Just used free OBDI scanner, some notes, help me make sense of it!!

I just borrowed a cable and got the free scanning software from www.carputing.com I drove and had my buddy take a look at the data since I can't do both at the same time:eek: Plus he has a lot of experience tuning, but it's mainly fords. Anyways, here's some notes that he took, I'd like any input, especially on the oxygen sensor voltage.......

1) Both O2 sensors fluctuate at idle and part throttle, but at WOT they are both pegged at 996mV. I know you can't pinpoint it, but is there a guesstimate of what 996mV is as far as A/F ratio?

2) On the data display it says "learn disabled", what does this mean?

3) Spark advance @ cruise 2250 RPM is 40-43. WOT @ 5000-6000 RPM is 24-28.

4) Up to 5.5* of spark retard @WOT in upper RPM range.

I also have a few questions about how my car idles. I'm running the stock tune so far, I have fully ported heads and a HOTcam. Sometimes the care idles ok, then sometimes the idle gets real rough and it tries to idle at 500 RPM. When I give it some gas to raise the idle speed sometimes it doesn't respond, it keeps idling rough for a second or two even if I keep pushing on the gas and then all of a sudden the RPMs will shoot up. Any idea what this is? Thanks a lot for the help, all mods are in the sig.

John

BTW I have a tune on the way from PCMforless.com.

My .02

1) Guessing an air/fuel with stock O2 is going to be extremely inaccurate...if not impossible. Its always best to dyno tune your A/F with a wideband. There is too much room for error otherwise.

2) Never heard of that....hopefully someone else will chime in.

3) and 4) The timing is down because the knock is up.
Stock timing at 100 kpa @ 6000 is 33 degrees. Take 5 degrees out of that and your reading of 28.

A lot of things can cause that....lean conditions, to much timing, false knock..(something hit something else), burst knock.

Has the car ever been tuned before?

Your drivibility issues may be due to a lack of timing in the lower kpa vs rpm. You might want to look into the stock LT4 timing tables. They are specifically designed for the hot cam but the lower rpm timing is much higher than the stock LT1 timing tables.

Hope I got ya thinking in the right direction.

Thanks Jeff, that helps a lot!!!

Well I just got my PCM in from Bryan at PCMforless, and drove it around. It feels great at part throttle!!!! I think he nailed htat. The part throttle response and off idle is great. I can't wait to hook up the laptop and read the O2 voltage now at WOT.

BTW I noticed that the engine temperature on the scanning software was completely diferent from what my gauge was showing. My gauge was showing 185-190 and the computer was telling me 210-215:confused: And also the gauge would vary from 185-225 and the computer would vary from 210-230...... So I don't know what's up with that......

John

Learn is disabled at WOT and open loop, the comp. uses the PE tables rather than feedback from the O2s for WOT. However learn *should* be enabled during closed loop, non PE operation.

Your 0'2 mv's should still read in the upper 900' mv's, at WOT your PCM enters to what is known as Fuel Enrichment Mode.

Originally posted by 96ZRDR
Your 0'2 mv's should still read in the upper 900' mv's, at WOT your PCM enters to what is known as Fuel Enrichment Mode.

Ah ok, this is what confused me. I just assumed the 996mV meant VERY rich. I guess I'm still a little confused, what exactly am I looking at? And also, what is the A/F range on the stock O2 sensor?

John

.450 mv is considered to be in the middle, anything below means the sensor reads lean anything higher is rich. I think they are suppose to max out .950. dont quote me on that.

Originally posted by FastZinTennessee
Thanks Jeff, that helps a lot!!!

Well I just got my PCM in from Bryan at PCMforless, and drove it around. It feels great at part throttle!!!! I think he nailed htat. The part throttle response and off idle is great. I can't wait to hook up the laptop and read the O2 voltage now at WOT.

BTW I noticed that the engine temperature on the scanning software was completely diferent from what my gauge was showing. My gauge was showing 185-190 and the computer was telling me 210-215:confused: And also the gauge would vary from 185-225 and the computer would vary from 210-230...... So I don't know what's up with that......

John
Explanation of why your PCM and gauge read different temps. (http://www.fierolt1.com/lt1_temp.htm)
You know, I wondered the same thing until I ran across that site. :)

Originally posted by brokenz
Explanation of why your PCM and gauge read different temps. (http://www.fierolt1.com/lt1_temp.htm)
You know, I wondered the same thing until I ran across that site. :)

Thanks! That was a very nice article, I was freaking out when the laptop was showing 30* more than the gauge:p

Thanks for the website brokenz, I was wondering about that myself. I was just observing that yesterday on my scanner, and I thought maybe I needed a new sending unit after 176,000 miles. I think I'll convert over to the 3 wire unit for a more accurate guage.