Im pretty new to prom burning but Im getting better. But I do have a few questions. I have a 94 K1500 suburban with a 16196395. Ive been keeping a close eye on the blm's, Int, and O2 sensor voltages. My blms usually hang around 135 but fluctuate b/t 128 and 140 at the leanest. At start up the O2 readings are about 450 mvolts. I thought that was lean though. I thought that it should be around 700-800 mvolts. But after it warms up a bit they drop to 40-100 mvolts and sometimes drop to 0 which I though was extremely lean. Now the int values usually stick to 128 but I did max them out at 158. So I burned a chip purposely rich. You could smell it was rich. Wasnt really really rich but you could definitely smell it. But startup readings were about 450-500 but they didnt fall of as fast. So i thought it was better but they then dropped to 60-100 sometimes falling to 0 still. Im not really sure. I just got datamaster working so Im going to try that instead of the autoxray ive been using. Plus I also have a hard time getting into closed loop. After a 20 min drive coolant temp may only be 160*. I think Ill swap to a 180 stat and see if that helps. Thanks in advance for the help.

Josh

 

The sensor has to warm up to about 600-800dF before it generates any meaningful signals. So it does take a while for it to respond.

If it's all stock yes run the 180 or a 195.

usually the startup routines are rich enough to even work with mild modifications. Once you have everything else done you might play there, but generally unless you have a problem, there is nothing to really be found there.

In closed loop the O2 toggle across .450 to it should be .1 to .8 to .1 to .8 etc etc.

Dont tune to get a particular O2 voltage, for WOT, they just aren't that accurate.

 

Grumpy,

Thanks for the help. No its far from stock but its not that wild either (383 SR Torquers 215/224 roller cam 9.6 cr). Im not tuning for WOT just for below 3000 rpm. Well I went out and did a run with datamaster and that was MUCH more meaningful. When It goes into closed loop (relatively early on) I got some meaningful o2 and blm readings. I usually around 135 at idle but once I give it some gas the blms may go to 105 so Im way rich at just off idle. Which you can smell. But the part that has me confused is that about 5 min after going into closed loop it went back into open loop and stayed there. No I was not getting into the throttle at all. Just nice easy take offs never going over 2000-2500 rpm at the max staying below 1200-1500 the majority of the time. I started to get junk info (well at least to me someone with more experience it might me something to). What do you guys think. Thanks for the help.

Josh

 

If you tune your BLMs all to 128 and for some reason, it looks like someone dug a valley in your lower table at really weird but constant points, you may find out that your purge system is not hooked up correctly. I had the problem any time purge duty cycle went over 0% and since I never looked at purge data, it took me a looong time to figure out. Took me a while to relaize that garbage in really did = garbage out.

 

HighHopes85 thanks. I would have never thought to check that. Ill play around and see what it likes. Thanks to all.

Josh

 

Are you using a heated 02? Im not sure but if you are excessively rich it may be cooling the O2 back to open loop.

 

87_TA,

Thanks, Well Its a 3 wire O2 sensor. Its technically for a van but thats what I pulled out when I bought a new one a while ago. The autoparts store said the book called out for a 4 wire one. I take it that since its a 3 wire it is heated but If not Im thinking I'd put one in if its not to hard. Well now my problem is I leaned it out and it was WAY to lean. Now I richened it back up to basically the same as the other chip which was very rich and its still way lean. Im thinking my O2 sensor is crapping out so Im going to yank it out and maybe replace it depending on what it looks like. Im also going to pull a few plugs to see what they look like. The thing is the computer says its really lean at idle but you can smell how rich the exhaust is. Thanks

Josh

 

Ok well I took out my O2 sensor and it confirmed what I thought that I was running rich even though the computer thinks I was very lean. So I cleaned alot of the carbon build up off of it. I also pulled the plugs (3 days old) to verify I was running rich and they were black as night. Well I put in a slightly richer chip. Well I jumped from being as lean as can be to being as rich as can be. BLM's went from 158 yesterday to 105 today with only mild changes to the chip. So I went back in and leaned it out. Leaner than I was yesterday yet my BLM's go straight to 105 and INT goes alot lower. This chips is leaner than the chip I was running yesterday (which was extremely lean BLM's 15x) yet Know my BLM's are 105. I dont know what Im doing wrong here. MY VE tables are really low yet its still rich. If someone could help me a bit here Id greatly appreciate it.

Josh

 

What is your set-up? You may just need to pull more.
What size inj are you using? whats constansts set at?
Is the car cammed? what intake? whats advance set at idle?
Yes the three wire is a heated,you can pick up a universal 3 wire from sorenson for $29.
If BLM'S are rich and you have all the tell tale signs,lean up.
Is the car cammed?

 

94 K1500 Suburban 383 SR Torquers 215/224 Roller cam 9.6 CR running a holley TBI w/ 65 pph injectors. The injector constants are set to 65 pph cylinder volume is set to the correct size for a 383. Im running the holley tbi intake. Ive got my base set at 6* but it idled pretty much the same anywhere from 4*-12* base. We decided 6* was just barely the best. I have the Initial spark advance set to 6* in the chip. Ive got the spark tables at in the 6-10* area in the idle area. The thing is my fuel tables at rpm's below 1200 rpm in the 40-70 map area (at idle my map readings are about 60-65 kpa) my ve is around 65% and yet it was crazy rich. I plan on doing some more playing around with it tonight. Burned a few more chips last night with each one getting a little leaner. So I can see what she likes and then dial it in from there. Thanks for the help.

Josh

 

Well I played around with it alot tonight and have my idle fuel table somewhat decent. Im staying around 126-132 ish. But Ive got VE set at about 45 ish around ilde areas. But Ive still got some work to do in the off idle fuel table. Quite rich on the low end and extremely lean above 2000rpm. So Ive got a new chip in the burner as I speak so I hope that will help out alot of my problems. Thanks to all for the help. If you got any suggestions let me ahve them though. I can still use all the help I can get.

Josh

 

May want to get idle timing up a little,maybe 20-25ish.
But see what it likes.

 

Ok I bumped timing up and got the fuel tables under control. Runs good for about the first 15-20 min. I took it out for a little longer cruise tonight about 1/2 hour. For the first 20 min it ran perfect. I was just a bit rich in a couple spots (124 int) and a bit lean in others (132 int) but I was within 1 of 128 for the majority of the time. Well I just had my handheld scanner along for the ride this time instead of my laptop with datamaster. After about 20 min all of sudden the blm's locked up at 135 and int at 128. So I looked at 02 sensor voltage and it was ranging from 0- 80 but 5 minutes before it was running perfect. Well shortly thereafter it threw a code for being overly lean. So unfortunately since I was a little ways from home I just babied it home and the exhaust didnt ahve the slightly rich smell it had before. What caused it to do this. I was thinking maybe am I pushing the dutycycle on an injector and then after a little while it stops functioning correctly or could my fuel pump be on the way out. The reason why I think this is because the trasistion form just a bit rich to extremely lean like you snapped your fingers. Didnt have a chance to make sure Im getting enough pressure from the pump. Looks like Ill be installing the fuel pressure gauge Ive got soon. I guess if it does it again Ill have to pull the air filter off to see what the injector is spraying like. Or am I on the wrong track.

Josh

 

Well I figured the problem out. One of the injectors on my holley tbi crapped out. It only sprays about 1/4 - 1/2 as fuel as my other injector at idle. Does anyone know the duty cycle on them. Before it died when I was in park when I rev to about 1600 rpm pulse width woudl be 4.x msec and it was about 128. So I wonder what its like in gear with a load on it. I dont know if its just clogged but Im kind of doubting it. Gotta tear it down now. Thanks for your help 87_TA and everyone else.

Josh

 

No problem Josh,
It makes me feel better to have helped someone.