vinhnguyen54

A8 Non Z51 1500 Miles

I pulled Fuse 42 and the car ran fine for several days. Car is a bit louder all the time right when you get on the throttle. The throttle also seem to be a bit more responsive and this is where the problem occurs.

Yesterday I was stuck in freeway traffic and was basically doing constant stop and go. The car jerks slightly but noticeably every time I get on the throttle from a stop. The jerks is most obvious when I am rolling 2-5 miles on idle and then give it gas as traffic picks up.

There was also one incredibly hard shift that occurred when I accelerated from a stop and then decelerated quickly as the car in front brake and then re-accelerate quickly as the car in front picks up. The jerk was so strong it felt like I literally got rear ended.

This car always has occasional rough slow speed shifts warm or cold. Pulling the fuse really make matters much worse. I put the fuse back in yesterday and the problem seem to go away. I will take my car for another slow speed stop and go test drive again later to see if the problem persist.

Anyone having worries about these A8 shifting harshly especially as slow speed?

dvilin

There have been several post about hard shifts with the A8 but none associated with pulling fuse 42 so npp is open all the time.

vinhnguyen54

Yes I read most of the harsh shift threads but this one is directly relevant to Fuse 42 pulled and I could not find any info on it.

I am wondering if the car started out in V4 instead of V8 and that is why the jerks occurs with the fuse pulled. I read the car starts out in V4 earlier if the fuse is pulled.... Also the very hard jerk might have been from V4 to V8...I read something about this and it seems to make some sense?

fireinv38

Put the fuse back!!!!!!!!

c6chaz

tranny needs a re flash, mine works excellent and 42 out

vinhnguyen54

I put the fuse back in and the car seems to run fine again...

Does the reflash basically make the car as though I just bought it without any miles? If yes does this mean the learning adaptive process is reset too?

scottjays

Why pull the fuse for NPP to stay open?? Just use engine sounds management settings to keep exhaust flaps open all the time, no?
Why do people pull the fuse when the engine management settings do the same thing? Am I missing something?

vinhnguyen54

Even set to track the flaps doesn't open until 1900 RPM

With fuse pull it's always open

meyerweb

The algorithm is a lot more complex than a simple rpm limit, but you're right that even in track mode the valves aren't always open.

vinhnguyen54

Agree...

So far putting the fuse back seems to make slow stop and go OK again.


I am also wondering if it has anything to do with transmission over heating. As that day the temp on the Tranny got to about 200F. Never been that high before.

May be I will try taking the fuse back out to see if the problem comes back. If it does then it's the fuse for sure.

meyerweb

I can't think of any reason pulling that fuse would affect shifting, and I haven't seen any other reports of that. OTOH, I certainly don't claim to understand all the complexities of the programming of these systems. I'm not sure anyone (even at Chevy) understands it all.

I'd be interested to see if you notice the same issue when you pull the fuse on a cooler day.

vinhnguyen54

Will try soon. I sure hope the problems comes back otherwise its a heat issue and that would be bad

vettekat2007

My A8 hard shifts seemed to settle down after I had a few miles on the car. Not sure at what point exactly the trans smoothed out but I have 2,600 miles now and trans definitely shifts better than it did when new. My fuse has been out almost from the beginning.

golden2husky

I am also wondering the same thing. Some have gone through some rather elaborate work adding switches, etc. and it seems that the settings on the center screen does exactly the same thing. Are there any differences?

meyerweb

This has been discussed many, many times. Setting ESM to track mode does NOT keep the valves open all the time. Period.

vinhnguyen54

OK I think the rough shifts was because the transmission was overheating in traffic. It was only like 70F that day too....Temp got to like 200

With the car cold this morning Fuse in or out does not change how the car shifts. Smooth shifts regardless of slow speed, fast speed, stop and go...

Man these A8 does seem to have cooling issues...Tracking this car in anyway would over heat for sure if it can't even handle stop and go traffic...

I sure hope things will improve with miles somehow...

Anyone notice car shifting rough during stop and go on a hot day?

BJ67

The pulled fuse keeps the exhaust valves open all the time, no settings will do this.