Hello all, I have a mk1 l&k with the 1.8t (150/aug) engine with auto (01m) gearbox. I used this car regularly 6 months ago but I went abroad for 3 months and the car sat still for this time. When I returned the battery was foobared so it was replaced with the one from my mk2 octy (61AH 330cca) and all is fine. However I've noticed I've struggled to get 29mpg(with conservative driving)recently but before I was seeing 44mpg(driving like an "average" person).

Now in an effort to restore my mpg I've done the following:

-new genuine green CTS

-NEW genuine thermostat

-Sai removal (with blank)

-n249 removal

-new vacuum pipes all round.

-new genuine PCV pipes(all)

-throttle body clean

-AIT clean

-MAF clean

-all engine earth's cleaned

-smoke tested the system

-no codes on car using VAG scan tool

The car is completely stock down to the headunit and drives perfect but after all that I can only achieve 34mpg. Now I'm aware with the cold weather mpg will be lower with rolling resistance increasing etc but I'm still down 10 mpg.

I've researched this for weeks now and I'm flat out of ideas, any help is most appreciated.

Thanks in advance :)

Have you checked your brakes are free as a seized or seizing calliper can drastically drop mpg. I had this issue with my 1.9 tdi where I was lucky to get 25mpg around town and 40mpg on a long run. I found out my drivers rear calliper was seized, I replaced the calliper and now get on average 45-50mpg around town now, haven't been on a long run yet to see the figure from it.

Other thought; when was the ATF last changed?

Have you checked your brakes are free as a seized or seizing calliper can drastically drop mpg. I had this issue with my 1.9 tdi where I was lucky to get 25mpg around town and 40mpg on a long run. I found out my drivers rear calliper was seized, I replaced the calliper and now get on average 45-50mpg around town now, haven't been on a long run yet to see the figure from it.

Thanks for the reply. I went for a run this morning using minimal brakes and just letting the car come to a stop naturally, I then tested the temp on all the discs and all were still cold after 10mins, to make sure I jacked the car and all wheels were free to spin. Would this be sufficient to test for a bind?

Thanks

Other thought; when was the ATF last changed?

Thanks for the reply. I forgot to mention the ATF was replaced with genuine VW oil less than a month ago,I had flare in 3rd- 4th shifting so the oil,all solenoids, harness, filter and gasket were all renewed. This fixed the problem and the gearbox now reports no codes and shifts smooth. Thanks

Also I forgot to mention the car had a full service including new oil, oil filter,fuel filter, air filter and sparks correctly gapped.

The coils are the latest revision and where checked out ok.

Thanks for the reply. I went for a run this morning using minimal brakes and just letting the car come to a stop naturally, I then tested the temp on all the discs and all were still cold after 10mins, to make sure I jacked the car and all wheels were free to spin. Would this be sufficient to test for a bind?

Thanks

Sounds like there running free from what your saying. Other thing is are you going off the mpg on the display as that's not always accurate, and need to be reset when you fill up to give a reasonable guide to mpg.

I get the point about the trip display, but IME that's always optimistic wrt a fill to fill measurement using the trip meter.

I've done a calculation from fill up to fill up and the trip is quite accurate on mine.

I've brimmed the car this morning and reset the mpg gauge, I'll calculate the real world mpg vs the OBC and let you know. Thanks

Decided to take a long trip to see some family today, used up half a tank mostly on the motor way, real world mpg was calculated at 33mpg OBC was 32mpg. This was mainly doing 60-65. Still very much down on mpg.

Thanks

Have you checked over and cleaned out your breather system. Ive had terrible mpg for a while now, actually struggling to achieve 25 mpg....... just this weekend i have cleaned all my breather system out as it was clogged badly, i actually replaced the rocker cover too in fear the main breather was blocked on that too. All sensors have been cleaned or replaced including injectors. Ive replaced the thermostat and carried out a general service. Im very pleased to as that to my surprise my 1.8t is now running alot smoother and has returned thus far an average 42 mpg! This is the highest it has ever been during my ownership.

Have you checked over and cleaned out your breather system. Ive had terrible mpg for a while now, actually struggling to achieve 25 mpg....... just this weekend i have cleaned all my breather system out as it was clogged badly, i actually replaced the rocker cover too in fear the main breather was blocked on that too. All sensors have been cleaned or replaced including injectors. Ive replaced the thermostat and carried out a general service. Im very pleased to as that to my surprise my 1.8t is now running alot smoother and has returned thus far an average 42 mpg! This is the highest it has ever been during my ownership.

Hey mate, that's good going! I've put a brand new genuine pcv system in including new pcv valve, all vac lines have been replaced also and all mikalor clamped In. I've not touched the injectors yet, may be a good idea to flow test them. Thanks :)

Oh forgot to mention that i did all maintainance as and when i could afford it. The ultrasonically cleaned injectors didnt really give a noticable diffence in mpg, smoothness or performance however replacing my fuel pressure regulator resulted in my car performing alot better overall. It cured cold morning stutters and actually saw my car into the low 30mpgs on avaerage. As your probs aware, the car isnt worth a great deal pf money hence i do everything i can myself. I cant justify big garage bills so this forum has helped me massively over the years with simple mods and simplifications. But buy the sounds of things it looks like the only thing you havent touched so far regards your issue is the fueling system....

Oh forgot to mention that i did all maintainance as and when i could afford it. The ultrasonically cleaned injectors didnt really give a noticable diffence in mpg, smoothness or performance however replacing my fuel pressure regulator resulted in my car performing alot better overall. It cured cold morning stutters and actually saw my car into the low 30mpgs on avaerage. As your probs aware, the car isnt worth a great deal pf money hence i do everything i can myself. I cant justify big garage bills so this forum has helped me massively over the years with simple mods and simplifications. But buy the sounds of things it looks like the only thing you havent touched so far regards your issue is the fueling system....

Hey mate what lead you to replace the FPR? We're you getting codes or just on a whim? I've changed the fuel filter and checked voltage at/ground at fuel pump but indeed fuel system, 02 sensors and cat are the only thing I've not poked around with yet. I have a spare 1.8t lying about so I'll switch the FPR and see if that makes any odds. Thanks :)

It was on a whim. Ive have a spare rocker cover, inlet mani complete with fuel rail, injectors and fuel pressure reg from a BAM engine lying around for years! I spent 10 years in the tuning industry and managed to pick these up from an old customer who have a big engine upgrade carried out. Hos car had only covered 42000 miles so i know these parts would be good to go (at the time i was going to carry out the welly cooler upgrade but one thing led to another with this and that never happened). So i swapped it all over. The car actually ran pretty well on BAM injectors too while my others were away getting cleaned.

Because the fuel pressure fluctuates, the ecu will not record this issue and log it as fuel starvation. Itll no doubt be logged as an O2 sensor fault or misfire as the ecu will cut timing to save motor. The only way to check this would be live time recording so a Air Fuel ratio guage, an actual pressue guage fitted to the fuel rail and ran into the car or to log Vag com as you drive.

I was lucky enough to just have this part lying around and i thought it cant do any damage as it was a like for like item (3bar fuel pressure reg) that had covered roughly a third of the mileage mine had.

Im going to invest in a fuel pump soon as i havee a noticable hick up under heavy load situations; its defos not a misfire. The old girls getting on now so im happy to replace parts when i can as a matter of course anyway.

Sorry i cant be any more technical in sourcing the issue....

Thanks for the info mate, the engine I have lying around is on 130k, where mine is on 75k,and the only known issue on it was the engine speed switch and head gasket. I'll swap the FPR this week hopefully and report back. Before you switch the pump you may want to check the pump relay as these are common issues for the car and a much simpler and cheaper fix :)