Hello everyone, New to the forum, I apologize in advance for my English, I use a translator.

The problem is not permanent, it may work fine for 4 hours out of 10 hours of use.
Both hot and cold.

However, it starts all the time with no problem.



I'm having some trouble with a Mercruiser 305cid 5.0 efi v8 engine using the Mefi 1.

-1 Slow down idlle. (400 rpm)

-2 no power (rpm limited)

-Smoke and oil consumption.



Using a code reader with a paper clip and a continuity multimeter. I get 3 fault codes.

-14 high temperature ECTs

-21 TPS Trothle Position Sensor (high signal)

-33 MAP manifold absolute pressure (signal high)



In case of doubt, last year I changed / realized:

The sensors:
(all new)
-Ect Temperature probe.
-Map sensor
-Tps sensor
- knock sensor.


-Ignition:
(brand new) distributor, coil, cable, spark plug

-injection:
new injectors, and TBI rebuild .and new kit fuel regulator pressure

- Check the electrical harness according to the mercruiser procedure. (pin by pin/connector by connector)

- Check engine compression. Over (10.5Bars) on all cylinders.



I'm out of ideas. (I'm afraid of a faulty MEFI 1 ECU)

By chance do you have any?

Thanks for reading.

Sorry again for my pronunciation and my writing.

Good day friends

I'd go look at the small black wires that are grounds and I would probe the sensors for 5 volts.

Thank's for you réponse, but All wire and ground are controlled.
all sensors is changed

Being that it is an intermittent, I'd say it is a problem in the wiring harness.
You need to hook it to Rinda scan tool or better yet, the laptop diacom and get live data when its actually having the problem.

Also, your translator did a good job

Thank you for your response, indeed the translator works well. (I'm trying to refine between knowledge and translation hahah)

I have already checked the beam, I will do it again to be sure.

I would like to have it diagnosed, but no personnal are techmate or Rinda in Northern Europe.

Sounds like the sensor ground circuit or 5v circuit has a bad connection somewhere.

yes I agree with you. This is why I tested the harness with a multimeter pin by pin. And mooving this. No apparent problem.

Additionally, Mercruiser in its workshop manual. indicates for code 33 (Map) at the same time as a code 14. (ect) that it is necessary to check the open ground via the pin. ckt 814. . which was done without success.

After much research, I came across a few topics, all of which ultimately resulted in a problem, at least with the cylinder head, or the cylinder head gasket. I ordered a leak test kit online. We will see what it gives.

A cylinder head or head gasket will not be intermittent.