98 Legacy GT 2.5L misfire code problem

[doublechaz]

I recently had trouble with misfire sometimes. Mine was mainly at idle rather than mid/high, but maybe worth looking at if you keep having this.

 

My trouble was the timing belt had jumped a couple teeth on one cam only. My troubles were much more severe than yours, but a tooth out will do strange things to the computer's perception of the world.

 

Many years ago I had the crank slip one tooth compared to the cams and the effect was so subtle that I thought my O2 sensors were a little weak, but no codes.

[GT6]

SBT - I have twin Strombergs which are similar to the HC's. I just rebuilt them about a year ago. I rebuilt them once before about 25 years ago. Balancing can be a problem, but this tool is indispensable. It's by no means digital, but it works pretty well for tuning: https://www.amazon.com/Edelbrock-4025-Carburetor-Balancing-Instrument/dp/B00062YC2E

 

Of course, Weber's are great, too, and they look sooo nice!

 

One thing that stung me - I went through two gearboxes and one differential before I found that GL-5 gear oil (recommended by my former import parts shop) dissolves shims and other like metals. If dealing with original or rebuilt, you need to use GL-4 gear oil, not GL-5. That was about a $5K lesson for me.

[GT6]

Still no misfire codes after several trips on the freeway. They took a little time to reappear last time, but hopefully the problem is fixed (accent on the "hopefully").

 

Thanks for your input, doublechaz. I can see how the timing belt can cause problems. I really hope that isn't the problem as I understand that changing out the belt can be a pain. Anyone - If I'm wrong on that, please let me know. Thanks!

[SBT]

GT6 - I think before I'd go to the expense of adding a Weber, I'd also get an aluminum cross-flow head to take advantage of the more laminar flow and upgraded power of that setup. Have a couple of MG tuning books that I'd been pouring through. Was considering getting into vintage racing, but with this recently damaged knee, am rethinking a lot of my motorsport fun-guns. And I do have that Stromberg tool.

 

And as far as the TB is concerned, if need be, pull off the outer TB covers (L&R) and then turn the crank to get the TB alignment marks trued-up, and if it's off, you'll know it immediately.

 

If the engine has jumped a single tooth, that can typically be remedied. Given how well the car is running puts this potential further down in the "check-it" list. Your Haynes should show you how to do it, but I can send you a copy of the FSM section so you can see the how-to of the process from the factory's position.

 

There's a Subaru tool that makes this easy, so if it is off, I can send you the TB stopper tool as well. LMK.

[Jdubgt530]

Misfire system kicks on when you go 55+. I have found that out because I had the issue on my old gt. I suggest checking the valve clearances, and fuel rail system. That was the cause behind my gt's CEL. Same thing too, migration of the misfire code.

[GT6]

SBT - Sorry to hear about the knee damage. I hope it isn't too serious and everything heals well and quickly. I had knee surgery once (torn medial meniscus). Wasn't a big fan of it while I was recovering, but in the end it worked out well. Thanks for the offer of the tool. Hopefully it won't come to that. I haven't had the time to check the Haynes for the timing belt info. I'll do that soon. I'll let you know if I need the copy of the FSM section you offered. Again, all your help is, and has been greatly appreciated.

 

Still no codes being thrown, but she hasn't spent too much time at 55+ since the new plugs were put in.

 

I kinda figured you had the Edelbrock tool. My GT6 is basically stock, with the exception of a few things: stainless sport exhaust, Pertronix ignition (fantastic), K&N carb filters, quick ratio steering rack, and slightly larger tires. It runs (and sounds) like a champ. Cosmetically, it needs paint, but I get compliments on it every day, and it makes getting to, and going slightly over the speed limit a lot of fun. I've always said if I ever won the Powerball, I'd still drive a vintage car. Hmmm, maybe a few of them.

[GT6]

Jdubgt530 - Thanks for your input. SBT mentioned that the codes could be thrown by valve clearances. It's been a really frustrating problem. If I had to choose between the valves and the fuel rail system, no question I wouldn't choose the valves! With as busy as I am with work, I don't see myself having the time to adjust the valves for my niece. Unfortunately, adding to it all, her finances are tight. So again, I hope the problem is solved. But since you've had the same problem, especially with the migrating codes, I'm not so sure it is.

 

Any idea what a mechanic would charge for adjusting the valves? I'll make some calls and I'll also search online.

 

Thanks again, Jdubgt530.

[GT6]

My niece is taking the car on a 4 hour round trip this weekend. The CEL hasn't come on since I've installed the new plugs. She's been on the highway for only a brief amount of time (15 or so minutes) since then, but she's said she's driven "aggressively" purposely trying to see if the codes return. Is the potential for damage to the CAT or anything else only when the CEL is flashing, or even when the CEL is solid? I don't want her to get stranded or to do damage to the engine. Would driving the car on this trip with a solidly lit CEL for the migrating misfire codes be unadvisable, given it comes back at all during her trip? I've told her to pull over and clear the codes every time they come on. She has always been able to clear the misfire codes without a problem.

 

On another note, the Haynes manual indicates that I can check the timing with my timing light. I wanted to do that before her trip, but that won't work as I am once again out of town. Will checking the timing with a timing light give provide any indication of a problem with the timing belt?

 

Again, the car runs "perfectly."

 

It's been suggested to me that carbon build-up could be causing a sticky valve problem, and the source of the misfire codes, even though the engine was rebuilt only 2 years ago. Someone else suggested Sea Foam. Any thoughts?

[GT6]

I went through that entry quickly. Again, the migrating misfire codes have only appeared at highway speeds.

[GT6]

SBT! You called it! This weekend, my niece spent over 4 hours at highway speeds between Seattle and Eastern Washington and back again without any CEL's. The trip included driving over mountain passes and some really hot weather, so there was additional strain put on the engine. What did it was the NGK PFR5B-11's. $60 for the set, but well, well worth it. I hope the misfire problem is gone forever.

 

So, SBT, twisty, RustyRuu, Thor294, Brighton96, doublechaz, and Jdubgt530, great thanks for the tremendous amount of help you offered. To me, an ECU neophyte, your help was indispensable!

 

Last note: After working on, and driving her car (outside of limp mode, that is), I now understand why Legacy owners are such rabid fans of their cars.

 

Thanks again, guys!

[GT6]

Hi guys. Well, after driving it on a demanding (heat, mountains) four hour trip at highway speeds and quite a bit of highway driving in Seattle without a problem, the misfire codes have returned. Again, the misfire codes have only appeared at highway speeds. They came back once, with the CEL initially flashing, then going solid, and my niece has been avoiding highways since. This time it was the P0301 and P0302 misfire codes. As I mentioned previously, they were migrating between P0310 & P0302 and P0303 & P0304 before. She had no problem clearing the codes. It's pretty frustrating as she likes to travel quite a bit and ski season is approaching.

 

I checked the timing and it was spot on. The car runs beautifully at all speeds. If the CEL for the misfires didn't appear, you would have absolutely no idea something was wrong. She has mentioned an occasional anomaly. Sometimes, while she's at a stop, the idle will briefly go up to about 2K, then drop back to a normal idle. It doesn't happen often, but again, it is being caused by something, so it bears mentioning. I have cleaned the IAC valve, so that shouldn't be the problem (accent on "shouldn't").

 

The engine was rebuilt by a reputable shop about two years ago. Another mechanic said the engine might need decarbonization. A friend said to try Seafoam. Any suggestions on whether or not a Seafoam treatment would help? At this point, I'm willing to try anything short of a psychic (I don't believe in them).

 

I hope it doesn't come to adjusting valves, as I have no time to help with that and a mechanic would have to do it. Jdubgt530 suggested a possible fuel rail problem, so I'll research how to troubleshoot that. Any suggestions would be welcome.

 

Summary of what's been done:

Engine rebuilt about 2 years ago.

 

Problem codes appeared simultaneously for the downstream O2 sensor, the MAP sensor, the MAF sensor, the speed sensor, the crankshaft position sensor, speed sensor, and an occasional neutral safety switch code.

 

Thoroughly Cleaned: MAF sensor (with MAF sensor cleaner), throttle body, IACV, EGR valve

 

Replaced: Coil pack, plug wires (new NGK), plugs (new NGK PFR5B-11'sNGK PFR5B-11's),downstream O2 sensor, Crankshaft position sensor, PCV valve, hose clamps, and a number of hoses (they looked OK, but I replaced them anyway).

 

Short list of what has been checked: Vacuum leaks, but none were found. I checked resistance on all the new plug wires and coil pack, and everything was per specs. Grounds are all rock solid.

 

All the codes, with the exception of the sudden reappearance of the misfire codes, have gone away with the aforementioned work.

 

Again, I'm a pre-computer controlled car guy, but as all the codes initially appeared together, I can't help but think that the failure of the O2 sensor was at the root of the problems. My guess is that the sensor shorted out against the heat shield when bumps, potholes, etc. were hit. I've included a photo of the sensor. I was wondering why a fuse wasn't blown, but it may have just been, as I said, intermittent shorting to the point where it damaged sensors, but didn't blow a fuse. The opening in the heat shield the O2 sensor passed through had to have been shifted (accident?) as the sensor body had worn an indentation in the shield. I enlarged the opening before installing the new sensor.

 

Thanks in advance for any help you guys can give!

 

[SBT]

Was the O2 sensor replaced with an OEM one? Many, myself included have had issues with non-OEM (eBay, Amazon, local parts store) versions. Like the NGK plugs, these engines like and respond better to OEM parts, so I've learned that wnen it comes to the drivetrain, go OEM.

 

And refresh my memory, was the upstream O2 sensor also replaced?

 

Parenthetically, the amount of carbon in that picture of the DS one looks like it was also loose in its bung as there appears to be carbonizing on the thread-end.

 

There are many YouTube videos of Subarus being SeaFoam'd. I personally use my own gasoline additive which comprises Marvel Mystery Oil, Acetone and Chevron Techron Concentrate - 4oz each for a total of 12oz, in all of my Subarus and now in my Dodge Cummins diesel as well. MMO provides lubricity for the pump and the injectors, Acetone helps to atomize gasoline and decarbonize the combustion chamber and valves, and Techron cleans the injectors - though that is also helped by the Acetone and contains Toulene which is an octane booster. Downstream benefits are cleaner catalysts as well. Immediate improvement in driveability, better (improved 3-5 mpg), smoother idle and acceleration.

 

For initial treatment, I add 12oz to an empty tank then refil, at 1/2 tank add an additional 12oz, and then 12oz to next full tank. Thereafter, I use one 12oz treatment at every second oil change. I buy each of these in 1 gallon bulk, so my costs are pretty low ~$2.00 per 12oz treatment.

 

To your issue - Cylinders 1 and 2 are reporting misfires... has the engine been compression/leak-down tested? If everything else is new/replaced and there are no electrical gremlins, i.e., grounded wires, fouled injectors, then I'm leaning toward valves and specifically valve clearance.

[GT6]

SBT. Thanks for the quick response. The downstream O2 sensor was the only one that was replaced. It was replaced with a Bosch 13445. I've included a couple of photos of the old sensor in place. You can see the indentation that was made over time to the heat shield. If the upstream sensor was bad wouldn't it throw a code? Of course, if the condition of the old downstream sensor is any indication, the upstream sensor might look a little rough, too. I'm not going to have access to the car for a while, but I'll check the upstream sensor the next time I'm under it. It may have been loose at one point, but even after being bathed in Kroil for a considerable amount of time, I still needed a cheater bar to break it loose. And yes, I was worried about breaking the bung.

 

I've seen the videos, but wanted to check to see if I got a "Don't use Seafoam" warning here. Your gas additive cocktail sounds logical, beneficial, and well-tested. I might give it a try before the Seafoam. Thanks!

 

The misfire codes are migrating. Sometimes they're on the 1 and 2, and sometimes on the 3 and 4, but never all four at once. If the valve clearances were incorrect, would codes for all 4 cylinders be thrown simultaneously?

 

And no, I haven't done a compression/leak-down test. All I currently have is an old compression tester that I have used periodically on the Triumph. I may have to pick up a new tester that would do both compression and leak testing.

 

Thanks again for the advice. I'd be lost without it. And I hope your knee is getting better.

 

 

[Osei]

Make sure the cam and crank sensors are not covered in dirt. I know the crank sensor is new, but check it anyway.

 

 

O.

[DOHCEJ22E1]

I personally use my own gasoline additive which comprises Marvel Mystery Oil, Acetone and Chevron Techron Concentrate - 4oz each for a total of 12oz, in all of my Subarus and now in my Dodge Cummins diesel as well. MMO provides lubricity for the pump and the injectors, Acetone helps to atomize gasoline and decarbonize the combustion chamber and valves, and Techron cleans the injectors - though that is also helped by the Acetone and contains Toulene which is an octane booster. Downstream benefits are cleaner catalysts as well. Immediate improvement in driveability, better (improved 3-5 mpg), smoother idle and acceleration.

 

For initial treatment, I add 12oz to an empty tank then refil, at 1/2 tank add an additional 12oz, and then 12oz to next full tank. Thereafter, I use one 12oz treatment at every second oil change. I buy each of these in 1 gallon bulk, so my costs are pretty low ~$2.00 per 12oz treatment.

 

I've been using this fuel service cocktail for years since you put me on to it years ago. I will and have used nothing but. It's not only more effective than Seafoam, but it's also less dramatic and you can definitely pick up on the car "clearing it's throat" around the middle of the 2nd refill.

[GT6]

Hi Guys - Thanks for visiting this thread. DOHCEJ22E1, thanks for that suggestion. SBT suggested that earlier in the thread. My problem with that is that I don't always have access to the car as my niece is living a very busy life right now. Time is always a problem. I like the "less dramatic than Seafoam." I've never used it, but from the YouTube vids I've seen, it looks like it could attract a lot of attention. As we live in the city, I'm not wild about attracting that much attention, but I'll do what needs to be done. Back to my niece. I think trying to get her to add that when it's time to get gas could be problematic. That being said, I will give it a try.

 

Osei, I'll recheck the cam and crank centers. At this point, I'll try anything!

 

In my long thread here, I tried to describe a sound that has recently become worse. As an old car guy, the sound reminded me of the sound of a timing chain hitting the surrounding housing. I thought it was a loose heat shield problem, but it seems to be secure. As the sound is worse when the engine is cold, it has me concerned that it might be something inside the engine... I obviously really hope that isn't the case.

 

I will see her either tonight or in the next few days and I want to record the sound. As I'm new here, is there a way of uploading an audio file for opinions? That would work better than me trying to describe it. e.g. "Have you ever put a whole egg in a blender then put it on medium?" When people who are trying to help ask, "Hard boiled, soft boiled or raw?" or "What kind of blender."

 

I really appreciate all the help I've been given here and by uploading an audio file I think that would help to save the time of the all those who are trying to help. If I can't upload an audio file, I'll try to figure out another way of doing it.

 

BTW, Osei, I noticed in your profile that you're interested in photography. I make my living as a graphics artist, web designer and photographer. I'm always happy when I find out that people are doing something creative. Photography is a great creative outlet. Of course, working on cars is also a great creative outlet. Logic usually applies. Computers in cars made me add "usually." It was said in Zen and the Art of Motorcycle Maintenance that "If you do A, and B, and C, D happens." For me, anyway, that logic is much clearer with old Triumphs! My niece recently commented that she thinks I secretly enjoy working on her car. She wasn't wrong. I love a challenge, but at least in this case, I wish it was over!

 

Thanks again for all the help.

[GT6]

Also, as evidenced by my entries, I need to learn to be brief and to the point...

[Osei]

Check the tensioner for the t belt. Especially if it's the one piece design.

You can imbed the audio file here.

 

I stopped with photography on the dawn of the digital age.

I am a Pentax man and haven't made the leap and probably won't.

I occasionally still do it, but my eyes and darkroom work don't get along well these days.

Now I only play with my Speed Graphic in 4x5.

 

O.

[SBT]

Definitely check the TB tensioner as Osei mentioned. These often mimic valve and sometimes bottom end issues and are typically a tick-tick-tick noise that increases in amplitude and repetition as the RPMs climb.

[GT6]

Hi guys,

 

First, serious thanks for all the attention you've given to this. I appreciate in and my niece does too. My delay in responding is due my getting called out of town.

 

There is a new noise and an increase in another. I've embedded some audio taken on a very cold day with the engine cold. The initial sound is a very high pitched, loud whine which goes away after about 30 seconds. I asked her if the sound was different under different conditions, cold start, warm start, warmer weather, etc. She says it's happening pretty regularly even when the engine is warm.

 

You know my lack of Subaru knowledge, but the sound makes me think of water pump bearings going bad, or a squealing belt. The other sound in the audio file sounds like a lifter. It might be wishful thinking that all these sounds are the result of the same problem rather than several different ones, but I'm hoping.

 

SBT, if the one noise is the result of a sticky lifter, I will try to get her to use the gasoline cocktail you use. My problem with that is to get her to use it regularly. Either way, I think it's advisable that I try to get her to use it.

 

In the audio clip I was being purposely aggressive to replicate the rattling noise I've been trying to identify. You can hear it on deceleration. However, the noise level is considerably lower. Could this, coupled with the new noises, indicate that they are related? Yes, again, probably wishful thinking.

 

I have had limited access to the car, so it's been frustrating for her and for me. As always, I look forward to your input.

 

SBT - I hope your knee has healed!

 

Osei - I was dragged kicking a bit into digital, but now I couldn't go back. I love digital. The benefit of not having to wonder if I got the shot alone is reason enough for me, but there are reasons too numerous to mention. My second DSLR was a Pentax MX. I've since moved to Nikon. I'm glad I learned with film. It made you pay attention to composition when you didn't have a lot of money for film or processing. I do miss darkrooms, though. There is a magic to them, not to mention the experience of the complete absence of light. As I do a lot of onsite food and interior stuff, getting acceptable photos for print at ISO 6400 is a plus. A former GT6 owner and a Speed Graphic 4x5 photographer? That just made me smile. A friend of mine has a vintage Horseman that he said I could use anytime I'd like. I just haven't found the time to do so.

 

Sorry about getting off topic, but as I said, I need to learn how to be a little more brief in my posts! I'll work on it.

 

A problem. I can't figure out how to embed a 600k mp3 audio file. I get an "invalid file" message. Understandable as the Manage Attachments lists the valid formats, and mp3 isn't one of them. Suggestions?

 

Thanks again, guys.

 

GT6

[GT6]

Hi again. I'll be brief. Honest.

 

I went to tinypic and uploaded the video file rather than the audio file. Here's the link:

http://tinypic.com/r/xgbl9d/9]View My Video

[SBT]

Hard to tell from the video clip, but I'd definitely check the Timing Belt Tensioner.

 

High pitched noise could be alternator bearings. I've never heard a Subaru water pump that sounded bad, but everything I'm hearing, sounds high and forward - TBT or valve train. Leaning more torward TBT.

 

Knee is doing well. Walking unaidedd (mostly), and now it's just a matter of strengthening it, gettting/keeping flexability, and losing weight gained during the down-time. Thank you for asking.

[Osei]

The 98 EJ25D in that car will probably need a valve clearance adjustment. It is an involved procedure, since it uses shims over buckets and would require half a day in warm weather.

First I'd pull the t belt cover off and see if the tensioner can be moved by hand. (it should not be)

Add the cocktail to the car and add whenever you see her.

PM sent

O.

 

O.

[SBT]

Have always thought that the valves needed adjustment. Likely too tight during engine rebuild and now sound, well, loose.

 

See attached Engine Noise Diagnostic from the 1998 FSM

[Brighton96]

Get yourself a mechanics stethoscope and start poking things.