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I need help


FUNDERBURKE14

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What’s up y’all, I got a 97 Malibu sunsetter with the monsoon 320. I had some issues in the past and replaced all fuel components and a brand new ecm, that fixed my last problem. Got my boat in the water for the first time yesterday since I have replaced everything. ( I have ran it out of water hooked up to a hose) but I go to put it in drive or reverse and it bogs down and then isles back up. It does it regardless if I’m in Neutral or not. It bogs down quite a bit and sometimes dies because it bogs down so much. What do I need to do??  Thanks in advance! 

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Could be the Idle Air Control valve. It should be compensating for the extra load on the motor when you put it in gear before you give it any throttle. When it doesn't die, are you able to give it throttle in gear and have it respond? If so, it sounds like the IAC.

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3 hours ago, jmack said:

Could be the Idle Air Control valve. It should be compensating for the extra load on the motor when you put it in gear before you give it any throttle. When it doesn't die, are you able to give it throttle in gear and have it respond? If so, it sounds like the IAC.

It’ll respond every time it just bogs down and either dies out or idles back up

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On ‎8‎/‎19‎/‎2020 at 8:23 PM, FUNDERBURKE14 said:

It’ll respond every time it just bogs down and either dies out or idles back up

I had the same symptoms with the same motor in a '96 Sunsetter. Replacing the IAC Valve solved it.

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Just did my IAC a few weeks ago. Very easy to do. Definitely made a good improvement on idle. My engine is an 02, and I think to make it perfect, I'll have to take the plenum off and give it a thorough cleaning.

Steve B.

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Update. Checked off all fuel components, all of that was just replaced, also checked ignition components, all was ok. Replaced the IAC and it is still doing the same thing.. I think it might be the end of my summer and it’s gonna have to go to a shop somewhere.. thanks for all the advice! 

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3 hours ago, FUNDERBURKE14 said:

I did, everything seemed normal

Could you provide actual pressure readings at key up, idle, and when it bogs down?

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On 8/21/2020 at 11:32 AM, jmack said:

I had the same symptoms with the same motor in a '96 Sunsetter. Replacing the IAC Valve solved it.

Where did you get your IAC? Do you have a part number? Bakes has them for $300 bucks...there's got to be an AC Delco one for cheaper.

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I got my IAC at summitracing. It was like $23.00. Sorry I can't find the receipt for the part #. I took mine with me and told them 99 Suburban. I'm sure all the auto places have them for cheap. Clean the heck out of the plenum and the porthole where the IAC does it's thing.

Steve B.

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39 minutes ago, Steve B. said:

I got my IAC at summitracing. It was like $23.00. Sorry I can't find the receipt for the part #. I took mine with me and told them 99 Suburban. I'm sure all the auto places have them for cheap. Clean the heck out of the plenum and the porthole where the IAC does it's thing.

Steve B.

What did you use to clean? Sorry for all the questions...

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No question is too small. I used WD-40 Carb/Throttle Body & Parts cleaner. Also from Summit. Works really well. You get the engine warm. Shut it off, open the butterfly and spray the heck out of it. Quickly after startup, give it some throttle, enough to open the butterfly, and you can see the soot get sucked away. When not 100% warmed up, it may still momentarily hesitate the slightest when putting in gear. However, after complete warmup, the engine runs almost new. Starting is so easy I can't believe it. Click-vrooom.

Steve B.

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On ‎8‎/‎29‎/‎2020 at 11:48 AM, CraigSim said:

Where did you get your IAC? Do you have a part number? Bakes has them for $300 bucks...there's got to be an AC Delco one for cheaper.

I took the old one and got it matched at a local parts store. It's an AC Delco part. The original "marinized" one was powder coated, the replacement I got was just zinc coated. I'm not into paying the extra $275 for powder coat......

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On 8/29/2020 at 2:21 PM, Steve B. said:

No question is too small. I used WD-40 Carb/Throttle Body & Parts cleaner. Also from Summit. Works really well. You get the engine warm. Shut it off, open the butterfly and spray the heck out of it. Quickly after startup, give it some throttle, enough to open the butterfly, and you can see the soot get sucked away. When not 100% warmed up, it may still momentarily hesitate the slightest when putting in gear. However, after complete warmup, the engine runs almost new. Starting is so easy I can't believe it. Click-vrooom.

Steve B.

Thanks Steve. Good stuff.

I take it you in the beginning when you are cleaning the throttle body you keep the IAC in. Wam the engine, clean the crap out of it, turn off the engine and replace the sensor. Correct?

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I wasn't sure the IAC was bad, so I pulled it first, cleaned it and the port it lived in. Replaced and tried. Same issue. So, replaced IAC and continued cleaning throttle body several times using method above. My butterfly and immediate area below it had a lot of soot and that is all gone now. However, I'd still like to pull the throttle body and make sure the runners are all just as clean all the way to the heads. Maybe a winter project.

Steve B.

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1 hour ago, CraigSim said:

Thanks Steve. Good stuff.

I take it you in the beginning when you are cleaning the throttle body you keep the IAC in. Wam the engine, clean the crap out of it, turn off the engine and replace the sensor. Correct?

The IAC is not a sensor, it is a stepper motor that controls air flow when the butterfly is nearly closed.  Yours is probably good if it idles correctly, but carbon and gunk buildup could limit its motion during transients.  I don't think you need to pull it to get it clean, but you certainly could do it either way.

Make sure that you clean all the way around the butterfly, and then open the throttle and clean the back side of the butterfly, the edges, and the throat where it contacts.  You may or may not have tiny bypass slits in the throat that need attention as well.  Next spray the larger side passages, which should get the IAC clean.  Any old can of carb spray cleaner will do.  Most of your spraying should be done with the engine warm but off so that you can manipulate the throttle to get everything clean.  After you spray it down, let it set for a few minutes, then crank it again to test it.

If this doesn't fix it, you could have a bad distributor module.  They are heat sensitive, and they can act up in a wide variety of ways.  You didn't really tell the whole story, though, so don't start throwing a bunch of parts at it without a good reason to.  Part of the story we want to hear is, after it bogs down when you shift to forward, does it run OK all the way to wide open throttle, or does it just not run right under load at all?  After you changed the fuel components, did you test the fuel pressure at key on, idle, midrange, and wide open throttle?

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3 hours ago, justgary said:

The IAC is not a sensor, it is a stepper motor that controls air flow when the butterfly is nearly closed.  Yours is probably good if it idles correctly, but carbon and gunk buildup could limit its motion during transients.  I don't think you need to pull it to get it clean, but you certainly could do it either way.

Make sure that you clean all the way around the butterfly, and then open the throttle and clean the back side of the butterfly, the edges, and the throat where it contacts.  You may or may not have tiny bypass slits in the throat that need attention as well.  Next spray the larger side passages, which should get the IAC clean.  Any old can of carb spray cleaner will do.  Most of your spraying should be done with the engine warm but off so that you can manipulate the throttle to get everything clean.  After you spray it down, let it set for a few minutes, then crank it again to test it.

If this doesn't fix it, you could have a bad distributor module.  They are heat sensitive, and they can act up in a wide variety of ways.  You didn't really tell the whole story, though, so don't start throwing a bunch of parts at it without a good reason to.  Part of the story we want to hear is, after it bogs down when you shift to forward, does it run OK all the way to wide open throttle, or does it just not run right under load at all?  After you changed the fuel components, did you test the fuel pressure at key on, idle, midrange, and wide open throttle?

Under load it chokes up and dies. Cranks right up with no issues. I can SLOWLY get to around 1200 rpm before is starts choking up, but if i just gun it, it dies. I've already changed fuel injectors, fuel pump, spark plugs and wires, distributor cap and rotor. Also had the old fuel drained and got brand new fuel. Now i was going to try sensors and other things like IAC and TPS. Changed the MAP sensor already. I am just at a lose of what is going on so I was just trying anything. 

Edited by CraigSim
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4 hours ago, CraigSim said:

Under load it chokes up and dies. Cranks right up with no issues. I can SLOWLY get to around 1200 rpm before is starts choking up, but if i just gun it, it dies. I've already changed fuel injectors, fuel pump, spark plugs and wires, distributor cap and rotor. Also had the old fuel drained and got brand new fuel. Now i was going to try sensors and other things like IAC and TPS. Changed the MAP sensor already. I am just at a lose of what is going on so I was just trying anything. 

You probably should test your fuel pressure.  The regulator is not the same as the pump.  Your fuel pressure should be roughly 44 PSI at all of the points I mentioned above.

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40 minutes ago, justgary said:

You probably should test your fuel pressure.  The regulator is not the same as the pump.  Your fuel pressure should be roughly 44 PSI at all of the points I mentioned above.

Forgot to mention, I replaced the fuel pressure regulator when I did the fuel injectors. I can check at start up for sure. I can't get to WOT under load though...can that be checked in while the boat is not in gear?

Edited by CraigSim
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2 minutes ago, CraigSim said:

Forgot to mention, I replaced the fuel pressure regulator when I did the fuel injectors. I can check at start up for sure. I can't get to WOT under load though...can that be checked in while the boat is not in gear?

The whole point is that the pressure should be the same at all load conditions, so just revving it up doesn't count.

If the pressure is OK, grab a timing light to see if the spark advance seems normal (roughly 10 to 40 degrees BTDC).  It should not jump around, and should basically follow RPM.  I have never really checked for that, but it would make sense that the spark might go wild if the distributor module is bad.

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