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Attempting to diagnose power issues; 97 OBS with franky. Technical info inside.

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So as I've mentioned in postings past, my 97 OBS has NEVER really run right. I've never seen good fuel mileage (I averaged 22mpg all year, 80% freeway) and ever since installing my franky, my symptoms have gotten worse.

 

Engine build:

1998 EJ25D block, balanced

1997 EJ22E single port heads

Delta 200 cams for roller rockers

NGK BKR6E11 plugs (OEM)

NGK blue wires

Grimmspeed 8mm phenolic spacers

"Redtop" 280cc injectors (OEM 2.5rs injectors, FPR, rails)

MAF

Stock drop in dry filter

Stock intake

2" UEL, stock cats, Bosch o2s, axleback eBay exhaust.

 

Pretty much all I can think of.

 

So after I installed the franky, I had a nagging P0304 misfire. I changed plugs, changed wires, changed injectors, and finally I replaced the stock "snorkus" and it went away.

 

However, I still have what feels like a misfire under low rpm loads, and serious stumbling when the engine is cold; like completely falls on it's face.

 

As I was driving into work this morning I hooked up my OBD 2 reader and am using a primitive and basic scantool until my new software arrives, so bear with me on my figures. I wanted to see what my MAF was registering as flowing, as well as my calculated engine load. I'm thinking I may have "MAF flu", being that the car dies if I disconnect the MAF meaning that it does read off the MAF, but the voltage may be out of range causing it to think it's flowing more than it really is.

 

During average cruising, 2800 rpm at about 70mph, I was registering 30 g/sec, but if I put my foot into the throttle more than a hair, it jumped to 55-60 g/sec.

 

My average engine load was 27-32%, however it got up to 71% going up a steepish incline at sustained 70mph speed.

 

My sneaking suspicion, is that my MAF is reading higher than my actual air intake, and therefore is causing my car to run rich; hindering performance and killing MPGs.

 

Thoughts?

 

My other thought is that my coil pack is bad/going bad. I have spark on all 4 leads (tested using spark tester and spare plug methods) but I haven't found any sort of comprehensive guide to testing resistance or continuity between plug leads.

 

Unfortunately I don't have access to another MAF or coil pack to test either of those theories, so I'm hoping to isolate my concerns before I buy any parts. Any help is appreciated.

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any way to check valve clerance i run into it with 2.5ds were the valves are to tight and sett misfire codes is it smooth hot at idle ? also have seen a cupple bad mafs latly but runs very ritch when bad or super lean. if your engine uses hydrolic lifters mabee one or two of the hlas is stuck in full out position have had thiss problem to. and last thing check your compretion no sense chasing a problem if it has a low hole good to at least know what you have. On the buggy race engine i comp test it before i run it so i have a base of what the comp was before i started is a good referance to chase problems

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thiss engine may pull harder on the maf and throw it out of range can you restrict the intake to the maf ? and have you tried it with the stock injectors ? and done a feul preshure reserve test ?

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I'm thinking I may have "MAF flu", being that the car dies if I disconnect the MAF meaning that it does read off the MAF, but the voltage may be out of range causing it to think it's flowing more than it really is.

 

This is pretty much normal. If the ECU loses the MAF signal it doesn't know what to do and the engine stalls immediately. It doesn't necessarily mean there is a problem with the MAF.

 

 

Valves seem a little tight IMO. Intake is probably OK, but the exhaust valves need to be a hair on the loose side because they wear faster.

 

Have you hooked up a vacuum gauge to it? Any fluttering or jumping of the gauge (more than 1 or 2") at idle could indicate valve problems.

 

Does the car have a MAP sensor? What is its value at idle? Other readings like ECT, throttle angle, fuel trims?

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This is pretty much normal. If the ECU loses the MAF signal it doesn't know what to do and the engine stalls immediately. It doesn't necessarily mean there is a problem with the MAF.

 

 

Valves seem a little tight IMO. Intake is probably OK, but the exhaust valves need to be a hair on the loose side because they wear faster.

 

Have you hooked up a vacuum gauge to it? Any fluttering or jumping of the gauge (more than 1 or 2") at idle could indicate valve problems.

 

Does the car have a MAP sensor? What is its value at idle? Other readings like ECT, throttle angle, fuel trims?

 

Valves are definitely perfect, got a 5 angle and new valves 14k miles ago, everything checked out fine and the machine shop who did it has been at it awhile. Plus my leakdown results were negligible.

 

No MAP as it's a 97. My TPS reads 0 to 89% as intended, fuel system loop goes open and closed as normal.

 

I guess the 2 main things I'm after are what my MAF should be reading at (The fact that it doubles under throttle worries me) and if there's a comprehensive coil pack test that I can do to make sure it's good?

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I would check or replace the knock sensor. Usually you get a code but sometimes they don't.

 

Front O2 sensor? I wouldn't expect that but I've seen crazier things.

 

Original 97 EJ22 intake manifold on those heads or something else?

 

Timing marks all look dead on and you have the correct timing belt installed?

 

Timing tensioner (new style probably?) isn't "bouncing" is it? Every one I've seen that does that makes noise, not sure if they can flop and not make noise?

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I would check or replace the knock sensor. Usually you get a code but sometimes they don't. Brand new OEM knock sensor when I built the engine (14k miles) Though I haven't checked to see if it's loosened up or something... I'll check into that.

Front O2 sensor? I wouldn't expect that but I've seen crazier things. New Bosch sensors front and rear. Cats are nice and clear

 

Original 97 EJ22 intake manifold on those heads or something else? All stock

 

Timing marks all look dead on and you have the correct timing belt installed? Timing is perfect (Done a lot of T belts)

 

Timing tensioner (new style probably?) isn't "bouncing" is it? Every one I've seen that does that makes noise, not sure if they can flop and not make noise? I actually modified the tensioner block to run the old piston style. Had a few of them and used the one that was in the best shape.

 

See bolded above.

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he shoots and he scores, well done!

sounds like this issue was present before the swap and all the work?

i think you're all over it then - try that MAF.

 

I'd also consider installing a used igniter, coil, and ECU as a test since those are so easy to do and rule out.

 

Two forum folks just cured some issues by swapping ECU's, one was Fairtax's 96 though the issues were different. I was surprised considering how rare Subaru ECU issues are.

 

I have a spare 1996 EJ25 ECU i'd mail you to test if you wanna ship it back.

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I have a 95 "parts car" that I have access to (That I forgot about until 10 minutes ago) that should have the MAF and coil pack, possibly the ECU that I can test against.

 

Thanks for all of the help. I'm trying to avoid having to go standalone and getting my car tuned, but that will be the last recourse if none of this pans out.:horse:

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95 ECU probably wont work. 95 ECU pinout differs from 96-98. The engine side harness is the same, but the ECU end is different for some reason.

 

Still would like to see some vacuum test results.

 

Coil packs (this style) don't usually cause misfire problems on just one cylinder. That would be spark plug, wire, fuel injector, something specific to that cylinder.

 

Plug wires are usually checked with an ohmmeter. All should be about the same resistance. Not sure off the top of my head what the spec is, but if one is significantly higher than the rest it could be bad.

 

What did you set your spark plug gaps at?

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Any progress on this yet? I am having a similar issue in my all stock 96 Leg Brighton. Car runs great until warm then starts having a stutter/miss randomly across the RPM range.

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get lots of cars with bad wires coils 02s but they all still work good check engine light ect if the engines good it should work. most runability problems i see are mecanical ishues not component problems.

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thiss engine may pull harder on the maf and throw it out of range can you restrict the intake to the maf ? and have you tried it with the stock injectors ? and done a feul preshure reserve test ?

 

I'm guessing injectors too.

 

I had trouble with an EA82T trying to run larger injectors without any retuning.

 

Had to go back to the stockers to get it to run right with stock ECU.

 

Through the Franky aspect and the cams in the mix......you need a tune.

 

 

Just a thought though......check what your Coolant Temp Sensor is reading cold and fully warmed up. If that is off, it can do strange stuff to fuel maps.

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I assume your ECU is also from a 97 EJ22? My 92 ECU is designed to work with the red top injectors, same as the EJ25D. What injectors came on your 97?

 

If you build/buy a SSM cable you will have so much more information. The second thing would be to get a wideband o2 sensor. I have the MTX-L and with EvoScan I can log SSM and WBo2 simultaneously.

 

With the cams you will run lean at idle. Same with the EJ25D shortblock. Combined you're likely exceeding the range of the ECU adjustment and running too lean at idle/low RPM. You said your ECU runs closed loop; is the o2 toggling while idling?

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funny thought i mixed up a roller cam with a hydro cam one day and had the wrong cam to match the valve train thiss ran ok but not good was the wrong profile. when i put cams side by side was very different is it posibble somewere you had thiss kind of mixup ? it still ran well but was just never right. Took me a long time to find thiss once the motor was togther and running.

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I started following this thread: http://www.ultimatesubaru.org/forum/showthread.php?t=137845

 

After I noticed my engine was pulling timing BADLY. Like down to 0*.

 

Before I noticed that though, I swapped out my MAF and coil pack with no changes. Just for grins, I threw a junkyard ignitor on and saw a little better performance, furthest I could pull timing was to 6*.

 

Then, I decided to try my old knock sensor. Voila! Hasn't dropped below 12* and that's completely lugging and sticking my foot it it. Drove about a full tank and got better fuel mileage than I have all year; on snow tires nonetheless.

 

I'm going to keep at this and see if there's anything else I can change out. 250k miles; I'm guessing my stock cats are probably in abysmal shape, so I may be building a track pipe to test out that theory too.

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I figured you were abducted by elves, seeing as you didn't answer any of the questions above. Sure must have been cold at the North Pole.

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The P0304 saga continues.

At this juncture, I have logged about 30k miles on the car since January of 2012. After being tuned by Pre a few months back, my loverly p0304 came back in force.

No I don't have snapshot data, don't ask or suggest it. Here's the funny part about this fault code.

I have changed out absolutely any and every single part on the engine that is related to misfires.

Engine itself
injectors
FPR
Fuel pump
plugs
wires
coil pack
igniter
IACV
MAF
Knock sensor
crank sensor
cam sensor
o2 sensors
cats

I shake my head about it, then pulled the bulb from my CEL. No more CEL. Problem solved!  :lol:

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At this point, maybe install a new coolant temperature sensor - they are fairly well known for getting lazy, dumping too much fuel, and not throwing a code.
Doubt it's an intake leak?

 

Swap in another ECU for kicks? I probably have one I can send you to test with....but they're not worth anything. someone else likely has one locally.


My guess is you already installed one and it won't help anyway but a new PCV valve wouldn't be a bad thing.

 

It's not an automatic is it?  There's a quarter sized round filter inline with a vacuum hose off the passengers side strut tower.  I had one with some hesitation/misfire like symptoms. Replaced that filter with a new one from Subaru and it never did it again...that was like 8 years ago and a friend is still driving that car. Ironically a 1997 OBS.  I doubt that's it though, that seemed like a very odd thing and it was predictable - it would do the same thing on inclines/under load. i've always wanted to intentionally clog one up again and see what it would do....

Edited by grossgary

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At this point, maybe install a new coolant temperature sensor - they are fairly well known for getting lazy, dumping too much fuel, and not throwing a code.

Doubt it's an intake leak?

 

Swap in another ECU for kicks? I probably have one I can send you to test with....but they're not worth anything. someone else likely has one locally.

 

My guess is you already installed one and it won't help anyway but a new PCV valve wouldn't be a bad thing.

 

It's not an automatic is it?  There's a quarter sized round filter inline with a vacuum hose off the passengers side strut tower.  I had one with some hesitation/misfire like symptoms. Replaced that filter with a new one from Subaru and it never did it again...that was like 8 years ago and a friend is still driving that car. Ironically a 1997 OBS.  I doubt that's it though, that seemed like a very odd thing and it was predictable - it would do the same thing on inclines/under load. i've always wanted to intentionally clog one up again and see what it would do....

 Did a new CTS early on, intake was smoke tested, pcv is Subaru OEM and cleaned monthly, 5mt, and the ECU is about the last thing I planned on replacing; almost not worth it at this point.

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Everything except the ECU? Are you still running the 2.2 ECU? Wonder if swapping to a 2.5 ECU would help? Maybe it would deliver a little wider fuel map at idle?

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