Continung Problems with 2.5 Legacy. New thread start

[welly]

This is part of the continuing issues I have. My earlier post detailed my decision to go ahead with HG replacement and then the bad running that developed recently.

 

Just as I was getting ready to do the HGs on the car and happy to do so it starts running bad - hestitating, juddering generally failing to respond. I thought it might be bad fuel so treated with Dry Gas. It seemed to be getting better (my imagination perhaps) but yesterday it finally threw a CEL when running poorly.So today I took it off to the Suby dealer and got a faulty AF (air flow meter) diagnosed as the CEL code. This part costs $580 + $140 to fit at the dealership:mad: . So rather than just go ahead with this, or the HG job I have booked it into them for a diagnosis on the AF sensor to see if it is broke before I replace. At the same time they will evaluate the car for the HG problem (external look only) including sniffing the coolant. I see from a search that the AF (I assume this is the MAF) sometimes benefits from a clean. To get to the dealers today involved city driving which I havent done recently and the car ran horribly in town even stalling when at the lights (a first) On the open road it seems to run much better - hence why I thought the problem might have been a fuel issue that was getting better. Now I can see that the AF is probably goosed.

 

Any comments on this are most welcome. I will post up the result of the diagnosis later in the week.

[idosubaru]

this should make you feel better. get your car out of the dealer. next time your CEL comes on DO NOT go to the dealer. go to Advanced, Auto Zone or any other major store that reads your codes for FREE. then post here and tell us what the code is (not what the person who pulled it thought the cause was).

 

your MAF sensor can indeed cause horrible running. the air flow meter could be cleaned with some Mass Air Flow Sensor cleaner, they have a specific cleaner for it at auto parts stores. if that does not work, do NOT buy one from the dealer. they fail so rarely that your best bet is a used one for $25-$50.

 

on a side note if you pull it out and see that one of the hair thin wires inside the air passage is broken, then that tells you it is indeed bad. the old ones are like this, i can't remember if the newer ones are as simple to see, but they probably are. this is a hotwire style anemometer if you've ever taken any engineering labs or anything remotely similar. same idea - just check out the wires inside, best to remove it to do that (very, very easy). if you can do any manaul labor at all you can replace this.

 

if for some strange reason you insist on getting a brand new one (bad idea), then buy one from one of the online parts suppliers, they are FAR cheaper. or ask your local dealer to match the online pricing, they will do that...then you'll be real PO'ed at those prices!

 

now having the head gasket done at the dealer isn't a bad idea if you don't have a good independent to take it too. moral of the story - ask here as soon as you can when something happens...like the check engine light coming on. we'll save you some hassle, money, and the sticker shock!

 

i'd be interested to know how the car will run with the MAF disconnected if it's faulty anyway. heck, you might want to check the plug just to make sure it's not bunged up.

[welly]

Grossgary thanks for your post.

 

Can someone post up a pic or a diag of where the AF/MAF sensor is so I can try the disconect and see how car runs and also try and remove and inspect it. I have good intermediate mechanic skills but no ramps or lifts so under car work can be tricky for me.

 

I do have a good independent to do the HG work and any other. Prices are way high for the sensor probably even compared to new in USA - remember I am in UK and it seems we are £ for $ over here.

 

If car runs OK with AF disconected is it OK to run it like this?

[OB99W]

Can someone post up a pic or a diag of where the AF/MAF sensor is so I can try the disconect and see how car runs and also try and remove and inspect it.[...]

You shouldn't need a pic. The only "lifting" needed should be that of the hood/bonnet -- find the air filter, and the next thing in the intake line should be the MAF. Before going further, would you note the part number, and post it here? It should be on a label, in the form "xxxxx AAxxxy" (where each "x" is a number, and the "y" may or may not be an additional character).

 

Because you're "over there" (), your car might not be outfitted the same as ones we're used to "over here". About 1999 (depending on model, etc.) Subaru changed from thin-wire to thin-film MAFs; some of them were very unreliable, and there were "improved" parts issued. The part number, and whether there's a green-colored dot on the MAF, might help in determining which one your car has.

[welly]

OK so is the MAF in the intake part of the engine? From OB99W's post thats what I understand.

 

According to the mechanic at Suby today this AF (as he called it) was in the exhaust side (exhaust itself?). He refered to it as AF sensor.

 

I think I might be confusing everyone - if so apologies.

 

I will check out the MAF and get the part number etc and post up.

 

Thanks for the contiuing assistance.

[idosubaru]

the MAF is basically attached to the air filter box. super easy to locate and remove. find where the air filter housing is. the first and only electrical component the air flow through that attaches to the air filter box and intake tubing is the MAF. very easy...just simple tools to get it off. no special tools or equipment needed, just pop the hood. should take a couple minutes, that's it.

 

air box is held on by clips, flip those back, then push the air box towards the engine and down to slide it past the inserts/tabs. after that it should be obvoius, just a screw drive or small ratchet/wrench to finish removing it. very easy.

 

i only suggested unplugging the MAF out of curiosity, i forget what it should do but seeing how it behaves when disconnected verses connected might suggest something to us. don't get caught on that suggestion too much.

 

not sure what is meant by the exhaust side. only sensor on the exhaust side of things is really the Oxygen sensor or possibly the EGR system related components. if that's the case then you might only need that $7 (US) little tiny in line filter. you'll notice on the passengers side of the engine a small round filter with a thin vaccuum hose connected to each side. when that gets clogged you start showing EGR related codes.

 

might want to let us know the exact code so we're not guessing and talking about two different thigns like i just did!?!?!?

[OB99W]

OK so is the MAF in the intake part of the engine? From OB99W's post thats what I understand.

 

According to the mechanic at Suby today this AF (as he called it) was in the exhaust side (exhaust itself?). He refered to it as AF sensor.

 

I think I might be confusing everyone - if so apologies.

Yes, it's likely there has been confusion. The A/F (air/fuel) sensor is often referred to as an oxygen (O2) sensor, and is indeed in the exhaust stream. Actually, there are likely two of them on your car, one preceding the catalytic converter, and one following it (assuming, again, configuration like US vehicles). The first one provides data to the ECU, and helps it determine A/F ratio and consequently fuel injector pulsing, etc. The second is used to check up on how effective the catalyst is in the converter.

 

Lack of lift or ramps is definitely more of an issue than if the MAF was the problem. On the other hand, an O2 sensor should be a lot less expensive than a MAF. Also, failure of that part on an '01 is fairly common, and replacement can solve some pretty poor running conditions.

[Durania]

I just had a similar instance of bad MAF on my 91 Legacy. The car would run fine at idle and when you would start driving it would run like garbage. I also found that tapping on it with a screwdriver handle gently affected the quality of my idle. I gave an all Subaru junkyard here in TN a call and found one for $75, right part numbers and everything. It is located upstream from where you change out your air filter, will have an electrical plug running to it. Yours might even say "flow" on it and pointing in the direction of intake pipe that runs to the manifold.

[OB99W]

Okay, this is going around in circles. Here's some info on A/F and MAF sensors, to help determine which we're talking about. Please don't me just because it's from Toyota.

 

A/F (Air/Fuel) (O2) sensors:

http://www.autoshop101.com/forms/h37.pdf

http://www.autoshop101.com/forms/h44.pdf

 

MAF (Mass Air flow) sensors:

http://www.autoshop101.com/forms/h34.pdf

[Skip]

Sir Welly,

The beginning of the confusion may be you state

your state as "Georgia" in your profile.

 

We yanks have a state named "Georgia"

 

We now know you are from across the pond.

Sorry for the confusion.

 

Next our kind and noble Mr. OB99W

clears up another matter of worry

e.g. MAF vs AF sensor (a.k.a. 02 sensor)

doing so

very concisely I might add.

 

I now would like to take the chance to muddy the waters

further

 

I believe Subaru went to MAP sensors in 2000

so your car may not have a MAF sensor.

 

The O2 (AF) sensor on my 03 is a very easy reach.

It is an H6 but yours may be in the same location?

(more muddy water -just what this bloke needs)

 

If you would like, I can take a photo of it's location.

 

Doubt this helps but tis good allinall

[Olnick]

It is located upstream from where you change out your air filter,

 

Actually, shouldn't that be downstream?

[OB99W]

[...]I now would like to take the chance to muddy the waters

further

 

I believe Subaru went to MAP sensors in 2000

so your car has no MAF sensor.[...]

Speaking of waters, "across the pond" they sometimes don't have the same configuration as we do here, even for a particular model year. If anyone is in the know concerning what welly's vehicle is likely to have, it could be useful.

[Durania]

I understand what you are saying Olnick. What my initial statement was meant to convey is that the air is traveling up from the filter box over the MAF wires. But like Skip said, it has a MAP sensor my previous statement is now nullified. I was just using my Legacy as a reference.

[idosubaru]

if you're having drivability issues - on older Subaru's you can disconnect the O2 sensor and the car will drive fine, this might be worth a shot on yours to at least narrow down the O2 sensor and make it drivable until you get it fixed.

wow what a lengthy mess, follow this next time:

post here and tell us what the code is (not what the person who pulled it thought the cause was).

[welly]

Okay last night I had a look at a subaru manual I bought off ebay on a Cd and in there it lists A/F(o2) sensor. This is the one forward of the cat towards the engine. I now think this is what the mechanic was refering to. But why it would cost $$$ I dont know. Thanks for all the continuing help. I wont have time till w/end to look at car but wil/ then get MAF/ MAP details and see if I can take electrical lead off )2 sensor and check running. For what its worth last night I did a trouble free 30 mile run and this morning when I started engine the CEL light had gone off. It ran fine today (15 miles) and again I am thinking maybe its bad fuel. Would bad fule, causing a missfire be sufficient to cause a A/F problem CEL? Will try and find another shop to pull any stored coded and post these up too.

 

Re my location I cant get it to show Aberdeen as being in Scotland , UK it just shows Georgia. Is there some way to correct this?

[OB99W]

[...]For what its worth last night I did a trouble free 30 mile run and this morning when I started engine the CEL light had gone off.

What, another variable?

 

 

It ran fine today (15 miles) and again I am thinking maybe its bad fuel. Would bad fule, causing a missfire be sufficient to cause a A/F problem CEL?

Sure, bad fuel (or a loose/corroded connection, or ...) could cause an intermittent problem. Oxygen sensors can be "poisoned" by contaminants; sometimes they'll burn off and operation will return to normal. (I'm not saying this is what happened, just that there are lots of things that could potentially go wrong, and that's why proper diagnosis is critical.)

 

 

Will try and find another shop to pull any stored coded and post these up too.

If the problem recurs, that's exactly what should be done.

 

 

Re my location I cant get it to show Aberdeen as being in Scotland , UK it just shows Georgia. Is there some way to correct this?

Can you change the "State" to "International"?