My Long Term fuel trim is running +9/138 on bank 1 and +15/145 on bank 2. These numbers are at idle. The O2's are new Delphi. New Delphi MAF sensor. No vacuum leaks that I can find or exhaust leaks that I can hear. The car is running really good and the only thing I can complain about is the idle quality. The MAF sensor helped that a lot and with throttle response as well. Short Term is spot on at 128 on both sides. Ideas?

 

That's not that bad if you have some mods, almost impossible to get em dead nuts on both sides usually, but if short term is dead nuts at 128 then "eventually" the long term should get to that, right?

How old is your IAC?

 

What's wrong with the idle quality?

How much data have you looked at to determine these are your fuel trim numbers? Typically you'll want to log a several minutes and then look at averages. Using a pivot table within Excel is a great way to do this. Looking at a single value...ie one data frame from a handheld scanner...is pretty pointless.

To fix fuel trims, the tuning will need to be adjusted. Typically the approach is to tweak the MAF table in the appropriate area. This is not unusual when using a larger cam.

 

FWIW, even with a large cam you can get the fuel trims within 5% of 128 and you want them to be less than 128. This is especially true as you approach the point where the PCM goes into PE mode (ie WOT).

 

If everything mechanically is correct fueling (pump etc.), sensors, leaks (et. all) is good then the tune would need more work. Based on the above data you posted it is lean. More logging is also needed to determine where it may be picking up other lean areas (load v.s. rpm, incl. de-cell, AE, etc.) as idle is probably not be the only suspect were it is lean. The reason the INT. (short term) is 128 is because it is not adding enough fuel to correct the blm (long term).

 

Thanks, IAC is a new Delphi about a month old. I cleaned out the passage way and the seat for it really well.

This data was taken with a Tech 1. It was a pretty normal 20 minute drive or so.

The idle in open loop is fine. When it goes closed loop is when the roughness starts. It is much better with this new MAF though. Maybe I'm just to picky with a LSA of 111.

I can't seem to grasp Excel. When I do a data log and save it as a CSV file the display in Excel shows it as a spreed sheet. I can't seem to figure out how to get it to anything else so I can send it to my tuner.

Thanks Mick. I believe every sensor on this car is just about new. Fuel pump is about a year old. FPR is new,O2's are new, MAP is about 6 months old, everything! If I can figure out how to get the data to him that is what I plan to do, more logging. He thinks maybe the injector offsets need tweaking a little.

I was hoping to get it to the track this Sat. so I could get some real time WOT logging but that looks doubtful at the moment. A southern snow storm has popped up and is supposed to be here Sat. Morning. Crap!

 

When you download the file to Excel, you set up the pivot table within the spreadsheet. CSV files can be saved as a typical .xls file.

The fact that the idle gets a little rough after it goes closed loop is due to the cam. With a bigger cam, some of the intake charge escapes out the exhaust, skewing what the o2 sensors report. The PCM then tries to compensate. Often times people will run open loop all the time in order to account for this.

 

Thanks for the tip on Excel. I'll see what I can do with it next time.

Are there drawbacks to running in open loop?

 

Takes a little more time to tune. Also tends to pollute a little more, especially at idle.

 

you're welcome, and there are corrections available to improve the split blms., typically with cam changes etc., more than that will need to be done. What I would recommend is getting the tune much closer before some real WOT runs. When entering wot the ecm will use the last "viewed" blm to use in part as calculations for WOT. Depending on what that might be, it will change performance and also potentially skew the AFR.
Personally, I look at tuning in OL as a last resort. I don't think your cam is that big were it can't be tuned in CL, it just takes time, and when doing mail order it will take longer.
To achieve a good CL. tune will require doing it in blocks. Since a dyno isn't available, you will trying to provide your tuner with "steady state" (holding it in various areas of rpm, then doing the same at higher load values) driving data. This will probably take a few sessions to correct and will allow for tweaking the air flow, fuel and spark tables (incl. decell etc. etc.), properly through out the driving range in the various values. This will provide smooth fueling and driving transitions in all of those areas/driving range. In a sense timing is a little bit more difficult without a dyno. Mainly because there is no understanding if max. tq. is achieved at each of those rpm/load areas above idle. Typically most tuners have some timing tables that provide a reasonable starting point. When that has been accomplished you would then address tuning AE, PE, etc....and most of all, try and have some patience