TPS sensor and lean condition.
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SY756
New member
Sounds like you were with Nick in his truck. Yeah, if the ecm isn't seeing 100% Throttle open position and it really is wide open, then yes the ecm won't put enough fuel in it for the amount of air going in causing a lean condition. Causing the low O2 volts. Not seeing 100% would also cause it not to go into open loop. The computer doesn't think that it's at WOT.
While speaking about WOT make sure that the butterflies in the TB are perfectly horizontal when you have the gas mashed.
While speaking about WOT make sure that the butterflies in the TB are perfectly horizontal when you have the gas mashed.
leroy
Donating Member
I respectfully disagree. TPS is not figured into the fuel equation for the most part. It is used to determine whether to use the closed throttle or open throttle VE table. If your TPS is really messed up it may affect the ecm's ability to enter PE and AE modes.
Hook up your scantool. Turn the key on, but don't start the truck. Push the gas pedal down slowly and watch the tps voltage/percentage. You should hava a fairly smooth increase as the throttle opens. If you don't get 100% at WOT, have a friend open the throttle at the throttle body to see if you can get more. You may have to bend the pedal to get things to work right. If you still can't get 100%, I would replace the tps.
I don't remember Diacom ever indicating open loop at WOT, but not sure about that.
HTH,
Jim
Hook up your scantool. Turn the key on, but don't start the truck. Push the gas pedal down slowly and watch the tps voltage/percentage. You should hava a fairly smooth increase as the throttle opens. If you don't get 100% at WOT, have a friend open the throttle at the throttle body to see if you can get more. You may have to bend the pedal to get things to work right. If you still can't get 100%, I would replace the tps.
I don't remember Diacom ever indicating open loop at WOT, but not sure about that.
HTH,
Jim
Better way to watch for it to go into open loop at WOT is watch the integrator value - it should go to 128. It goes into PE (Power enrichment) mode at WOT, integrator is forced to 128. BLM goes to 128 if it is leaner than 128 normally, if it is normally richer than 128, it will remain at that value.
I agree with Jim on the TPS thing, it just isn't used for the main fueling equation, like it would be for a MAF car. It is partially used to determine when to step to PE mode, as well as for acceleration and deceleration fueling.
I agree with Jim on the TPS thing, it just isn't used for the main fueling equation, like it would be for a MAF car. It is partially used to determine when to step to PE mode, as well as for acceleration and deceleration fueling.
SY756
New member
smeagol said:
I stand corrected. I know that there is alot more variables involved in the fueling tables and such. I just figured that if the computer wasn't seeing 100% WOT it might be supplying fuel for about 3/4 throttle since the TB blades are 100% open and the computer thinks they are only 3/4 open, therfore getting more volume of air in the engine than the computer sees. I do know that the boost PSI will be the same to the computer but the volume of air will be different due to the blades being 100% open rather then 75%. Let me know if I am wrong about this.
Thanks to Brian and Jim.
leroy
Donating Member
Larry,
What you are saying makes some sense, but the fueling strategy is well-documented in the P4 document in Section 9. The volume should be the same for a given pressure (at the same rpm and temperature). Feel free to read up on it here: http://www.sunflower.com/~leroy/P4/section9.htm
HTH,
Jim
What you are saying makes some sense, but the fueling strategy is well-documented in the P4 document in Section 9. The volume should be the same for a given pressure (at the same rpm and temperature). Feel free to read up on it here: http://www.sunflower.com/~leroy/P4/section9.htm
HTH,
Jim
The fueling is really run off of manifold pressure / rpm (main factors).
I just figured that if the computer wasn't seeing 100% WOT it might be supplying fuel for about 3/4 throttle since the TB blades are 100% open and the computer thinks they are only 3/4 open, therfore getting more volume of air in the engine than the computer sees.
The computer just doesn't look at TPS for the fueling calcuation directly. It does look at manifold pressure, RPM, air temp, etc. I don't think that having the throttle at different positions will yield the same manifold pressure & RPM value (except once the wastegate kicks in).
I just figured that if the computer wasn't seeing 100% WOT it might be supplying fuel for about 3/4 throttle since the TB blades are 100% open and the computer thinks they are only 3/4 open, therfore getting more volume of air in the engine than the computer sees.
The computer just doesn't look at TPS for the fueling calcuation directly. It does look at manifold pressure, RPM, air temp, etc. I don't think that having the throttle at different positions will yield the same manifold pressure & RPM value (except once the wastegate kicks in).
SY756
New member
Thanks guys, I may just be thinking in the wrong type of application. The only reason for my thinking is if you have a 1/2" line with 120 psi and a 3/4" line with the same pressure, of course the 3/4" line will have a larger volume of air going through it. That's why I'm thinking the way I am. I do realize that there are alot of tables that work in conjuction that control the fueling. I guess I may be just trying to put more into than needed. I will read up on that. I do appreciate all your input.