Running fine when cold but rough when warm

[Thor101]

My 2002 !.9TDi Fabia has started running rough when it is warm, I have changed the temp sender and now it seems worse than before. Has anyone got any clues.

[tomilipin]

My first post here, so... hello

 

Have you got any problems when starting the car or do they occur when it's already running? How does the engine behave when you drive the car? 

 

Changing the engine temperature sensor usually solves this problem in gasoline engines. It's also a good idea to look at the throttle, especially the gasket under it - might suck additional air. 

[sepulchrave]

23 minutes ago, tomilipin said:

My first post here, so... hello

 

Have you got any problems when starting the car or do they occur when it's already running? How does the engine behave when you drive the car? 

 

Changing the engine temperature sensor usually solves this problem in gasoline engines. It's also a good idea to look at the throttle, especially the gasket under it - might suck additional air. 

 

It's a diesel, so no throttle to look at. However the MAF may be tired.

[Thor101]

Starts fine, just runs really rough except when cold. What is a MAF.

thanks for you help guys

Edited 5 March, 2017 by Thor101

[Thor101]

Starts fine, just runs really rough except when cold. What isa MAF.

thannks for you help guys

[fabia145re-map]

Mass Air Flow sensor

 

[tomilipin]

Here you can find instructions on how to clean it: https://www.youtube.com/watch?v=gRfaPfTcfOM

 

[KenONeill]

If you suspect the MAF is faulty, try disconnecting it. This forces the main Engine Management System onto a default airflow map, and if the car runs better, then you do indeed have a faulty MAF.

 

If the MAF is good, you could have a faulty Coolant Temperature Sensor, since that has separate channels for the EMS and for the gauge.

[Thor101]

Hi

 

I thought it was coolant temp sensor, so replaced it and it made no difference. Tried unplugging the map sensor and that made no difference. What ever is going on it would appear to be temperature related, when the engine is cold it is fine, it starts running rough as it warms up, one fully warm if i turn it off wait a few seconds then start it again it will sometimes but not always run ok.

[badger89]

Could also possibly the Injector Loom, these tend to show wear when oil / engine is warm.

[sepulchrave]

There is also a fuel temperature sensor which can play up.

[corndog]

did you unplug the MAP or MAF or both?

[Thor101]

4 minutes ago, corndog said:

did you unplug the MAP or MAF or both?

The one by the air filter 

[corndog]

Just now, Thor101 said:

The one by the air filter 

ah yeh that's MAF

[Thisday]

How rough is rough? I used to have an issue where it was fine when cold but as soon as it hit 90 degrees it was misfiring/no power. This was an injector loom issue but I DID get warning lights on the dash. Have you scanned it? If you can, you can also record maf values etc and post them on here. 

 

Someone with more knowledge than me will be able to tell you if they are correct or not.

Edited 9 March, 2017 by Thisday

[Thor101]

 

2 hours ago, Thisday said:

 

Not getting any warning lights and nothing showing on hand held scanner so far.

 

Edited 9 March, 2017 by Thor101

[Thor101]

16 hours ago, corndog said:

ah yeh that's MAF

Is the MAP the one on the other side will lots of small pipes coming out of it?

Edited 9 March, 2017 by Thor101

[Thisday]

1 minute ago, Thor101 said:

Is the MAP the one on the other side will lots of small pies coming out of it?

The MAP I believe is attached to the intercooler, if not its def not on top of the engine. The Maf is on the pipe coming from the airbox.

 

You mentioned that unplugging the MAF didn't change anything? Question for the wider audience, doesn't that mean the MAF is knackered? If it got worse then it would mean it was fine???

[KenONeill]

No. Unplugging a FUBAR MAF forces the EMS onto a default air map that is worse than good values, but better than nonsense ones.

[Thor101]

On 08/03/2017 at 19:30, badger89 said:

Could also possibly the Injector Loom, these tend to show wear when oil / engine is warm.

It seems to be when it is warming up rather than when warm,