Started getting an intermittent misfire occurring recently, typically at highway speeds, but no CEL. Yesterday the stumble occurred again, this time more severe with the engine nearly stalling on the highway - was lucky to get to the shoulder of the road, then engine smoothed out after slowing down. This time the CEL illuminated, and after limping home with no further stalls the scanner indicated a P0351 ignition coil malfunction. So my plan is to swap coil #1 with coil #4 and see if I get the code to come back as P0354. If so, it's a replacement of that coil. If the code occurs with P0351 again (or P0352 or P0353), would that mean that the coils are OK, but it's the engine control module failing? That's a concern I have based on how the stall occurred on the highway - didn't seem like just one coil failing as the engine pretty much lost all power. The car is 19 years old now, with 108k on the odometer, so is it likely the ECM is the culprit as opposed to the coil(s)?

 

Swap coils as you state. If still the same could could be an wiring issue to the coil.

 

So I swapped the #1 and #4 coils, and so far no CEL, and no further events where it nearly dies (yet). It does seem to have a misfire that can be felt at highway speeds, but hasn’t thrown any codes yet.

Can anyone recommend a good diagnostic device to plug in to the OBD port that will provide deeper analysis of the cause of the misfire? Otherwise until it logs another failure code I don’t know where to start troubleshooting.

 

Any chance of a wiring issue that worked itself out when changing coils?

What are you trying to accomplish and how? There are hand held scanners, Bluetooth, USB connection to laptop, etc. Price range?

You will need a scanner that reads ODBII and Toyota codes.

Might change all the coils as SOP with a decent brand name.