Possible misfire?

[willnando]

I have been driving my S4 for a while now and I've noticed that on certain RPMs the engine kinda "lets off" and starts pulling again. I notice it the most at 60mph at 2100rpms .
I noticed the same thing happening on my GTI while back and turned out it was a bad engine coil. I replaced all 4 on the GTI and the problem stopped.
Could the same thing be happening on my S4? I don't have any lights on the dash.. Thoughts?

[Lucca M]

Scan it with vcds if you have access to it. Even tho you dont have engine light on there might be some codes stored.

[willnando]

Thank you. Looks like I have to go to my buddies house and scan it.

[924Carrera]

I've noticed the same exact issue with my car, both before and after doing a ton of work to it including all new coils. Scanned again with VCDS, 0 stored codes, 0 misfire count, etc. It's definitely annoying though. I'm wondering if it has to do with the throttle body as it only happens (to me) when I'm applying light, constant throttle.

[924Carrera]

It's still doing it, 2200-2400 RPM in every gear, a bucking or lurching as long as you hold constant, light throttle. As soon as you tip into it, car has full power and takes right off. It also doesn't do it with the throttle plate held in a more open position, just that one spot. 0 codes, car runs fine otherwise. I'm going to log data in VCDS this weekend if possible, see what exact throttle angle/pedal percentage is causing it, and see what the fuel trims look like. It almost seems like it's running lean in that range, but not enough to alert the ECU. Brand new coil packs, plugs, etc just done, and 0 misfire count anyway.

[924Carrera]

So, I went out for a drive with my friend running the logs on my laptop and pulled some data, and I have conclusively figured out my issue. Based on OP's description, it may be his as well. The issue is actually nothing that is malfunctioning, but rather a consequence of the way the electronic throttle works. The bucking/lurching starts happening right at the edge of the pedal's range. Even with my foot being held as steadily as I can, the pedal starts fluctuating between 0% and the next value up. When this happens, the throttle plate starts rapidly fluttering between 0 and 8% and the ECU starts adding and cutting fuel. Obviously, this manifests in the form of a bucking or surging feeling because that's literally what is happening. It basically only happens when going down hills for the obvious reason that you need less throttle to maintain speed when gravity is helping you out, and therefore on level ground it is almost never an issue because you have to give more than 0-8% throttle angle to keep the car moving at speed.

What's odd is that I only started to notice this issue more recently (although I started commuting with the car more and I have a 60mph downhill stretch that I get to every day, so that's more than likely the reason I started to notice). As for OP not noticing until recently, he may have a different problem, but his description of speed/RPM and the symptoms of the car matches mine pretty well. The other thing that's odd is that the pedal is so "touchy" like that without any kind of DBW remap (stock tune for me at this time).

[willnando]

I really appreciate all the feedback guys. Whats weird is that it happens frequently not going down hills, but opposite going up hills. Sometimes it even does it on level ground. Maybe it is the throttle body? I have noticed it only happens on light constant throttle as well.
I have not got the chance to scan the car yet..

[wstpride92]

I really appreciate all the feedback guys. Whats weird is that it happens frequently not going down hills, but opposite going up hills. Sometimes it even does it on level ground. Maybe it is the throttle body? I have noticed it only happens on light constant throttle as well.
I have not got the chance to scan the car yet..

i've been having the same issue. holding the gas at a constant place at low rpm i get a sort of bucking. nothing hard but still annoying. I also sometimes feel it when the throttle is mashed to the floor though.No CEL i will scan the car though when i get chance. I've had similar issue in a another car i had, tuned out to be a bad MAF. had no CEL but would lightly buck until i mashed the pedal.

[willnando]

I went through the gears with a decent amount of throttle today and it does it in every gear now.. also noticed rough idle parked at work. Still have no got the chance to scan it. Been crazy few week with work and school. Haven't had any time to meet with my friend to scan it.