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CEL comes on only on deacceleration??

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Old 07-30-10, 09:13 PM
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CEL comes on only on deacceleration??

Ok driving my car today when im applying throttle weather it be full or very slight my cel is off but the slight second i take my foot off the pedal the cel come on, i can do this over and over....and when i let off the gas and let it go to idle it tries to but dies... If i come to a complete stop turn the car OFF and let it sit for a second then crank it back up it idles perfect untill i start to drive then it does the same...i pulled codes and got nothing 89 TII rtek 1.5...what could cause this??
Old 07-31-10, 01:42 PM
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would a bad boost sensor cause this??
Old 07-31-10, 03:07 PM
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pull the code out! that's why its there
Old 07-31-10, 03:44 PM
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like i said i pulled codes and got nothing.... read!
Old 07-31-10, 05:12 PM
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Originally Posted by currdog
like i said i pulled codes and got nothing.... read!
hmm weird, i'd suspect the TPS before um anything else
Old 07-31-10, 07:34 PM
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i set the tps at 1ohm after i warmed up the car...and that made it start to do the bouncing idle??? so i just adjusted it until it didnt do that anymore and i drove it with no cel...but no my alternator is only putting out 12volts!!!!!
Old 07-31-10, 10:27 PM
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I had this last week new cats and all is good I also no codes 1990 na vert.
Old 07-31-10, 10:30 PM
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your phone goes off when you deccel cool you shouldt fix that its a good parlor trick....
check the O2 sensor... just a though had it happen to a 89 tII a month ago or so
Old 07-31-10, 10:34 PM
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Originally Posted by currdog
i set the tps at 1ohm after i warmed up the car...and that made it start to do the bouncing idle??? so i just adjusted it until it didnt do that anymore and i drove it with no cel...but no my alternator is only putting out 12volts!!!!!
Use the multimeter to check for voltage output in case you're relying on the voltage gauge. Red lead to the B+ connection on the alternator and black lead to ground and measure while idling w/no accesories turned on.
Old 08-01-10, 01:29 AM
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did that i messured it right out of the back of the alternator...just put a new bosch o2 on 3 days ago also
Old 08-01-10, 02:37 PM
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Originally Posted by currdog
i set the tps at 1ohm after i warmed up the car...and that made it start to do the bouncing idle??? so i just adjusted it until it didnt do that anymore and i drove it with no cel...but no my alternator is only putting out 12volts!!!!!
the CEL for most things (the exceptions are in the FSM, and its clearly labeled) only come on for an open or short circuit.

i like to adjust the TPS with the lights, as in the FSM. the lights are an output FROM the ecu, the 1ohm is an input TO the ecu. the lights are the ecu's way of telling you its happy. the ohm meter method does not take the wiring harness or any variance in the ecu into account. its not wrong, but i feel the FSM method is better. and certainly put the ohm meter on the tps and check for dead spots

so if the TPS is correct at idle, but has an open spot somewhere, it could cause the issue. the 02 doesn't have a direct code, it has 17 and i think 15, which relate but aren't directly tied in. again the FSM has a clear definition of the codes, but i think 17 is something like o2 sensor voltage is too high too long, which could be a bad o2, or it could just be too rich for another reason

however since the battery voltage is really low, i'd worry about that, low voltage might also cause the CEL.
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