98 Legacy with 2.2L engine, 150K miles

 

The acceleration is not bad, but the MPG is abysmal, about 22MPG on highway.

 

Upon acceleration, in the review mirror, I can see black smoke so I know it's running really rich.

 

I am getting codes P301 and P302.

 

The plug wires and spark plugs are new.

 

What else could it be other than the coil pack?

There may be a problem with the crank sensor signals but the coil would be the biggest suspect I would think. You could try swapping the coils and see if that changes things.

All coils are replaced as a single unit as far as I understand?

 

Where is the best source to get one, the local dealer? I am not sure I would trust with this to an aftermarket part.

onlineparts, dealer oem parts cheaper, but you either have to plan ahead or wait.

 

https://www.subarugenuineparts.com/oe_parts_cat.html

 

http://www.subarupartsforyou.com/cp_partlistbymod.php?model=Legacy&subcat=Exhaust%2C+Front+Pipe&year=1999

 

https://www.1stsubaruparts.com/partscat.html

I've got used ones for 20 bucks plus shipping.

 

Mostly Diamond brand.

 

They rarely go bad (especially these Diamonds).

 

But if you plan on keeping the car a good long time I'd probably buy a new one to have a firmer foundation in the future when accessing wires and plugs.

You got mail.

 

Plus thanks for the links above.

davebugs,

 

Thank you.

 

I put the new coil pack in yesterday, cleared the codes, drove about 60 miles since then in all kinds of conditions -- no codes. The coil pack the car came with was bad, as were the spark plugs and the wires. I replaced these too (a few months ago) and that helped also.

 

The mileage improved unbelievably. It was incredibly bad before, I don't think I was hitting 20mpg even. It was drinking gas like a V8 and doing that scary CEL flashing so I knew it was misfiring.

Now at 60 miles since fill-up and the gauge is only at 1/8. I know the gauge is not accurate but it was abysmal before the coil pack swap.

 

Mental note: Coil packs go bad.

Glad it worked for you. We like happy endings and resolutions to threads.

 

Mileage like that can't be good for cats and they are expensive.

I figured so.

 

I got this Legacy at a dealer only car auction. I paid $1200 for it plus about $500 in fees plus about $300 in parts, around 2 grand total. I think I did "OK" but I see similar deals on Ebay, sometimes with lower miles and in better shape but usually with 5 speed it seems. This time, I just had to have a auto.

 

The point here, coming from the auction, I don't know how long it was driven in this misfiring condition with codes P301/P302 and such. I hope not long. In any case, I don't see the loss of power that happens (I presume) with a plugged cat.

Still, a scary thought on how much unburned fuel must be in the system if it got maybe 20mpg.

 

My next mini project is to replace the O2 sensor, the upstream one, to improve MPG. At 150K miles, the current one must be half-dead.

7/8" box wrench and your favorite penetrating oil, and a hammer to break it free. I'd try and get it in the air as much as possible.

 

If you unplug it the box end will fit over the connector.

I had a similar experience to ETC's. The car was 1-2 mpg less than advertised and eventually I got some misfires in the morning when the engine was cold before the P301 MIL came on.

 

The coil packs are right in the front of the engine and when I tested mine, the secondary resistance was nearly double than what was speced in the Haynes manual.

 

I change the coil pack out for a Borge-Warner. I was glad that the price was much more reasonable than other individual coil systems ($88 for the pack of 4 verses $60 for one).

 

The misfire problem is solved. I'm eager to get a mpg readout! From the feel of the car, I moved in the right direction.