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96 T&C problem

Looking for a little advice.

1996 T&C 3.8L, 150K miles.

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.

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.

Here's what I have been thinking:

I'll replace the oxygen sensors (are there only two?). The light has been coming on and off periodically for over a year. Now it seems to be on constantly. The appearance of the problem is coincident with the check engine light constantly on. It appears to be more pronounced and more consistent; it gradually has gotten worse.

Might a faulty O2 sensor cause intermittent timing signals which results in a surge under acceleration? Remember, it doesn't hesitate at all when revving without a load.

I thought about the spark plug wires (these are still the originals) but concluded that the problem would still be evident at idle and when revving the engine, which it is not.

I read someplace about transmission slippage. The vibration is not accompanied by changes in engine RPM, which I would expect to see if something in the transmission were slipping.

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

Any other thoughts would be appreciated.

Thanks,

Ken

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

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 flash flash

flash flash flash flash flash flash flash flash

flash flash flash flash flash 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.

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

No.

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

False.

So?

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

Reply to
Daniel J. Stern

Your van is exhibiting the typical symptoms of a bad, inner CV joint.

Reply to
SN

Daniel,

Thanks so much for the great feedback. Please see my comments:

The wheel would stay out of balance when the speed is constant. Another poster also mentioned the CV joint. Would it also tend to clatter on sharp turns?

Absolutely correct. The code was "21". My mistake.

I drew this conclusion from other cars that behaved this way.

It is also periodic, i.e. not erratic. A wheel out of balance, for instance, would have a periodic characteristic and would also occur at a constant speed. Would injector problems not be erratic?

While the fuel filter probably needs a change, would it not cause an erratic response?

, O2 sensors,

air filter - done

spark plugs - done

Thanks. I appreciate your help with this.

Reply to
KWS

How do you diagnose which one is bad?

Thanks!

Reply to
KWS

Theoretically, yes. Practically, most of the time, yes. Occasionally...no!

Usually it's the *outer* CV joints that make snapping/popping/clattering noises on sharp turns. Sounds like one or more of your four CV joints is badly worn.

Wondered if it might've been 21.

Lean surge is periodic.

Lean surge is periodic.

DS

Reply to
Daniel J. Stern

If the vibration worsens when steering to the right, it's on the left side. And vice versa.

But you still need new plug wires and suchlike.

Reply to
Daniel J. Stern

Thanks, Daniel. I'll check it out.

Ken

Reply to
KWS

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