#1 misfire

[jseabolt]

Can some one explain how the misfire monitor works on a 2003 Baja?

 

I mean does it actually monitor the ignition system or can an issue with a fuel injector cause this to also set off the monitor?

 

I have a 2003 Baja 2.5 non turbo, 5 speed with 62,000 miles on it and all of a sudden within the last couple of days I noticed the engine idles rough on a cold start.

 

Then at times even after the engine has reached normal operating temperature, I can feel it misfiring at idle and even see the RPMS drop when this happens. And I can feel it under slight accelaration sometimes.

 

This morning after getting off work I started the car and allowed it to warm up because it was so humid my windows kept fogging up on the inside. After a couple of mnutes the check engine light came on.

 

When I got home, I plugged my code reader in and it said the engine monitor detected a #1 misfire. I cleared the code and restarted the engine. The check engine light never came back on.

 

This afternoon, I started the engine and it started rough again and was around 75F instead of 40F this morning and it misfired at redlights on the way to Wal-Mart even after the engine had already warmed up. But the check engine light never came on. After leaving Wal-Mart and onto work it I never noticed anymore misfires.

 

It seems to be a randomly occuring event with no particular pattern.

 

But this isn't the first time this has happened.

 

This time four years ago the check engine light kicked on as I was driving down my driveway. Then before pulling out onto the road, all of a sudden it went off.

 

Highly unusual that the check engine light would go off on it's own. With other cars I've always had to disconnect the battery for 30 minutes or have Autozone reset the ECU to get the light to turn off. And usually it comes back on with 30 seconds.

 

I took it to the dealer to get it's 30K mile checkup and told them about it. They said the ECU stored a #2 misfire code and they said they cleaned some corrosion off the plug wire.

 

Supposably they also installed new spark plugs but not new wires. Are new plugs part of the 30K mile checkup?

 

A few months ago at 60K miles I pulled the plugs and they looked good. I beadblasted and regapped them anyway and put them back in. Maybe the cheap way of doing it but I've done it on other cars and lawnmowers I've owned.

 

I'm just curious is it common for an 8 year old Subaru to need new plugs or plug wires this soon? Usually a set of plug wires are good for about 100K miles.

 

I think the cheapest thing to start out with are new plugs, see what happens before installing new plug wires. Since they are not standard plug wires (extra long boots) they can't be resonable.

 

What I don't understand is the engine is obviously misfiring but the monitor has only detected it once in this latest eposide. Looks like if it's misfiring every 15 to 30 seconds, it would detect it more often.

 

Just wondering what my plan of attack should be. I guess if the plugs don't fix it, then try new plug wires and if that doesn't fix it, then suspect the coil pack perhaps?

 

Anybody have any experiences or opinions with this same issue? Thanks.

Edited April 15, 2011 by jseabolt

[Rooster2]

Just wondering what my plan of attack should be. I guess if the plugs don't fix it, then try new plug wires and if that doesn't fix it, then suspect the coil pack perhaps?

 

Your above statement is exactly what I would do in that order. It does sound like an electrical ignition problem. You might wait until dark, start the motor, then spray water or Windex on the wires to see if you can induce an electrical arc (spark) from a bad plug wire shorting out. This is an ez and cheap way to find a bad plug wire.

[johnceggleston]

my 97 outback did this every now and then. the worst time was whan the weather went from cool to warm and humid over night. the conditions were so weird, moister was condensing on the engine block and heads.

 

it also happened after several days of hard rain.

 

i would suspect the wires or coil before the plugs since those are more exposed to the weather. but the plugs are not too expensive, at least bot for 96 - 99 ej25, so doing them as well can't hurt.

 

a test you might try. at night with the engine running, use a water mister to spray around the engine, look for ''lightning''.

[94Loyale]

Any oil in the plug wells? Bad plug well seals (extremely common) will make a good misfire when oil leaks in there. Otherwise, I would probably change the plugs. Coil packs are not the common of a failure. When I do see them fail, they fail good and crack on the outside, then you can really see arcing.

[unibrook]

If you haven't replaced your front 02 sensor in the last 40k miles, try that.

Worked for me.

[MilesFox]

I bet on the wires themselves. if they are the oem original wires, 60k is long enough on them.

 

if you read about misfire codes often enough, the general consensus is plug wire related, and that subarus are finicky about cheap wire sets versus NGK oem sets.

 

go for the NGK brand, and use dielectric grease on the boots. this should cure you, and the problem is always wires and never plugs.

[jseabolt]

I bet on the wires themselves. if they are the oem original wires, 60k is long enough on them.

 

if you read about misfire codes often enough, the general consensus is plug wire related, and that subarus are finicky about cheap wire sets versus NGK oem sets.

 

go for the NGK brand, and use dielectric grease on the boots. this should cure you, and the problem is always wires and never plugs.

 

Thanks the suggestion about misting the wires with water. I got home and did that and my #1 plug wire looked like a Tesla coil! I could even see blue lines from the boot at the coil pack.

 

Now the car starts idling really rough and the check engine light started flashing!

 

I looked at the number on the coil pack and sure enough it was the #1.

 

I went to Advance and got a new set of NGK plug wires for $47. Installed them in 15 minutes, cranked it up and it idles like a new car.

 

I cleared the code and all seems fine now.

 

Now why did the #1 plug wire crapped out but the others seemed to be OK? Well I discovered that the boot had popped off the spark plug or I did not get it on very well when I pulled the plugs 3000 miles ago. So juice must have been was jumping from the boot to the spark plug.

 

Could that have cased this wire to go bad?

 

By the way, you mention Subarus use NGK plug wires? Well just like Subaru oil filters are made by Purolater , Advance auto sells both Purolator and NGK plug wires. For what it's worth.

Edited April 16, 2011 by jseabolt

[jseabolt]

If you haven't replaced your front 02 sensor in the last 40k miles, try that.

Worked for me.

 

Yep that thing already crapped out a year ago. $200.

[MilesFox]

new subaru oem filters are made by honewell out of canada. go to napa and opt for wix, napa silver or gold.

 

purolator, pennzoil, fram, may as well be re-badges of the same parts maufacturer.