85irocinjected

Not sure if this is the correct thread but, anyway....I deleted the rear o2 sensor out of my PCM and due to a header change at the time did not have the front o2 sensors installed (pluged the holes) Anyhow, WITHOUT any o2 sensors hooked up the car runs fine, but as soon as I plug in my front o2's the car runs like crap and misses and cuts the fuel trims to lean it alot..If this will help the codes where cleared when no o2's where installed. Could that make the PCM learn this condition (no o2's) and adjust for it? Meaning when I plug in o2's it does not know what to do? Sorry for the long winded explanation. Thanks

brad8266

iTrader: (23)

of course the PCM trimmed fuel when the O2's were plugged in, thats what they are suppsoed to do.

When you took the O2's off the PCM went inot open loop operation.

85irocinjected

I understand they are supposed to cut or fatten the fuel trims. What I am trying to figure out is why the vehicle runs like sh*t when they are plugged in but fine when unplugged.

brad8266

iTrader: (23)

if it runs like **** with them then they are probably not working properly and you may want to replace them.

85irocinjected

I did replace them..I thought about that as well. I suppose I should have said that in the original post as well.

brad8266

iTrader: (23)

Hook a scanner up and see if they are switching OK.

85irocinjected

Thanks for the help brad and I don't want to sound like an *** but I have done all that...today I got it to run fine with the o2's in..I just replaced the spark plugs & fuel filter then hooked them up and it didnt miss or anything. The old plugs where not even fouled or anything.. The only problem now is I lost ALOT of power, I can barely feel it surge while driving but it does surge ever so slightly.(I have also checked fuel pressure which was a constant 58psi) To give yall an idea of the power lost...With them not plugged in the car would light up the tires in 2nd from a stop. With them plugged in I can't even light up the tires in first. All my numbers are good, i.e CO, CO2, HC, O2. Thay all look great on the 4 gas. I cleaned my MAF and still the same. Anyone have any ideas other than just run without o2's (even though Im thinking of doing just that untill I can figure this little problem out.)??

85irocinjected

Just if anyone is interested I may have found the cause to my problem. My '00 LS1 motor and t56 are in a '84 Z28 (FYI) Anyway I tapped into the ECT (Engine coolant temp. sensor) wire for my temp. gauge so that I know the engine temp. Well since I did that my scan tool has show the ect always at -38 degrees. So needless to say I am going to unhook my gauge and go from there. That possibly is the problem because the ECT has an effect on the fuel trims. Anyway, just thought that couldbe usefull to anyone having problems with a lean condition for no apparent reason. Check your ECT.

85irocinjected

PE Modifier Based on ECT (Engine Coolant Temp. Sensor)

EQRatio is a value centered around stoichiometry (14.7) where 1.00
indicates perfect stoichiometry. Values
less than 1.00 indicate a LEAN condition, values greater than 1.00
indicate a RICH condition.

So if 1.00 is stoichiometry than at 1.00 - .35/.39 will cause a LEAN
condition.

When the ECT reads a temp of:

-30 then it is subtracting .35 (Units - EQ Ratio)
-40 then it is subtracting .39 (Units - EQ Ratio)

There for causing a LEAN condition.