View Single Post
Old 01-20-2013, 07:52 PM   #15
Registered User
Join Date: Dec 2012
Location: Kansas City, MO
Posts: 128
My Ride: 2004 325i
Originally Posted by jfoj View Post
I am a bit confused about about a few things based upon your graphs.

Maybe you can add more detail for me about what is going on.

Assume your horizontal axis scale is in minutes?

Anyway around 20 on the horizontal axis your throttle position crashed to 0 and stayed there. Did you back off the throttle and coast down a long grade? Or is something else going on with the throttle position data as the engine RPM never seemed to drop below about 2300 RPM??

Between 16-21 on the horizontal axis for Ignition Timing you had some dips.

Can you regraph the Ignition Timing for this time frame with a total scale of about 10 degrees? I want to see how much and how rapidly your timing is dipping. This timing dip may be justified, but it may also be what you are feeling with the power instability.

Can you rescale Bank 2 Fuel Trim to be +/- 20 even if it pops off scale briefly, I want to compare the slope to Bank 1 on the same scale.

I may also need to see your long term fuel trims as well.

Note sure the Fuel Trims look correct?

Need to get a better look at the O2 sensors and make sure things are plugged into the proper bank and there is not a lazy sensor.

I find it best to graph O2 sensor Voltages from a cold start so you can see the baseline O2 sensor Voltage and the warm up cycle into the switching cycle.

See what you can do with O2 sensor graphs. The O2 sensors can usually be ruled in or out as a problem pretty easily with graphing from a cold start. Unfortunately MAF testing is much more difficult and subjective.

Once we know the O2 sensors are behaving as expected, then we can move onto other areas.
It's in seconds, not minutes. That would be some extremely poor acceleration if, at 75% throttle, I was only able to gain 10MPH over the course of 10 minutes. I'm guessing they'll make a little more sense to you now.

Here's what this graph shows... I'm driving down the highway, a little more than 60MPH. I push on the throttle to increase speed to 75MPH without kicking it into passing gear. As we get to about the 12 second mark, the stuttering begins, and lasts about 7 seconds before I start to gain on traffic and let off the throttle and decelerate.

On rescaling the timing advance, I don't think that's going to get us anything. It's at 21 degrees to start, and fluctuates a little between 19.5 and 21 degrees during the increased throttle application. It increases to 29.5 for a while, while there's 0 throttle applied. As there's no huge downward fluctuation, it kind of steers me away from the knock sensor being involved at all.

The fuel trims look like the most suspect item here, so figuring out why they're fluctuating wildly would likely help.

The post-cat O2 sensors seem to operate normally. They fluctuate between .1 and .7 and move around quite a bit. Upon startup they show .45, and in a short time, they warm up, dip down in voltage, and slowly climb back up, until they're really nice and warm, and then the voltages seem to correspond with the short term fuel trims I monitor.

However, with Torque Pro, I still do not get any data from my my precat O2 sensors. It's not stuck at a voltage, it's like they aren't a module that exists in the OBD2 data. It doesn't light up green, as something that's ever sent data. It's just...nothing. It doesn't necessarily mean anything, it could be a bug with Torque or my ELM327 device. Or, it could be the source of all of my woes. Who knows?

Out of curiosity, is English your native tongue?
Is your car a Stu Stu Stammering Stan at 2800 RPMS? FLASH THE DME!
Enco B046 Android 4.04 Root/FAQ/Help:
PainBreak is offline   Reply With Quote