1999 Z28 will not go in to open loop at wot. please help

 

need more info, please post

 

car is running lean can only get wide band down to 14.1 at wot hooked a scan tool to car, it stays in closed loop at wot is it supposed to ? i thought not but mechanic told me newer cars stay in closed loop at wot. if this is true how am i supposed to richen the car at wot with predator, as of right now the pretador enrichment is maxed at 5%. checked for vaccum leaks fuel pressure and volume tried installing oem maf sensor and no help car still runs between 14-15 at wot. i cant understand that predator cant give my car enough fuel with the few mods i have. any suggestions please desperate thanks

 

hmmm... has the car always done this or did it just start doing this?

WOT is open loop on our cars (not sure of any newer cars that stay closed loop at WOT, but suppose it's possible... specially on some imports that come w/Wideband from the factory)

how is the car at normal driving? does the wideband report around 14.7:1 ? (bouncing between 14.5 and 14.9 or so)

Can the predator scan commanded air fuel ratio? if so scan that... if the commanded stays at 14.62:1 or so then there's definetly a problem ... possibly TPS sensor since TPS plays a role in going into PE (though should set an inactivity code .. unless it's maxing at like 35% or so)

You can measure the TPS sensor w/a volt meter... should be .5 volts or so closed , 4.5 to 4.7 volts WOT ... measure at the TB first, if that checks out measure using the gas pedal (car off but in run position) .. possibly your throttle cable has too much slack and isn't opening the TB up enough to require PE mode...

Also check the car when you first start it up... log commanded AFR if you can, but also check the wideband... when you first start your car it should default to open loop until the car's warmed up... so check what the AFR is on startup

doubtful that your injectors are maxed since it sou8nds like you don't have a ton of mods (but would be useful if you'd post up what you've done to the car) ... if you can log Injector Pulse width w/the Predator that'll tell you if it's the injectors maxing...

also if you have a bad fuel injector it'll cause a ton of air to go downstream making the wideband think you are lean when you may not be...

But to start... if you can log commanded AFR it'll tell you if the car is actually going into Open loop or not (also as mentioned , check your AFR on the WB at startup to see if it's running richer than when in closed loop) and check your closed loop AFR to make sure that's ok (make sure the wideband is reporting accurate values)

Checking the TPS sensor w/a volt meter is the easiest way to start though ... (or if the predator can scan TPS Voltage you can do it through the OBDII port)

 

wide band seems to be correct stays around 14.6-15 ish durring cruise. tps is working correctly goes from 0% to 99.5 using tech 2 scanner but scanner says the car is still in closed loop at wide open throttle with tps @ 99.5% there is no way injectors are maxed from what i understand but you say that the car should go to open loop at wot?

 

ttt!!!!

 

hmmm... at WOT and initial startup the car goes open loop ... as far as I can tell the PCM uses engine temp, MAP , and TPS to determine Power Enrichment at WOT (which is a form of open loop)

looking at a stock tune, so long as MAP is >15kpa , engine temp is below 284, and TPS > 54% at 4000 RPM , it should use the Power Enrichment to add fuel at WOT...

the PCM will default to the richest condition... either the PE or the Open Loop vs ECT table...

at startup what is the AFR on the wideband? what is the commanded AFR ? (should be a commanded AFR pid , or AFR commanded... not sure if Tech II can check it but it exists)