QuestionThanks for the quick response !!
Does it make sense that when I unplug the TPS it makes no difference ? I understand that when it is unplugged under normal conditions the computer runs in a sort of default mode. I would think that if the TPS system was the real problem
when I unplugged it when it was in the rough running condition it would default and run better.
Mike
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Followup To
Question -
I have a 91 Olds cutlass ciera with a 3.3 V6 and Multi Point Fuel Injection. The car is setting a 21 trouble code which relates to the throttle position sensor. I replaced the sensor and am still getting the same code. The problem is intermittant. When the light comes on the RPM's increase and the engine runs extremely rough and sometimes stalls and is extremely hard to start. I checked the voltage to the the TPS and it measures per spec. but have not been able to check it when the check engine light is on. I can drive the car for hours and it will run fine and suddenly the check engine light will come on and it will start running rough and die. I have checked vacuum lines for leaks and wiggled most of the underhood wiring and found nothing. I have unplugged the TPS connector while it was running fine and driven the car and and it doesn't seem to make a difference. I also managed to unplug the TPS while it was running in the rough mode thinking that it might improve and it did not change. This leads me to believe that it must be another component, not the TPS setting the code 21 but I don't know logically what part to replace next.
Any Ideas ?
Thanks for your help !!
Answer -
Hi Mike,
I would just need to check both ends of the wires. A loose connection is what it sounds like. If you are good at that type stuff, get the little tool that pushes the connector ends out of the connector, and one at a time, tighten them up. Check the condition of the crimped on ends also, as well as feel the wire for breaks inside the sheath.
But you will need to go to the ecm also, and check the same wires on that end.
A couple others to check are the ground wires at the engine, and under the dash, near the instrument cluster.
Van
AnswerHi Mike,
The mode you are talking about is called the limp-in mode.
When in that mode, sensor values are not used to calculate and change the fuel/air mixture. Like you said, default values are used.
I would assume it is already in the limp-in mode when you unplugged the tps, and therefore, no difference will be noted.
When in that mode, you do change the amount of air entering, since that is a mechanical control to the throttle plate, but the fuel doesn't change.
The rough running condition is what the default mode should cause, since the mixtures and timing are only guesses, and not ecm controlled .
