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Old 07-07-2018, 07:07 PM   #1
Imfozzybear
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Default 99 2.5 n/a MAF won't rev above 3k rpm

Long story with the car... Before I get into my question I'll list everything I've done to it (work not done because of this problem)

Timing belt
Water pump
Thermostat
New head gaskets
Intake gaskets
Rear main front main
Oil pump o rings
New MAF (not factory, problem was present before)
IACV (not factory )
Plugs, Ngk blue wires
Coil
Cam pos sensor
Crank pos sensor
Knock sensor
Fuel pump
Fuel filter
Front and rear 02 sensor


So the problem is, I can not rev above 3k rpm before it starts bucking and breaking up.. Several months ago it started, every now and then it will let me rap it out to 6 grand.. I hooked up my Bluetooth obdII scanner, and I was watching readings while driving... At idle there are times when the STFT will hit +18% I've seen it peg out at +28% while idling.. It's very inconsistent. It's showing I have 23 inches of vacuum at idle. I did a compression test and got dry
140-129 range across all cylinders. This is a manual transmission car BTW. I just checked fuel pressure, and at idle from the filtered side of incoming fuel, I'm getting 55psi at idle.. Seems to be 10 or so pounds to high... I shut it off and it dropped to around 30 psi standing on the line, I just went back out there and I'm seeing 0 psi after 40 mins or so... Ive sorta narrowed it down to FPR or injectors.. I am getting a rear 02 sensor CEL, no other hard codes.. Sometimes I will get a pending miss on 2 or 3 cylinders.. It idles somewhat rough... How can I have high fuel pressure at idle and the ECU is still seeing it needs more fuel? Any help would be great, I'm about ready to set this mother on 🔥
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Old 07-08-2018, 12:37 AM   #2
CosmoTheCat
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Try unplugging your front O2 sensor and see what happens.
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Old 07-08-2018, 08:20 AM   #3
Imfozzybear
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No change
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Old 07-08-2018, 02:02 PM   #4
Elbert Bass
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Are you sure you don't have a vacuum leak somewhere?
Will it run better with the MAF unplugged?
What is your fuel pressure with engine running and the vacuum hose unplugged from the fuel pressure regulator?
Did you adjust the valves?
Are you sure your engine is timed correctly?
What is your engine coolant temp sensor reading when the engine is warmed up?
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Old 07-08-2018, 02:27 PM   #5
Charlie-III
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Good comments thus far, follow them.

When were plugs and wires done last?
Does it run better if the ECU has been cleared (clearing codes through a scanner is usually enough).

STFT's can jump quite a bit, what are the LTFT's?

Your compression numbers sound low to me for a Subaru NA.

Did you try a wet test of compression? That helps rule out rings, but not likely your issue.

A MAF clean may help short term.
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Old 07-08-2018, 03:10 PM   #6
Imfozzybear
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There may be a vacuum leak, I'm just not sure where it would be, I've done some checking in and around the engine bay. As far as timing goes, I am confident, I am dead on the marks. Fuel pressure does not change with vac line on or off... Coolant temp I'm seeing 193, running up to 204 before it drops back down. Plugs and wires were done less than 20k miles ago. The car will shut off if I unplug the MAF, and it runs the same if I reset the computer, and let it relearn till the cooling fans come on. I didn't get a wet test on compression, I agree it seems somewhat low.. It's odd to me that occasionally It will run like there is no problem, and then most of the time the problem is present. I did not adjust the valves. Side note, it quite hard to do much to the car, as it is my daily, but in the same breath if I don't get it figured out this pile will blow and leave me with nothing
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Old 07-08-2018, 03:39 PM   #7
Charlie-III
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Stupid question, does the engine go to crap if humidity is high?

Fuel pressure should change (go higher) with the vacuum line off.
You may have multiple issues.

Without a smoke test.....engine running, use brake cleaner or carb cleaner on every vacuum line. If revs change, you are sucking additional fuel in, thus a leak.
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Old 07-08-2018, 05:56 PM   #8
CaptainSlowbaru
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Rear o2 code makes me think the cat is clogged. That certainly would explain the rest of the symptoms.

The only other thing I can think of... were the head gaskets done after the plugs were replaced? I once sent a head out to the machine shop with the plugs left in- they apparently never took them out when they did their thing. Afterwards, the car was missing badly at high RPM, high load. New plugs cleared it right up.
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Old 07-08-2018, 06:04 PM   #9
Charlie-III
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Quote:
Originally Posted by CaptainSlowbaru View Post
Rear o2 code makes me think the cat is clogged. That certainly would explain the rest of the symptoms.

The only other thing I can think of... were the head gaskets done after the plugs were replaced? I once sent a head out to the machine shop with the plugs left in- they apparently never took them out when they did their thing. Afterwards, the car was missing badly at high RPM, high load. New plugs cleared it right up.
OK, seems like a valid point.
My issue is the "comes and goes" which (to me) negates this.
But, worth the comment.

Waiting on the OP.
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Old 07-08-2018, 06:31 PM   #10
Imfozzybear
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I forgot to say, I did pull the muffler and the cats out to look at them... Everything I could see of the cats looked brand new.
I am confident that timing is dead on... I added another ground wire to the block thinking that may be an issue... I have noticed the alternator may not be putting out like it should. The lights at night dim slightly and then when I hit the gas it brightens up. Maybe a low voltage issue?
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Old 07-08-2018, 06:40 PM   #11
Charlie-III
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Quote:
Originally Posted by Imfozzybear View Post
I forgot to say, I did pull the muffler and the cats out to look at them... Everything I could see of the cats looked brand new.
I am confident that timing is dead on... I added another ground wire to the block thinking that may be an issue... I have noticed the alternator may not be putting out like it should. The lights at night dim slightly and then when I hit the gas it brightens up. Maybe a low voltage issue?
Engine off, batteries should be about 12.6 or more.
Idle, battery should be low 13's.
High idle, battery should be mid 14's.

Bad power or ground may dip high load circuits.

I will guess none of this is your issue.

Dang it.....fill in at least a state or Provence if in North America.
Fill in year, model, trans, mods in your signature.

Sheesh.......
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Old 07-08-2018, 06:53 PM   #12
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Have you tried looking at the coil pack?
It might be on its way out and causing the issue.
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Old 07-08-2018, 07:05 PM   #13
Imfozzybear
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I replaced the coil around 5k miles ago
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Old 07-08-2018, 07:27 PM   #14
91 RS RA
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Quote:
Originally Posted by Imfozzybear View Post
I replaced the coil around 5k miles ago
That was all I had sorry.
Apart from maybe a bad ground some where? Have you checked all the earth straps to the car?
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Old 07-08-2018, 07:34 PM   #15
Imfozzybear
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I appreciate your input... Good thinking... I have added an extra ground, maybe I need more
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Old 07-08-2018, 08:08 PM   #16
91 RS RA
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Quote:
Originally Posted by Imfozzybear View Post
I appreciate your input... Good thinking... I have added an extra ground, maybe I need more
Could also be original ones need cleaning up. My last legacy I went round and took off all earth straps, cleaned the connections till shiny and then gave the body points a quick sand till it was shiny as well and then reconnected
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Old 07-08-2018, 08:20 PM   #17
Elbert Bass
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OK, so you can rule out coolant temp sensor. Let me clarify the MAF question. Disconnect the MAF, then start the car and drive it with the MAF unplugged. Does it drive better? Cat is definitely a consideration if it doesn't fall on it's face all the time. Does the exhaust smell like gas or have a very strong smell?

One way to make sure that is not the cat clogging from too much fuel is to drop the exhaust and see if it runs better. If the cat is stopping up because of the fuel enrichment you still need to sort that out - is it a true lean condition (vacuum or exhaust leak pre-A/F sensor & cat)or a faulty sensor (MAF, A/F, TPS) throwing it rich.

Quote:
Originally Posted by Imfozzybear View Post
There may be a vacuum leak, I'm just not sure where it would be, I've done some checking in and around the engine bay. As far as timing goes, I am confident, I am dead on the marks. Fuel pressure does not change with vac line on or off... Coolant temp I'm seeing 193, running up to 204 before it drops back down. Plugs and wires were done less than 20k miles ago. The car will shut off if I unplug the MAF, and it runs the same if I reset the computer, and let it relearn till the cooling fans come on. I didn't get a wet test on compression, I agree it seems somewhat low.. It's odd to me that occasionally It will run like there is no problem, and then most of the time the problem is present. I did not adjust the valves. Side note, it quite hard to do much to the car, as it is my daily, but in the same breath if I don't get it figured out this pile will blow and leave me with nothing
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Old 07-08-2018, 09:32 PM   #18
Imfozzybear
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Now that you mention it, I am getting a sulfer smell quite often... The car will not run at all with the MAF unplugged.. Maybe the cats are blocked up, I'll pull it down again tomorrow, and persuade it to work... Is it possible, assuming the cats are backed up, that would throw the computer for a loop and make the mixture crazy?
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Old 07-09-2018, 01:11 PM   #19
Imfozzybear
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Update:

I've pulled the exhaust system down, and started the car
(no cats no 02 sensors) same result, cuts out a little higher 3300 rpm, the exhaust smells very fuel rich...

Will check for vacuum leaks later in the day
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Old 07-09-2018, 02:24 PM   #20
Charlie-III
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Deleting parts and no ECU reset (usually a code clear is enough....usually) the ECU is fueling based on learned values, thus you may be forked without a reset.
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Old 07-10-2018, 04:25 AM   #21
CosmoTheCat
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Wait what, no change to fuel pressure with the regulator disconnected? That's odd. I haven't seen it, but I've worked with people who have seen regulators fail internally and dump fuel through the vacuum line into the intake.

Also, don't forget when checking for vacuum leaks, disconnect and plug the brake booster line.

Does that have EGR?
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Old 07-10-2018, 12:06 PM   #22
Imfozzybear
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I'll check again, I might need to check my fuel pressure gauge and make sure it is operating correctly. No EGR on this car... I drove down the road again after clearing the CEL and watched fuel trims again... LTFTB1S1 was showing at time of being -20% STFTB1S1 was +17% and climbing at idle.. As soon as I took off from a stop light I could tell it was choked out with fuel... Both trims cut fuel up to 12%... CEL came back on, not I have an Evap code aa well as the B1S2 code... It did spit out that B1S2 was out of range. It appears the sensor is working based on the voltages I am seeing thru live feedback while driving..when I am rolling along and let off the throttle both trims go to -2.34% not sure that means anything, I'm still learning how to read all the data, and I'm not doing that great of a job it doesn't look like..
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Old 07-10-2018, 12:17 PM   #23
Charlie-III
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My mnemonic is.....low voltage (below 0.5 volts) is lean.

FT's show what the ECU is doing with fuel. Lambda shoots for "1.000", older shoots for "0.000 trim".
Older, +/-10% is OK, 15 is getting there, 25 or so pops a code since the ECU maxes out.

Lean (low voltage) may be intake leak post MAF, low fuel pressure, etc.

More often than not, BxS1 controls fueling, some use BxS2 for fine tuning.
Thus, if the front O2 is wonky, ECU ignores that and makes a best guess.

I still say a clogged CAT is always there, not a sometimes thang.
A clogged CAT WILL restrict flow, so gutless wonder under load. Yes, had an issue on a 99 Camry I4. I could watch fuel mileage drop over time, then power.

Last edited by Charlie-III; 07-10-2018 at 11:25 PM.
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Old 07-10-2018, 04:51 PM   #24
Imfozzybear
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I'm not sure I understand.. Are you saying my cats are blocked? I pulled them out yesterday and they look brand new, no soot or blockage of any of the honey comb. I found one vacuum leak at the top evap vacuum port, and found that the evap solenoid barb was broken off the valve... I will be getting a new one... The car ran awful today, it's very hot and humid today...
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Old 07-10-2018, 06:30 PM   #25
Charlie-III
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Quote:
Originally Posted by Imfozzybear View Post
I'm not sure I understand.. Are you saying my cats are blocked? I pulled them out yesterday and they look brand new, no soot or blockage of any of the honey comb. I found one vacuum leak at the top evap vacuum port, and found that the evap solenoid barb was broken off the valve... I will be getting a new one... The car ran awful today, it's very hot and humid today...
Who rev you replying to?

I don't think a clogged CAT since it usually is clogged, or not.
Not a "now and then thang".

I can see a post MAF vacuum leak driving LTFT's to higher positive numbers since the BxS1 O2 sensor sees a lean condition, thus it adds fuel.
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