TCombs UrS4, Possible misfire.

[TCombs]

Pull injector connectors off at idle while misfiring and find the bad cylinder then check the plug and replace the coil if needed. Hope you have upgraded ignition

Good idea. Will do. Just pull each one, one by one and when there is no change, there is that bad plug/coil, I am assuming. Ha luckily I do. I have LS2 coils with Magnecor wires. I actually have a second set in a box that I bought from a fellow on MG a few years ago when I bought my first S4.
Thanks for the info.

[ringbearer]

Sounds like you are ready to troubleshoot! I’d replace all the plugs if they are close to due but I live in coastal California so I have no idea what real winter is

Good luck

[PRY4SNO]

Also your coolant temp sensor (G52) could be on the way out, chased that one with a shotgun for a while.

[TCombs]

Also your coolant temp sensor (G52) could be on the way out, chased that one with a shotgun for a while.

Oh really? Does that cause the same issues?

[PRY4SNO]

Shaking at idle, misfire at steady load / stepping on it, reduced mileage, fluctuating tach.

I swapped out plugs, upgraded to the 2.5 coils and wiring (which were planned upgrades anyways) then found the G52 fixed the issue.

[TCombs]

Shaking at idle, misfire at steady load / stepping on it, reduced mileage, fluctuating tach.

I swapped out plugs, upgraded to the 2.5 coils and wiring (which were planned upgrades anyways) then found the G52 fixed the issue.

Good to know. Thanks for the info. I’ll find some plugs and swap them in and if it doesn’t fix it change that out. Might be worth changing out out regardless.
I know that this has been brought up a lot, but what plugs do you guys run. I ran the Bosch F5DP0R in my last S4, for the week or so I had it. Are they still having issues with them failing?

[PRY4SNO]

Those Bosch or NGK BKR6E at stock or mildly tuned levels, or a 7E (one step colder) for higher power.

Key is to make sure you get the plugs with the resistor.

[themagellan]

I was a devout OEM plug lover, but have since changed to bkr7e like most folks here - super cheap and work well. It's always worth checking the gap.

- Check your boost hoses - especially the reference line to ecu
- Check your resistance on your crank/rpm sensors - make sure your wire routing is not interfering with the ignition wires
- Check the Idle Control Valve - I chased a hardstart/bad idle issue forever. A simple test for this is to unplug it while it's running - if everything seems to improve you can isolate this issue.

Like others suggested - just unplug the ignition from each cylinder. One important thing is to wear some insulated gloves if you haven't done that before or else it can be quite a wake up call.

[TCombs]

Changed out the spark plugs on Saturday. Had the OEM Bosch plugs in. They didn’t look super bad but worth replacing. They NGK plugs are cheap. Drove around quite a bit on Saturday. Got the temps up and steady and the car ran like it should. Started it up Monday morning, it was about 15-19 degrees out. Ran fine for about four or five minutes and then start misfiring again. So now I am thinking it might be temp related. I googled Audi aan coolant sensor and SJMauto came up and I read up a bit about the sensor using different other sensors to get temp. New temp was ordered, should hopefully be here this week.

[PRY4SNO]

Sounds a lot like the issues I was experiencing.

Here's hoping it is simply the G52 sensor.

[TCombs]

Sounds a lot like the issues I was experiencing.

Here's hoping it is simply the G52 sensor.

Ran fine yesterday morning and it was about 25-30 degrees. Started it up after work and it was stumbling again. Pulled it into the shop at work, changed out the sensor in a matter of a minute or so and the car ran fine. Only one night and one morning in so far but it hasn’t stumbled yet.
Thanks for the help. Would have taken me awhile to figure this one out. Now on to tackle some little things like interior lights (only the drivers footwell works), fix the fender, look at some options for the hood paint, possibly coolant leak from the upper hose and leaking washer fluid, and a few other items just to set the car up a little better.

[ringbearer]

Hope that does it!

[PRY4SNO]

Sounds a lot like the issues I was experiencing.

Here's hoping it is simply the G52 sensor.

Ran fine yesterday morning and it was about 25-30 degrees. Started it up after work and it was stumbling again. Pulled it into the shop at work, changed out the sensor in a matter of a minute or so and the car ran fine. Only one night and one morning in so far but it hasn’t stumbled yet.
Thanks for the help. Would have taken me awhile to figure this one out. Now on to tackle some little things like interior lights (only the drivers footwell works), fix the fender, look at some options for the hood paint, possibly coolant leak from the upper hose and leaking washer fluid, and a few other items just to set the car up a little better.

That's fantastic! Hope it holds up. Took me a while shotgunning parts I'd intended to do anyways but once I got over my dislike for the format on quattroworld I was able to dig up some good info.

[TCombs]

Well it started again so I swapped the top plug and connector from coil three to coil five. Didn’t drive the car a old weekend and ran fine yesterday morning. Started it up after work and it was missing. Pulled the fuel injector plug for cylinder five, no change. Nice! At least I thought all I had to do was change out the coil. Pulled out my other set of coils and plugs only to find out that they are a different coils with a different mounting plate as well a different plug. So I am trying to find a coil like I have now or have to get a new kit with bracket. The wiring harness on the kit I have had for a few years looks bad. The wires seem in decent shape but the harness is just a bunch electrical tape and even some butt connectors if I remember correctly.

[TCombs]

Did some digging around, and I believe I found the coils I need. They look very similar to a coil from a Mercury Optimax outboard motor..
Which are cheaper than the 034 HO coils. Wonder where they sourced them from.