1. Home
  2. Subaru Cars Forum
  3. 04 Forrester missing on damp mornings

04 Forrester missing on damp mornings

My 04 Forrester is missing on wet mornings - enough to get the "check engine" light to come on. Once warm, everything is ok. There are 136k km on the electrical parts of the engine, but only 50k km on the short block. Had the thing undercoated about 3 weeks ago with "Rust Check".

My guess is probably plug wires ($134.00 from dealer) or coil ($218.00 from dealer). Neither are a huge expense, but more than expected.

Any thoughts from the group? Will the OBC put the engine in "rich" mode after it detects a fault? Will it clear automatically or do I have to clear the memory with an OBD reader? Gas mileage has dropped a bit. I have yet to start it up in the dark and have a look for leaking plug cables - its been raining and very windy here for the last week from a storm front.

Thanks in advance.

Reply to
4orrester
Loading thread data ...

It does sound like classic high voltage problems. If you want to track this down for DIY purposes, one trick is to look around at night for arcing as you seem to know. Also, using a mister bottle to isolate - say - one side of the car from the other or coil/wires etc. is an old trick. Did the misfire code(s) come from the same cyl? If it's all cylinders - and has persisted for more than a coupla tanks of gas, could be igniter/coil (does you car have a single 'coil pack' or individual coils?) if the code is always the same cylinder - could just be that wire, or even a single bad plug. You'd expect a plug not to be sensitive to moisture - though I suppose the ceramic could crack....?????

If the car is experiencing a miss, gas mileage will drop. After you make any repairs/adjustments the car will 'adapt' after a few drive cycles, and everything should be OK.

Reply to
1 Lucky Texan

pull the wires off the coil and look. Sometimes one coil post and wire will be badly corroded. Also get the codes read and see if its a specific cylinder.

Reply to
StephenH

pull the wires off the coil and look. Sometimes one coil post and wire will be badly corroded. Also get the codes read and see if its a specific cylinder.

I found the culprit ( I think!). The single coil pack on top has what appears to be a wormhole through the bakelite just under where the plug wire attaches on #3. There was also the telltale white streak of an arc radiating from the boot of #3 wire at that point. I put some Si grease on it for now to seal out the moisture. I have no OBD reader, but should probably buy one. The check eng light is on constantly now. Will the fault clear itself or do I have to clear it by disconnecting the negative battery terminal or use an OBD reader? We've had 146% of normal November rainfall - and it is only the 7th, with 4 more days of rain on the way.

Thanks everyone!

Reply to
4orrester

Some of the auto parts stores will read/clear codes for you for free...on the assumption that you are going to buy the parts to fix the problem from them. FAS (Fleenor's Auto Service) is one such in Indiana...don't know where you are/who the stores are there, or which would do it for free in your area?

Reply to
Jack Countryman

Around here, Autozone and similar will read - but claim they are not allowed to clear - codes.

Disconnecting the battery, stepping on the brake pedal, and waiting several minutes(10-15) SHOULD reset the ECU. Because the monitors will need to complete, and, especially on older cars, because the ECU will use the 'factory map', you will not pass most State emissions tests and the car may run oddly for the first few drive cycles while the ECU readjusts for older sensors.

If the check eng. light comes back on - do have it read as there may be another problem. It is not uncommon to have several codes and some folks don't scroll down past the first one on the readers.

Reply to
1 Lucky Texan

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.