348 engine start trouble

Dear all,
I don't know if you remember, but last year i had some troubles to start the engine when it was hot.
With your help, I found the solution, i replaced the 2 fuel pressure regulators (right side was defect).
The result was perfect!
The car went to Ferrari for the maintenance (with timing belt), and everything was ok.
But now, I 've got some troubles to start the engine.... I must push the gas pedal just a little bit.
it is the same when hot or cold.
This morning, i made an ECU reset. I switched all electric items (radio, etc....) ofdf, I disconnected the battery for 2 minutes and started the engine wihout touching the gas pedal.
It started but it stopped 2 times after 3-5 seconds.
Then it definitevely started but with a low rpm and a lot of vibartion.
After more than 5 min, when the engine was hot, it immediately changed and ran correctly.
When hot, RPM is +/- 1000.
Do you have any ideas ?
Ok, Maybe the easiest way is to go bak to the Ferrari dealer, but I want to understand where is the problem.

 

1 or more water temp sensors are bad is very possible as if it reads wrong thinks its hot when its not it can send more fuel in and cause gargle and bottle.
Crank sensors or cam sensor "maybe" but its odd that its cold only, that rules out O2 sensors.
My car had a similar issue when cold starting the idle would run up to 1000 then down do like 100 and almost stall then go back up.. Turns out it was the MAF.

 

It is very strange, when i touch the gas pedal, it starts more or less correctly.
And during a trip, the engine is perfect...

 

Could tell me where is the temp sensor that send the info to the ECU ? One or two ?
Do you have the part réf ?

 

Under the intake manifold in front of the oil filter there are two blue sensors. There's a threat out here on replacing the water temp sensors.

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Thank you for your comment !

 

https://www.ferrarichat.com/forum/threads/replacing-coolant-temp-sensors.229830/

 

Very good, thank you very much.
I shall buy 2 Bosch (OEM) 0 280 130 026.
May I have to use copper washer to seal it ?
I must have all the parts before i start the job....

 

yes you can see the various washers on the parts diagrams.

 

If only one sensor has failed, you could compare the resistances of the sensors at their respective Motronic ECU connector pins. I don't know how hard it is to access the ECU connectors on a 348 (it may be easier just to change the sensors).

Do you have a 2.5 or 2.7?

Pins 30 and 45.

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ECU 2.5

 

Although the image shows a 2.7 connector, the same pins on the connector are used for coolant temperature.

 

Thank you so much

 

I'm not saying a coolant temperature sensor is faulty, but it's good to check them before you go further.

Pushing the pedal gives you more air and fuel. You may be lacking one or both (or the ECUs think you are).

Extra air valve fault?
MAF fault? (as previously mentioned). If you disconnect them one at a time, does the engine behaviour get better or worse or not change at all?

Maybe you could remind us what work has been done on the car in the past?

 

Sounds like the issue is starting not idle issue once started? Any check engine lights?

 

I don't think Euro cars have Check Engine lights.

After the relearn, it seems like the car is starting, but not running properly until warm. The car knows when it is warm when the coolant temperature sensor hits a certain temperature. Wouldn't that mean that the temperature sensors were ok... or are there timing circuits, too? With the car warm, it should go into closed loop mode and start using the O2 sensors. Before this, isn't it working with MAF data, throttle position and fuel tables?

(EDIT: after reading the manuals, I see that fuel enrichment during the warmup phase is partly based on coolant temperature)

 

When cold yes it runs on tables until the air injection valves shut off and it goes into closed loop about 300 degrees on the cats if I recall, but still gets air information from MAF I believe, just no feedback from the O2.

But... I had this funky issue where when cold my idle would hunt between almost stalling and 1000 rpm for about about 2 min until the car got warm, little bump of throttle helped when starting helped most times. Funny thing is if I killed it and restarted immediately it, 99% it started and idled like nothing was wrong.

Replaced O2 sensors, water temp sensors, every fuse, every relay, FPR, fuel pumps, IAC, Cam Sensor, Crank Sensors, plugs, wires, had injectors cleaned, I mean you name it I had replaced it, but much of it before the issue started just for good measure. MAF was the ONLY thing not replaced. I found 2 new in the box Bosch units, replaced them both. Starts and runs like a champ. Turns out it was MAF.

 

Thank you for your comment.
Just to explain deeper, Hot or cold, if i push on the gaz pedal, the engine work perfectly
But normally, i don’t have to touch the pedal to start the engine up.

 

There are no check engine lights on Euro cars...

 

I’ve just received the 2 temp sensors.
I shall install the sensors tomorrow or saturday.
Next thursday, i shall restore the fuel pumps.
I don’t know if it will help, but I want to be sure there are ok

 

Hi
There are check engine lights on the Euro cars.
It's only the bulbs that are missing. I used the seat belt warning bulbs so now I can read all the codes with the help of a paper clip......
Br
Bertil

 

Don't forget the copper washers. There's nothing special about them if you don't have them you can get them at a hardware store.

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Goog info to know....

 

Bertil, are Euro cars fitted with a 3 wire harness for an (optional) test button... or are you removing the backshell of the ECU plug and using the paperclip to short out pins?

 

I dont remember if it's 2 or 3 wire. I think there are just two wires to short. I'll check tomorrow and come back to you.
Bertil