semi stall help 2007 4.3 mpi - is it ecm?

[perdobarnes]

My engine constantly tries to stall at low revs.
I get a warning bleep the engine almost stalls and then kicks back up and returns to idle.

Diagnostic shows no faults as at point of stall the power drops and loses communication with laptop.

Anyone had a similar issue and managed to correct it?

 

[alldodge]

Since you hear a beep I would think the motor is loosing 12V, either by hot or ground. Could also be a alternator going out or loosing connection. How are your cable connections, clean, shinny and tight?

 

[perdobarnes]

Had a full inspection:

1. on connecting the laptop it was found that communication was lost at point of stalling, this pointed to a voltage drop or loss of ECU voltage at the time the stall occurred.

2. checked all earths and live feeds to engine

3. using a volt meter i checked the input voltage to the entire system at the MPR (main power relay). this was constant during fault.


4. next i checked the output voltage from the MPR, voltage dropped at fault.

5. i then checked the earth return path (switched earth) to the MPR which is switched through the ECU, this went open circuit at fault.

6. bridged the live across MPR and tested engine, fault still present

7. bridged the live across the fuel pump relay, fault still present

8. bridged the earth from MPR to ECM to earth, fault still present

9. checked voltage from CPS, TPS - all correct

10. we have also swapped the IAC valve for a new one, fault still present

Checked injectors also

 

[alldodge]

Have you tried swapping MPR for Fuel pump relay?
What is the voltage reading during idle?

Also what is your serial number?

 

[Fun Times]

Hi, welcome to iboats!

Do you have an Alpha stern drive?
Does this happen while on the trailer or in the water only?
Boat in gear or out of gear?

If in the water and in gear you may want to also try very carefully performing the shift interrupter switch test found in the following link on page 3 of 3 to see if it just may help any with your issue.....Please read the "Caution" before trying the test in the water though.
http://marinemechanic.com/merc/distributors/mercurymarine/sterndrive/gmefi-nostart.PDF

Below are two places that may be able to repair faulty ECM's if found needed.
http://simonmotorsports.com/
https://whipplesuperchargers.com/index.php?dispatch=products.view&product_i d=73