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mercruiser mefi 3 discussion
- bud37
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mercruiser mefi 3 discussion
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Re: mercruiser mefi 3 discussion
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Re: mercruiser mefi 3 discussion
bud37 wrote:Source of the post ....what is in charge of controlling the fuel when you pull the throttle back to idle quickly.....
The ECM/computer controls fuel delivery at all times based on data received from all the sensors. It takes this data then refers to an on-board table to determine how long it should open the injectors for.
- km1125
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Re: mercruiser mefi 3 discussion
It is not really the plate that is the issue (well, I guess if one got REALLY gunked up!)... but it is the sensor in the throttle body. Not sure of the exact model on yours, but if there is a wire running across the opening then clean that CAREFULLY.
That's what senses the flow of air and density so that the ECM can meter out the right fuel.
The IAC is also a good suspect. If you bump it in and out of gear a few times and it dies that's what I'd check first.
Vacuum leaks could also be giving the engine trouble and having the IAC and ECM work "overtime" to keep things in shape.
- bud37
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Re: mercruiser mefi 3 discussion
There is no wire (mpi), sensor is in the manifold......the only thing that was different about this side was the flame arrestor was filthy, I cleaned it but made no change....there was actually a bit of crud on the edge of the throttle plate.......Mathews finally scored, nice.......
- bud37
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Re: mercruiser mefi 3 discussion
- km1125
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Re: mercruiser mefi 3 discussion
You should have two temp sensors... coolant temp and intake air temp... but either way...
Could fail either way (short or open). However, the ECU should be able to determine that it failed because it is way outside of "normal" temperatures, for example showing a temp of 400 degrees or minus 100 degrees. Once the ECU detects that out-of-range condition, then it "assumes" something safe... and will usually skew to a slightly richer fuel mixture.
RE: "and the same for the rpm sensor, would it fail showing high rpm or low"
RPM sensor is different. It's just sending pulses as the crankshaft turns and counting the pulses. If it fails, then the ECU doesn't even know if the engine is turning and probably won't start at all.
- bud37
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Re: mercruiser mefi 3 discussion
Viper wrote:Checking the readings with Merc diagnostics will help. I think you're on the right track with the IAC and filter. Since you already have a new one, try replacing it and only it first then try to duplicate the problem before you replace another component. You can also swap a component from one engine to the other and see if the symptom follows the part. That will leave no doubt but again, swap only one part at a time then run the engine.
I agree., am a great supporter of the change only one thing at a time camp......I will check every connector first as this was the side with the plugged deck drain.......
- bud37
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Re: mercruiser mefi 3 discussion
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Re: mercruiser mefi 3 discussion
bud37 wrote:Source of the post I would have thought that the intake air temp would have a much smaller effect on the fuel pulse width than the engine coolant temp, yes /no??.....a question, is there a head temp sensor in this package??........
All inputs together make a difference in pulse width control. Air temp is just as important. Air temps have an effect on fuel burn so the ECM needs to compensate for that.
No head temp sensor.
Do you have serial number handy for your engine that you can post?
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