zmike

I don't have any datalogging software at the time, just access to a tech2 at work. Put it on a dyno at my local dyno day and is running way lean - like in the 14's. New AFS75 O2's and getting ready to put in a racetronix fuel pump and hot wire kit.
Vehicle Speed: 0
Engine Run time: 7:18
Engine Speed: 1043 RPM
CKP Engine Speed: 0 RPM
Desired Idle Speed: 900 RPM
CKP:Lo Res. Angle: -29 degrees
Ignition 1 : 13.5 Volts
Air Fuel Ratio : 14.7:1
Short Term FT Avg. Bn1: 16%
Short Term FT Avg. Bn2: -3%
Long Term FT Avg Bn1: 14%
Long Term FT Avg Bn2: 9%
Short Term FT Bank 1: 18%
Short Term FT Bank 2: -3%
Long Term FT Bank 1: 25%
Long Term FT Bank 2: 14%
Fuel Trim Cell: 16
This is all at idle. Can any of you decipher any of this? Gettin pics uploaded to a hosting site to display screen shots.

Injuneer

The left bank is running very lean (or would be, if it wasn't for the PCM corrections) at idle (Cell 16) and the PCM has bumped the long term fuel trim (LTFT) up to the maximum extra fuel it can add (+25%) and it's still not meeting the target A/F ratio of 14.7:1. Then it ramped up the short term (STFT) for the left bank to +18%. The right bank isn't quite as bad.... its adding 14% extra fuel at idle. The STFT for that side is probably toggling +/- a few % on either side of 0 like it's supposed to.

If you look at the average LTFT and STFT the problem with needing a lot of extra fuel to prevent it from running lean is spread across the other Cells (variations of RPM and engine load as measured by MAP), but it probably isn't quite as severe in the higher load cells.

The big cam (probably with a narrow LSA) doesn't help. With high overlap, at low RPM the incoming air/fuel blows through the open exhaust valve and fools the PCM into thinking its running lean, when it isn't.

There's not a lot to be learned in a single frame like this. But it does point to a problem with the engine running lean, if it weren't for the PCM's ability to add extra fuel when the O2 sensors indicate it's running lean.

Have you ever checked the fuel pressure? Have you ever checked for vacuum leaks or large quantities of air bypassing the MAF? Is it possible you have an exhaust leak before the O2 sensor on the left side? Large number of misfires on the left side? Tech-2 can retrieve the misfire count by individual cylinder.

zmike

When I saw the difference in sides, I did check for misfires on the Tech2 on all cylinders and there were none. No codes either. I sprayed ether everywhere trying to see if I had an intake manifold leak or other vacuum leaks, there wasn't a change in the way it ran that I could tell. Haven't put a fuel guage on it to test fuel pressure because I don't have one. I did just get a new Racetronix pump and hot wire kit that I am about to put in. Here is what I have done: Cleaned the MAF, checked for vacuum leaks(Ether), checked intake manifold bolts, put in new AFS75 O2 sensors. Trying to figure out how to post pictures so I don't have to type in all the information. Before I forget....Thank you for looking at this for me.

Injuneer

Did you check for tears in the inlet elbow, or the lower edge of the elbow not being on the throttle body?

zmike

Yes, removed, inspected and replaced. I was able to borrow a fuel pressure Gauge and found 4 psi at prime, 38 psi idling, drop to close to 30 when reving up to just over 3k, and a quick drop to around 4 psi when motor is shut off.

byrons1502

The fuel pressure should not go down on shut off. Will not cause running issues. Did you get the new pump in yet. What is the maf g/sec at idle. With the larger cam you should be around 6 with a min of 5g/sec. If it is you might just have to tune at idle.

zmike

Fuel Pump & Hot wire kit is not in yet. Haven't had time to work on it. The MAF is at 13.38 g/s the last time I had it on the Tech2 after I put in new AFS75 O2 sensors.

zmike

Got new Racetronix fuel pump in and hotwire kit. After a bad teflon hose that came with the new pump, pressure is all good. I need to get datalogging software and stop messing with the Tech2 but is this within normal specs (All at idle 950 rpm):
Spark = 26* at idle and 46* at 2500 rpm
Knock Retard =0*
KS Activity = 898 counts (this is my concern)
Air Fuel Ratio = 14.7:1
IAC Position = 18 counts
Learned IAC = 10 counts
TP Angle = 0%
MAF = 14.48 g/s
MAP = 63 kPa & 2.82 volts