Fuel trim fault code

[MaverickTDi]

Been playing around with VCDS today and got this;

Not sure how long it's been there?

Any ideas what it could be?

Cheers.

 

[aragorn]

Its a "current" fault by the looks.

Could be a bad sensor or an air leak.

 

[MaverickTDi]

Its a "current" fault by the looks.

Could be a bad sensor or an air leak.

How can you tell it's a current fault?

Bad sensor? What we talking MAF, O2, FPR?

Unless a leak has recently occurred the only degraded vacuum pipe I found was this;

I've replaced that section of pipe.

 

[aragorn]

If the fault had gone away, then on the bottom line it would say "intermittent", Because it doesnt, it means the fault is still there.

Could be a bad MAF, bad lambda etc.

The ECU uses readings from the lambda to adjust the fuelling to maintain stoich.

That fault code means that despite the ECU's best efforts at trimming out fuel, its reached the maximum amount it can trim out, and still hasnt managed to get the readings correct, and its still rich.

Now obviously this could be a bad lambda sensor, but it could also be a bad MAF giving the engine incorrect readings, blocked FPR causing the fuel pressure to go too high etc etc.

The one extra piece of info you've got to work with, is the "(Add)" part, which means its an additive error. There are two types of fuel trim, additive and multiplicative. Additive adds a fixed amount of extra fuel and is mostly used to tune idle, whereas the multiplicative trim is a multiplier and scales the whole range.

http://wiki.ross-tech.com/wiki/index.php/17545/P1137/004407

If i remember correctly, didnt your original Autoscan results from the other week have a code for a bad lambda sensor? It may be the lambdas getting old and lazy and isnt responding correctly at idle, giving incorrect readings.

 

[MaverickTDi]

If the fault had gone away, then on the bottom line it would say "intermittent", Because it doesnt, it means the fault is still there.

Could be a bad MAF, bad lambda etc.

The ECU uses readings from the lambda to adjust the fuelling to maintain stoich.

That fault code means that despite the ECU's best efforts at trimming out fuel, its reached the maximum amount it can trim out, and still hasnt managed to get the readings correct, and its still rich.

Now obviously this could be a bad lambda sensor, but it could also be a bad MAF giving the engine incorrect readings, blocked FPR causing the fuel pressure to go too high etc etc.

The one extra piece of info you've got to work with, is the "(Add)" part, which means its an additive error. There are two types of fuel trim, additive and multiplicative. Additive adds a fixed amount of extra fuel and is mostly used to tune idle, whereas the multiplicative trim is a multiplier and scales the whole range.

http://wiki.ross-tech.com/wiki/index.php/17545/P1137/004407

If i remember correctly, didnt your original Autoscan results from the other week have a code for a bad lambda sensor? It may be the lambdas getting old and lazy and isnt responding correctly at idle, giving incorrect readings.

Cheers for the info mate, your always full of good gen

Yes your right the Lambda sensor was a recorded fault, I cleared it and checked again last night, having been driven some 150 miles since cleared and there was no reoccurrence.

The Lambda probe is screwed in to the exhaust manifold isn't it?

I'll rescan tomorrow to see whether the fuel trim code has reappeared.

Thanks again.

 

[MaverickTDi]

Still getting Fuel Trim (too rich) code. Today I've replaced the section of pipe, as seen above, with new silicon hose, see if that makes a difference? Had a route around the engine bay today, couldn't spot anything glaringly obvious. Going to change some original hose that goes into the intake manifold with the new silicon hose just as precaution.

Other than replacing either the MAF or Lambda sensor I'm not sure??

I have noticed that on initial start up the engine does smell very rich. When I get out the drivers door you can clearly smell it, any ideas? It's had a new downpipe recently but jacked the car up today to make sure all was sealed properly and it looked ok?