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Help Diagnose '96 Frankenmotor, Low Power, w/ Torque Graphs


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I have two Legacy wagons, both manual trannys, a 1997 Brighton 2.2L that has run like a swiss watch for 6 years, 60,000 miles or so, now has 304,000 miles. And I have a 1996 Frankenmotor (2.5 block) that has been our second car. The Franken ran ok when I got it, though it did drink oil fairly well compared to the 2.2, and never had more power than the 2.2L. The 2.2L gets about 25 mpg, and the Franken got 16 mpg last tank (though it used to be around 20).

 

At some point, a couple years ago, I came to the conclusion that I had a burnt #4 exhaust valve in the Franken. It sat for a long time, until I finally got around to it, took the heads off, and everything looked A-OK. New head gasket and everything back together. If I remember right, my diagnosis came from #4 misfire and low compression in that cylinder. I may not have tested compression well (or maybe old head gasket was bad?).

 

Anyhow, I've done a lot of stuff to the Franken, and the low power still makes it mostly undriveable (stalls easy, has trouble getting up steep hills). New fuel pump a couple thousand miles ago, I assume I put a new fuel filter in...and new plugs and wires. I was still getting the #4 misfire on occasion, I swapped the injector with #2, and I don't get the misfire code on either cylinder now. I put a new coil pack on. New air filter. New PCV valve. New #1 O2 sensor. Cleaned MAF. It has an issue of pulling (pushing?) oil into the air intake (through valve covers or PCV?). I clean the oil sometimes. I took the whole breather apparatus off the 2.2L and put it on the Franken (so no oil and likely good MAF), but that didn't help.

 

Its starting to seem dubious that its a good strategy to keep throwing new parts into a poor-running engine. Especially parts that wouldn't transfer over to the 2.2L (like fuel injectors). So hoping for some insight, or at least some practical things to try from the community here.

 

I got the Torque app, and a reader, a couple months back. That led me to change the o2 sensor. I made a graph of both cars taking the same trip. Its all hills here, but towards the end I tried to hold near 2200-2400 rpm in a flat area, and then let idle for a minute.

 

 

 

 

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I believe the valves have the hydraulic lifters.

 

When I did the compression test a long time ago, I did a leakdown, and #4 seemed to leak out of the exhaust, but not the intake. (Maybe I wasn't right at TDC #4? I think I used a screwdriver in spark plug hole to *feel* top of piston) That's how I came up with burnt exhaust valve. When I finally pulled the head (just the right side) last fall, I took it to a skilled machinist. He gave it a lookover and said it was all good, no work needed done. He tested for valve leakage by putting some liquid (window washer fluid?) in the cylinders and nothing leaked. Also, he said if I had leaky piston rings I would have had carbon buildup on the valves.

 

Is there something else I should check on valves? Compression test won't be today, will try to get it in tomorrow.

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#1,2,3, have 228, 235, 242 psi not respectively.

 

#4 cylinder has 68 psi.

 

All spark plugs are light tan to gray, with some yellowing away from the spark, and oil on the threads.

 

So...valve problem? What did I miss when I pulled the head off, and do I need to pull it again (and replace a brand new headgasket?!?)

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Leakdown test:

 

At #4 TDC air leaked out the throttle body and all air hoses : valve cover vents, PCV, and that big horizontal one that's near the IAC.

 

At other TDC air streamed out the same areas.

 

Valve clearances:

Zero valve clearance on cylinders 2 and 4. Will research now to see how this pertains to HLAs.

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With valve cover off, air into spark plug clearly leaked from exhaust valves and a little from intake valves. I took off rocker arm, and cleaned the 8 HLAs. Not quite sure how to tell which ones are good and bad. A couple sit up higher, and a couple can be moved without holding in the little check ball.

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Roughly estimated leaking on #4 leakdown test with rocker assembly removed:

 

55% #4 exhaust valve, mostly the one closest to firewall

*maybe* a tiny 5% from #4 intake valves

25% #2 exhaust valves

10% #1&3 valve cover vent hose

10% PCV bypass hose

(note: spark plugs were returned to other cylinders, since I couldn't feel what air flow was coming from them)

 

nothing noticeable through TB intake, exhaust, oil dipstick, or radiator'

 

Interpretations?

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I tried tapping valves while doing test. No perceivable difference in leakdown.

 

It seems my machinist was wrong? But I'd think a guy who has run his business for years....and has a good reputation...wouldn't declare a head good, and everything tells me I still have very leaky exhaust valves in #4....I saw a youtube video the guy put water on his valve heads facing up, then blew air from the bottom to see bubbles....the liquid didn't leak through tiny cracks...like the machinist's theory woulduv....

 

so take off head again...? and bring to a different machinist to seat valves? (maybe I could do it myself, but I don't have much inclination to at the moment)

 

and assume I also have some leakage past piston (for air to get to other side of engine)...but it should run decent if valves seal up...and I can look for another car/engine in the next couple years...this one has a decent body, and tranny seems good...

 

am I on the right track? I'm certainly not looking forward to taking the head off again...always easier the second time however...

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The car was being used plenty as it started losing power...seems strange that anything would be frozen or stuck

 

And when I say the car sat, I still started it every month or so, and sometimes would drive it up the steep hill to town.

 

The car has a recently new pcv valve.

 

I'll pick up some MMO. I gotta wait anyways for my HLAs to arrive. Even if I'm going to take the head off I want to at least drive the car to the garage.

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What year heads are on it?

I've heard of some of the late 90s heads having problems with the valve guides dropping and holding the valves open.

 

Maybe weak valve spring on that cylinder was causing valve float and the valve burned between when it was checked out and now? Or the machinist just didn't give a ....

and hit them with some cleaner and said they were fine...

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Fairtax, I think they are '95 heads. I believe jboymechanic who used to be on here built it.

 

I took it apart once and there wasn't a burnt exhaust valve. Would be odd that I still have same symptoms...but a different cause...

 

Yeah, I was with the machinist. Like I said above, he used water to check for leaks. No water leaked out, so he checked for warpage, and gave it a 20 sec. clean, and said it looked fine. He's a nice guy....he didn't charge me anything...but I know he didn't clean the valves at all..

 

rocketman...you are going a little over my head...I've taken two heads off in my life...but I'll give it a go:

 

lifters not noisy from what I can tell, compared to other Subes I've heard. Both of my subes can be a little tick-tappier on a cold morning...and if the oil starts getting low, I can hear it in the valves (I think)

I'll be able to see the cam lobes tomorrow, they will be right where I took the rocker arm off, yes?

IF I remember, I thought the cylinder was scored when I first looked at it, but it was a crosshatch pattern which I assumed should be there.

I did not notice a ridge ring. I think I would have noticed. I did spend some time looking at everything.

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