PDA

View Full Version : Terrible mpg when car is cold



sacha35
12-12-2016, 02:13 PM
Hi All looking for some help or advice.

2008 Audi A4 2.0TDI CAGA engine

A few months ago I change the cambelt and water pump and followed everything to the book, but ever since then I have suffered with bad MPG when the car is cold and on short trips averaging between 20 - 30mpg, on long runs everything seams to be normal averaging between 48 - 54mpg dependent on speed.

the above figures have been reached using tank fill meathead, but what I have noticed is when looking at the did display it shows 15mpg when first started and struggles to get to 30mpg when cold where before the cambelt was changed it would read 15mpg when first started but would then quickly move up above 38mpg and above.

the above problems seem to be like too much fuel is being injected into the engine but there is no singe of smoke or rough running at all if anything the car feels better with lots of power thought the rev range. One thing I have noticed though is the temp gauge is taking some time to get up to temp, I have changed thermostat but am wondering if the problem could be with the temp sensor?

I have scanned the car and all is good without faults and captured some data which seems fine also.


Please see attached images. I hope you may be able to throw some light as to why I am having this problem and if there are any other tests I can do to find the problem


3219432195321963219732198

FLAPPERJACK76
12-12-2016, 02:21 PM
Sounds normal to me.

Sent from my SM-G900F using Tapatalk

zollaf
12-12-2016, 02:23 PM
maybem just maybe, you have the timing slightly out..

Crasher
12-12-2016, 02:26 PM
What did you lock the cam and crank with?

sacha35
12-12-2016, 02:37 PM
What did you lock the cam and crank with?

Hi Crasher & Zollaf



I used the locking tools as to Elsawin and set as instructed.

I have logged with hot engine.

IDE00021 Engine speed 836 /min
IDE00405 Crankshaft speed (RPM) 839.5 /min
IDE00406 Camshaft speed (RPM) 418.3 /min
ENG106252 Synchronous angle 0.00

from what I can see with Synchronous angle the timing looks to be spot on.

This one has got me baffled.

Deanoc
12-12-2016, 02:50 PM
Did you own the car last winter? My old 2.0TDI easily dropped 10mpg in winter on a 15 mile trip i did a fair bit

Sent from my SM-G935F using Tapatalk

sacha35
12-12-2016, 02:54 PM
Had the car from new, There is a problem the car is drinking fuel when cold and dong short trips or stuck in traffic.

FLAPPERJACK76
12-12-2016, 05:11 PM
My usual weekly commute in my 1.9 pd is 30. Last week same commute 45. I brim the tank every Sunday and that's how I know. It's down to the recent cold spell.

Sent from my SM-G900F using Tapatalk

Crasher
12-12-2016, 07:46 PM
Check the actual coolant temp in measuring blocks when you are cruising at a steady speed, don't take any notice of the dash display, look at in in engine 01.

Rob69
12-12-2016, 08:12 PM
Don't those CR engines have two stats in the system ??
My 1.9 PD engine mpg has tailed off recently and a check with VCDS showed temp at low 70's even though dash says 90' and stat set point is 85'. stat change coming up after christmas to hopefully improve mpg, all else looked ok on my engine.

sacha35
12-12-2016, 09:07 PM
Check the actual coolant temp in measuring blocks when you are cruising at a steady speed, don't take any notice of the dash display, look at in in engine 01.

Did that mate, are the images not showing your end at the start of the thread. if not here is the coolant temp.

32204



Don't those CR engines have two stats in the system ??
My 1.9 PD engine mpg has tailed off recently and a check with VCDS showed temp at low 70's even though dash says 90' and stat set point is 85'. stat change coming up after christmas to hopefully improve mpg, all else looked ok on my engine.

Not to sure about this one? have changed the main thermostat. heating gets nice and toasty so hopefully can rule out air locks in the system.

sacha35
13-12-2016, 04:31 PM
One of the guys on another forum has picked up on the temp readout saying: 25 minutes to come up to 80C is a long time especially as the car was being driven and not standing when recording this log.

What are your thoughts is there anything else I can test?

rowdy-999
13-12-2016, 05:30 PM
One of the guys on another forum has picked up on the temp readout saying: 25 minutes to come up to 80C is a long time especially as the car was being driven and not standing when recording this log.

What are your thoughts is there anything else I can test?

The gauge may read 90*, but to actually get a true 90* will take a long time. On another note, to get oil to a proper temp takes an age!
To the OP I would change the CTS even if you're not getting any codes.

Crasher
13-12-2016, 06:59 PM
One of the guys on another forum has picked up on the temp readout saying: 25 minutes to come up to 80C is a long time especially

Is that gauge or measuring blocks?

sacha35
13-12-2016, 07:44 PM
Is that gauge or measuring blocks?

All logs have been done using measuring blocks.

FLAPPERJACK76
13-12-2016, 11:04 PM
Tried cardboard in front of the radiator?

Sent from my SM-G900F using Tapatalk

Crasher
14-12-2016, 12:01 AM
Diesels do take a long time to warm up, it is not so much the time to hot I am interested in, more if the temp drops as you are cruising along as Flapperjack is alluding to above.

sacha35
14-12-2016, 12:27 PM
Tried cardboard in front of the radiator?

Sent from my SM-G900F using Tapatalk

Not tried this as the temp is not my main problem it is the amount of fuel being used when the car is cold or stuck in traffic, but will give this a try.


Diesels do take a long time to warm up, it is not so much the time to hot I am interested in, more if the temp drops as you are cruising along as Flapperjack is alluding to above.

Hi Crasher thanks for the reply, yes I know Diesels do take a while to get hot I have had the car from new, as stated the car heater gets hot very quickly but this is not the problem it is the amount of fuel being used when the car is cold or stuck in traffic. It has never been this bad in all the time I have owned the car even when we had a cold winter with temps at -7c.

Anyway will try the cardboard and report back.

Crasher
14-12-2016, 06:03 PM
What I was wondering was that if the engine over cools the ECU will increase the fuelling.

sacha35
15-12-2016, 09:55 AM
What I was wondering was that if the engine over cools the ECU will increase the fuelling.

Thanks Crasher,

This is my thoughts also as the ECU has different maps for the temp of the engine so over fuelling could be the result of the engine just taking to long to get hot.

Could it be that one of the non return valves have gone or would you think the hose thermostat could be the problem as main thermostat has been change with genuine and tested before putting in or would you think it may just be a case or an air lock still in the system or maybe it is just the G62 coolant temperature sender.

I hate this cooling system layout, far to complicated and over engineered in places and not great with the temperature sender being where it is, no coolant results in low temperature being displayed on temp gauge resulting in engine cooling problems, unlike cars of old where the temperature sender would be located in the head giving hot reading and warnings enabling you to shut the engine down before damage occurs.

Thank you once again for your help and input.

Crasher
15-12-2016, 12:38 PM
I had to work around one of those systems last week so I could get at the crank speed sensor, as you say, far too complex. Have you studied the coolant temp as seen by the ECU when on a long steady cruise?

sacha35
15-12-2016, 05:28 PM
I had to work around one of those systems last week so I could get at the crank speed sensor, as you say, far too complex. Have you studied the coolant temp as seen by the ECU when on a long steady cruise?

As Audi say vous spring technic or as translated how make things more difficult to repair with every new model Audi make. I have studied the coolant temperature logged from the ECU it does somewhat fluctuate as soon as the car slows down or gets stuck in traffic, when cruising it seems to remain around the 85c mark hitting 90c then dropping back which I think is right as 85c was stamped on the thermostat I changed.

What has got me baffled is that the heater gets very hot very quick for a diesel around 5mins and its like toast, this has not changed at all from when I had the car from new ( so possible I could rule out an air leak as the matrix is the highest part so if any air was trapped it would be stuck up in the heater matrix)
The only thing I can think is possible the electric hose thermostat or one of the one way valves in the system have broken causing overflow of the cooling system thus keeping it colder for longer. It just strange that this problem has happened with a camel and water pump change :1zhelp:

Crasher
15-12-2016, 06:31 PM
What has got me baffled is that the heater gets very hot very quick for a diesel around 5mins and its like toast,

That's part of the idea behind the twin thermostat. You are right though, cars, even ordinary day to day types, are now way to complex for their own good and Audi are the worst of the VAG group, we call them "The four rings of doom". Yesterday we had a Q5 in with both DRL's/sidelights out, it needs 350 of new LED controllers. On this car, if you break one headlight you have to fit a later ones housing which may or may not (according to a twelve odd line dual column left/right interchangeability of components table)... mean you have to do the other side so one broken headlight on an HID/DRL car can mean a 2000 bill, that is simply insane.

zollaf
15-12-2016, 06:33 PM
at that price i would be retrofitting some 7'' halogens as used on landrovers, and some cheap chinese drls' . new wires to the battery and a new light switch, less than 150 notes fitted. might not look great but if it saves nearly 2k ???

sacha35
17-12-2016, 01:08 PM
That's part of the idea behind the twin thermostat. You are right though, cars, even ordinary day to day types, are now way to complex for their own good and Audi are the worst of the VAG group, we call them "The four rings of doom". Yesterday we had a Q5 in with both DRL's/sidelights out, it needs 350 of new LED controllers. On this car, if you break one headlight you have to fit a later ones housing which may or may not (according to a twelve odd line dual column left/right interchangeability of components table)... mean you have to do the other side so one broken headlight on an HID/DRL car can mean a 2000 bill, that is simply insane.

So would you say I can rule out the hose thermostat as the heater is getting hot and I know I changed and tested the engine thermostat so leaves possible temperature sender, why cant Audi give out test procedures and resistance values or measuring block details. as for the four rings of doom, I have never had any problems with Audi of which I have owned from mid 80s right up until now. The old Audi used to be built like a house and would just keep going, simple to fix and reliable. The cars of today are just getting far to complex, technicians (mechanics) just seem to change parts these days rather than being taught about mechanics, I think if you mention the word white metal bearings to 70% of the mechanics today they would not have a clue.

As you rightly said 2000 for what is a bulb, its getting more than a joke now. :aargh4:

Crasher
17-12-2016, 07:33 PM
All that sort of information is now contained in the Guided Fault Finding system section of the VAG diagnostic ODIS package which to get legally you have to jump through hoops of fire to use, I have tried pirated versions and they don't work at at all well, if at all! There is an early 90's Audi 80 type 8A for sale on fleaBay with less than 2K miles on it, those were THE last of of the well built "brick **** house" Audi's, from the A4 reliability went out the window in the sake of chasing BMW and Merc for volume sales and max profit. Better cars to drive in many ways but fragile...

zollaf
17-12-2016, 07:34 PM
Audi 80 Barn Find Classic 8350 genuine miles | eBay (http://www.ebay.co.uk/itm/332062573100?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT)


car for life. if only we knew then what we know now, that cars would get worse, not better....

Crasher
17-12-2016, 10:03 PM
My senior mech showed me that last night as I was just leaving, I was tempted to bid 2K but where would I put it? A 90PS 2L, if you can get the parts (Audi Tradition is a life saver) it would last you forever, seriously strong engine and box, they never ever rust and you could take on a tank and survive. There is one fly in the ointment, if it can get onto classic status it is safe but if it falls foul of the upcoming rules it will be as much use as a paperweight...

sacha35
19-12-2016, 09:14 AM
My senior mech showed me that last night as I was just leaving, I was tempted to bid 2K but where would I put it? A 90PS 2L, if you can get the parts (Audi Tradition is a life saver) it would last you forever, seriously strong engine and box, they never ever rust and you could take on a tank and survive. There is one fly in the ointment, if it can get onto classic status it is safe but if it falls foul of the upcoming rules it will be as much use as a paperweight...

Brings back memories, as Zollaf has said if only we knew then what we know now. A couple of my old cars that at the time I did not think anything off and turned out to be worth a fortune today. MK1 Ford Escort 1.6 Mexico, MK1 Ford Escort RS2000, My First Taste of Audi with the original 2.1 L 10v Engine Quattro, great car and even to this day miss it.

I then moved onto updated cars like the Audi 80 1.8e, A4 B5 1.8 20v, A4 B6 2.0 20v and to the present day A4 b8. Little did I know that things would have gotten far worse and more complex than a space rocket to fix.

zollaf
19-12-2016, 10:02 AM
amazingly enough, looking on ebay, the 2 escorts and the audi quattro would all be worth about the same amount today, if in really good condition, about 30k each.. :boggled:

sacha35
19-12-2016, 02:42 PM
amazingly enough, looking on ebay, the 2 escorts and the audi quattro would all be worth about the same amount today, if in really good condition, about 30k each.. :boggled:

yep saw that a few years ago that if I had keep just one of the cars it would have netted me about 30K, Still I have had it worse When I was 16 I had the chance to by an immaculate Aston Martin DB6 for 3K, not having the money and only been in work a short time I asked my father if he would lend it to me, he said no and that was the final say on the matter. The rest is history the cars are often being sold for 100K+.

Crasher
19-12-2016, 06:35 PM
have you seen the price a Mk1 Crapi is fetching, nuts! There was a more doors Golf 2 GTI 8v in Autocar last week, red late bumper and very very clean and 60K odd miles, they were asking just under 11k...... :1zhelp:

zollaf
19-12-2016, 07:28 PM
its this nostalgia thing, wanting the car you had in the 80's, or could never afford, or what your dad drove. i have a rover p6 v8 i am rebuilding. finished it could be worth 4k, next year it could be worth 40k. ???

Crasher
20-12-2016, 12:00 AM
i have a rover p6 v8 i am rebuilding.

Awwwww, P6 heaven, my wife seriously likes P6's and thinking about it she used to have a thing about Welsh boys.... :buttkick:

sacha35
20-12-2016, 09:45 AM
its this nostalgia thing, wanting the car you had in the 80's, or could never afford, or what your dad drove. i have a rover p6 v8 i am rebuilding. finished it could be worth 4k, next year it could be worth 40k. ???


Amazing Engine, one of the best V8 around, I remember squeezing one of these with a 3 speed auto box attached in a moggy minor with some modifications back in the late 80s for a customer, cut down jag rear axel and beefed up suspension and breaking system. Needless to say it went like a bat out of hell.

Crasher
20-12-2016, 09:57 AM
I have asked Santa for the new book just out about the SD1.

zollaf
22-12-2016, 10:19 AM
Audi 80 Barn Find Classic 8350 genuine miles | eBay (http://www.ebay.co.uk/itm/332062573100?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT)


car for life. if only we knew then what we know now, that cars would get worse, not better....

3450 ???? it sold for 3 1/2 grand...

Crasher
22-12-2016, 11:05 AM
A little strong, I hope it is looked after and not run into the ground.

zollaf
22-12-2016, 12:24 PM
you could look after that and use it as a daily for the next 20 years without it costing anything..