Wierd idle...cam wear or rough idle?

F250_JR

Veteran Member
Joined
May 13, 2008
Location
Birmingham
TDI
2005.5 Jetta TDI Special Edition
like the title says, I have started noticing my TDI idling a little rougher. It doesn't really shake the way most people mention in the rough idle threads. The idle is just slightly louder, rougher, and has a little more pronounced loping. In the past couple of days I have started noticing a very slight knocking sound as well. This could be just the loping, but not sure.
This roughness is only present at idle...I can rev the engine and it instantly smooths out. If I rev it, then let off, the idle will smooth out for a little while, then gradually get rougher. Also, when the engine idles slightly faster under increased load, it is slightly smoother.


The one reason I don't really think it is the cam at this point is because it has started over such a short period of time, and because I have had no loss of power. The car revs just like it always has, and pulls just as hard.


So what do you think? Is it cam wear, or is it just rough idle which can be fixed by slightly advancing the timing? FYI, I am going to go ahead and pull the VC and check my cam sometime in the next few days.
 
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Mach1

Vendor , w/Business number
Joined
Sep 27, 2005
Location
Spicewood, Tx.
TDI
05.5 Jetta 5 spd, 06 Jetta DE DSG, 04 F250 6L, 2000 F250 7.3L
Ben, is it colder there today, different fuel fill up? Could be ambient temp, could be fuel...Could be cam.

If you haven't pulled your VC yet..you should consider, when you get a chance, but dont freak out just yet, its preventative, you will then know when to expect failure, I drive mine across the US and need to know if its going to fail, so I can take care of it instead of being on the road somewhere.
 

hid3

Banned
Joined
Apr 28, 2007
Location
Lithuania, Vilnius
TDI
Golf V 1.9 TDI-PD 105 HP
Colder outside temps, winter fuel.

My cam was worn (some chamfer missing) and I had no rough idle sympthoms. Idle was smooth for a diesel. Actually at that moment I still had a failing flywheel (DMF), BTW. Just a knocking sound could be heard. When I replaced my cam, nothing changed. The knocking sound remained. Seems like it was a valve knocking. Then I replaced my flywheel with SMF and a leaky EGR valve. About that time the knocking sound just went away itself.
 

05_new_jetta

Veteran Member
Joined
Aug 28, 2005
Location
Van Wert, OH
TDI
MKV Jetta TDI
2nd pulling valve cover, doesnt hurt to look. If it is valve train it is probably a lifter failing.. only reason i knew mine failed for sure is that i could hear it in the exhaust, didnt really notice a loss of power per say tho, just missed slightly.
 

F250_JR

Veteran Member
Joined
May 13, 2008
Location
Birmingham
TDI
2005.5 Jetta TDI Special Edition
Yes, it has been pretty cold lately...and I just filled up with what might very well be my first winter fuel for the year. I don't know for sure, just a possibility. Thank guys...I feel better after you mentioned the cold and fuel thing. I didn't really think all of that through. I am going to go ahead and pull the VC during the break though; I am curious, and would really like to know if it is failing.

About that knock though...is there any chance that it could be part of the rough idle, or does that sound more like cam or lifter failure? While I can see there being rougher idling during the cold, I wouldn't really expect to hear a pronounced knock. Don't get me wrong, it is not loud at all, but it is a knock, and it is there.
 

Mach1

Vendor , w/Business number
Joined
Sep 27, 2005
Location
Spicewood, Tx.
TDI
05.5 Jetta 5 spd, 06 Jetta DE DSG, 04 F250 6L, 2000 F250 7.3L
Ben, fuel knock is huge in the world of diesels, caused by several things, including/but not limited to, FUEL QUALITY, cetane rating, fuel additives-or lack of fuel additives, ambient temp, and load.

Lets be positive here and just say that you got some #1 or bad fuel..

Pull your VC when you get a chance and you will know more when the time arrives.

I really like fuel additives this time of the year.

Happy holidays..
 

F250_JR

Veteran Member
Joined
May 13, 2008
Location
Birmingham
TDI
2005.5 Jetta TDI Special Edition
Sounds good Mach1.

I know I am probably making a whole lot out of a relatively minor issue, but I am pretty anal about my car. I usually notice slight changes in the way my car sounds and behaves, and I like to be able to explain every one of those changes. Not necessary all the time I know, but it keeps me on top of my car's condition and health.

I'll post back with what I find under my VC!
 
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