Need help with cruise control surge - what to datalog?

[speertp]

Hi-

 

I have a 2005 5EAT with 178,000 miles on it. Ever since I had some front suspension work done by a shop last year, I have noticed a slight surging when on cruise and a slight bit of sluggishness from a stop / idling roughness. It MAY also be there when the transmission is in sport mode, but I'm not sure about that.

 

Some things that may or may not be relevant to this issue:

 

I was at Cobb stage 1 from 30k to 120k. Had bad rings at 120k, had engine rebuilt, and went back to stock.

 

The suspension part was replaced last fall, and this surging showed up.

 

Had issues this winter of the engine cutting out and throwing a CEL when on boost - shop thought it was wastegate control solenoid and replaced it - issue seemed to be ok, but car ran bad. I checked vacuum lines the best I could and found one off by the new solenoid - CEL light and boost cut started up again. Had shop check my turbo - had bent arm on wastage, couldn't open - replaced with a new OEM turbo.

 

Thought I would try to find cause of surge this spring - found a vacuum line on the driver side on the intake manifold off (I think) - didn't fix surging.

 

The problem persists, and I was thinking yesterday that it was the front oxygen / A/F sensor after some forum digging and data logging (I'm no pro at this), but think this might not be the case, as the logs may just show the sensor bouncing between some very low values. I have a sensor coming from Amazon and decided I need to verify before I just throw parts at the issue.

 

Long story short - I have a datalog here, but I'm sure it's not exactly what I need to check. I know that as soon as I turn on the cruise control, many sensors start to go up and down, but I'm sure many of those are a symptom of the issue, not the cause. If anyone has any input on what I should log / how to log it, I'm all ears.

 

Edit - my datalog is too big for the upload - I'll relog if someone gives me parameters.

 

Thanks so much!

[Max Capacity]

By front suspension work...do you mean wheel bearings/hubs ?

 

If so you need to use OEM front hubs, or your CC will surge and possibly CEL.

 

It's well documented here, there is one after market but for the best, just get OEM fronts.

 

 

I would also get your car to a Tuner or talk to one of the E-Tuners here. I use Mike Kinsman, http://www.tuningalliance.com check the Vendor Forum for his web site. Support those that support the forum.

 

Where do you live ? may be there is a closer Tuner to you.

 

"cryo" a member here is good too.

[speertp]

Yes, actually. It was a right front bearing / hub, knuckle, and both lower control arms. I'm going to see if the shop used OEM parts or what the story was.

 

Thanks for your help!

[speertp]

So I'm working with the shop to see what they can do about the issue. It is a non-OEM hub / bearing assembly. I was thinking I could datalog from the TCU and get the wheelspeed sensor's data, but I only see front or rear, not front left vs front right. Does anyone know how to view the data from each of the wheels to show what the sensor is showing?

[Max Capacity]

I used my mechanic's Computer that he installed in the car and told me to go drive and check all four wheel speeds.

 

All four were with in spec. I put a OEM hub in and the problem has not come back.

 

I posted all that in my thread.

 

Check the DIY threads for front wheel bearings. hint, Post #126 http://legacygt.com/forums/showthread.php/front-wheel-bearing-diy-walkthrough-86994.html