Hello All

 

Long time lurker - first time poster.

 

I'm really desperate for a bit of advice and wondered if anyone could help, I'm at my wits end at this stage.

 

Car is a 2001, 2 litre petrol AQY engine with 104k.

 

I have a chronic misfire/splutter under load for example when driving uphill or under acceleration.  On the flat or under gentle acceleration the car runs fine.  It's been getting worse to the point where I now start from cold and it sounds like its running on 3 cylinders until it gets warm and clears and idles fine.  When it starts to splutter you can usually drop down a gear and power through it until it clears.

 

Car has had a new coolant sensor (aftermarket not original), replacement maf sensor about 4 years ago, fuel filter, leads, coil, and plugs every 6 months as they were getting so fouled up.  It does feel like it's running rich as there is quite a bit of discharge from the exhaust.

 

It has recently been to a garage who hooked it up to a diagnostic, when I asked if any particular faults had shown they said none specific just multiple misfires, they installed a new coil and it improved for a brief period of time, but the view was they I should just try it and see how it drives then look again, which seems like a really expensive way to go about it replacing bits here and there.

 

The car is also quite thirsty for oil and uses a good amount, and I read somewhere that piston rings may be an issue with the resultant pressure in the sump forcing oil in through the intake, thus burning it's on oil.  But I had thought this was more likely at higher mileage?

 

In desperation I put the car up for sale last week but was really disappointed at the level it made, struggled to make £200.  So I am now thinking is it time to have a last ditch attempt to fix it, or should I just accept the inevitable and consider it too past it's best. 

 

Tax and MOT are out this month so I'm now struggling to take it to a proper place with VAG com, any ideas or hints, or this sounds familiar, etc would be hugely appreciated.

 

Many thanks

 

Peter

Aftermarket CTS is your first mistake.

 

Oil consumption is often high(er) on cars that were driven gently from new, so that the rings never got properly bedded in. if you really suspect this, you could try doing a dry and wet cylinder compression test. If the top pressure is higher on the second wet test, you have leaky rings.

Thanks Ken

Appreciate your thoughts and will look into getting a compression test done.

In the meantime I had a look inside the throttle body tonight, looks like a build up of crud at the bottom, but the butterfly still operates. The flexible air intake however is wet with oil. I wonder how much oil here is normal?

Genuine coolant temp sensor is an absolute must.

Have you had a diagnostic done?

Thanks for the advice.

I paid £40 to have one done but all the garage said is that it showed multiple misfires. When I asked for specific codes they said it didn't show any.

Needless to say I was a bit miffed, even more so when they left the plastic engine cover off and I had to go back and get it. Next time I'm going to make sure someone has a proper vag com.

Cars now out of mot and tax and sorn so I'm struggling to get it to a garage. Other thing I noticed is steady drips of of unburned fuel from the exhaust. Maybe going nuts but every time the battery is reconnected after work such as replacing the alternator/coil it seems to run better for a while.

Going to take another look tomorrow and will replace the CTS for an original.

Thanks again

 The only way they would know it showed multiple misfires is by codes it had logged in the ECU. The most common cause of misfires on VAG cars is failed coil packs.

Find another garage.

Hello all

A quick update.

I have taken the plugs out and cylinder 3 very caked in ash like its been burning oil. Think this would certainly struggle to fire correctly.

So I tried a compresion test, screw in type nightmare to get in. Cylinder 3 read 13 bar, cylinder 2 read 13 bar, but cylinders 1 and 4 just over 14 bar.

So I'm now starting to think I have compresion problems. As the cylinders are next to each other logic might seem this is a head gasket, but how would oil get in, I can understand coolant, but struggling to think how oil could leak in? And why would only cylinder 3 look like it was really burning oil?

If the rings were worn, would this mean that all the cylinders would show loss of compression?

Sorry, 101 questions here, I'm hoping that someone might have been down this route before and any suggestions would be seriously appreciated.

Thanks again

Peter

I'm guessing that you only did a dry compression test? And got a 1/14 (about 7%) variation across the cylinders.

 

The next thing is to put a tablespoonful of engine oil down each plug hole and repeat. If the pressures rise significantly, then you have worn bores and/or siezed or broken piston rings. In which case you need to take the head of to find out which.

 

As matters stand, I don't think you have low compression, but am suspecting a worn valve stem seal on #3. You might also have a bad plug or coil pack there, so I'd start with a new spark plug which you probably need anyway.

Hi Ken

Thanks very much for this, I will repeat with oil and see what happens.

It's actually quite encouraging to hear you think it might be a valve stem seal on cylinder 3. I was thinking that it was definitely rings and therefore terminal, and I really don't want to scrap the car. Previously I had been replacing the plugs very frequently which cured the misfire until number 3 fouled up again. With new plugs the car runs very well.

Thanks again, I'll post up the results with oil in the cylinders.