2000 Legacy miss ... still

[mtsmiths]

Took our Leg in for a deep scan this week. All the profiles are in spec except, the 'learning curve?" which was .038 above tolerance.

 

Random onset miss, always a full cut-off EXACTLY every three seconds, followed by EXACTLY two seconds of coasting and a sputtering restart, then repeat, over-and-over-and-over-and ... sometimes for three or four minutes, once for two hours.

 

Dump in a can of Techron for an instant miracle cure that will last two tanks of gas, then the cycle starts over.

 

Only comment from the service dept. was that we needed plugs and wires, and had weeping valve cover gaskets, but even they didn't pretend that was the problem.

 

No one seems to have a clue what is wrong ... Zone Rep?

 

BTW - ordered parts from Johnphil from the vendor forum. Less than 1/2 the over-the-counter quote from the local dealer, and delivery in two days, instead of a five day wait at the store. Can you imagine a dealer NOT keeping 2.5L plug wires and plug sleeves in stock?

[mtsmiths]

Does no one have an idea what might be wrong with this thing?

 

Yesterday it ran fine all the way to work (15 miles), then fine for the first ten home. By the time we were in Whitefish it was cutting out so bad we had to coast to the curb during each outage ... then it would catch and go another half block.

 

I've ordered new plugs, wires, etc., but I've never had a car behave like this just 'cause it wanted a tune-up (in fact, I've never had a car behave like this, period) ... and ' computer learning curve' BAH!

[cannonball]

How many miles on those plug wires? I would start there as I have had wierd missing problems that were related in the past with different vehicles. Other than that you may want to replace the fuel filter while your at it.

[mtsmiths]

How many miles on those plug wires? I would start there as I have had wierd missing problems that were related in the past with different vehicles. Other than that you may want to replace the fuel filter while your at it.

Too many ... but I must say that I have run pulgs and wires to a point of failure on other cars, and have never had one act like this. The tune-up kit should arrive in today's mail. Fuel filter was the first thing I did.

 

If it's still missing after the new plugs, wires, gaskets, etc. I'm gonna replace the coil. Just because if this was a '55 Chevy and I wasn't distracted by sensors, and computers, CELs, and digitezed read-outs from the dealer; I would immediately assume it was suffering from a coil with an intermittant internal fault.

[mtsmiths]

Changed out the plugs and wires. The plugs certainly were shot, some of he worst I've ever seen. But, as I stated previously, it isn't acting like bad plugs and wires, I KNOW that symptom.

 

And with all new, NO CHANGE!

 

Hell, looking under the hood I don't even know what the damn coil looks like! I think I need a mid -fifties Chevy six, THAT I can diagnose and work on. I don't know what's wrong with this Legacy. And apparently, neither does anyone else ... including my local Subaru dealership, they just want to start throwing expensive parts at it.

[1 Lucky Texan]

Seems odd to me tthat the Techron consistently helps matters(even though its temporary). Wouldn't that point to injectors or possibly ignition?

 

 

When the car is idling, can you pull, push and twist sensor wiring and create any problems?

 

In what manner were the plugs bad? just worn down? carboned up? etc.

 

I dunno

[mtsmiths]

Seems odd to me tthat the Techron consistently helps matters(even though its temporary). Wouldn't that point to injectors or possibly ignition?

 

When the car is idling, can you pull, push and twist sensor wiring and create any problems?

 

In what manner were the plugs bad? just worn down? carboned up? etc.

 

I dunno

 

You 'n' me both Tex! I've poked all around under the hood, and nothing seems amiss, can't create the fault. Just plain ol worn out plugs, all pretty consistent, no carbon or oil foul, the rear plugs were a tad darker brown that the fronts (that doesn't surprise me on a boxer), but not black by any means.

 

The cut-out and re-start are SO consistent when it's doing it that I think something is shutting it down. Like I said, if it were a pre-computer car, I would be certain it was a failing coil.

 

But, then the 'Techron cure' throws me for a loop. I don't know if there's a sensor that could be temporarily being cleaned by the techron, then is fouling again.

 

Yesterday as we drove out of our heated garage (with brand new plugs and wires) and it cut in and out for about 1/2 mile, then ran perfectly all the way to my wife's office, about fifteen miles. On the way home it ran fine the first two miles, then ran like crap for the next five. We stopped at a store and it sat out in 10 deg cold for 1/2 hour. The rest of the way home it ran fine.

 

This morning it ran perfectly all the way ... this thing is making me crazy. AND, we are making a trip to Seattle for Christmas, sure can't take this car, and won't take the Tracker. I'd rent a new car, but in Montana all rentals charge mileage.

[cookie]

To switch parts from to test? If you lived around here we could just swap a few parts one at a time.

I would suspect the coil first also, but then there are two or three culprits I would look at. Since they are cheap I would change the knock sensor and the temp sensor just for insurance. After that I would look at the air-fuel sensor in the air cleaner.

I don't know how your car is set up but my coil would take about 1 minute to swap.

[1 Lucky Texan]

You 'n' me both Tex! I've poked all around under the hood, and nothing seems amiss, can't create the fault. Just plain ol worn out plugs, all pretty consistent, no carbon or oil foul, the rear plugs were a tad darker brown that the fronts (that doesn't surprise me on a boxer), but not black by any means.

 

The cut-out and re-start are SO consistent when it's doing it that I think something is shutting it down. Like I said, if it were a pre-computer car, I would be certain it was a failing coil.

 

But, then the 'Techron cure' throws me for a loop. I don't know if there's a sensor that could be temporarily being cleaned by the techron, then is fouling again.

 

Yesterday as we drove out of our heated garage (with brand new plugs and wires) and it cut in and out for about 1/2 mile, then ran perfectly all the way to my wife's office, about fifteen miles. On the way home it ran fine the first two miles, then ran like crap for the next five. We stopped at a store and it sat out in 10 deg cold for 1/2 hour. The rest of the way home it ran fine.

 

This morning it ran perfectly all the way ... this thing is making me crazy. AND, we are making a trip to Seattle for Christmas, sure can't take this car, and won't take the Tracker. I'd rent a new car, but in Montana all rentals charge mileage.

 

 

Is it more consistently associated with cold conditions (not operating temps)? I don't remeber if the front O2 sensor was changed. Does this car have MAP or MAF - ever run a K&N style filter? maybe crap/oil on the MAF filiament.

 

I dunno. Once you get to the point where everything has been replaced, its time to wonder about the replacement components. maybe the Techron is a fluke and this is an intermittent crank or cam sensor?

 

just thinking out loud. maybe if you could manage to stop the car sometime when it starts misbehaving and look at a plug to see if its wet with fuel?

 

Sometimes a vacuum gauge can show sticking valves or intermittent vacuum leaks - mabe a hose is cracked or something? maybe attach a vacuum gauge and drive around for a while? Or maybe the alternator diodes are marginal and you've got ripple on the 12 volts confusing some electronics? Might be worth just going through and cleaning up some ground connections - dude, I got nothing

[mtsmiths]

To switch parts from to test? If you lived around here we could just swap a few parts one at a time.

I would suspect the coil first also, but then there are two or three culprits I would look at. Since they are cheap I would change the knock sensor and the temp sensor just for insurance. After that I would look at the air-fuel sensor in the air cleaner.

I don't know how your car is set up but my coil would take about 1 minute to swap.

 

THANX cookie, I'll have a look at the sensors first, although NONE of these turned up on the dealer scan. If I borrowed your parts, I might have them a long time, sometimes this thing runs perfectly for two or three weeks at a time, then starts acting up again.

[mtsmiths]

Not temp sensetive at all, started on a trip in June, outside temp was in the eighties. Has misbehaved at all temps and all operating temps. Fuel filter and clean/tighten all grounds was the first thing I did. Regular air filtration system, new air filter, and no oil or crud in air box.

 

Car is on it's third front O2 sensor, I've checked connections at the cat.

 

Here's another clue, if you floor it, it will pull full power without missing. At it's worst session we got it about twenty miles (from Hwy 95 to east Spokane, on Trent) by shifting into second and driving about fifty (Brighton, no tach).

[cookie]

to me, but so many parts can cause similar symptoms. It seems like you are slowly chasing it down.It has nearly driven me crazy to find a part that passed all the book tests and set no code. I just changed a BMW cam sensor that cured a sputter and die problem and according to my Chilton's and multimeter it is fine.You don't want to change every part on the engine to find one small sensor with an occasional failure.

[1 Lucky Texan]

Not temp sensetive at all, started on a trip in June, outside temp was in the eighties. Has misbehaved at all temps and all operating temps. Fuel filter and clean/tighten all grounds was the first thing I did. Regular air filtration system, new air filter, and no oil or crud in air box.

 

Car is on it's third front O2 sensor, I've checked connections at the cat.

 

Here's another clue, if you floor it, it will pull full power without missing. At it's worst session we got it about twenty miles (from Hwy 95 to east Spokane, on Trent) by shifting into second and driving about fifty (Brighton, no tach).

 

Hmmm...that does seem like air/fuel problem. or TPS. I don't know at what rpm the IAC becomes inactive - maybe someone can tell us.

 

yeah, intermittent problems are the worst!

[farmer]

I know this is an old post, but thought I'd give it a shot.  Trying to find the fix for this Legacy.  I have the same problems exactly on a 2000.

 

Have changed filter, pump, map sensor, TPS - all for different issues over the last two years.  Wires and plugs (NGK's) changed about 6 months ago (from a misfire code).  Then I had a code for the cannister purge solenoid, which I changed.  Ran really well after that - for about three weeks, then back to "normal".

 

I see where the plug wires were changed on this one, but it didn't help, apparently.

 

Great car - just this nagging problem that I hate to give up on.

 

Appreciate the help

Edited March 28, 2013 by farmer