(T) Rough Running

Hi, I have a 2004 Seicento. I started running rough a couple of months ago so my garage to check for codes, there were none.

I changed the plugs, leads and ignition coils. It still ran rough. It dies when I depress the throttle.


When I sprayed carb cleaner into the throttle body it ran fine.


Next, I checked the signals to the injectors and they were all getting signals.

The fuel was flowing through the injector rail as I checked the schrader valve on the end and it was pumping out.

I removed the injector rail and then connected the fuel line and electrical plugs, I put bottles over the ends of the injectors and they were all pumping out fuel and all the bottles have the same volume of fuel.

It sounded better when on the driveway and would fully rev but when I try and drive it, it just dies and there is no power. Also now the EML is on.

Does anyone have any ideas?

Checkd for any vacuum leaks, specifically on the pipe to the map sensor.

Low fuel pressure perhaps? Does sound like it could be running lean from your description.

Could be worth trying to measure the fuel pressure while it is running to see if that sheds any light on things.

Is it better when warm or worse?

You could try unplugging different sensors one by one and see if any of them make a difference. Afaik it should run OK with just one (any of them except crank) sensor disconnected.

Engine light on is good news. Read the codes and they might give you hints on what is wrong.

Not checked the vacuum or MAP sensor, that was my next stop. It runs about the same cold and hot. It is running so bad that don't think it will make it to the garage to check the codes

Unplugged the MAF sensor while running at revs and it ran worse, started hunting.

Took both Lambda sensors out and cleaned them. If I disconnect them while running the engine cuts out.

Worth checking the fuel pump mesh filter...when this is contaminated it will cause a loss of power without throwing up any codes. Another possibility is the crank sensor connector at the top left of the cylinder head where it joins the main harness. A faulty connection here causes chaos.

Where is this filter? Do I need to drop the tank to access it?

If the eml is constantly on. Get the code/s checked.

If you can't get the car to a garage, a mobile mechanic would come to you. Once you have pinpointed the issue, you can fix it.

The fuel pump is accessed from inside the car...under the back seat cushion..beneath the diamond shaped metal pressing. You need to use common sense in messing around in this area due to the risk of serious fire from exposed fuel and vapour. The pump is easy enough to remove but a bit of a fiddle as it's a single unit including the level float. The mesh filter is located at the pump inlet within the plastic bowl which is clipped together. Fairly common design for this type

Thank You. Will check it over the weekend.

UPDATE

Took the fuel pump out, a slight build up of crud, not enough to prevent fuel flow but cleared it out.


The EML is not on


Still the same problem. I can start the car fine but if I suddenly floor it then the engine dies. When it starts to die I put carb cleaner in the throttle body and it picks up. So fuel starvation


If I build up the revs slowly then I can get the revs up.


If I get high revs and try to pull away, the engine dies.

I removed the fuel supply from the rail and put it in a bottle, turned the engine over for about 30 seconds and there was 750cc of fuel, so plenty of fuel.

I have already removed the rail and injectors and blown through the rail.

Cannot think of anything else other than replacing injectors although they are getting a signal. connected a test light to each of them and flashed on tick-over and went to constant when revs are full on.

I tested them while removed on ignition startup and they were all putting out fuel and all the same quantity of fuel.


Do you think if I try starting the car with the injectors out but squirting carb cleaner into the throttle body I can start the motor and measure the injector flow with the accelerator depressed. As it seems this is when I am getting loss of power.

Hi..

If you can SLO W L Y raise revs to a decent rev ceiling.. then surely you have fuel..

I would be looking for a different issue.

AFAIK no fuel issue will raise a MIL.

Any suggestions?

Checked:

Sensors
Fuel filter
Signal to Injectors
Fuel pressure
REPLACED:
Plugs
Ignition Coils
Plug Leads

NO EML

Not sure it NEEDS lambda input.. ordinarily.

What fuel pressure do you have when the car is running? Have you changed the fuel filter in the line, not just the fuel pick up on the pump.
What voltage do you have at the pump when it is running?