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94 3.5L Rough Idle, No codes or MIL code 12


mimzie
05-07-2010, 08:33 PM
We recently got this car from a guy that had the transmission rebuilt, ran maybe 2k miles on it, went over some railroad tracks (I'm guessing a little fast but no clue) it starts sputtering. He took it to a shop where they said a sensor was out so he parked it. (He does not remember which sensor, I'm guessing his isnt mechanically inclined?) Now 2yrs later, we have this car and trying to figure out what the problem is?

The first day we got the codes from the key switch and we got Code 12 (battery had been disconnected) Then we got the code for the throttle positioning sensor so we changed that, same problem, no change at all. We then unplugged the MAP sensor to see if it would throw that code, it did, plugged it back in, code eventually went away. We changed some gaskets (manifold gaskets? Not sure what they were all called but we had a lot of stuff off so changed them because it just made sense to do it then instead of waiting til it really needed it) We changed wires and plugs also. We took the EGR valve off and cleaned that out, put it back on (we did not test it with a vacuum but it seemed to work fine) Same problem, Loosened the catalytic coverters, louder but no change. Got a used PCM from junk yard (didnt want to buy new if it wasnt the problem) Same thing, got a 2nd used one (traded it) just in case that was bad, same problem, no change. Also unplugged the O2 sensors, no change.

Yesterday after unplugging all the sensors we could get to it threw a bunch of codes 12, 14, 23, and 24 if I remember correctly. It did give them in random order too, not sure if that's normal but it gave me 12, 23, 24, then 14? Today all codes are gone except code 12!! HELP!!

Adding a bit more info that I just remembered: It idles VERY rough, it will idle fine for a few seconds (maybe 5-10 seconds) then idle down like its going to die, sometimes it dies, sometimes it doesnt. If it doesnt die, it goes back to normal idle and idles fine again for 5-10 seconds (there's no pattern in it though). If you press the gas it idles very rough, we havent drove it really but it would be very hard to drive with it sputtering like it does when you press the gas! When it almost dies, the cruise light flashes, sometimes the check engine light flashes also but not normally, only did yesterday when we unplugged sensors.

Rachel

j43rsr2
03-06-2011, 02:41 PM
on spme of those throttle body posotioning sensors they need to be set with an ohm meter

mimzie
03-06-2011, 03:10 PM
The timing was off on this car which was making it idle rough and all the other problems it had!! We checked EVERYTHING, changed a few parts out, then took the timing cover off and saw the 1 mark was barely off!! Fixed it and it has run great since!

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