C7 BiTDI Lurching/chugging sensation

[Sam Tap]

Hi all, hope you all are well. Just looking for some help or anyone who has gone through a similar issue with their car. Not long had the car when I noticed it started to wobble in the low rpm band between 1k-1.5k under very light throttle. I'll give the list of what's happening although it is very inconsistent. So when I first set off, it it lurches and stutters most noticeable whilst crawling, sometimes in second gear but not often. It also 1st of all it doesn't always do it, I'd say 50% of the time, and only seems to do until engine gets to full temperature. Doesn't do it at all when accelerating normally or flooring it and all gear shifts are smooth. Cars on 90k miles, full service history and I've had a gearbox service recently out of fear (my last gearbox blew up 😂) . 

Any help or tips would be appreciated and can't wait to here from you all! Cheers sam 👍

[spartacus 68]

The biTDI engine is a nice bit of kit. As a matter of course you need to run diagnostics using VCDS and see what's happening. Is it a temperature sensor, fuel-related, or mechanical? If there are any existing DTC errors - then they'll show up on the scan.

One thing I would check is the fuel-filter. Should be done every 20k miles. Lives under the driver's side on right-hand drive cars and is straight forward to replace. You can use VCDS to prime after changing. MANN or genuine OE if you're changing it. Check the history to see it's been done.

That's a Tiptronic 8-speed gearbox and practically bullet-proof. If it was serviced, was it done using genuine ZF oil and filter? Audi say sealed for life, but should be done by 8 years or 75k miles. Cheaper than a new gearbox as you say.

Any performance MAPs or running genuine ECU that you know?

[Sam Tap]

Thanks for the time to respond.

I've had my diagnostic on it and the independent specialist had his on aswell, neither of them had any relevant faults. I'll have to look into the history on the filter. It was serviced later than usual as soon as I got the car, somewhere around the 85k, but better late than never 😂 genuine zf fluid. No maps or ecu changes, just the standard car. 

Biggest annoyance to me is the fact that it doesn't always play up this way, for example, left for work this morning and it did it for the first 2 mins of driving, left work 10hrs later and didn't do it once, like I said before seems to be 50/50 on start up. 

[Steve Q]

Could it be an injector issue? Is it worth having them tested? 

[Sam Tap]

16 minutes ago, Steve Q said:

Could it be an injector issue? Is it worth having them tested? 

I did think this at first, but I'd hazard a guess that it's not, it's quite inconsistent in when it happens, and generally goes away after a few minutes driving. 

[Sam Tap]

4 hours ago, spartacus 68 said:

The biTDI engine is a nice bit of kit. As a matter of course you need to run diagnostics using VCDS and see what's happening. Is it a temperature sensor, fuel-related, or mechanical? If there are any existing DTC errors - then they'll show up on the scan.

One thing I would check is the fuel-filter. Should be done every 20k miles. Lives under the driver's side on right-hand drive cars and is straight forward to replace. You can use VCDS to prime after changing. MANN or genuine OE if you're changing it. Check the history to see it's been done.

That's a Tiptronic 8-speed gearbox and practically bullet-proof. If it was serviced, was it done using genuine ZF oil and filter? Audi say sealed for life, but should be done by 8 years or 75k miles. Cheaper than a new gearbox as you say.

Any performance MAPs or running genuine ECU that you know?

My reply to your statement is above, just forgot to mention you in it 

[spartacus 68]

Pulling the injectors could potentially be down the road if the problem persists, but I think if I was going to do that - then I'd have them measured with VCDS first to see measuring blocks if there's anything amiss. Pulling injectors is never straight-forward, plus you'll need to seat them with new washers and new stretch bolts torqued to specification. There might even be 'o' rings on the body of the injector. In addition, a new injector if that was the case needs to be coded to the car.

Also check vacuum hoses for splits.

If it's inconsistent, my advice would always be try cheap route first. Forte diesel conditioner straight into your fuel tank when the fuel light is on and drive it like you stole it. Top up with premium diesel and replace the fuel filter as a matter of course. There's not much I'd put in my car additive wise, but Forte is quality. Used to use it on an old A4 quattro V6 around about MOT time to bring down emissions.

Good video here on cleaning and reseating injectors on a 4-cylinder from Dave Sterl.

 

[Sam Tap]

6 minutes ago, spartacus 68 said:

Pulling the injectors could potentially be down the road if the problem persists, but I think if I was going to do that - then I'd have them measured with VCDS first to see measuring blocks if there's anything amiss. Pulling injectors is never straight-forward, plus you'll need to seat them with new washers and new stretch bolts torqued to specification. There might even be 'o' rings on the body of the injector. In addition, a new injector if that was the case needs to be coded to the car.

Also check vacuum hoses for splits.

If it's inconsistent, my advice would always be try cheap route first. Forte diesel conditioner straight into your fuel tank when the fuel light is on and drive it like you stole it. Top up with premium diesel and replace the fuel filter as a matter of course. There's not much I'd put in my car additive wise, but Forte is quality. Used to use it on an old A4 quattro V6 around about MOT time to bring down emissions.

Good video here on cleaning and reseating injectors on a 4-cylinder from Dave Sterl.

 

Thanks, I'll watch the video for future reference just in case. When I took it to the independent specialist I did put the queries forward to them but they didnt think it was injector issue or misfire as nothing came up during diagnostics. 

I think it's just going to be one of those issues where I won't find it, until it goes wrong. Think my biggest concern was the auto box, I have very little knowledge regarding them and have had some previous bad experience with the previous gen tipronic 😞