Check Engine Light and EPC light?!

[Nodster]

Hi all

Need some advice please, I took the car out for a quick drive as it hasn't moved in like 3 weeks. Just a quick loop to warm it up and straight back home. Car oil was up to temperature, so I popped it into manual. Flicked it to M and put my foot down in M3 and it hit 5k rpm and I heard a clunk from the engine bay, car lurched forward and I got some pops from the exhaust. Felt like I'd hit a wall. Yellow EPC light is on and Engine Warning Light. Tried it back in Sport, but no real power and it revs really slowly. So I think it must be in some sort of protection mode. The car drives fine in D. No noticeable issues. Turned the car off and back on but the lights are still there and the issue still remains.

Really bizarre. I wonder what has gone wrong. Obviously no garages are open so I'm left to wait.

Any ideas?

Cheers.

[monkeyhanger]

I just had an email from my supplying dealer (Listers) asking if I'm a key worker in need of essential maintenance, so it seems that some garages are keeping their service departments open on a reduced service.

How loud were the exhaust pops? Louder than normal upshift pops?

The car is probably in limp mode. - is it reduced power in both D and S gearbox modes? Is it allowing manual changing via paddles or gearstick slotted left?

The clunk doesn't sound good - something has gone where it shouldn't during the drive, and (depending on how big the pops were), a little (normal) or a lot (abnormal) unburnt fuel has got through the engine and ignited in the exhaust.

[Nodster]

I just had an email from my supplying dealer (Listers) asking if I'm a key worker in need of essential maintenance, so it seems that some garages are keeping their service departments open on a reduced service.

How loud were the exhaust pops? Louder than normal upshift pops?

The car is probably in limp mode. - is it reduced power in both D and S gearbox modes? Is it allowing manual changing via paddles or gearstick slotted left?

The clunk doesn't sound good - something has gone where it shouldn't during the drive, and (depending on how big the pops were), a little (normal) or a lot (abnormal) unburnt fuel has got through the engine and ignited in the exhaust.

Aye cheers mate, I think limp mode as well. So I've been out and done some diagnostics. Forgot I had the Torque Pro app and the OBD reader.

So the engine light is for P0101 - Mass Air Flow Sensor Circuit Range/Performance (https://www.samarins.com/diagnose/p0101.html). I've taken the MAF housing off and cleaned the sensor with electrical cleaner. And also the Manifold Pressure sensor. (which had a slight oil film over it, most likely due to the recirculating of the oil vapours). I then cleared the error, and started the car. Gave it a few blips on the drive and it coughed and stalled. So I turned the car off, disconnected the MAF sensor, started the car back up and it runs smoothly (ECU default parameters I guess). Then whilst running, re-attached the MAF sensor... gave it a rev, coughed and stalled.

So I think the sensor is jiggered. Would you agree?

I think the clunk I heard may have just been because of the drastic lurch forwards from the car when it hit this imaginary "wall" so to speak. I've had a good look around and no tubes are loose and no sensors are disconnected. Looks solid.

Cheers for the help.
-James

[monkeyhanger]

Sounds like the MAF sensor thinks the car is getting more or less air than it actually is and either getting an implausible value and reverting to limp mode (if it does that immediately on the fly, that could be your "thump" - massive engine braking effect from a car that is suddenly starved of fuel at 5000rpm in a low gear.

The fact you disconnect the MAF and the car works seems to suggest you haven't got any air leaks in the intake system letting more air, bypassing the MAF, han the MAF accounts for when working normally.

How much is a new MAF sensor? If it's literally a tenner and can easily be removed and reinstalled, might be better than trying to put it in the garage at this time.

Have you changed the stock air filter for some oil soaked one? Could be a cause of contamination for the sensor.

[silverhairs]

You did a loop around the block, the water temp was up to 90 degrees, so you decided to whack it up to 5,000 RPM, then everything went t**s-up.

[Nodster]

You did a loop around the block, the water temp was up to 90 degrees, so you decided to whack it up to 5,000 RPM, then everything went t**s-up.

I did a few before giving it some more acceleration. I'm not an idiot so stick your roll eyes. If you can't accelerate for worry of a part breaking then why own a car. MAF sensor failing has nothing to do with me accelerating hard, it's just bad luck. Jeez. The car is an ex-demo. Do you think that's had an easy life and warmed up fully by all the patrons testing it before I purchased it. Probably not and most likely the reason for a premature parts failure.

[stuartrendall]

It sounds like an easy and relatively cheap fix, I would have done the same in regards to accelerating. A new car like that if it has a problem now may as well get it out of the way instead of it happening months or years down the line. And not really any need for attitude or rolling eyes. Just don't comment if you aren't going to be helpful or supportive.

[Chungster]

The EML triggered on mine last month.

Took the dealer 2 goes to decide it was the HPFP and it needed replacing.

All done under warranty luckily. First question from them was “is the car modified / remapped”

[emoji2]


Sent from my iPhone using Tapatalk

[Nodster]

Never fedback what the issue was.

So yes, nothing to do with me accelerating.... I called out VW roadside assistance (forgot I had that). Absolutely amazing! Very thorough examination of everything. Lots of diagnostics performed and engine tests performed. Couldn't nail the issue down. Swapped all the parts back that I had changed, asked me lots of questions which led on to (somehow) me mentioning the garage I purchased the car from had fitted a new AC unit / radiator. The chap immediately started poking around the front of the car, then jacked it up and whipped the undertray off and low and behold, the boost / charge pipe from the main intercooler was off! And this wasn't off due to me, the clip had never been tightened. He said it's been like that from the garage. It was unscrewed and hanging on the pipe. He was amazed I'd had no problems until now and I just said "I usually drive like miss daisy and no boost". He said if I hadn't done what I had done we may have never have found it, or worse, it could have blown off whilst going down a motorway etc. So pushed it on and tightened the clip. Problem solved.

I made sure to reply back to VW to tell them their breakdown service was amazing.

Happy days.

[Nodster]

The EML triggered on mine last month.

Took the dealer 2 goes to decide it was the HPFP and it needed replacing.

All done under warranty luckily. First question from them was “is the car modified / remapped”

[emoji2]


Sent from my iPhone using Tapatalk

Glad you are all sorted.

Yeah the roadside assistance asked me but when he plugged his laptop in he said, oh no, it's all stock that is fine. To be honest, I said it had a different panel filter in the airbox and he was fine with that. Said all the MAF readings were nicely within tolerances.

[Nodster]

It sounds like an easy and relatively cheap fix, I would have done the same in regards to accelerating. A new car like that if it has a problem now may as well get it out of the way instead of it happening months or years down the line. And not really any need for attitude or rolling eyes. Just don't comment if you aren't going to be helpful or supportive.

Thanks.