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Cadillac Repair/wont pick speed and stalls out
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Question
i have 1999 seville sts , when press the gas the slows{drags}, wont change gears but doesn't redline, if force it will stall out, and not start for few min, then start like nothings wrong, once warmed, still drags but i can feather the pedal pass 1st gear, wont go above 40mph(takes near mile to get there), if you floor it, it will stall not out, but not gaining speed, also just had major tune-up, replaced coil packs, new mass air flow sensor, map sensor... please can u help me
Hello,
It is a possible transmission problem, but more sounds like a plugged catalytic converter, which could have been induced by a bad mass air flow or map sensors.
Chances are good both sensors had not failed at the same time, however the failure of either sensor puts the computer out of loop and the engine will not run properly with a rich condition plugging the cat.
I would also bet on this being the problem because un burned exhaust with a mixture of gasoline will plug the cat.
You can drop the cat in and if available, install and drive down the rod and see if power changes. Some guys used to run these in place of the cat, but is illegal and the computer is designed for the back pressure of the cat. Running without one for any extended time is bad on the engine.
You could take the vehicle to a service garage with a dynomonitor and they can pull the cat and immediately see the difference in power. Have a cat installed and you should be good to go.
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Rob Painter
Expertise
Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?
Experience
Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.
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