7.4 MPI serging @ idle and cold
05-01-2004, 05:20 PM
#12
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Rockie You know your stuff. I set up the DVOM like you suggested and found an initial reading of .55V. I adjusted the TPS to its stop and achieved .638V. My service manual said I should have .7V @ idle stop. I decided to set the idle stop up slightly to achieve the .66V you had suggested. It ran great in the driveway, I still have a little hesitation just off idle but I think I will try it on the lake before I draw any conclusions. It runs good Thanks for the suggestion.
05-03-2004, 08:02 AM
#13
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COOL, I'm glad that fixed your problem. I only know this because I have had to do this on a few boats. Now you know and can help your friends.
If you looked at blown formula's procedure, you will notice what he said, that there is kind of a relationship between the 2 settings and you may need to set the other IAC also to get the hesitation out.
At least you can do it without buying a $500 scanner or being an aero space engineer.
Pat McPherson, did you have any luck on yours over the weekend?
If you looked at blown formula's procedure, you will notice what he said, that there is kind of a relationship between the 2 settings and you may need to set the other IAC also to get the hesitation out.
At least you can do it without buying a $500 scanner or being an aero space engineer.
Pat McPherson, did you have any luck on yours over the weekend?
05-03-2004, 06:39 PM
#14
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Hi Guys,
I did adjust the throttle plate stop some, did help a little. The 7.4 MPI only has one throttle plate that I could see. I could not change out my IAC though, one of the screws was stripped. I did not want to pull the throttle body off because I didn't have another gasket. I stuck my finger were the IAC should let more air in, no change. I don't think the IAC is opening at all so I do need to change it.
Got out on the water, and the boat ran quite well. No stumble and awesome throttle response out of the hole.
The engine seems to stop pulling hard at about 4200 and max rpm was about 4700. I was warned that this would happen with the GM MPI... I was hoping for 4800+. Still we are up about 150-200rpm from last year.
I pulled a couple of spark plugs to read. If anything it looks to be running rich. I'm going to take some picture and post them for comment.
Thank Again!
I did adjust the throttle plate stop some, did help a little. The 7.4 MPI only has one throttle plate that I could see. I could not change out my IAC though, one of the screws was stripped. I did not want to pull the throttle body off because I didn't have another gasket. I stuck my finger were the IAC should let more air in, no change. I don't think the IAC is opening at all so I do need to change it.
Got out on the water, and the boat ran quite well. No stumble and awesome throttle response out of the hole.
The engine seems to stop pulling hard at about 4200 and max rpm was about 4700. I was warned that this would happen with the GM MPI... I was hoping for 4800+. Still we are up about 150-200rpm from last year.
I pulled a couple of spark plugs to read. If anything it looks to be running rich. I'm going to take some picture and post them for comment.
Thank Again!
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Patrick
Patrick
Last edited by Pat McPherson; 05-03-2004 at 06:44 PM.
