bucking then stall, now running fine

[ron917]

'99 Legacy Outback wagon, auto trans, 108K miles. Head gaskets, timing belt, all engine seals, water pump, spark plugs, belts and hoses replaced 2 months ago.

 

The car has seemed a little sluggish intermittantly lately - power would be off a bit, then it would recover. It hasn't been bad enough to force me to investigate.

 

This morning, as I accelerated from a stop light, the car started bucking, then recovered. After the next stop light, the car started bucking again, then stalled - at this point, the CEL came on. Coasted off the road, and tried to restart, but it wouldn't catch.

 

I opened the hood and poked around a bit. Two ignition wires on the coil pack, both on the passenger side, seemed a bit loose. I reseated those. The car started instantly when I tried again, and I made it to work with no further issues.

 

Check engine light is OFF. This is the first time I've had a problem with an OBD-II car, so I'm not sure if the ECU would store a code and not turn on the CEL. So, is it worth it to stop at AutoZone and get it scanned even though the light is off?

 

What are the usual suspects for this type of problem on this car? I'm guessing the coil pack or crank position sensor. Or maybe I got lucky, and it was just loose ignition wires.

 

Thanks for any advice.

 

-Ron

[ron917]

OK, now it stranded me on the way home from work. Sputtered, then stalled, was able to restart and go another mile or two. Repeated that twice before I parked at a shopping center and called my wife for a ride home.

 

Still no Check Engine Light, except when the car stalls after running for a bit. The CEL goes out when (if) it restarts.

 

When it's running, there's a definite miss and no power.

 

I'm debating weather to get it towed home or to a shop tomorrow.

 

-Ron

[friendly_jacek]

Yes, the code is probably stored in the memory, CEL off indicates that there is no detected fault at the present.

 

Double check the ignition wires. It the wires/coil is OK, get the code, maybe O2 sensor?

[ron917]

Thanks. Went to fetch the car this morning, and it's running fine again

 

I was hoping the ECU would store some info. I did some more research, and looks like OBD-II will store a code and snapshot sensor info when the CEL lights. Hopefully, there is something useful in there.

 

I ordered a scan tool and the FSM, both of which I've been meaning to get for a while now. Not cheap, but they will probably pay for themselves quickly.

 

These intermittant problems are the worst. I'll get to the bottom of it eventually, I've been through this before on other cars. It's always something simple, but it takes forever to track it down.

 

I'll update the thread when I know more, hopefully it will help someone else.

[ron917]

The car has been running perfectly for over a week now, so I guess I can call it fixed.

 

The problem was....loose connector on the crank position sensor.

 

What's annoying is, car never threw a code or lit the check engine light. Since it wouldn't misbehave in my driveway, checks with a VOM and oscilloscope were inconclusive. I found the problem by disconnecting and reseating every connector I could find. The CPS connector wasn't "clicked" on to the CPS - it came right off, and I had to push hard to get it to click. I guess the connection was OK until it heated up a certain amount, then it would get flakey, and on cool-down, it would be OK again.

 

Prior to finding the loose connector, I checked the spark plugs (new Densos, all good) and all sensors per the FSM. The O2 sensor was a little sluggish, everything else was OK.

 

Yesterday, I changed out the O2 sensor. I also replaced the fuel filter, ignition coil, ignition wires just because of age/mileage. That cleared up some roughness when idling.

[idosubaru]

if a loose connector was the suspected cause might be worth the trouble to have a look inside the connector and make sure there's no corrossion or dirt in it from not being seated tightly.