Hi all,

My 1.8T (ARX) 4x4 has poor idle and a shortage of power for the first minute or two. After that it seems to run flawlessly.

Once started, the revs will hunt (about +-100rpm or so). Power will be also very limited and seems to come in surges (the ride feels jerky nomatter how hard I try to keep my foot in the same place). If I can coax it above 2000rpm, power suddenly returns to "normal" and the car accelerates suddenly.

Recently it has been getting worse. When I started it yesterday, it sounded like it was only firing on three cylinders and the revs were hunting between about 700 and 1300rpm. The car felt like it was struggling to avoid stalling, and putting my foot down made no difference (I couldn't increase the engine speed for about 10 seconds).

I've put new plugs in (which made no difference) and the coil packs are all new (so the previous owner told me - going to check the part numbers now). There seem to be lots more avenues of investigation but I'm not sure which one to pursue. MAF? Vacuum leak? Oxygen sensor? Secondary air pump?

Thanks in advance.

EDIT: About a week ago it threw a 17535. My garage cleared it and said they would investigate it if it came back, but that "they sometimes do that when the weather turns cold".

Update: Checked the coil packs. Cylinders 1 and 2 (driver's side) are revision 'L', which I think is "safe", right? Cylinder 3 is revision 'J', which this thread says is prone to failure. I haven't checked cylinder 4 yet as it's more of a pain to get to.

Is there any way to check whether a coil pack is working?

I've also read a lot about the "splutter" problem. Is cleaning the throttle body generally regarded as the most likely fix?

Would the CEL definitely come on if the car was misfiring?

Update: The secondary air pump appears to be working. That is to say, when I started the engine with the bonnet open, it sounded like someone was using a hair drier in there for the first minute, then it quietened down.

The more I read, the more I think I have the dreaded splutter. It looks like the throttle body is due for a good clean.

check out this thread seems to point to temp sender but i'm no expert.

http://www.briskoda.net/forums/diagnostics-vag-com/been-running-like-dog-when-cold/43898/

Thanks, martziniuk.

I've ordered a new "green" temperature sender (059919501A) from VAG Parts for £20.57 including postage. For that price, I'd rather just replace it and keep my fingers crossed. Interestingly, the part description says "This replaces the earlier switch which can cause starting problems".

Does anybody know where this sensor lives on the 1.8T, or whether I'll have to drain the cooling system?

It is to the right of the engine as you look from the front, sensor is in a pipe.

Wait until the engine is stone cold.

Then just pull the open ended clip out and replace. There should be very little coolant loss due to the vacuum.

The earlier switch was black like mine was.

The "throttle body splutter" usually happens when warm too.Mine happened in third gear.When i put my foot part down it used to hesitate for about a second then back to normal.

I may have a similar problem too. On cold start for the first minute or so I get a random misfire, as soon as the revs drop and the secondary air pump switches off it is fine. I am not 100% on this but I think it only happens when I am running on LPG mode (I know it starts on petrol) but when I run on petrol all the time it doesn't seem to happen - I am still trying to track down the problem.

In terms of fault codes I have the dreaded 17705 and if I leave it long enough i get fault codes related to misfires (with no particular pattern).

So far I have replaced the plugs upgraded the older coils and swapped them round, replaced fuel filter, temp sender, pre-cat O2 sensor and MAF - no improvement.

Things still to try:

Compression test - hope not but as you know lpg can burn out the exhaust valves.

Wiring harness - take the engine cover off and start the car in the cold and when pitch black and see if any shorts.

Still to speak to my LPG installer.

Hope this helps and doesn't confuse matters. Good luck.

Thanks

Lescargot, interesting to hear that you're running LPG - I am too. Mine's the OMVL Dream kit. What about you?

I haven't considered the LPG system as being part of the problem because - as you say - the problem occurs when the engine starts, when it is running on petrol. However, I'll try starting mine in petrol-only mode to see if it makes any difference. I probably won't know until next week as the problem is worst when the car's been sitting in the car park at work all day.

Re: Wiring harness: I have noticed that a lot of the wires connected to my coil packs have split, leaving copper exposed. I haven't really looked into the cost of a replacement wiring harness yet but it's on my long-ish term to-do list.

Mines rough as hell until the air pump cuts out. Vibration, noise, miss fires, lumpy idle- the works. Fine as soon as the air pump cuts out though. Its a 02 vRS for the record

I am still having problems and it is getting worse as the mornings are getting colder. I don't think it is an LPG problem now (after a bit more testing) as it happens when running solely on petrol. It is definitely related to the secondary air pump but i have yet to pin point the exact problem - maybe a cracked hose or something.

BTW - Will I am running the same lpg system.

I think we're all suffering from the same problem described in the sticky thread, "Splutter is doing my head in".

I'm still waiting for the temperature sender to arrive from VAG Parts, and if that doesn't help then I'll try cleaning the throttle body. If there's still no improvement I'll probably just sit it out until somebody else comes up with a miracle cure as there seem to be plenty of people in the same boat.

I have this problem as well. I also had it on my Clio 172 Sport, so it doesn't bother me too much. No faults showed up on Vag-com.

I just sit idling for a couple of mins till the revs drop. Its a bit of a pain when you want to get away from work, but at least it gives chance for the oil to circulate:D

I've got this too. I've cleaned the throttle body (which sorted a rough idle when warm), replaced the temp sender (again, solved another problem) and the plugs have been changed. Mine runs fine until you try to drive, then it splutters and tries to die. Once the air pump thingy has stopped, it's sweet as a nut. 52 plate vRS.

I just sit idling for a couple of mins till the revs drop. Its a bit of a pain when you want to get away from work, but at least it gives chance for the oil to circulate:D

Once the air pump thingy has stopped, it's sweet as a nut.

This is exactly how I "cured" the problem tbh I think it's just a trait of the engine

As oggy say's it's a good chance to let the oil get round I just sit a roll a fag whilst the the air pump is doing it's thing and no soon as the revs drop I'm off

Have not tried driving the car off straight away when cold since I had the thing owing to the jerks and splutter's (much to the annoance of my daughter when she late for school)

FYI I never suffer with any other problems when warm (03 vrs)

This is real strange problem.

My 03 vrs with 100000 on the clock runs sweet as a nut in the morn, just a little more jerky but otherwise excellent.

Good luck in finding the prob.

I get the same issue - revs drop slightly for approx 1 min, runs rough sometimes on idle but mostly under load like when pulling away. Almost feels like it's running on 3 cyl, not four or something. But then, all of a sudden, drive it for a min and its fine again. I agree with the theory on getting the oil to circulate. Wonder has anyone had any success with changing the oil type they're using? No idea what I have in it - whatever synthetic the garage put in at the last service.

It is to the right of the engine as you look from the front, sensor is in a pipe.

I feel another plug coming on! It's for the Fabia, but ought to point you in the right direction if martziniuk's instructions weren't clear enough (then again, it's hardly rocket science!)

Also, I could have sworn it posted later was somewhere in that thread, but it seems to be good practice to replace the thermostat body at the same time. You can get them as a pack for not much more than the sensor on its own, and one sits inside the other. I guess it's a bit like the advice to replace the waterpump at the same time as the cambelt - while you're messing about in that area, you might as well kill two birds with one stone!

HTH

Thanks, ap0gee.

Phil, what "other problem" was sorted by replacing the temperature sender? I'm *still* waiting for mine to arrive...

This is exactly how I "cured" the problem tbh I think it's just a trait of the engine

As oggy say's it's a good chance to let the oil get round I just sit a roll a fag whilst the the air pump is doing it's thing and no soon as the revs drop I'm off

Have not tried driving the car off straight away when cold since I had the thing owing to the jerks and splutter's (much to the annoance of my daughter when she late for school)

FYI I never suffer with any other problems when warm (03 vrs)

So you mean that cleaning the throttle body doesn't solve everything after all? :eek::P:rofl:

Ahh yes it does rough idle when warm , not early morning cold start jerkyness though

Having said that it may help

Stupid thing wont let me do smilies without a message

:P

Temperature sender finally arrived and - touch wood - appears to have fixed the rough idle. A couple of points I feel are worth sharing:

1. The temperature gauge on the dash was already working perfectly.

2. When I took out the old sender, I forgot to remove the old O-ring, so when I put the new sender in, it didn't sit quite low enough and when I put the plastic circlip back on it was bent too wide and snapped. Only cost 43p from a nearby Audi dealer but it was a pain! Why not use a metal clip?! For reference, a bent hair clip serves as an excellent substitute.

Temperature sender finally arrived and - touch wood - appears to have fixed the rough idle. A couple of points I feel are worth sharing:

1. The temperature gauge on the dash was already working perfectly.

2. When I took out the old sender, I forgot to remove the old O-ring, so when I put the new sender in, it didn't sit quite low enough and when I put the plastic circlip back on it was bent too wide and snapped. Only cost 43p from a nearby Audi dealer but it was a pain! Why not use a metal clip?! For reference, a bent hair clip serves as an excellent substitute.

In response:

1. The 4-pin sender as used on your Octy has two sensors - AIUI, one sends to the ECU and the other to the dash. Therefore the ECU one was knackered but not the dash one;

2. Stupid isn't it? I used to have a Xantia, and the suspension on them used to fail if the level sensor came unclipped - held on with (you've guessed it!) a plastic clip!