Stumbling at idle- Datalog Questions?
 

Hey guys, got a few questions:

This is data is based off of a data log of about a forty minute trip- some highway and some city driving. The problem I am having is that when sitting at a stoplight/sign after the car is warmed up, I can feel the car stumble, which will correspond with a misfire showing up in the log (AutoTap). I already replaced my IAC motor, which changed nothing (although I did not have a datalogger when I did this).

http://www.yourfilehost.com/media.ph...ug_31_Morn.csv

There is a lot of unnecessary data on this, and I will be logging some more this afternoon a little bit cleaned up.

Now before I go after my distributor, is there anything else I should do/check?

The value is 0 for all my "EGR Decel Filter" and "EGR Test"- does that mean it is clogged? If it does, why haven't I seen any codes yet?

The average value of all my "Ignition Timing Advance" is about 32.8 degrees

The sum of my "Misfire Current Cylinder" values is:
1- 0
2-312
3-132
4-136
5-986
6-310
7-108
8-158
(this is just the sum of the values, which gets reset after a 200 crank revs- I did not subtract values which were repeated within the set of revolutions)

If you guys have any suggestions/incite about what might be causing these problems, I'd appreciate it.

Thanks

Re: Datalog Questions?
 

You've got to get the time stamps off every item.... it just makes the file too unwieldy.

You have 2 columns labeled "O2 Sensor - Bank 2 Sensor 1 (mV)()" ????

You are missing a lot of good stuff like MAP, MAF, IAT, CLT, Cell, LT's that help show the engine operating conditions.

Re: Datalog Questions?
 

I rescanned after changing a good bit of what I had it record. I went on a 15 minute trip around my neighborhood, it didn't do too bad at stopsigns, but was still struggling at low RPMs.

http://www.yourfilehost.com/media.ph..._1_Update2.csv

I would be much oblidged if someone would take the time to look at it.

Thanks

Re: Datalog Questions?
 

The average value of the Long Term Fuel Trim Bank 1(%) and Bank 2 values were -6.35 and -5.21 respectively.

From what I read, doesn't the negative sign mean the PCM is trying to lean out the engine? If so, is the fuel system unable to reduce the amount of fuel moving through the lines, as shown by the values always being negative (and being reflected in my 16 mpg)?

Thanks

Re: Datalog Questions?
 

The negative BLM's mean the PCM's standard fuel calculation is supplying more fuel than the engine needs. The "long terms" are multipliers that correct the calculations to get the fuel where it belong. In your case, its reducing its standard calculation by 5 to 6%, to correct for a perceived rich condition.

That has nothing to do with the "fuel system (being) unable to reduce the amount of fuel moving through the lines". The only thing the fuel system controls is the rail pressure. It does that completely mechanically, using the fuel pressure regulator. A fuel pressure higher than stock (43.5psi, with no vacuum) will cause it to run rich, and the LT's to go negative. A pressure in the range of 48-49psi would cause the LT's you are seeing. Check the fuel pressure and eliminate that as the cause of the problem.

-5% to -6% long terms are not all that bad. When was the PCM last "reset"? That wil determine how valid the numbers are, since a recently reset PCM will have a lot of "0%" readings for Cells you haven't driven in, making the "average" long term invalid.

Re: Datalog Questions?
 

Alright, just got my fuel pressure gauge. I only tested it once, but it was consistently 38 PSI at idle and low RPMs in Park.

I don't know if this is my only problem, but I think I might know why this happened.

I replaced my oil pan by using three bottle jacks below the block/transmission and fear I may have bent the fuel lines by raising it about three inches.

When this data was logged, the battery had been connected for about two weeks from when it was disconnected for maybe two hours.

I guess my next step is to check the fuel lines.

Any advice would be appreciated

THANKS

Re: Datalog Questions?
 

How would raising the engine bend the fuel lines? They are flexible plastic.