APR Stage 1 and the Italian tune up

[Wharfbanger]

I have owned my 2008 2.0T Quattro for 1 month. 6MT. 93,000 miles. Went APR stage 1 last week and put on a 034 rear sway bar. Stage 1 made a big difference, wonderful. Yesterday I went for a drive and noticed some detonation in 4th after flooring it on steep uphill from about 1800-2000rpm. Backed off and repeated. Repeated again. Definitely detonation, no doubt about it. At the top of the hill I pulled over and did a U-turn. The engine missed a little and belched some smoke as I pulled away in 1st. Then, it ran fine as I headed home without loading the engine or attempting to make it detonate.

Worried, I did some googling and read that carbon deposits in the cylinder can cause detonation (I am pretty sure my octane grade was correct). The theory is that carbon builds up and raises compression and this causes detonation. I am aware that the 2.0 TFSI engine is prone to carbon deposits.

One of the recommendations was an Italian tune up. Basically take it out for a spirited drive, enough to hit the red line a bit. All the heat and energy will hopefully dislodge the carbon. Hot dang! To cut a long story short I did the "tune up". The car seemed to love it, and I loved hearing the cats tick away after I stopped. Afterwards, I repeated the uphill stretch in 4th and it would appear the problem is solved - same fuel, no detonation.

Happy for any thoughts or input as I realise it is not wise to jump to conclusions, and it may be premature to consider the issue solved. I will also get a fresh tank from a different gas station.

Oh yeah, compared to the very noticeable APR tune, the 034 sway bar mod is much more subtle. I suspect the mechanic may have installed it on the softer setting. Car is handling great though.

[danbfree]

Good to hear your tune worked nicely, I have '06 almost same exact miles, owned for same amount of time, still debating which tune to go with, the top 5 or so are all pretty good it looks like... Do you have the maintenance history on yours? Mine got new coils at 32k, new intake motor flap, new PCV, HPFP, pressure regulators, numerous ECU flashes when new, and a complete cam follower repair at 80k all covered under the CPO warranty by PO. I would say if you don't know when the coils were done I'd start there, some peace of mind for $100, but you're right, driving it hard once in awhile IS good for it, but you can also ask a mechanic about a carbon cleaning job, I think they are a couple of hundred bucks.

[Brillo]

I believe that the 'carbon cleaning' is of the intake valves which would not have any effect on pre-detonation or combustion chamber deposits. Also, don't know if anyone does a combustion chamber cleaning for a couple of hundred bucks. Stick with a top tier gasoline and the occasional Italian tune up to keep the combustion chambers deposits in check. I wonder if the APR tune might be causing a rich mixture. Anyone know? Also, OP, how do you know if you have pre-detonation versus knocking or pinging?

[Wharfbanger]

Not much history. 2 owners and the car is in great shape. Did the coils, plugs and front O2 sensor a couple of weeks back. Will think about a carbon cleaning job when I do the cam belt in 10000 miles or so. Unless I have more detonation issues. The tune will make you grin - these cars are great. Cheers.

[rongeur]

Its no sectret that you should drive these cars like you stole it now and again to help redice carbon deposits. Next do it just for fun :)

[Wharfbanger]

@Brillo. Yes I agree valve carbon probably would not raise compression. The APR tune will cause an increase in pressure and heat in the chamber on boost, which makes the chamber more susceptible to multiple "explosions" per spark (when there should be only one explosion per spark). This is known as detonation. Carbon deposits will aggravate this by increasing pressure (compression) inside the bore beyond what the tune is expecting and perhaps by providing lots of little carbon hot spots (like lots of little spark plugs) within the bore that can ignite the mix.

My apologies if you already know this stuff - I enjoy writing about it.

My understanding is that running rich would alleviate detonation by lowering cylinder temperature. Does this sound correct?

[Wharfbanger]

Its no sectret that you should drive these cars like you stole it now and again to help redice carbon deposits. Next do it just for fun :)

😀😀😀

[danbfree]

I believe that the 'carbon cleaning' is of the intake valves which would not have any effect on pre-detonation or combustion chamber deposits. Also, don't know if anyone does a combustion chamber cleaning for a couple of hundred bucks. Stick with a top tier gasoline and the occasional Italian tune up to keep the combustion chambers deposits in check. I wonder if the APR tune might be causing a rich mixture. Anyone know? Also, OP, how do you know if you have pre-detonation versus knocking or pinging?

Good info, thanks... I always use Top Tier, I don't know why anyone wouldn't when even Arco and Costco are Top Tier now... But I did hear about a carbon cleaning available that can be done, it was in other threads here.

[danbfree]

Not much history. 2 owners and the car is in great shape. Did the coils, plugs and front O2 sensor a couple of weeks back. Will think about a carbon cleaning job when I do the cam belt in 10000 miles or so. Unless I have more detonation issues. The tune will make you grin - these cars are great. Cheers.

Correct me if I'm wrong, but aren't the cam followers under a 10 year warranty? That's the first thing I'd get checked, mine completely failed at 80k (before I owned it) so maybe yours has been updated already?

[KingWulfgar]

Correct me if I'm wrong, but aren't the cam followers under a 10 year warranty? That's the first thing I'd get checked, mine completely failed at 80k (before I owned it) so maybe yours has been updated already?

10 years/120k miles. Mine lasted every bit of 98k miles and wasn't worn through. I replaced it as PM since I am now outside the 10 year mark. Definitely check/replace that if you don't know it's history!

[Charles.waite]

We generally get carbon buildup in the head, in the valve ports, not inside the combustion cylinders.

Also if you were having detonation, your engine would be toast. You mean misfires? Could be as simple as bad coils or old spark plugs. Likely plugs since you said the high load high heat cycle fixed the issue so to speak. That high heat probably burned off any buildup on the plugs that was causing the issues.

If you haven't checked out the plugs I would recommend giving that a go. Could be old and worn. Especially since the car is new to you. Replacing the plugs is one of the first things I do when I get a new car.

[drmonkey]

Correct me if I'm wrong, but aren't the cam followers under a 10 year warranty? That's the first thing I'd get checked, mine completely failed at 80k (before I owned it) so maybe yours has been updated already?

From what I've read, the warranty only covers up to 2007.

[Charles.waite]

From what I've read, the warranty only covers up to 2007.

Yes. Sometime in mid/late-2007 it no longer applies. 2008s are exempt from the extended warranty. Which blows.

[Wharfbanger]

We generally get carbon buildup in the head, in the valve ports, not inside the combustion cylinders.

Also if you were having detonation, your engine would be toast. You mean misfires? Could be as simple as bad coils or old spark plugs. Likely plugs since you said the high load high heat cycle fixed the issue so to speak. That high heat probably burned off any buildup on the plugs that was causing the issues.

If you haven't checked out the plugs I would recommend giving that a go. Could be old and worn. Especially since the car is new to you. Replacing the plugs is one of the first things I do when I get a new car.

Thanks Charles for your comments. I replaced the plugs and coil packs last week so those should be eliminated as a possible cause. I am surprised and a bit concerned to hear that my engine should now be "toast" after a little bit of detonation. Are we talking about the same detonation? I know the difference between detonation and misfiring.

I am getting my information on detonation and carbon build up from here:

http://www.misterfixit.com/deton.htm