Pls help diagnose and evaluate: exhaust restriction (cat?) 1995 Legacy, EJ22

[slowchops]

(I'm a forum newbie and a newbie auto mechanic - I just retired and don't need to pay our mechanic to fix the car immediately so I can go to work - so I'm trying to learn to do what I can. I'm handy and resourceful, just never applied it much to cars since my 1965 Dodge Dart! This is my first experience with EFI and OBDII.)

 

1995 Legacy wagon L, EJ22; no EGR; 5-speed manual; ~243K

 

Have owned since ~49K and done oil/fluids maintenance myself. We live in PA, so we have annual inspections. All repair work has been done by pros and, I think, by pretty good and reliable ones. We've tried to hit the maintenance milestones per Subaru and my trusty Haynes manual. 

 

The car has been very reliable until:

- driving to the local store and experienced rough idle and running

- another local trip and it stalled - engine just quit - started up without problem and got me home

- would start easily but would not idle without goosing gas

- had it towed to shop; they said it needed a new MAF, new plugs and wires, and had an exhaust leak

 

I replaced the MAF with a unit from NAPA and was able to drive it home from the shop.

 

At home:

- I replaced the plugs and wires. Our records show they had not been done since 150K

- I replaced the PCV valve

- The donut gasket at the joint from the second cat to the pipe to the muffler was bad, so I replaced that and the 2 spring bolts.

 

Still had intermittent idling and running problems. When it ran well, it ran great - better than before.

 

After consulting several Youtube sources, bought a SCAN tool and a vacuum gauge.

 

With Autel AL519 SCAN tool:

- O2 sensors indicate that downstream sensor is jumping around instead of maintaining a small range around .5 volt. I understand this suggests that catalytic converter/s is/are not doing its/their job ) (have 2 inline).

- Shows PIDs P0100 and P0101. I did not reset these because I suspect the MAF is affected by an exhaust restriction

- As near as I can tell (limited experience) most other live data looks pretty good.

 

With the vacuum gauge connected post-intake:

- Idles around 650-700 RPM (before stalling) and draws ~17-18 Hg

- At 2500 RPM, drops to 8-10 Hg - I understand this suggests an exhaust restriction

 

Assuming the exhaust restriction is downstream of the engine internals, my plan is to disconnect components starting at the muffler and work my way upstream until the restriction is eliminated. I have already disconnected the pipe to the muffler at the donut gasket that connects to the second catalytic converter. The vacuum backup is unchanged. I need to buy or borrow tools to work upstream from there. A buddy says I can remove an O2 sensor from each catalytic coverter to see which cat is the problem (assuming both are not bad).

 

Question 1 - I'm thinking it's probably a bad/clogged catalytic converter - and maybe the root cause for that problem is that we didn't change plugs for nearly 100K. What say ye of the collective wisdom to these assertions?

 

Question 2 - If testing shows that only cat 1 or cat 2 is bad, should I still replace both?

 

Question 3 - Am I missing something here or overlooking something else I should investigate?

 

Question 4 - Is this all worth the trouble? I would like to keep this around as a utility vehicle. We live on 8 hilly acres and it's kinda nice to have 4WD to haul a little firewood, or the kayak, or the bikes, or to hook up a trailer to go get stuff from Lowes or mulch or whatever. I'd like to feel confident to drive it across the country, but I'll take just a few more years of local duty until we absolutely need to replace it. So, Question 4B - what signs should I look for that it may be time to abandon it and find someone who just can't resist another EJ22?

 

Thanks so much for any thoughts, suggestions, insight!

 

-Paul

 

 

[1 Lucky Texan]

with the throttle open, vacuum will be less so, not sure that you're seeing a problem. I think the youtube video i watched showed the vacuum gradually reducing as pressure built-up in the exhaust, if THAT is your observation - could be a restriction.

 

 

Knock sensor and IACV might be areas to investigate.

 

EDIT; video below sems to suggest your vac numbers ARE too 'low'.(higher pressure than ideal)

Edited September 28, 2016 by 1 Lucky Texan

[DaveT]

I once had a blocked cat on one of my older ea82s. Idled ok, but gutless when trying to drive. My test for suspect exhaust blockage is to unhook the pipes from the heads, but I have stainless nuts on the studs, and anti seize compound on them also. Use wire or the like to secure the pipes, just leave at least a 1/2" gap. It will be loud but if it runs normally, it's something in the exhaust. You likely will need new gaskets if you try this .

[1 Lucky Texan]

if you have another car, hook up the vac gauge, start it, have a helper carefully block the exhaust with a length of wood ,push with a foot if needed, w'ever, to see what the gauge does?

 

 

 

 

based on this, I thinkthe numbers you have DO indicate a possible problem - vacuum leak or blocked exhaust ?

 

wonder if spraying some carb cleaner or starter fluid around the vacuum lines and intake manifold might show a vacuum leak? Dropping the exhaust might be best as suggested above.

Edited September 28, 2016 by 1 Lucky Texan

[Rooster2]

I would suspect something other then a blocked converter.

 

Years ago, I had a car with a converter that rattled. The media inside the converter had broken loose. On a long trip the media jammed itself in the outlet pipe to cause major back pressure. The car would idle and drive fine up to about 45 mph. Then the back pressure was so great that the exhaust could not easily escape from the engine. As a result, the car would not accelerate beyond 45 mph.

 

Still could be a blocked converter, but would check other things as well.