Hey guys and gals,

I'm having an issue with my B6 S4 that I'm hoping y'all can help with.

I have an extra rattling sound at startup. Both the B6 S4s I've had have the super common momentary rattle at start up, so I know better than to worry much about that. But now mine has an additional rattle at the very end of the start up (after the normal rattle). A couple fellow VW/Audi owners listened to the sound the other night and without hesitation, one said, "Intake runner flap - don't worry about it." But listen to it...how can you not worry? Again, it started after an oil change (Mobil 1 5w30) . It may be a coincidence, but it's worth mentioning. It happens almost exclusively on cold or coldish starts. I haven't noticed any performance issues and the noise never happens while driving.

Another thing I'm noticing is that the car is idling roughly for a bit at start up. It used to start up and immediately get to purring, but now it takes a good 3-4 seconds of the tach needle going between about 500-1000 rpms to smooth out. If the noise is the intake flap, these would likely be unrelated issues, right? If the noise is a chain slapping around, this explains the momentary rough idle when starting, right?

A recap:

1) Knocking noise on most starts (rarely on warm starts). Clearly audible between seconds 6-8 in this video http://www.youtube.com/watch?v=Iwd_CknVm9g
2) Unusually bouncy tach (but no flashing CEL) for a several seconds on start up.
3) No noticeable performance deficits. Knocking sound and rough idle only occur at start.

Thanks for any advice!

 

What's your mileage like, how is the timing? just a thought

 

75K.

What do you mean?

 

your timing may have slipped just a tiny bit have you had the timing belt replaced ever?

 

The 4.2 has a timing chain which does not require replacement.

There's a documented rattling sound that almost every B6 S4 owner reports. It comes from the camshaft chain tensioners and does not require any repair. I also have that sound...the new noise is in addition to the camshaft adjuster. It could be a new symptom of the same issue. It started when I got the oil changed, but that was around the time when the weather changed from spring to full blown summer. It could be that the heat makes it that much harder to get the oil pressure up so I'm hearing the usual sound amplified. I'll be switching to 5w40 on the next oil change, but I'm concerned that my issue is something other than the chains getting going.

 

have you thought about the timing chain? I just talked with a tech about that and thats what he said. He said it'll start with a rattleing sound and a tougher than normal start (all with no CEL) then progress into misfires and CEL's being thrown to full on rough idles and general loudness.
Ouuuch as the the whole engine needs to be pulled...keep us updated!

 

If it's anything to do with the cam adjusters or chain, there's not much I can do about it until I have to, you know? It fires up just fine and the few misfires I've had have been resolved with a new coil pack and some fuel injector cleaner. I'm also not convinced the sound IS coming from the back of the engine, which is a relief. I need to have someone start it while I'm listening again, but it's hard to pin point the source...one time, I'll think it's coming from the back of the engine and then next, I'll be sure it's coming from the manifold.

To be honest, I'm looking for an older 4Runner that I can pay cash for and sell this. There was a time when driving the nice car mattered a lot to me, but I'm over that. Between gas, insurance, and my payment, I'm paying almost $1000/month for the privilege of driving it. I don't have credit card debt, I'm almost done with my student loans, and $1000 more a month towards my house would pay it off in 5 years. Man...it'd be nice to be debt-free.