P301-304 codes and poor mileage

[etc]

98 Legacy L, 2.2L auto 150K miles

 

Constantly getting very poor mpg, 160-180 miles/tank in mixed driving.

 

P301, P302, P303 and P304 codes all the time, the CEL is flashing while driving. It's running rich, the exhaust smells like raw fuel sometimes.

 

Poor acceleration at times, hesitation.

 

Spark plugs, wires and O2 sensor are new, OEM.

 

Should I try replacing the coil? I replaced it once with a used unit with no change. I cannot think of what it could be other than the coil.

 

 

Edited October 4, 2009 by etc

[OB99W]

P301, P302, P303 and P304 codes all the time, the CEL is flashing while driving. It's running rich, the exhaust smells like raw fuel sometimes.

Are those the only codes? If so, one possibility is the CTS (engine coolant temperature sensor) going bad. If it's telling the ECU that the engine hasn't warmed up when it actually has, you can get the symptoms you've described. The ECU doesn't have a way of knowing the CTS data is wrong, and therefore doesn't generate a code.

[etc]

These are the only codes.

 

sometimes 302,303,304 and sometimes all 4 cyl misfire.

 

 

Where is this engine coolant temperature sensor located and where do I get one?

 

Still worth trying to replace the coil with a new one?

[nipper]

When was the last time this car had a good old fashioned tune up?

 

When was the last time the timing belt was changed?

[OB99W]

The CTS is screwed into the water (coolant) pipe, kind of buried under the intake manifold. Before replacing parts, some more info and diagnosis might be helpful. When was the air filter last replaced? When was the PCV system last looked at (valve checked/cleaned or replaced, tubing checked for obstructions)?

 

Subaru gauges can be highly inaccurate. How many actual gallons are you using to do the ''160-180 miles/tank'' you mentioned? The tank holds nearly 16 gals -- if we assume refilling of 14 gals, averaging 170 miles on that would imply about 12 mpg. Should that be the case, it's surprising that such low mileage is only generating misfire codes.

[etc]

When was the last time this car had a good old fashioned tune up?

 

When was the last time the timing belt was changed?

 

Tune up, what has been replaced is the plugs and wires and the O2 sensor. That's about all.

I need to double check the air filter but the last time I looked at it, it was fine. I cannot image that the air filter could cause something like this.

 

Timing belt hasn't been changed in a long time, not sure when last time. I don't think it's the timing belt issue? I mean, this sounds like an ignition issue. Could a Timing belt cause these misfires and code P301 through P304?

 

In frustration, I think I will just replace all of these, in this order:

 

1. Coil

2. Fuel filter

3. CTS

4. Air filter

[etc]

The CTS is screwed into the water (coolant) pipe, kind of buried under the intake manifold. Before replacing parts, some more info and diagnosis might be helpful. When was the air filter last replaced? When was the PCV system last looked at (valve checked/cleaned or replaced, tubing checked for obstructions)?

 

Subaru gauges can be highly inaccurate. How many actual gallons are you using to do the ''160-180 miles/tank'' you mentioned? The tank holds nearly 16 gals -- if we assume refilling of 14 gals, averaging 170 miles on that would imply about 12 mpg. Should that be the case, it's surprising that such low mileage is only generating misfire codes.

 

PCV has been replaced.

 

Looking at the gas guage, I know it's not accurate, but it's approaching empty when the miles are at 160-180. It's not normal even for a AWD Legacy which is not gas frugal to begin with.

 

If I calculate the mileage divided by gallons, I still get a figure way under 20. Maybe 16mpg in mixed driving. On highway I get 22-23mpg.

 

We also have a 2000 Legacy OWB with 2.5L and auto (and 200K miles on it) and it gets 29mpg, so I know it's something misfunctioning here.

There must be a reason why this 98 Legacy L is running so rich, you can smell raw gas out of the exhaust.

[nipper]

20 mpg per gallon is a little low, but not tragic. Its sounds like you are only 2-3 mpg too low in local driving.

 

Always do MPG mathmatically, not by the fuel gauge.

 

2.2 is due for a timing belt every 60,000 miles. When in doubt replace it. Yes it can cause a misfire code on all four cylinders. The carnk position sensor is used to determine spark timing, the cam is used to determine fule injection timing. If the engine thinks that these two sensors are out of synch it will throw multiple misfire codes, as well as cause you to have poor gas mileage.

 

Replace your fuel filter.

Replace your PCV valve.

 

What brand wires, o2 Senosr and plugs did you use?

 

 

nipper.

[OB99W]

Keep in mind that smelling unburned fuel in the exhaust doesn't necessarily mean that the mixture is too rich -- sufficient misfire alone can cause that symptom. If the exhaust is sooty/black, that's a better indicator of an excessively rich mixture.

 

Assuming the engine actually is running too rich, a possible cause is FPR (fuel pressure regulator) failure. The diaphragm can rupture, and fuel can be directly sucked in via the FPR's vacuum hose. Pulling that hose at the FPR and verifying that there isn't gas there might be worth doing.

[etc]

Where is FPR (fuel pressure regulator) located?

[OB99W]

The FPR is located at the rear of the right (passenger) side fuel rail (the rail is what the fuel injectors are mounted to). The rubber vacuum hose should not have any fuel in it. If for some reason the FPR has to be removed, be sure to depressurize the fuel system beforehand. See page 10 of http://endwrench.com/images/pdfs/Fuel.pdf for some general information about the FPR and how to release fuel system pressure.

 

Based on your questions, I assume that you don't have a service manual for your car that provides details. If that's the case, I'd suggest getting one, which should make diagnosis and repair easier. Some manuals are available for a reasonable price on CDROM.

[etc]

I have both FSM, Haynes and Chiltons and still am confused. I will look into it.

I think my first thing to replace here will be the coil, as the most likely issue. If that doesn't help, I will try other things listed.

[nipper]

That would be the last thing I would replace, but hey its your car.

 

I am going to bow out out of this thread, good luck.

 

 

nipper

[etc]

 

The Legacy has trouble moving when it's totally cold, meaning punch the gas pedal - and nothing happens. It just doesn't move!

 

That has to be a dead give away as to what's wrong, I think pointing to engine coolant temperature sensor? The olde P301 through 304 are flashing like crazy upon acceleration so it's misfiring like h!#*

 

Edited October 8, 2009 by etc

[Fairtax4me]

Why are you punching the gas when the engine is cold? You're gonna eat up the rings doing that.

 

Did you ever check the Fuel pressure regulators vacuum hose for gas?

What else did you replace besides the coil?

[etc]

I am not really punching the gas - it's not moving no matter what.

 

Apparently that's a fairly common issue.

 

I just replaced the fuel filter to no avail. I had a similar issue once where the fuel filter fixed it.

 

Anyway, the next thing is to replace the Coolant Temperature Sensor, any idea where to get it? I think I will visit the local dealership, they must have it.

 

This replacement appears to be well explained here:

 

http://www.lovehorsepower.com/SubaruDocs/CoolantTempSensor.html

 

 

Secondly, if this doesn't fix it, I will check the fuel pressure regulator.

 

I read the docs on the site - http://endwrench.com/images/pdfs/Fuel.pdf but I "don't get it", what do they mean by "disconnect the fuel pump and start the engine" -- I understand the engine part, but what do I do to disconnect the fuel pump?? Remove the fuse? Or the "In" fuel line that goes to the fuel filter?

Edited October 28, 2009 by etc

[outbackusjunkus]

I had multiple missfire codes recently, turned out several of my fuel injectors took a crap at once. Bad gas maybe? Ran like crap, no power, just replaced one by one and the corresponding codes went away. Only time I've personally seen all four codes at once was a 2.5 with a bad rod knock. I think it was playing heck with the knock sensor. Could it be a bad knock sensor with yours? Just wanted to help muddy the water...

[Fairtax4me]

Secondly, if this doesn't fix it, I will check the fuel pressure regulator.

 

I read the docs on the site - http://endwrench.com/images/pdfs/Fuel.pdf but I "don't get it", what do they mean by "disconnect the fuel pump and start the engine" -- I understand the engine part, but what do I do to disconnect the fuel pump?? Remove the fuse? Or the "In" fuel line that goes to the fuel filter?

 

It's not difficult to check the regulator. Takes all of 30 seconds literally. You don't have to remove anything or drain anything or disconnect anything else except the vacuum hose. If gas pours out or it looks wet in the hose then the regulator is leaking and needs to be replaced. If it's dry then it's fine and you put the hose back on. Simple as that! Look from the front and stick your hand around behind the intake tube and reach down. Give the hose a firm twist to break it loose and then pull it off. If the hose breaks it needed to be replaced anyway.

 

Pull the fuse for the fuel pump. It's much easier. But honestly I've never bothered. Put a rag over the fitting where ever it is that you disconnect the line to prevent spraying all over the place. I will recommend that you loosen the filler cap first though. Pressure can build in the tank and you will lose a LOT of fuel before that pressure gets low enough to stop pushing it out.

[etc]

It's not difficult to check the regulator. Takes all of 30 seconds literally. You don't have to remove anything or drain anything or disconnect anything else except the vacuum hose. If gas pours out or it looks wet in the hose then the regulator is leaking and needs to be replaced. If it's dry then it's fine and you put the hose back on.

 

Yeah, simple enough. Checked that hose going into the Fuel Pressure Regulator -- it's dry. No gas came out of it.

 

Also just replaced the Water (Coolant) Temperature Sensor - to no avail. It was pretty tight getting to it. Had to disconnect half a dozen vacuum lines. Anyway, it did not make any difference. The engine is lacking all power, barely moves the car at all. I assumed that like before, it will improve with warm-up.

 

I cleared the codes and immediately got misfire on a few cylinders. It seems to be random, sometimes 2 cylinders, sometimes 3 and usually all 4 misfire. (Codes P301, 302, 303 and 304)

 

Also replaced the fuel filter without any results.

 

I am at a loss here -- any idea what to try next? I am thinking about swapping the coil, since the one I got is used, maybe it's root cause?

Edited October 30, 2009 by etc

[Fairtax4me]

So the misfire happens at idle and when driving?

 

 

Have you hooked up a spark tester and checked for consistent spark at each plug? Have you checked fuel pressure? Compression? Engine vacuum at idle?

Try checking the resistance across the fuel injectors.

There's not really a way to check the fuel injectors spray pattern or flow rate on without special equipment, but if you can find a shop in your area that can test and clean them it might be worth a shot.

 

You should also remove the timing belt end covers and see if the cams are in alignment.

[etc]

So the misfire happens at idle and when driving?

 

 

Have you hooked up a spark tester and checked for consistent spark at each plug? Have you checked fuel pressure? Compression? Engine vacuum at idle?

Try checking the resistance across the fuel injectors.

There's not really a way to check the fuel injectors spray pattern or flow rate on without special equipment, but if you can find a shop in your area that can test and clean them it might be worth a shot.

 

You should also remove the timing belt end covers and see if the cams are in alignment.

 

I don't know if it's the misfire that happens when it's idling and cold. It won't move in that condition when you push the gas pedal so it indicates something is wrong. However I don't recall actually seeing the codes when it's sitting at idle, they come up when it's moving at throttle.

 

I need to check the fuel pressure, what is the tool I need to use and where do I get it?

 

How do I check engine vacuum at idle? (You need to be as specific as possible because I've never done it)

 

I am not sure compression has anything to do with it, as the problem improves when it warms up. I still get misfired, but at least it can move unlike when it's cold.

 

Also the problem occured more or less at once, so I don't see how a few or all injectors can go bad all at the same time?

[Fairtax4me]

There are two different types of fuel system pressure testers. A fuel injection system pressure tester kit is what you need. Most any auto parts store will carry them, but expect to pay $50+ in a store. Ebay or Amazon will have cheaper alternatives.

A vacuum test gauge can also be bought at any nearly parts store. Be sure to ask for a vacuum TEST gauge, not a dash mount vacuum gauge. Most will look similar to this http://www.amazon.com/dp/B000CPINHA/ref=asc_df_B000CPINHA950299?smid=ATVPDKIKX0DER&tag=googlecom09c9-20&linkCode=asn&creative=380341&creativeASIN=B000CPINHA and can double as fuel pressure gauges for cars with carburetors and low pressure mechanical pumps. Do NOT try to use that style of gauge to test high pressure fuel injection systems.

 

Compression improves once the engine is warm due to expansion of the pistons and rings. Compression tests are generally done on a warm engine if possible to get a more accurate reading. So yes it is possible it can be a compression related issue.

 

Yes, it would seem pretty unlikely for the injectors to all go kaput at the same time. But it's not impossible.

 

You might have to consider taking this to a shop for a diagnosis. I think you're gonna be looking at quite an investment just for the tools to check into this further. And throwing parts at it is hit or miss. You could replace every sensor on the engine and still not have an answer.

[etc]

I took it to an auto repair place that was recommended to me as competent (place proper diagnosis and not replace a dozen things blindly)

 

Well, the professional diagnosis is it's out of timing. That the crankshaft is loose and something self-destructed inside. That to fix it, you have to pull the engine. I will try to get a more specific description. But I did see it up close and it did look bad. The crankshaft wobbles when running. The timing was right on the mark however, I saw, with the timing belt covers off.

 

If someone can explain this to me more intelligently, it's welcome.

 

I think I am going to either sell it or more likely use it as a parts car. I have a new timing belt and WP and kit (not yet installed), new radiator and other new parts in it like windshield, great to use as a parts car IMO.

 

I don't want to fix it due to other issues - serious oil leaks, plus the engine at 150K miles is kind of "high". I think it has been abused by the PO, the miles feel like they were all city miles. It just feels a bit "beat up".

 

I found another Legacy "L", nearly identical to my 1998 but from 1999 and with 90K miles, looks good, at least on pics. I wil check it out in person soon. Should be able to get it for 2 grand maybe, or 2.5K.

 

All the input is greatly appreciated.

Edited November 2, 2009 by etc

[Fairtax4me]

As I said in your other thread. I'd bet it's still fixable. The pulley is replaceable. I bet the crank timing is off a tooth from the cams. The sprocket may be damaged, but again, it's replaceable.

 

This is a pretty common problem on Subarus, and despite a grim diagnosis, is usually repairable.

[MRossmiller]

98 Legacy L, 2.2L auto 150K miles

 

Constantly getting very poor mpg, 160-180 miles/tank in mixed driving.

 

P301, P302, P303 and P304 codes all the time, the CEL is flashing while driving. It's running rich, the exhaust smells like raw fuel sometimes.

 

Poor acceleration at times, hesitation.

 

Spark plugs, wires and O2 sensor are new, OEM.

 

Should I try replacing the coil? I replaced it once with a used unit with no change. I cannot think of what it could be other than the coil.

 

 

 

 

I am posting this for those of you that may be experiencing the P301, P302, P303 and P304 codes - I had the same problem with my 97 Subaru Impreza.

 

After replacing the plugs (needed) and plug wires, knock sensor, and fuel filter yes the car seemed to run fine - but there was a more serious problem. Having recieved all four cylinders showing misfires, I intuitively thought the problem would have to be with a central function of the ignition system - not a single cylinder problem.

 

Turns out that the crankshaft alternator belt pulley bolt had loosened causing the pulley to dislodge from the crankshaft and timing sprocket. This caused the pulley and sprocket to walk - damaging the crankshaft, sprocket and pulley when the shaft key wore away. The choice now is an expensive replacement of the engine crankshaft (hopefully no piston or valve damaged) or replace the engine.

 

My suggestion to all concerned it to have your timing belt, crankshaft pulley and timing sprocket checked ASAP - if this is the probelm it would most certainly result in the four cylinder misfire codes P301, P302, P303 and P304.

 

Good luck.