AWX Poor fuel economy

[S4_dan]

Guys,

I've got a Passat with the AWX engine. My mates A4 is loads better on mpg than mine. He can get 53mpg without trying to hard.

I've given it a full service (flushed the oil and and oil/air/fuel filters replaced)
and still struggling to get over 38mpg, where as my 1.9tdi AVG A4 and 2.0tdi AZV Touran managed early 50's without problem, doing the exact same routes and driving conditions.

There are no fault codes with vcds. In the logs everything looks be OK. Timing is spot on as I've just replaced the water pump last week and it was all double checked.

Out of ideas as to why to car is down on power a little bit and poor fuel economy.

Only other thing I can think of is when changing gear and the revs drop, all the dash lights and headlights dim quickly then go Straight back to full brightness.
Either battery or alternator, but car starts fine and strongly every time.

At a loss with this one.

Any pointers?

Cheers.

 

[DALE_AVANT]

Clean out the EGR valve, will help no end.

Also get the engine temp sensors etc changed.

Try running it on VPower diesel too, few more pence but is a cleaner fuel

Cheap fixes that will make it run better

 

[desertstorm]

Alternator sounds a bit dodgy to me. Check the voltage on idle with the lights o main beam and the rear heated screen on. should still be at least 13.7v.
Poor fuel economy can be many things, as above dodgy temp sensor is quite common. Camshaft wear problems, MAF , blocked vanes in the VNT all can cause issues. Does it go into limp mode any time ? .

 

[S4_dan]

Cheers guys,

Forgot to mention that I've replaced the black CTS with a genuine green one from Mike off here.

EGR is oily on the outside. No worse than my friends though, but I will remove it and give it a deep clean.

I always use Tesco diesel and have never had any mpg issues, but I will consider using a higher cetane rated fuel.

No limp modes no matter how I drive it. (Not like my Touran used to do!)
It does drive better once the engine has been ran for a while. It's more noticeably down on power from cold, especially in 1st when trying to set off.

I will try cleaning the maf but the logs indicate it's working as it should be....

Camshaft.....hmm, it's has 150k full vw service history but suppose I should check the cam for wear.

When I first got the car, there was a fault codes for injector #4, intermittent fault. I cleared it and it's never come back on so assume that it's resolved itself or it was maybe an iffy connection.

Cheers.

 

[desertstorm]

There is always oil on the outside of the EGR's on these,It's not an issue just makes a bit of a mess on the outside of the EGR.
http://www.myturbodiesel.com/wiki/camshaft-lobe-wear-inspection-and-replacement-on-tdi-pd-engine/
You could try logging an acceleration run in 3rd gear blocks 10 and 11 go from 1400 - 4200 rpm
https://sites.google.com/site/1810martin/vcds-data-log
https://sites.google.com/site/1810martin/vcds-and-pd-tdi-engine-health-check

 

[S4_dan]

Forgot to reply with voltage test this morning aster arriving at work.

With all lights on, rear heated window on, demisters on full and radio on, the battery voltage was 13.92v

If I blip the throttle, the lights dim and go back bright quickly. When driving, if I get the traction control to kick in, the headlights and dash lights, fan speed dips with each flash of the TC light on the dash.

So either battery or maybe a bad earth somewhere possibly?


I'll have a look at the EGR valve on Friday, will also do that log on same day and post the results.

Many thanks.

 

[desertstorm]

The alternator sounds good electrically. I would check the one way pulley is working correctly. It may be seized.See if the tensioner is bouncing.

 

[S4_dan]

I have checked that, all seems good. Had to replace my sisters alternator clutch pulley on her passat due to the belt jumping around. Still have the spline tool.

 

[desertstorm]

Check the earth strap on the engine then. May be loose or starting to fail. Check the connections on the back of the alternator are good.

 

[DALE_AVANT]

A clean of the EGR valve is 100% worth doing. It may not solve your issues but it can only help.

The inner circumference of the valve gets smaller and smaller the dirtier it gets, therefore allowing less airflow into your inlet.

It should look something like this:

But they can end up looking like this:

 

[S4_dan]

Finally I got around to removing the egr valve today!

Bit of a pain of a job. The lower bolt on the egr face was loose already, possibly explain the vast oil everywhere.

There was no gasket between the egr pipe and valve however there was writing marks on the egr face, indicating that there has been a gasket present at some point. So the egr may have been removed before. Certainly not by my mate though.

It wasn't full like the image above. I will upload a pic later. Got it nice and clean like the one above though. 2 hrs of soaking and scrubbing.

Car seems a little better at low rpm. Only did a short run so can't speculate on mpg difference yet. Off to work soon so will know more when I get there.

Also Mr muscled the turbo seeing as I had the car in bits.

Will keep you posted.

Cheers

Dan

 

[S4_dan]

Well the mpg has remained the same. Gutted.

Car seems to start a bit quicker/easier and a little more grunt low down. But remaining performance is the same.

Still need to get vcds onto it and do some logs. Will try this weekend to get some done!

 

[DALE_AVANT]

Shame it didn't fix the fault, at least you know it's running cleaner

 

[Mark Garfoot]

I've had bad mpg the last few weeks, struggling to get 40mpg, avf engine, changed my injector harness now I'm averaging 49mpg without trying

 

[S4_dan]

Did you have any faults coming up about the harness?

 

[Mark Garfoot]

Did you have any faults coming up about the harness?

No faults at all mate on vcds
I occasionally had a poor idle on cold start up which is now sorted

 

[S4_dan]

Idle and start up seems better now that the egr was cleaned out.

My mate has a MAF which I'm going to try. Failing that, I will look at the harness. I did change my mates harness on his AVF A4.

Do you know the part number for the harness?

Cheers.

 

[Mark Garfoot]

Got mine from darkside developments as they came in slightly cheaper than Audi. Didn't think to try the parts section on here.
http://www.darksidedevelopments.co....vw-1-9-2-0-8v-tdi-pd-engines-038-971-600.html

 

[S4_dan]

Tried the replacement MAF. Has made a very slight increase of 2 mpg. Seems to pull ever so slightly better over 2k rpm.

On a run this afternoon, I filled the car and put in some diesel redex treatment. Car seems livelier again but mpg just won't go over 40.

Think I'll try the harness next as everything else appears to be in order.

 

[S4_dan]

New harness ordered!

 

[Mark Garfoot]

Hopefully that will do it mate, warm the new one up well

 

[S4_dan]

Well, fitted the new loom yesterday at work. 40mins and still no ****** difference in mpg. Gutted.

Think it'll be getting sold at this rate lol.

 

[Gazwould]

What were the camshaft lobes looking like ?

 

[desertstorm]

How many MPG is it doing ?. Have you measured it accurately by filling the tank , driving it and filling it again?.
One of the guys on UKP has changed loads of things on his AWX chasing mpg issues and hopefully looks like he may have found the issue with the tandem pump change.
http://www.ukpassats.co.uk/phpbb/viewtopic.php?f=8&t=88727

 

[Mark Garfoot]

Sorry to hear that mate

Well, fitted the new loom yesterday at work. 40mins and still no ****** difference in mpg. Gutted.

Think it'll be getting sold at this rate lol.

 

[S4_dan]

What were the camshaft lobes looking like ?

They looked really good. No scores or wear in the centre and no 'lips' on the edges of the lobes.

Unless they do wear down evenly?

If so, does anyone know what length the lobes should be and I could try my micrometer on there?

 

[S4_dan]

Sorry to hear that mate

One of those things.....

 

[S4_dan]

How many MPG is it doing ?. Have you measured it accurately by filling the tank , driving it and filling it again?.
One of the guys on UKP has changed loads of things on his AWX chasing mpg issues and hopefully looks like he may have found the issue with the tandem pump change.
http://www.ukpassats.co.uk/phpbb/viewtopic.php?f=8&t=88727

I have considered the tandem/fuel pump.

We have been away for the weekend with mixed driving but mostly motorway at 70mph - calculated to a smidge over 38mpg. DIS actually was showing 41.5 for most of the journey.

I'll have to search on how to test the pump with a gauge (like mentioned in the link above). I too, don't have any visible leaks from the pump. My exhaust gases smell strange but there are no oil or coolant loss at all. I don't stick my nose near the tailpipe, its from when the gasses waff up if I've been around the boot etc with engine running.

Cheers.

 

[Gazwould]

With the lobes it tends to be the odd few .

Bad

New

Also all the lifters tend to end up dished .

 

[S4_dan]

I couldn't see any wear like that on the lobes when the cover was off. I didn't rotate the cam though. I'll have a look at the during the week when I get chance.

 

[desertstorm]

http://www.myturbodiesel.com/wiki/camshaft-lobe-wear-inspection-and-replacement-on-tdi-pd-engine/

 

[S4_dan]

Here is a log of groups 3, 11, & 13.

Any ideas?

Cheers.

Dan

 

[S4_dan]

 

[S4_dan]

Can't work out how to post the file as a .csv??

 

[DieselJake]

Can't work out how to post the file as a .csv??

Should be able to host it on Dropbox/Google Drive/other service then link to it, worst comes to worst drop us a pm and I'll send you my email address then host it on my private server (... yes... yes I do work with websites/computers for a living haha).

 

[desertstorm]

Had a quick look at those figures on the data log and I can't see anything particularly amiss. The MAF readings look reasonable. The boost is being controlled OK with the N75 duty cycle just hitting 80% right at the top end of the RPM range.
The injector balance looks OK, It's in spec and all 4 are less than + - 1.

 

[S4_dan]

Should be able to host it on Dropbox/Google Drive/other service then link to it, worst comes to worst drop us a pm and I'll send you my email address then host it on my private server (... yes... yes I do work with websites/computers for a living haha).

Cheers Jake. I have Photobucket, so will see to it.

Had a quick look at those figures on the data log and I can't see anything particularly amiss. The MAF readings look reasonable. The boost is being controlled OK with the N75 duty cycle just hitting 80% right at the top end of the RPM range.
The injector balance looks OK, It's in spec and all 4 are less than + - 1.

Cheers Karl, thanks for your time.

A fitter at work thinks it could be the tandem pump not producing enough fuel/pressure. Possibly like the link to the UKPassat forum you posted above.

Will try and obtain a fuel pump pressure gauge before splashing out for a new pump. Unless some one has a good, known, fully working used on for sale.

I was also thinking about trying a Blacksmoke remap on it, for the cost of the map and I already have MPPS. I believe the car to be original map/ecu, can't see an original map going bad?

Dan

 

[desertstorm]

Maps don't go bad. That's why they have checksums on them, any corruption to the map in the ECU and the car doesn't start. Wouldn't be very good if the driver demand map got corrupted and 5% throttle pedal resulted in 100% acceleration.
Putting a map on a car that has pre existing issues never usually helps.

 

[S4_dan]

I'll hang fire on the remap then.

Next course of action I believe is to check the tandem pump then.

 

[Darran]

fuel mileage is determined by torsion value, if you dont have this right you will lose economy or power or both, changing cambelts without checking TV before change is classic sign of torsion value being slightly out thus giving your problem.

So step 1 check torsion WITH VCDS and post results plz.