Rough running......

[Boydie60009]

Right. This is starting to annoy me now.

2001 vRS, 100,000 miles and its suddenly started running rough. On start up from cold it will run for about 10-15 seconds then start miss firing and running on 3 cylinders, but after a few gentle revs it clears and ticks over sweet as a nut at 800rpm. While driving, theres been a constant shudder/missfire.

Number 3 spark plug was loose which we dealt with last night. Also bought a new Bosch coil pack. Fitted it to number 3 cylinder as the old one was pretty manky with the plug being loose.

Started up and still missfired. Started unplugging the coil packs to identify the missfiring cylinder and No1 seemed to be the culprit, so i put the old coil pack on this, and it started and idled perfect at 800rpm. Took it for a drive but the missfiring/juddering under acceleration is still there.

With out replacing the other 3 plus the 4 plugs, is there anything else that might be so obvious to current owners that im not aware of??

Please help. I rely on my car alot and dont want to take it far incase a full brakedown accours.

[skud missile]

have you tryed running it with the MAF disconnected?

if it runs better then your MAF`s had it

hope this helps

[Boydie60009]

have you tryed running it with the MAF disconnected?

if it runs better then your MAF`s had it

hope this helps

Not yet. Had my mates diognostic onit just now and its showing fault code P1296.

[skud missile]

Coolant temp sender.

http://forums.vwvortex.com/showthread.php?1287042

But odd how that could cause rough running.

I would try the maf and go from there as usually when there on there way out they don't show up codes

[Boydie60009]

Im just wondering if this has been an old fault code that hasnt been cleared, as i agree that a coolant temp sensor wouldnt make the engine run rough..........

[skud missile]

Well typical when coil packs give up or start at least they work when cold then once they heat up that's when the **** hits the fan. Easiest way to think of it is as follows:

TEMP UP / RESISTANCE DOWN

TEMP DOWN / RESISTANCE UP

A coil pack is basically a resistor which builds and discharges current at a measurement of ohms I think lol

You can try and measure them with a good quality multimeter.

Hope this helps

[DBP]

Maybe be talking out of the back end here, but can't the temp sensor control how the engine idles and if it fixes open/closed it can cause all sorts of issues?

[Liverpool-Lad]

Wel, it just really tells the ECU the coolant temperature, hence fuelling is adjusted accordingly.

[Boydie60009]

Iv just started it for going to work........perfect. No miss fire or nothing.

I unplugged the MAF sensor to see what would happen and the engine idle dipped slightly then returned to normal............in my experience with MAF sensors frommy Scooby STI, when its unplugged it ran like a bucket of bolts......

Any suggustions?

[Liam-6]

I had a very similar problem a while back,

Please take a look at my video below. Ignore the SAI pump but does yours do and sound similar?

If so, mine turned out to be a split pipe under the INLET manifold. Very hard to diagnose as the pipes a pain in the arse to get to and find a split. But it solved my problem.

[Boydie60009]

I had a very similar problem a while back,

Please take a look at my video below. Ignore the SAI pump but does yours do and sound similar?

If so, mine turned out to be a split pipe under the INLET manifold. Very hard to diagnose as the pipes a pain in the arse to get to and find a split. But it solved my problem.

Mines does this after start up...........BUT, i unplugged the MAF sensor and seems to be running fine, plug it back in and it does this again!! I really dont understand what the hells going here!!!

[Boydie60009]

have you tryed running it with the MAF disconnected?

if it runs better then your MAF`s had it

hope this helps

Just looking back and seen your post mate.

Ran it today with MAF sensor disconnected and ran fine. Is there another way of checking to just to make sure?

[skud missile]

Well when u disconnect the maf the engine no longer knows what air flow is entering the engine so it resorts to a default setting and sort of guesses which is why it runs better disconnected if the maf sensor is shagged as a damaged one will feed the wrong info to the ecu.

U should also get a orange/yellow warning lamp come up on the dash when disconnected.

Once u get a new one that light usually goes out after a couple of re starts of the engine. There not cheap to replace (£100ish) and don't be tempted by flea bay ****e unless genuine oem ones. Skoda operate an exchange basis on these and makes it a little bit cheaper... But not much lol

Hope this helps

[Boydie60009]

Ok guys.

New Bosch MAF sensor fitted just now, and still running rough. As said before, been runing with it unplugged since Saturday and its been sweet as a nut, plug new one in and started it up and the rough iddle on start up is back. Will it take time for the ECU to recognise a new sensor since its been unplugged for so long?

Also noticed that it missfires when i take my foot off the accelerator and just let the car the car slow down on its own...........

Loosing patience with it now................