On Mon, 3 Jan 2005, KWS wrote:

> I've been noticing a vibration while accelerating that seems to go away
> once the speed is constant. When the car is at a stop, the engine revs
> freely. This vibration is not accompanied by a loss of power. It feels
> like a wheel badly out of balance or, perhaps a driveshaft weight has
> fallen off.

Could be an out-of-balance wheel. Could be a worn-out inner CV joint.

> The "check engine soon" light is on and the (on off on off on) code reads
> 12, oxygen sensor. The oxygen sensors have never been replaced in the car.

Code 12 does not indicate a faulty O2 sensor. Code 12, retrieved via the
flash-code method, means "Start of Codes".

To check the computer codes:

With the engine off, switch the ignition key on-off-on-off-on,
leaving it "ON". Do not
go to "start", just "on" during this procedure.

Watch the "Check Engine" or "Power Loss" light. It will turn on, then go
off, then will begin to flash-out any trouble codes that have been stored.
For instance, if it flashes:

flash <pause> flash flash
<long pause>
flash flash flash <pause> flash flash flash flash flash
<long pause>
flash flash flash flash flash <pause> flash flash flash flash flash

Then you have a 12 (one flash followed by two) a 35 (three and five) and a
55 (five and five). 55 means "end of codes" or, if by itself, "No codes
stored. Check the codes and report what you find.

> I'll replace the oxygen sensors (are there only two?).

Believe so. Use Mopar, NAPA Echlin, NTK or Standard-Bluestreak. DO NOT use
Bosch.

> Might a faulty O2 sensor cause intermittent timing signals

No.

> I thought about the spark plug wires (these are still the originals)

You're long overdue. Replace them. What else have you been neglecting
aside from the O2 sensors and the spark plug wires?

> but concluded that the problem would still be evident at idle and when
> revving the engine

False.

> Injector problems: again...it only happens under acceleration.

So?

> Any other thoughts would be appreciated.

Step one: Catch up on all the periodic maintenance you've let slide. That
means new plug wires, service the entire PCV system, clean the throttle
body and AIS, new fuel filter (which all by itself could very easily cause
your surge), O2 sensors, air filter, spark plugs.

Step two: Check the codes correctly and post what you find.

Step three: Proper diagnosis rather than guessing.

DS