Cupra TDi Running issues

[selfagg]

Hi guys, got some issues with MPG and bad running at the moment and looking for some advice, I've noticed for a few months that it seems to be lumpier than normal when idling, enough to shake the car and make you feel sick. This only happens when the engine is cold. When the engine is cold it is also down on power, it's like the car is running on tar, it's gutless for the first few minutes...

So the car is at the moment averaging about 37mpg whereas it always normally achieves about 48mpg.

I've had a look around on the forum and I guess it could be either coolant temp sensor, or the MAF. I can test the MAF at the weekend with VAGCOM, I'll be able to read any fault codes then too, just looking for some opinions on what I should be looking for if you all don't mind

 

[Topper Harley]

I had similar symptoms, turned out to be the EGR valve stuck open.

 

[selfagg]

Oh damn... I turned that down in vagcom a few months back...

 

[KarlB1]

mine's been like this for the last month or so..then the other morning i started it up and it ran fine.
my guess was down to the temperature, it's been aroudn -4 every night here and recently it's been getting warmer and then one night the temp didn't drop below 4 or 5 degrees..come out in the morning to run the girlfriend to work and it ran spot on!

..however on the way home i managed to blow the turbo, so it may have also been down to that since it wasn't boosting at all when it ran like crap until it was warm?

 

[selfagg]

Oh man. Deffo hope it's not the turbo. I'm beginning to feel like I should trade it in and cut my loses. :/

 

[KarlB1]

It probably won't be tbh, I think I just got extremely unlucky with mine.

Like I said, mine seemed fine when we had a warm night and it didn't get too cold.
Could be any number if things, people told me to check for camshaft wear but I haven't got around to it.

I'd keep hold of the car, they're lovely things with lots of potential
Try and put a little bit of cash to the side each month incase something goes wrong. The only reason mine is giving me so much stress ATM is because I have no money right now to sort it, I knew something was up and I didn't get prepared

 

[selfagg]

Yeah. My missus lost her job just before Christmas so I haven't really been saving for the car. But I would prefer to keep it. I know the cams are ok, my mechanic checked them when he cleaned the egr.

Hopefully I'll have the spare cash this month to get this looked at

 

[aymen_a22]

Turning the EGR DOWN will only improve things. Many people carry out an EGR delete which completely blocks the valve. I wouldn't say the EGR is your issue.

Test the MAF because that sounds like the culprit. You can try unplugging it and plugging it back in a few times (with the ignition OFF) as this can clean the contacts on the MAF connector. Using DIELECTRIC GREASE in the connector after this can also help and a lot of people do it as a precaution to stop moisture getting in.

One other thing to consider is how reliable your garage is. They may have forgotten to reconnect something or tighten something enough.

I wouldn't sell the car as they are not that difficult to diagnose and when running well they are nice cars.

 

[selfagg]

Ah, I know my mechanic can be trusted, I usually end up helping out!

I'll try the contacts before I head out to work. Just trying to get my bluetooth OBDII to work with a jailbroken iphone, bloody nightmare, should have stayed with Android!

 

[aymen_a22]

Fair enough, at least you know he can be trusted so that rules that out.

If you know you will have the codes removed soon, you can try removing the MAF connector and take it for a drive. You WILL get an engine warning light come up however if there is no change in the way the car drives then you know what the problem is.

I have the bluetooth OBDII on android and luckily I have no issues with it. I have no idea how to sort out an Iphone sorry.

 

[selfagg]

Well, I tried to remove the sensor connector, that thing must be superglued on!!!

Is there a trick to getting it off?

I've given up on using my phone, will have to get my laptop on it at the weekend!

 

[aymen_a22]

Try pushing the connector on a bit further than it already is. Then move the little tab inwards (before pulling the connector).

Once the tab is free then you should be able to remove it more easily.

 

[selfagg]

Right. Ran the car up the road with the Maf disconnected. It ran like a non turbo diesel. I'll give it a good run later now I've checked that connection.

I'm gonna try and get vagcom on there later too.

 

[selfagg]

So. Vagcom has been on. Coolant temp is correct and matching on block 3 and 7.

Long drive home driving like an old man at 70 on dual carriageway and then a short bit of 30mph road. I reset the trip computer when warm and still only averaged 41.4mpg.

I use Shell fuel. I'm not due a service until July. The MAF reading was a bit out but I suspect that is because I turned the EGR down. What else could it be? Need some serious help here guys!!!

 

[nigxl]

I have the vcds lite unregistered version and would like to check blocks as you have, do you know if I can do this as I have very similar symptoms to you. Would be interested to hear your findings as I have no fault codes but about 42 to 43 mpg driving like a granny.
Car goes like a rocket with no hesitation or misfires but is just down on mpg even after an air and fuel filter change.

 

[selfagg]

I'm not sure to be honest. I use an old version of VAG-COM with an ebay cable to test.

I'm pretty much lost now as to what my problem is. Performance is exactly the same when warm, still takes ages to warm up, but that's to be expected.

 

[Topper Harley]

Try pulling the hose off the EGR and blocking it with a bolt. If it runs better then that's your problem. It doesn't cost anything and would at least definitely rule it out.

 

[selfagg]

Yeah, I'll give that a go tomorrow... I had the EGR turned down in VAG-COM and cleaned about 6 months ago, could that still be the problem?

I've heard that it could be water in my fuel filter and that there is a plug to drain it... Is that right? I've not had the fuel filter changed since I got the car about 2 and a half years ago.

I'm really pulling my hair out over this now!

 

[cleverspoon]

Try changine fuel filter and filling it with injector cleaner. If your car takes ages to warm up it could be the thermostat....which would reduce mpg.

 

[selfagg]

Cool. Do you mean fill the fuel filter with injector cleaner? Or put it in the tank with my diesel?

Also, is the thermostat the same as the coolant temp sender?