For over a year now I've had terrible mpg. Changed many things over time (some which needed it and other changes that weren't as necessary). But the same issue is still there, bad mileage. Got A Fabia vrs pd130 BLT engine with 1756 Hybrid turbo and had it mapped but removed the map when I blew my cams. Changed the cams for uprated cams but still bad mpg. Before someone says it's a timing issue, the timing is spot on as checked by vcds and also had the timing belt and water pump replaced a week ago. 

Since then had the boost leaks all sorted, fmic works fine, 4 injectors replaced as the values were all over, now idles smoothly but still **** mpg. Had it tested for vacuum leaks and nothing there either. Currently got it standard with no map but even with no map it's got bad mileage. I get 35 miles off a TENNER.

It always seems to have a start-up issue too. Sometimes with it getting up to 600 revs, then dropping and then climbing up to 900 revs or so. Does this randomly, sometimes it'll start perfect, other times it'll do this, sometimes it will even sound like it's misfiring halfway up. I keep the key turned over for an extra 2-3 seconds while this happens. It fires up right away, just doesn't catch onto 900 revs for a few seconds. Anyone got any idea what that is?

 

Genuinely can't figure this car out for the life of me. Vcds shows the map sensor has 0 on specified but shows numbers for the actual maf figures. Is that normal since it's a BLT?  Vcds also shows the IQ is very high at 9 on idle. Any help? 

Sounds like you have a fuel leak somewhere under the car when it's running, that mileage is so terrible it must be pouring out somewhere because it would be smoking like a chimney if it were actually burning it!

1 minute ago, sepulchrave said:

Sounds like you have a fuel leak somewhere under the car when it's running, that mileage is so terrible it must be pouring out somewhere because it would be smoking like a chimney if it were actually burning it!

 

I had this issue. Check to see if it's leaking around the fuel filter etc.

I'd assume it'd be a fuel leak too but haven't noticed any leaks below the car besides coolant leaking from the radiator leak but I'm replacing the radiator next. For that much fuel to be leaking I'd surely have noticed it, or at least my mechanic who's been trying to find out the issue too. Feels like the car is just injecting way too much fuel. It has black smoke from the rear when I put full power down and smells of diesel but during normal driving it seems fine. Wouldn't even notice it has an issue until I'm back filling up again. 

Where was your leak exactly? From the pipes connecting to the fuel filter? I had the filter changed today by mechanic with a service hoping it'd fix the issue maybe but no success. 

Have you had the car up in the air while running?

3 minutes ago, DiazFabia said:

Where was your leak exactly? From the pipes connecting to the fuel filter? I had the filter changed today by mechanic with a service hoping it'd fix the issue maybe but no success. 

 

Came from the filter directly.

 

6 minutes ago, DiazFabia said:

I'd assume it'd be a fuel leak too but haven't noticed any leaks below the car besides coolant leaking from the radiator leak but I'm replacing the radiator next. For that much fuel to be leaking I'd surely have noticed it, or at least my mechanic who's been trying to find out the issue too. Feels like the car is just injecting way too much fuel. It has black smoke from the rear when I put full power down and smells of diesel but during normal driving it seems fine. Wouldn't even notice it has an issue until I'm back filling up again. 

 

I do think that this you describe here is more than a leak. I'll leave it to the smart folk to work out what to sort etc etc.

25 minutes ago, sepulchrave said:

Have you had the car up in the air while running?

Yes the mechanic had it running for an hour whilst lifted from the front to check for coolant leak a few weeks ago but it didn't leak as the radiator only leaked whilst off. But he didn't notice anything else leaking either, no fuel or oil. 

35 minutes ago, DiazFabia said:

Feels like the car is just injecting way too much fuel. It has black smoke from the rear when I put full power down and smells of diesel but during normal driving it seems fine.

That just could be it. Is there any evidence of the engine running cool (and don't quote the temperature gauge unless it's reading low).

2 hours ago, DiazFabia said:

Before someone says it's a timing issue, the timing is spot on as checked by vcds and also had the timing belt and water pump replaced a week ago.

The torsion value displayed in VCDS being "spot on" is actually a great big red flag that the valve timing is significantly out.

 

If it is outside of the VCDS parameters which are only a couple of degrees + & - then it will display a default zero torsion angle, whilst it is possible to time it "spot on" and get a genuine zero torsion value it takes the patience of a saint and a feather touch moving a shaft  against a huge valve spring loading.

 

To check whether you have a genuine or false zero displayed value rev the engine while watching the parameter in measuring blocks it should go slightly negative (might be positive I can never recall) when revved as the belt stretches.

 

My money is on incorrect cam timing being responsable from what you have written.

17 hours ago, J.R. said:

The torsion value displayed in VCDS being "spot on" is actually a great big red flag that the valve timing is significantly out.

 

If it is outside of the VCDS parameters which are only a couple of degrees + & - then it will display a default zero torsion angle, whilst it is possible to time it "spot on" and get a genuine zero torsion value it takes the patience of a saint and a feather touch moving a shaft  against a huge valve spring loading.

 

To check whether you have a genuine or false zero displayed value rev the engine while watching the parameter in measuring blocks it should go slightly negative (might be positive I can never recall) when revved as the belt stretches.

 

My money is on incorrect cam timing being responsable from what you have written.

By spot on, I doesn't mean zero. It's pretty close to zero but moves around when revved last time I checked. I thought timing was the problem but had timing checked professionally and through vcds and both seem to show no issue. 

18 hours ago, KenONeill said:

That just could be it. Is there any evidence of the engine running cool (and don't quote the temperature gauge unless it's reading low).

I also thought it could be running cold. Maybe the CTS had gone bad. But the temperature on vcds more or less matches with the gauge. Takes a while but gets up to 80s eventually. Not bang on 90 but close enough to not be an issue I believe

1 hour ago, DiazFabia said:

I also thought it could be running cold. Maybe the CTS had gone bad. But the temperature on vcds more or less matches with the gauge. Takes a while but gets up to 80s eventually. Not bang on 90 but close enough to not be an issue I believe

 

Don't forget there's a fuel temperature sensor as well that could have failed.

1 hour ago, DiazFabia said:

the temperature on vcds more or less matches with the gauge.

That's actually sort of helpful. I've got a feeling that it may be running rich on high throttle, hence the black smoke.

23 hours ago, KenONeill said:

That's actually sort of helpful. I've got a feeling that it may be running rich on high throttle, hence the black smoke.

Yes it could but is it possible for it to be running lean when on idle as well? Isn't that what a high IQ means usually. 

 

On 25/05/2022 at 18:15, sepulchrave said:

 

Don't forget there's a fuel temperature sensor as well that could have failed.

I believe that was around 40°C or so but I'll have to check again next time I put the vcds on