BW5 rough idle

[redbaron73]

My BW5 has 600 miles. Around 400 the idle changed. Now the car has a vibration when idling. It is slight, but noticeable. It was definitely not doing that when I purchased new.

I have not connected my data logger to the car yet. What values would I want to monitor? I assume fuel trim and spark data, but don't know the specific values to look for.

I have been using 93 octane, and will try a different fuel brand/station on the next stop.

I have not yet run it at WOT, as I want to get past 1500 before I drive it hard.

 

[raptor5244]

My BW5 has 600 miles. Around 400 the idle changed. Now the car has a vibration when idling. It is slight, but noticeable. It was definitely not doing that when I purchased new.

I have not connected my data logger to the car yet. What values would I want to monitor? I assume fuel trim and spark data, but don't know the specific values to look for.

I have been using 93 octane, and will try a different fuel brand/station on the next stop.

I have not yet run it at WOT, as I want to get past 1500 before I drive it hard.

Misfiring? Does it stumble when you start to accelerate? If you can log misfires check to see if any of the cylinders have a much higher count than the others.

 

[Slick Blackwings]

Manual/automatic?

 

[redbaron73]

Manual/automatic?

Manual. The other symptom is the gear shift bouncing around while idling and in neutral...ever so slightly, but enough to notice.

 

[redbaron73]

Misfiring? Does it stumble when you start to accelerate? If you can log misfires check to see if any of the cylinders have a much higher count than the others.

Thanks, now I know what to log. I will collect some data and report back.

 

[Mcard23]

Sounds like it may be similar to an issue i had…needed a new spark plug, cylinder 6. The issue started where it was minor enough I was questioning if I was just being hyper sensitive to bad enough to throw CELs

 

[Furinax]

How much variation in the RPMs? My 4BW is idling rough with around 50-100 variation, but what I see from random threads is that this is "normal" for the LF4 engine. I'm not convinced that this is "normal" but from what I can tell it's harmless so far.

 

[Neveready]

Manual. The other symptom is the gear shift bouncing around while idling and in neutral...ever so slightly, but enough to notice.

That awesome gear shift shimmy is completely normal. There is less isolation and stiffer bushings. That's why the shifts feel so crisp and mechanical.

Could the idle have something to do with ambient temperature changes?

My 5BW has a lumpy idle but I chalk it up to being a performance car.

 

[redbaron73]

That awesome gear shift shimmy is completely normal. There is less isolation and stiffer bushings. That's why the shifts feel so crisp and mechanical.

Could the idle have something to do with ambient temperature changes?

My 5BW has a lumpy idle but I chalk it up to being a performance car.

I can see why the gear would shimmy...and agree it does feel very performant.

I also have a 21 M3, and the gear box is overly germaned. I used to like it, but after driving 5BW, I am starting to feel less enthusiastic about it.

Hoping to finally get the computer logger on tomorrow. We had terrible weather today, so the car stayed in the garage.

 

[Nadnerb]

I can see why the gear would shimmy...and agree it does feel very performant.

I also have a 21 M3, and the gear box is overly germaned. I used to like it, but after driving 5BW, I am starting to feel less enthusiastic about it.

Hoping to finally get the computer logger on tomorrow. We had terrible weather today, so the car stayed in the garage.

Check sparkplug wires. For some reason the LT4 has coil packs and then sparkplug wires running to the actual sparkplugs and those wires have come loose on a few of our cars. Mine went into the shop for a huge misfire after I just had the motor replaced and it turned out to be just the wires.

 

[MatthewAMEL]

And it's not just a Caddy/GM problem...we got my wife a new JL Rubicon last year. I stalked those forums as well and one of the things they said to do before you left the dealer was to open the major fuse block under the hood and re-seat all the fuses.

Sure enough...4 of hers were almost out at delivery. The guy who drove it over to us was like, 'yeah, I wondered why the backup camera wasn't working'.

 

[RDATLTE]

And it's not just a Caddy/GM problem...we got my wife a new JL Rubicon last year. I stalked those forums as well and one of the things they said to do before you left the dealer was to open the major fuse block under the hood and re-seat all the fuses.

Sure enough...4 of hers were almost out at delivery. The guy who drove it over to us was like, 'yeah, I wondered why the backup camera wasn't working'.

I guess lack of a good PDI isn't just a GM problem.