Sudden drop in MPG and wooly throttle response

[SamsterXX]

I've a Fabia Estate 1.9TDi with 155K on the clock. It's always pulled brilliantly and returns over 50mpg, up to 56mpg if I try hard!

A week ago I started it up and I stalled it twice coming off of the drive - seemed strange. Then I noticed I couldn't achieve better than about 30mpg, and also the throttle response was strange. I have to push the throttle quite a bit to get it to pull, whereas before it was really responsive and would pull well with only the slightest pressure on the pedal. It feels really wooly / fluffy if you know what I mean?

Initial thoughts are the fuel injectors? What about that stuff that you add to the diesel - anybody tried it?

I've not run the car low on diesel or put anything untoward in the tank.

Any ideas? Anybody else experienced this?

Cheers....................Sam

[TeflonTom]

dont bother with injector cleaner/additives.

you need to get your car hooked up to vag-com or the dealers diagnostics equipment to find out what fault codes are logged..

it might be caused by the valve timing being slightly out. the camshaft pulley has a kind-of vernier adjustment, remember on the pd diesel engines the camshaft also operated the fuel injectors, and hence if the cam timing is wrong the injection timing may be wrong too, this might of happened by the sudden jolt of being stalled

or i could (as usuall) be totally wrong

[SamsterXX]

Cheers for the response Tom - the cause of the two stalls was the problem itself!

I've also noticed that the idle speed is fluctuating quite a lot..............

[TeflonTom]

to be honest it's just a wild stab in the dark, without seeing (or hearing) it it's almost impossible to diagnose stuff like this... could also be one ot the other common problems like MAF, EGR etc etc

[SamsterXX]

I'll get it hooked up to a Skoda dealers diagnostic kit.

Haven't been on here for years since selling my Octy vRS, this VAG-COM looks bloody brilliant, well useful.

[TeflonTom]

if you ask nicely there may be a kindly member who can help you out rather than paying a rediculous price for dealer diagnostics time

[Tom_vRS]

I think this is a problem with the coolant temperature sensor, and this fault may not show up on VAGCOM. For what they cost, and how easy they are to change, I'd give it a go.

It could be the MAF, but in this case I suspect its not - an easy way to see if this is the problem is to disconnect it and go for a drive - if it drives better the maf is at fault.

Could be the EGR, may just need a good cleaning. Probably only an hours job with some carb cleaner (EASY DIY), so that might be worthwhile too.

Good luck with a fix, keep us posted.

[SamsterXX]

Tom - excuse my ignorance, what's the MAF? - something to do with air flow?

EGR is a valve in the exhaust isn't it?

Why would the coolant temperature sensor cause these symptoms? And if it could, where can it be located to be changed?

Cheers............Sam

[ncarring]

Coolant sensor change has just been nicely written up by Ap0gee in the technical guides section. EGR is the exhaust gas recirculation valve - and yes MAF is Mass AirFlow sensor - the thing that measures how much air is getting into the engine and therefore how much fuel to add.

Search for any of those terms using the search function and you'll find oodles of previous posts on the various subjects.

[ap0gee]

Originally Posted by ncarring

Coolant sensor change has just been nicely written up by Ap0gee in the technical guides section.

Ta for the plug, Nick!

Just be aware (Samster) that the guide is based on an MPi engine, so there may be some slight differences for your diesel lump. It's not a tough job, but if you discover anything that may be of use to other users, please let me know and I'll amend the guide!

[Tom_vRS]

Well that sensor is used to tell the engine how much fuel is needed etc. It may think the engine is hot, and thus not pumping in enough fuel to let the engine run well on cold start, hence the stalling. If when the engine is hot, it thinks its even hotter, it may run a touch lean thus giving you poor throttle response etc.

Crap explaination, but you get the jist!

[Davy-B]

I had a coolant sensor go on a 1.6 Polo. The main thing I noticed was that it ran OK cold but once it warmed up accelleration became hesitant and the revs were high at idle.

When I've seen injectors go the engine's been clearly 'missing' and obviously lumpy. Doesn't sound like yours.

[P-A]

Doesn't sounds like the MAF. Usually when a MAF goes up the creak you'll get a flat-spot in the rev range. I don't think it causes a loss of power like you're experiencing.

[ric04vrs]

Originally Posted by P-A

Doesn't sounds like the MAF. Usually when a MAF goes up the creak you'll get a flat-spot in the rev range. I don't think it causes a loss of power like you're experiencing.

it depends how bad the MAF has gone faulty , on the Ford Galaxy with the PD130 engine (exactly the same MAF as the Fabia VRS ) the engine will not pull you out of bed and takes forever to get to 60mph

as has been said above , disconnect the MAF and see what it runs like , if its noticeable better , then replace the MAF

[SamsterXX]

You won't believe what this turned out to be!

Suddenly things got REALLY bad, it stalled in traffic and took 30 seconds to restart, then the following morning an absolutely horrendous noise at tick over.

I popped the bonnet and started it again then immediately shut it down. Ripped off the cambelt cover and the fookin' thing was so loose that I could pull it sideways off of the top pulley by hand. One edge of the belt was chewed up badly.

So bingo! - that's why my fuel consumption was ****e and the car fluffy to drive - it had obviously jumped and the timing was screwed.

Now bear in mind that Ashmore Skoda in Newbury gave it a new belt, tensioners etc back in December at 146,000 - I was a little pissed off (car's now done 159K). It turns out the mount for the tensioner has literally sheered off, the result being one flapping cambelt. Nobody's been able to answer why this happened or what caused it - I was thinking seized water pump or something.

Anyway, £380 sheets later and it's as good as new. Ticks over much quieter than it's ever done before as well. Bring on the next 50K!

Cheers to everybody who responded to this thread - appreciate it!

[ric04vrs]

Originally Posted by SamsterXX

Cheers to everybody who responded to this thread - appreciate it!

even if we were all wrong

[TeflonTom]

haha.... now.. how do i claim my prize??

glad you've finally worked out what it was