'99 2.5 mild missing/vibration

[94.GT.Wagon]

Since we bought it this fall, my wife's Outback has had a subtle miss or roughness at idle, then seems to go away and then appears again around 2500 rpm and goes away again around 3000 rpm. It's mostly consistent but not there all of the time and also has gotten a little better as we have continued to put some miles on it. When I first bought the car I replaced plugs and wires and also tested the coil. Anybody have any thoughts? Much appreciated!

[wtdash]

Hi,
Also check here: http://www.ultimatesubaru.org/forum/

Did you use OEM parts for the plugs/wires? The NGK's are $$ but I've read often that anything else may cause your issue.

Was it missing/rough before you changed the parts?

good luck

[log1call]

Plug gaps are critical on some cars too for some reason. You could try setting them to the minimum recommended.

[Matt Monson]

The BKR6E-11 plugs that are spec'd for this car, are copper, $3 each and pregapped at .044. If you used anything other than those that could be your problem. Some of those cars came with total garbage Champion spark plugs in them. Never ever replace them with the champions. Only ever use the plug listed above.

There's no need for platinum or iridium on this car.

However, the stumble could be other things. You could have a dirty MAF. You may also be starting to get the infamous DOHC Ej25 head gasket failure. Are there any other symptoms at all that we should know about? Smoke on start up? Running hot sometimes? Etc.

[94.GT.Wagon]

Yeah, I don't touch the Champions either. Actually though, the owners manual specs the high-dollar NGK PFR5B-11 platinum plugs for the 2.5, so that's what I bought. Other than the little stumble, she's a peach. Right around 100k on it, no smoke, no erratic temp, no fluid comsumption, generally great running and driving. I hadn't thought about the MAF sensor being dirty, I'll have to take a peek. Any precautions when cleaning one? Carb cleaner or something more gentle?

[wtdash]

Suggest you use MAF-specific cleaner...no residue....and I think it's a lighter pressure spray...those dang things are sensitive.

[94.GT.Wagon]

Really, no other guesses? No love for the 2.5? Let's pretend it's a 2.2.....

[codfizzle]

Here Bro, I had a similar problem, but was able to find out what was causing it. Here is a link to a previous thread in which I discussed the topic quite thoroughly. Hope it helps.

http://bbs.legacycentral.org/viewtopic.php?t=38303

I also reccommend the NGK V-power plugs.

[94.GT.Wagon]

Good info, I'll definately double check the plugs. Can't say that I'm real hopefull though. The problem was the same before and after changing plugs and wires, plus the plugs on this car are located in the center of the valve covers and the wires have big boots on them to keep debris out, so dirt getting in the way of seating the plugs is a little less likely. Can't hurt to check though. Thanks.

[gijonas]

The head gasket issue can be very elusive and confusing.At first it may not overheat,consume fluid ect.Try smelling the coolant and checking for residue of oil in the radiator.Another of my favorite tricks to blip tha throttle by hand while watching the overflow,sometimes some exhaust pressure breaks the seal and causes bubbles in the reservoir after hitting the throttle.And a little coolant leakage into the cylinder isnt always drastic enough to be evident.Do the simple stuff first,i agree about the plugs and maf,might as well change the fuel filter as well.

[codfizzle]

Actually 2.2 engines have the same big rubber spark plug boots to keep debris out, but trust me, LOTS of stuff still manages to get down there. My problem was also apparent both before and after I changed plugs and wires. It wasn't until I looked for that specific problem that the problem went away. And the symptoms I experienced were pretty much exactly the same as yours; I thought something much more serious going on with mine, but no. And it's definitely worth the time to check all the plugs, because you'll really be kicking yourself if you do a head gasket job or something big like that (which I almost did do) and then later find out that one of your plugs was only half way screwed in.

[gijonas]

then later find out that one of your plugs was only half way screwed in.

Been there lol!

[94.GT.Wagon]

Did a little tinkering last night. I took a look at the MAF, not a speck of dirt or residue on it or in the upper air box so I didn't do anything with it. Are there any simple resistance tests or anything to test the sensor? I also loosened the plugs, blew out the holes with compressed air and hosed with brake clean. No dirt came out. Took the plugs out and everything looked normal. Put them back in and there is no change to the symptoms. I also tried blipping the throttle while looking at the coolant bottle and there were no bubbles. The coolant looks great, never lose any, and the oil looks normal as well, so if the head gaskets are going there sure aren't any signs of it yet. I noticed when I would blip the throttle that when you first touch the throttle the engine stumbles just a touch before it takes off. Is that any sort of clue?

[gijonas]

Are you sure that its rpm related or throttle position related??.Thinking maybe this stumble takes place at a certain point in the pedal travel rather than rpm,meaning look at the TPS as a candidate as well.

[94.GT.Wagon]

Not sure what to think. That little hesitation seems to happen as soon as you move the throttle even the slightest. I've never noticed that before but can't say I really ever blip the throttle either. The "miss", if that's what it actually is, is most noticeable if you hold the RPMs at about 1200, then again if you hold it around 2300 or so. The 2300 range is where it's the worst. Wife says she doesn't really even notice it anymore but I do and it bugs the hell out of me. Maybe I should just get off my wallet and let a pro take a peek.

[94.GT.Wagon]

I should add that when I said the stumble happens when you move the throttle even the slightest, I meant from idle, not just any time you move the throttle....