Rough Idle?

[SMG]

Hey guys,

My car has been idling like crap since I got home on Thursday after a 300km drive, and this morning it finally blew a CEL.

It's been intermittent, and if it lets me get the engine warmed up, it's normally alright, I thought it was bad gas with maybe some water in it, but I put $20 worth of supreme in it and it's still doing it.

Any idea what this could be?

I'm kind of stranded here, at my parents house, it's Thanksgiving weekend, and I have to be in class, (300km away), on Tuesday morning, so I have to get it working..

Thanks guys!

SMG

[hannaco]

Unfortunately the DTC code would tell us what is wrong. Any way to get it scanned?
The common cause is one of the vacuum hoses has sprung a leak. Over time they rot and leak. What happens is that air gets sucked into the motor causing it to run lean. Then you get a bad idle. You can try cutting off about .5 cm off the end and putting it back.

[73standard]

Originally Posted by SMG

Hey guys,

My car has been idling like crap since I got home on Thursday after a 300km drive, and this morning it finally blew a CEL.

It's been intermittent, and if it lets me get the engine warmed up, it's normally alright, I thought it was bad gas with maybe some water in it, but I put $20 worth of supreme in it and it's still doing it.

Any idea what this could be?


Thanks guys!

SMG

Putting Supreme in it will not help the problem, only make it worse. Just because it says Supreme does not make it better gas. Think of it this way, some engines are made to run on high octane (my old beetle for example), and others are made to run on low octane (my '99 New Beetle and '05 Jetta, both are 2.0). Putting a higher grade gas in a car that is designed for lower grade can mess your engine up, and cause all sorts of little noises.

Here's a better article on fuel octane
http://auto.howstuffworks.com/question90.htm

[callisto9]

Originally Posted by 73standard

Putting Supreme in it will not help the problem, only make it worse. Just because it says Supreme does not make it better gas. Think of it this way, some engines are made to run on high octane (my old beetle for example), and others are made to run on low octane (my '99 New Beetle and '05 Jetta, both are 2.0). Putting a higher grade gas in a car that is designed for lower grade can mess your engine up, and cause all sorts of little noises.

Here's a better article on fuel octane
http://auto.howstuffworks.com/question90.htm

great article. thanks for the post!

[callisto9]

Originally Posted by SMG

Hey guys,

My car has been idling like crap since I got home on Thursday after a 300km drive, and this morning it finally blew a CEL.

It's been intermittent, and if it lets me get the engine warmed up, it's normally alright, I thought it was bad gas with maybe some water in it, but I put $20 worth of supreme in it and it's still doing it.

Any idea what this could be?

I'm kind of stranded here, at my parents house, it's Thanksgiving weekend, and I have to be in class, (300km away), on Tuesday morning, so I have to get it working..

Thanks guys!

SMG

sheesh, i keep following your posts, because it seems like i have the same problems; engine clatter (ping, in my case), ticking all all kinds of other unidentifiable noises. i am biting the bullet and taking it to be scanned at the dealer next week. i really don't want to spend $55, but it might be worth it for piece of mind.

[hannaco]

Is the CEL light on? If not, it may just be a waste of money. The scanner will only read the codes that are in the memory of the computer. Most dealers will not take the time to look at all of the different measuring blocks, just to see if something is a bit odd.

[Porkchop]

If we're just guessing with no codes, maybe a dirty throttle body? You could try cleaning it to see if that helps.

[yellow99]

I have had the same problem 3 times in one year, the problem has always been the Mass Air Flow sensor, and they are covered under warranty at your local VW dealer. I hope this helps!

[AlisonLS]

When this happened to me it was a bad MAF sensor. The first time I was able to get it covered under an extended warranty - mine was done in Sept 2003. The second time Sept 2005 because I had 75072 miles I had to pay for it @#!!%%% not a happy camper!

[SMG]

Oh, I solved my problem by the way.

If any of you guys aren't running injector cleaner, you ought to. I bought a pricey bottle or what claimed to be a heavy duty injector cleaner for really tough jobs. Anyway, I ran it, and now it's smooth as butter, the car has never ran so good.

They say run a bottle every 4 tanks, and I'm about due soon, but the car is still acting pretty darn good.

Edit: And no, you don't need the expensive bottle every time, every so often it helps, but cheap STP does the trick every 4 tanks.

SMG

[speedie]

It is generally a good idea to run injector cleaner before you change your oil (contaminants go into the oil and oil change interval is easy to remember).