Erratic RPM Variations

kplaya186 · Post by **kplaya186** » Thu Nov 15, 2007 12:39 pm

During normal operation of driving of my car I am experiencing erratic RPM variations. Sometimes the RPM's drop, or sometimes they are higher than they should be. It seems to happen at random, but only when the car is in one of the gears (Drive or Reverse). This led me to a few ideas that could bet the problem:

1) Dirty Air Filter : I have a K&N, but I haven't recharged it in a while

2) Bad Plugs or Wires: A similar thing happened to me last year (Sputtering upon acceleration), and when I changed the plugs and wires the problem was solved.

3) The cold weather: Every year when winter comes around my car has a tendency to act up. I also have 10w-30 M1 in right now, but that is not the problem.

Anybody have any other ideas of what could possibly be wrong?

Post by **occasional demons** » Thu Nov 15, 2007 2:51 pm

Possible gear select switch getting toasted. most atx cars raise the idle speed slightly when put in gear. So there is usually some kind of communication between the tcm and the pcm... not sure how it is acheived with the Neons. Since it only seems to happen in a drive gear position leads me to that assumption....

kplaya186 · Post by **kplaya186** » Fri Nov 16, 2007 11:09 am

I would assume that once the gear selector is gone, the transmission will not operate correctly anymore? I wonder how difficult it is to change the switch?

half_twisted · Post by **half_twisted** » Fri Nov 16, 2007 1:36 pm

Sounds to me like a vacum leak somewhere. you need to check fuel pressure and make sure the pump is working, also check the spark in the coil. make sure its getting to the spark plugs. might also be a stuck open thermostat, the throtle position sensor might be loose.
have you done any recent work on the car before it started.

kplaya186 · Post by **kplaya186** » Fri Nov 16, 2007 3:09 pm

half_twisted wrote:Sounds to me like a vacum leak somewhere. you need to check fuel pressure and make sure the pump is working, also check the spark in the coil. make sure its getting to the spark plugs. might also be a stuck open thermostat, the throtle position sensor might be loose.
have you done any recent work on the car before it started.

Besides an oil change, I haven't done a single thing to the drivetrain.

Post by **occasional demons** » Fri Nov 16, 2007 7:57 pm

kplaya186 wrote:I would assume that once the gear selector is gone, the transmission will not operate correctly anymore? I wonder how difficult it is to change the switch?

The trans. would work fine just the signal to the pcm to raise idle speed will be lost, but I don't know exactly how it's acheived on the newer stuff. My 89 raider just has a microswitch in the floor shifter but I'm sure OBDII is more sophisticated. I'll have to research my FSM to see what I can find..

edit:

Post by **occasional demons** » Sun Nov 18, 2007 8:19 pm

Bump....