4.3 Gi won't idle

Kahouna

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Hey crew! Getting tired of beating my head against the hull on this one. The last trip to the shop for another issue produced codes 21 and 33. I dutifully installed a new map and tps to round out the only items left not replaced on the tbi. Here is the problem... it won't idle. Runs over 2k like a dream but as soon as you pull the throttle back she sputter and dies. I pulled the vacuum line off the map sensor and it will hold idle for 15-30 seconds before fading out. I can keep the motor running if I am constantly revving it. I haven't seen if the codes are back, but this has been an ongoing issue that no one can figure out? What am I missing/forgetting?
 

wrench 3

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Re: 4.3 Gi won't idle

It's time to start checking grounds! A high reading on a sensor could be caused by a poor ground to the sensor. Due to the close physical location of the MAP & TPS, their grounds are probably spliced into the same wire.
 

Don S

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Re: 4.3 Gi won't idle

Which 4.3Gi do you have?
 

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Kahouna

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Re: 4.3 Gi won't idle

Unknown which one. A new long block was put in 2004. There are no identifiers except the casting number. I got it to run but the MAP does not have the vacuum attached. As soon as I plug the line it drops and dies. The TPS and MAP are within range when probed according the a voltmeter. It has to be something small, but I'm getting frustrated with the 'ol girl.

I am not able to clear the codes with the paperclip/led trick. I unhooked the battery for an hour and the codes are still showing.

All grounds were/are clean. Good thought and one I started with.
 

Tail_Gunner

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Re: 4.3 Gi won't idle

Take a neon light and light up the spray pattern of the injectors along with taking a pressure read of the fuel rail. The injectors should produce a nice conical pattern and the fuel pressure should be 30psi +- 3lbs
 

Don S

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Re: 4.3 Gi won't idle

What is the year of your boat?
From the picture below, which ECM looks most like yours?
Trying to determine year of your engine so I can look at the proper diagnostic manual and wiring diagram.

GM-MEFI.jpg
 

wrench 3

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Re: 4.3 Gi won't idle

What voltage readings are you taking? Did you test the grounds from both sensors with an ohm meter? If the grounds are bad, the signal voltage will be above the normal range. You would have a hard code that would reset as soon as you turn the key on. Is your 5V reference voltage OK? That would also set a hard code.
 

Kahouna

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Re: 4.3 Gi won't idle

TG- Injectors are good...brand new. High and low pressure are good as well.

Don- The first one.

W3- Tested all three wires on the tps. Good ground. Five volts. .05 through 4.4 wot (a little low). Three wires on the map were all good. I could only collapse one lung to test the resistance. Both items are brand new.
 

Don S

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Re: 4.3 Gi won't idle

One more time..... What year is your boat ??????????????
 

Kahouna

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Re: 4.3 Gi won't idle

Don- Sorry sir, 97 Crestliner. I'm at work chasing bad guys and I can only use my phone for this until I get home.
 

Don S

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Re: 4.3 Gi won't idle

Hoping you actually have a 97 and not a 96 model as the wiring is different, and I don't have a good 96 manual. So you can download the manual HERE
Section 6 gives you detailed instructions on what to check for DTC 21 and 33. Wiring diagrams in the back of the book.
 

wrench 3

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Re: 4.3 Gi won't idle

Dons manual should give you pin-outs at the computer. You can check the wiring from the sensors to the computer with an ohm meter. If they are OK it sounds like a bad computer.
But run through all the tests in the manual and see what turns up.
 

Kahouna

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Re: 4.3 Gi won't idle

Thanks Don! Looks like some of the books I have but a little more detailed in some areas. I will get on it and report back.
 

Kahouna

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Re: 4.3 Gi won't idle

I finally got a chance to get the manual printed out and some time "under the hood". Here is the results and it looks like I will need some help.

Followed Diagnoses section for DTC 21: Step 1. Reading was over 4 volts..Step 3. Reading was over 4.0 volts...Step 5. Connected to + side of battery and terminal- light on...Step 6. Unhooked J1 and J2, Connected to + side of battery and terminal...NO LIGHT...REPLACE ECM

Followed Diagnoses section for DTC 33: Step 2. Reading was over 4.0 volts...Step 4. Reading was over 4.0 volts...Step 6. Unhooked J1 & J2, connected to + side of battery and terminal...NO LIGHT...REPLACE ECM.

Sooooo, what does one do to go about replacing an ECM??
 

wrench 3

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Re: 4.3 Gi won't idle

Sooooo, what does one do to go about replacing an ECM??

I presume you are asking how to acquire a replacement. Replacing is simply disconnecting the battery, unplugging it and unbolting it.
Other than trying the dealer, Standard Blue Streak rebuilds automotive ECMs but I'm not sure about marine. Check with your automotive jobber.
 

Kahouna

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Re: 4.3 Gi won't idle

Replacing isn't a problem. Finding a replacement could be? I can only imagine what one costs from a dealer. Is there a flanking maneuver that can be done?
 

Kahouna

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Re: 4.3 Gi won't idle

Forgot to add, what is the part number for the ecm so I get the right one ordered. Thanks again for all the help guys.
 

Don S

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Re: 4.3 Gi won't idle

Post the numbers that are on your present ECM. You don't even have a model or serial number for your engine, so there is no way to look up the proper ECM for your engine.
 

Tail_Gunner

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Jan 13, 2006
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Re: 4.3 Gi won't idle

Hey crew! Getting tired of beating my head against the hull on this one. The last trip to the shop for another issue produced codes 21 and 33. I dutifully installed a new map and tps to round out the only items left not replaced on the tbi. Here is the problem... it won't idle. Runs over 2k like a dream but as soon as you pull the throttle back she sputter and dies. I pulled the vacuum line off the map sensor and it will hold idle for 15-30 seconds before fading out. I can keep the motor running if I am constantly revving it. I haven't seen if the codes are back, but this has been an ongoing issue that no one can figure out? What am I missing/forgetting?

You need to be more spefic about what you have done to this boat. It wouldn't run if you had a bad ecm or highly unlikely.. they are little more than a eprom and they work or they don't....no signal at all. You said it metered gas that is a indication it is working is this ecm original to that boat or is it new to...Your fuel cell and distributor are they new aka is this rebuild new and old parts patched together

As Don stated part number's are needed

OBD Diagnostics, Inc. - MEFI 4B Controller

There's a replacement source give them a call.
 
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