y5mgisi

Been trying forever to figure out a shitty idle situation on my truck on finally logged some data. Wanna take a look and see if you see anything strange?

jim_in_dorris

I would first fix your O2 sensor problem. Your IAC counts look like you have a huge vacuum leak. At idle I have IAC counts of about 35 or so. A vacuum leak will also show lean on your O2 sensor, so I would look there first. Your are getting a code 44 O2 sensor lean error, but I would start with vacuum.

y5mgisi

Thanks for takin a look! How were you able to look at it and decipher it? You know, I have been under the impression for a long long time now that i have a vacuum leak. I have done everything i can think of to try and find/fix it but with no results.

y5mgisi

Also, do higher IAC counts mean the pintle is more shut or open?

y5mgisi

Also noticed my rich lean counter stays at zero all the time. That mean anything?

jim_in_dorris

well, I imported your log into an excel file and looked at it that way. Open excel, then open file and select your log file. It will be a comma delimited file and will work just fine.
I looked at your malfunction flags and saw a code 44 so I looked at your o2 voltages and they were very low.The O2 voltage should swing around .5-.6 volts. One problem looking at logs is the frequency of the samples, but with all the other symptoms, I would go there first. Your BLM's are dangerously lean. they should be 128 +_ 5 I saw one place in your log where they hit 172. Your idle iac counts were up above 100 which I only see under throttle and load. I would start by taking a propane torch, not lighting it (don't want fire) and turn the propane on and hold the nozzle around all the vacuum hoses, and intake manifold. When the motor picks up you have found your leak. If it is a major exhaust leak, it won't really help, but that should be easy find. If you can't find a leak, then the next step would be to try replacing the O2 sensor. They do go bad. Use an AC Delco O2 sensor, the Bosch sensors can cause a problem. If your O2 sensor is in the collector on a header, you might need a 3 wire heated sensor.

y5mgisi

Jim thanks for your help man! Lets see if i can help you help me... The funny thing about the BLMs is that i THINK that when they shoot up to 172 is when i THINK it goes into "limp mode". Thats when the check engine light comes on and it seems to run way better. If you'll notice, the o2 readings hardly change it all in closed or open loop. Now sense during open loop it doesnt "listen" to the o2 it should effect how its running at that time right? Only in closed loop the o2 effects the computer correct? So that trips me right out. Im going to have to bet it needs replaced but it should be ok in open loop is my assumption.

The IAC counts i havnt been able to determine what they mean. Closer to 0 is closer to closed and closer to 100 is further open? or opposite?

Vacuum leaks, I have gone round and round and round again with that... I believe in my heart that there are none but im not foolish enough to rule them out. I have done the carb clean thing (similar to propane) and found nothing. Add to that that i have replaced the throttle body base gasket and the intake manifold gaskets and rebuilt/resealed the throttle body, removed and plugged all the vacuum lines(inluding brake booster), replaced and sealed up the EGR valve, and re adjusted my rockers. All of that with difference or signs. I would be glad to try the propane thing just for fun though.

Exhaust, its stock manifolds(no A.I.R.) and stock Ypipe with a magnaflow cat and flowmaster 50 series. Seems to be very well sealed up. No leaks that i can hear. At least nothing of any significance. The o2 is in the stock location and is newish but i dont remember the brand.


Again, Thank you very much for taking the time to try and help me out!


EDIT: Also i was able to open the file in excel. Worked perfect.

jim_in_dorris

ok, just a quick check here, 90 burb should be 7747 ecm what xdf are you using? here is a copy of a log I did a year ago, my truck purrs like a kitten, just to show you what it should look like. You have some strange values showing up in your log.

y5mgisi

Im not sure on the xdf. I can tell you its stock and is the 7747 ecm. For what its worth, i got a complete ecm out of the junk yard and it made no difference. I will take a look at yours and compare.

y5mgisi

Any ideas about my rich/lean counter staying on zero?

y5mgisi

new log with heated o2. quite the difference!

jim_in_dorris

Better, but still some very strange stuff. When you go into closed loop, your IAC starts dropping, so that looks ok. However, negative voltage on tps is not right. With your foot off the throttle, the TPS should read around .4~.5 volts and go smoothly to 4.5~5 volts as you increase throttle to WOT. That new O2 sensor now shows you going extremely rich after it warms up. you might look at your plugs.

y5mgisi

I dont know why it comes up that way in the log. When i watch it on the screen its right at .55v. The plugs are virtually brand new. 0 miles on them and maybe 1hr maximum. they are autolite 26's and didnt change anything when i put them in place of the old autolite 25's. I do need a new set of plug wires though as i noticed one of the boots is burned clean threw and another has some burn marks on it.

jim_in_dorris

is it idling any better when it warms up now? does your exhaust smell like unburned gas? Are you using a usb to serial adaptor and how is it set up?

y5mgisi

Yes it is ideling alot better. Still not perfect but good. Now, instead of idling too low, it idles a bit high. The exhuast smells pretty much right on. Used to smell insanely rich. Just realized also that i need to re adjust my timing. I had bumped it up to around 9-10 just to get it to run as good as it did. Now i need to bump it back down cause i shouldnt need it that high anymore. Im just using the usb aldl cable from aldlcable.com and using winaldl. works perfect.

jim_in_dorris

ok, adjust the timing, fix the bad spark plug wires and see how it is now. Sounds like the new O2 sensor helped a lot. Also you might want to try tunerprort v4 just to see what that log looks like. You will need an ads and xdf for the 7747 ecm. they are available on moates.net. I use both, winaldl is certainly simple to use. but TunerproRT will assist in tuning when you get that far.