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Joe
Joe, Marine Mechanic
Category: Boat
Satisfied Customers: 7136
Experience:  ASE, electronics, Marine mechanical and electronics, pwc, wiring, all around repair tech,
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I have a 5.0 mpi that still wont idle after a new iac

Customer Question

I have a 5.0 mpi that still wont idle after a new iac
Submitted: 1 year ago.
Category: Boat
Expert:  Joe replied 1 year ago.
Hello,

Thank you for your question, my name is ***** ***** I will be glad to assist you with your concern today.

Can you please discribe to me at idle what the engine is doing?

Thanks,
Joe
Customer: replied 1 year ago.

Hi Joe

I.m Mike

i just got the boat it ran fine on Fri wouldn't start except by putting in nuetrl and quick shifting into gear on Sat

Ireplaced the IAC (the one i took off looked like a new one)

same problem rund fine but when it hits idle it dies

2003 5.0 mpi

Expert:  Joe replied 1 year ago.

Hi Mike,

I would start by checking the tps - throttle position sensor, which is located on the throttle body, on the opposite side of the linkage attached to the shaft. Using a voltmeter and checking voltage at idle (engine not running but key on) .045-.065 vdc closed throttle and wide open throttle around 4.5 to 5vdc.

Depending on model it may be adjustable, if you find numbers are off and adjustment does not help then it needs to be replaced. Know that first you would remove the flame arrestor and see if it runs better and cleaning it if needed then checking throttle body around butterfly if a dirty ring the throttle can hang and give an incorrect reading/air.

If above is all good and iac counts on a scan tool are correct then move on to checking engine for air leaks with a leak down test, large enough and engine will stall. Also you would want to check fuel pressure to start and no misfires.

Since it does not even idle let alone a problem shifting then I do not suspect a drive cable issue.

Also note if you did not already know even though and iac could be replaced it does not mean that the passage on the throttle body is not the problem instead, a throttle body can sometimes get dirty and require cleaning sort of in the same aspect as a carb just a different unit.

Thank you!

- Joe

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