I've been looking at other threads but nothing is coming up. The problem is my mpg seems to low, the car has had the timing belt & water pump done-egr replaced with a new one-lower boost hoses replaced- liqi Molly diesel purge as well as using it in full tank of fuel.
I've done mixed driving 50% motorway A roads and around locally, full tank done just over 400 miles and I'm not driving crazy :-(
The car has done 138k with two previous owners, should I get a remap to see if it helps with the mpg etc ? Only thing is its £200 and will it work ?
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the car has had the timing belt & water pump done
Unless great care is taken to lock the cam wheel, correct timing will be lost when the belt is changed. These engines are vey sensitive to timing.
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Has this problem only occured since the cambelt was changed?
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Re-maps are well proven not to improve mpg. The sellers always carefully word their adds to make it look like it will but if you read close its always something like "may improve your mpg upto 5%", in other words it probably won't.
Even if it did work out how long it would take to get your £200 back.
And don't forget you will need to inform your insurers and they will increase your premium. If you do't tell them they would revoke your cover if they found out.
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Ah !! Ok thanks for that.
I'm hoping to figure out the poor mpg before a full front suspension rebuild, obviously don't want to spend £430ish on parts if I'm still going to be getting 400 miles to a tank :-(
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I'm not sure as it was done about 2000 miles before I bought it, belt pump auto tensioner all done as well as the egr. On a decent run I get 55mpg according to comp but recently down to 46+ on a run and between 28-36 locally. I'm a bit stumped...
Any ideas on checking timing ? Or do you think it will need redone ? Belt off and refitted ?
Or should I just strip front and check all the timing marks line up ?
Any help appreciated :-)
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I'm not sure as it was done about 2000 miles before I bought it, belt pump auto tensioner all done as well as the egr. On a decent run I get 55mpg according to comp but recently down to 46+ on a run and between 28-36 locally. I'm a bit stumped...
Any ideas on checking timing ? Or do you think it will need redone ? Belt off and refitted ?
Or should I just strip front and check all the timing marks line up ?
Any help appreciated :-)
Are you sure the fuel consumption figures you quote are that bad. You said you used to get 55mpg but this has dropped to 46mpg. I have a Skoda Superb 100pd and the fuel economy usually is not as good in cold weather. Was it a lot warmer when you got 55mpg?
Re 28-36 locally - Both your Passat and my Superb are big heavy cars.I average just short of 50mpg (lower when very cold) measuring between tank fills (my on board computer reports 3-4mpg less!) . However during my 32 mile journey to work for the first few miles the trip/journey computer only shows low 30s whilst warming up and driving around town with the average only getting back towards 50 (46-47 on the computer) by the end of the journey. I.e. if I was just driving around town I would also be getting a low mpg.
Ignoring the computer on a long run would you get 600miles out of a tank of diesel?
Be careful how much money you spend on a problem that may not exist. How well is it running and is the Engine Management Light on?
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I though I would try unplugging the MAF to see how the car would run with it off, there's no difference whatsoever. It still feels the same...lacking power and slow to pickup, slight power coming in at around 2500 mark.
I would say its for the bin then...would you agree ??
I had it on Vagcom yesterday and the MAF value was sitting at 440 whereas Rosstech says it should be between the 800-1100 parameter, this is why I though I'd try MAF off. I got 408 miles out a full tank and that was after doing a Moly diesel purge last week, the lacking power and low mpg is what made me think MAF...
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Problem sorted, there was a vacuum hose that had come undone so the turbo wasnt kicking in hence shocking fuel figures.
I had been getting 400 to a tank with 50/50 driving with no power, car is running fine. I shall be replacing all vacuum hoses with silicone ones asap
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Would a front off and check timing marks lining up do or off completely and refitt ?
Also used OB11 reader and no codes coming up so don't see it being anything else.
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No, 'chalk and pray' isn't good enough! Remember, the injectors are driven by the cam, this is why timing is so critical. Ideally, you need VCDS to obtain the Torsion value and find out if it is in spec. The cam sprocket can be rotated relative to the cam if you loosen the bolts. Here's an article showing a crude version.
autospeed.com/cms/title_Big-Changes-from-Tiny-Adju...l
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Ok thanks, I'll get a hold of my mate and see if he has VCDS at his garage. If not he can prob borrow one (and someone who will read it right :-) )And failing that a vw/diesel specialist near me.
I've looked at the article in the link and I'm slightly wary of adjusting as the car starts first(second) time in the recent cold -6 so I'd hate to think it might give me an awkward startup, but I suppose if I don't try it I won't know...
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You don't need VCDS to set the valve timing on a PD engine, the best solution is peg and plate as God, sorry VAG, intended. Curing high fuel consumption problems on a TDI can be difficult but start with a code read. If nothing comes up consider changing the thermostat and the Air Mass Meter.
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I was wanting a VCDS reading to see if everything was fine, I've checked with OB11 reader already and it was clear of any codes.
I've already done the thermostat and temp sensor as it was sitting around 70, the car was running up to temp fine when I first bought it a few months ago.
It's my first PD so not wanting to jump in head first without checking with anyone first due to the sensitivity of the engine.
Looks like I'll be doing the MAF then, thanks
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It is possibly the AMM if the thermostat is regulating the water flow correctly and not over cooling the engine and there are no codes but it is a gamble. What I would strongly recommend you did is to buy the AMM genuine exchange from a VW dealer and nowhere else, myself and many others have had terrible problems with them from other sources, even genuine Bosch, allegedly...They are not an awful lot more from VW anyway, typically around £110 inc. VAT for part number 038 906 461 X.
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You were almost right, it's £120 exchange at vw. I'm going to just have to try some CRC MAF cleaner just now until I've got spare money, ive already spent £430+ on front arm kit & shocks etc etc. If I can't get a result in cleaning or changing Ill need to rethink my front end rebuild, no point spending time & money if I've got mpg issues :-(
Fingers crossed, thanks for the advice.
(still to get a VCDS read)
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I think a VCDS read is worthwhile. Getting a torsion value should either confirm or rule out a timing error and reduce the diagnosis by substitution problem.
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Well I'm booked in tomorrow and for a reasonable £25, all readouts shall be emailed to me as well as a verbal explanation.
I'll post any codes I get, cleaning the MAF today just to see if I notice any difference and also to see how much dirt it's holding.
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I managed to get the VCDS scan today, I had 2 errors. One was to do with a flap/valve and cant remember the other. Cleared both and rescanned...nothing came up second time round. I think one was from a lower boost leak as I replaced the hose about 2 weeks ago.
The MAF value is meant to be between 800-1100 but when idleing is was sitting around the 440 mark so I think it's knackered, I'm waiting on the guy speaking to someone at Ross-tech to find out what the reading really means.
I'll find out what the 2 error codes were if I can, everything else seemed to be running within the correct parameters...especially the injectors. They were more or less spot on, the Moly diesel purge must have worked.
Just a case of waiting to see what I find out tomorrow.
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What was your torsion (KW) value?
A MAF value of 440 could mean that the EGR valve is fully open (giving roughly 50% EGR) and hence cutting your intake mass flow by~50%. This could be the EGR valve itself, or its actuation, rather than the MAF.
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I never kept a record as we were watching the figures live, I'm going to go back and see him tomorrow afternoon and plug in and get a record of everything again.
Is there anything you could think that I should get readings of ?
The Egr valve is pretty much new do hopefully it's not sticking, I'll find out tomorrow by seeing what readings the Egr is throwing up.
Cheers
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I though I would try unplugging the MAF to see how the car would run with it off, there's no difference whatsoever. It still feels the same...lacking power and slow to pickup, slight power coming in at around 2500 mark.
I would say its for the bin then...would you agree ??
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Not necesarily. If It was sending bad data to the ECU, then there should be a discernible difference when the incorrect data is taken out of the equation.
Just quickly check that there isn't a vacuum leak on the EGR vacuum hose/connections.
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Well what can I say...you were right. The EGR is letting too much through, the MAF is showing readings.
The VCDS scan has been sent to Rosstech to get a better idea but I've noticed soft brakes today so I'm thinking vacuum related rather than N75 problem, going to have a look at vacuum hoses down the rear of engine tomorrow.
Would I be able to see a crack in pig tail pipe from above or underneath ?
Lol is there anything else you might think I should look for ?
17964- charge pressure control: negative deviation
P1556-35-10---
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Well what can I say...you were right. The EGR is letting too much through, the MAF is showing readings.
The VCDS scan has been sent to Rosstech to get a better idea but I've noticed soft brakes today so I'm thinking vacuum related rather than N75 problem, going to have a look at vacuum hoses down the rear of engine tomorrow.
Would I be able to see a crack in pig tail pipe from above or underneath ?
Lol is there anything else you might think I should look for ?
17964- charge pressure control: negative deviation
P1556-35-10---
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The vacuum setup feed three things:-
1) EGR
2) Turbo variable vanes
3) Aniti shudder valve
Check all the vacuum lines (the flexible ones rot or rub- not always obvious, the hard ones can rub through with vibration - happened to me)
Near the brake servo there is a T piece/valve in the large brake vacuum pipe this is where the vacuum originates from. Temporarily disconnect the small T off pipe and start the engine to check vacuum here (should be a sucking noise) - reconnect!
This then connects to a flexible pipe that feeds a solid pipe that crosses the bulkhead across to operate the EGR solenoid (via flexibles/ oneway valves etc..)
Then back across the bulkhead down to two solenoids and a vacuum resevoir operating the anti shudder valve and variable vanes.
Does the engine "shudder" when turned off? - If so it's a sign you are lacking in vacuum! You should be able to see the anti shudder valve operating when turning off the engine by looking under the bonnet over the OS wing looking at the valve just below the plastic engine cover.
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Good afternoon :-)
I took the covers of fans disconnected the air box to turbo and low and behold one of the vacuum piped had come off. Looks about 3-4mm reconnected and volai-brakes good-turbo working :-) thank you for your insight
I'm looking to replace all the vacuum pipes now and was wondering if there's anywhere you would recommend to buy the tubing from lol obviously not VW
Just to check ? Would I be looking for 3/4mm and 6mm vacuum hose ?
Again thank you :-)
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Good afternoon :-)
I took the covers of fans disconnected the air box to turbo and low and behold one of the vacuum piped had come off. Looks about 3-4mm reconnected and volai-brakes good-turbo working :-) thank you for your insight
I'm looking to replace all the vacuum pipes now and was wondering if there's anywhere you would recommend to buy the tubing from lol obviously not VW
Just to check ? Would I be looking for 3/4mm and 6mm vacuum hose ?
Again thank you :-)
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Lol meant to read and not fans lol, on my phone with predictive text :-)
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