Vehicle: 1997 Legacy Outback with 260k with manual transmission... but it has a replacement 2.2L engine so actual mileage on engine is unknown. 

Sometimes when I am in traffic and come to a stop suddenly, the engine stalls. When I restart it only is firing on 3 cylinders.  If I drive it for a little then turn off the engine.. and wait a minute then restart, it is back to firing on all 4 cylinders. 

 

So far, I have replaced plugs, plug wires and ignition coil and I have regularly added SeaFoam gas treatment to the tank when filling up.  Driving it does not clear up the misfire but stopping it and restarting seems to do the trick. 

 

I should add that when I bought the car in September, it had no exhaust system... it has separated in front of the cat-converter.  It's not required in a car of that age in Michigan so I had the exhaust system fixed absent the catalytic converter and just let the O2 sensor hang there... (I guess).  

 

Also, I just noticed that if I drive the car hard (which I never do) and floor the gas going through the gears, before I hit full revs, the car cuts out.  I have only done this twice as I am afraid I might make something worse... or permanent. 

 

I would like to have some idea of what is wrong before I take to a mechanic.. in case I can't fix it myself so I am not victimized. 

 

Thanks in advance for any suggestions as to what might be going on here.  I've been around cars and tinkered with them for years but this is a first for me. 

 

Thanks

Edited May 13, 201411 yr by revtim

Is it the front sensor that's just hanging or the rear sensor?

Rear sensor doesn't matter you can remove that entirely it won't affect the way the car runs.

Front sensor it needs for fine tuning the fuel mixture or else it will just run in open loop all the time. This will cause strange power problems and possibly misfires and stalling.

 

The other big things to cause stalling, especially when coming to a stop, are vacuum leaks or a sticky Idle control valve.

I'd say you have 2 choices, either install a cat and put the o2 sensor in or engineer/install an aftermarket injection and ignition system.

 

You're probably wasting a quarter of your gas anyhow.

 

 

Vehicle: 1997 Legacy Outback with 260k with manual transmission... but it has a replacement 2.2L engine so actual mileage on engine is unknown. 

Sometimes when I am in traffic and come to a stop suddenly, the engine stalls. When I restart it only is firing on 3 cylinders.  If I drive it for a little then turn off the engine.. and wait a minute then restart, it is back to firing on all 4 cylinders. 

 

So far, I have replaced plugs, plug wires and ignition coil and I have regularly added SeaFoam gas treatment to the tank when filling up.  Driving it does not clear up the misfire but stopping it and restarting seems to do the trick. 

 

I should add that when I bought the car in September, it had no exhaust system... it has separated in front of the cat-converter.  It's not required in a car of that age in Michigan so I had the exhaust system fixed absent the catalytic converter and just let the O2 sensor hang there... (I guess).  

 

Also, I just noticed that if I drive the car hard (which I never do) and floor the gas going through the gears, before I hit full revs, the car cuts out.  I have only done this twice as I am afraid I might make something worse... or permanent. 

 

I would like to have some idea of what is wrong before I take to a mechanic.. in case I can't fix it myself so I am not victimized. 

 

Thanks in advance for any suggestions as to what might be going on here.  I've been around cars and tinkered with them for years but this is a first for me. 

 

Thanks

Edited May 14, 201411 yr by uniberp

I didn't know there were two sensors.  Can you tell me where the front and rear sensors are located and attached?  

 

Also, is the idle control valve something one replaces or cleans when it is sticking?

Edited May 14, 201411 yr by revtim

One O2 sensor is screwed into the front cat and the other is into the rear cat.

I pulled the trouble codes on the car.  It showed one O2 sensor failing.  That would be the rear one as the small cat converter is still in place. Only the big cat convertor was gone when I bought the car.  The codes also showed random misfires but nothing on vacuum leaks or the idle control valve.

 

is it possible there are vacuum leaks or that the idle control valve could be causing the problem even though there are no codes indicating such? 

Yes. All the computer can look for is an electrical problem. There is no way to monitor every vacuum hose in the car for breakage. Well there is, it would just be expensive as hell to put a sensor on every hose.

 

The IAC can be stuck and the computer wouldn't know because its still electrically connected.

 

Was the O2 code for sensor 1(front) or sensor 2(rear)?

If the ECU can't control te idel through the IAC it will cut fuel to #1 cyl to limit over rev.....

 

fix the other weirdness.....and clean or replace the IAC.

Single or dual port heads?

 

I have dual port y pipes and cats,  Shipping would be a bit from CO but cheaper than buying new.

How do you know only one cylinder isn't working when the trouble happens? Have you proven that? I could see two not working due to an electrical problem but not just one, unless there is a mechanical problem with the cylinder.