Expert: Roland Finston - 8/1/2011

Question
we have a 2002 Chrysler Concorde. originally, it has a 3.5 engine.  It died and we told we could replace that engine with a 3.2. We did, but the car is not working. Should we now replace the computer box?

Answer
Hi Keisha,
The 3.2 and 3.5L engines are basically identical except for the bore of the cylinders differ in diameter by 4 mm. While there is presumably a programmed factor in the engine controller that differentiates the volume of air and therefor the concurrent volume of fuel injected to balance that 10% difference in dispacement, the engine controller wiring and functioning would otherwise be identical. My inclination would be to determine exactly why the 3.2L engine is not functioning rather than buying another part and hoping that will solve the problem. Unless a code readout shows that the fuel/air mixture is out of balance, I would believe that there is something else that is causing the 'not working'. Do you mean it won't start and idle?
There is a self-diagnostic capability that can be accessed both with the ignition key and by a plug-in fault code reader. If the vehicle is still in the shop ask them to find out the fault codes and take action accordingly. If you have it and you don't have a fault code reader, then turn the ignition key "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see the mileage be replaced by a four digit number preceded by a P. Let me know and we'll go from there.
Putting in a replacement engine has many details so I would believe something has been overlooked rather than that an engine controller needs to be replaced, at this stage. If you get codes also let me know what exactly is happening when the starter is tried.
Roland