fuel pump. The heat aspect still confuses me.

JimN, can you tell me what he fuel pressure should be? Confirm for me that the fuel pump is in the tank and how how hard it is to replace?

Thanks! BTW, the engine never overheated.