loss of power - sudden burst of power - repeat

[milty60]

09 suby forester manual 240K 

Idle speed a bit low lately. Son on highway this morning - doing 65 - sudden loss of power - floors gas pedal - nothing - a couple of seconds later - sudden burst of power - repeats behavior - pulls of highway - I head out to rescue him - I do quick check under hood - nothing jumps out - I swap cars - idles smooth - around 750rpm - drive on highway back to work about 20 minutes runs perfect. Hope to resolve over weekend  - hope I get home tonight - son said same behavior happened once before - one time - seems to occur on the highway only after running for 30 40 min. Does this sound like a clogged fuel filter - fuel pump going bad? assume both are in tank? Something else? Thoughts advise.

Thanks, 

Milty

 

 

[el_freddo]

My sister’s liberty did a similar sort of thing in the driveway when idling. The issue for us was the IACV, I’d fiddled with it and caused an issue.

Our fix was to reset the computer. No problems for the rest of today. 

Got any codes? 

Cheers 

Bennie

[milty60]

Have had a code for front catalytic converter sensor for a couple of weeks. Wonder if the IACV needs to be cleaned? We have reset the computer a week back to see if check engine light would go out - disconnected reconnected battery after 10 minutes or so - check engine light stayed off for a few weeks

Thanks, 

Milty 

[brus brother]

Does it by any chance happen while going uphill?

The reason I ask is from reading posts on the message board where catalytic converter material had broken apart and under certain conditions where gravity would move the material it would obstruct the exhaust.

In fact I was in a friend's Ford van where gradual loss of power got to the point where the car wouldn't even move. Disconnected the exhaust before the cat and it ran fine (albeit LOUD AS HELL) . BTW, the hills in this case were minimal.

BTW what is the exact code you are getting?

Edited October 4, 2019 by brus brother

[1 Lucky Texan]

^^^^ yeah, what he said

 

codes could be very helpful

[milty60]

Code P0420. loss of power happens up hill down down hill flat road 

Thanks, 

Milty

 

[milty60]

Replaced plugs, cleaned MAP sensor, and throttle body, replaced air filter, could not remove PCV - entire housing would turn - sprayed it WD40 couldn't separate from housing. Repalced hose to PCV - hard as a rock - reset the computer. Did the re-idle procedure. As before, engines idles around 350-400 rpm - sprayed carb cleaner on all vacuum lines, fittings, intake manifold mating surface, brake power booster - idle remained the same. Wonder if water in gas had caused my son's power loss issue - still need to do a long highway test drive. Any thought on low idle - only code is P0420 - cat sensor.

Thanks, 

Milty

[1 Lucky Texan]

rig a vacuum gauge to watch, see if there's a big change when the power loss hits. that might condemn the catalytic converter as mentioned above.

[brus brother]

On 10/5/2019 at 10:57 AM, milty60 said:

"Have had a code for front catalytic converter sensor"

While the problem may be related to front sensor, P0420 is catalytic efficiency below spec bank 1 (passenger side)

there are many possible causes (and remedies)

live data would help in diagnosis instead of throwing your wallet at the car

 

 

[Hellzbellz1234]

pretty sure my aunts subi had this problem and it was a cracked intake manifold. swapped it and it ran like a beauty. till it ended in a river

[milty60]

A possibility but I sprayed carb cleaner with that tiny spray straw at and all-around intake manifold, vacuum lines, etc, didn't budge rpms per tach from about 500K - frustrating - sometimes it will even drop to 400 k or so - first purchased Suby - hung around 750k at idle.  Maybe I should drop cat and see if idle goes back to 750k. Thoughts or any other ideas on low idle? Keep wondering if some fuel/air or spark advance/retard devices are messing with the idle? 

Thanks, 

Milty 

[milty60]

Update - replaced the downstream oxy sensor last week - son bought an odbc tool - Oxy code is now gone but found 4 more codes - 2 current faults - P0204 powertrain injector circuit - cylinder 4, and P3100 powertrain, also 2 pending faults - P0104 powertrain mass or volume air flow circuit intermittent - P2000 Powertrain - NOx trap efficiency below threshold bank 1.

At first start in the morning - with the engine warmed up car idles a little rough, never stalls, and sits at about 350 RPM. Driving around at stoplight in neutral tach first sits at 350 but then will go up to 750 RPM and stay or drop down a little bit - it seems like the ECM is attempting to bring idle to the correct level. Repeats this behavior at most stops but not all. 

Black soot? is at both tailpipes - cleaned off a week ago - currently, it's back but very lightly coated. I don't see black smoke coming out of tailpipes. Gas mileage is about 28 on the highway.

I don't feel any hesitation or power loss as I move through gears from standing still, in town, on the highway , up steep hills, etc. 

From the codes above is the highest probability next step replacing the fuel injector at cylinder 4? Please Advise? 

Thanks, 

Milty 

 

 

 

 

 

[Rampage]

3 hours ago, milty60 said:

volume air flow circuit intermittent

This is one thing to check. The Main Relay contacts might be starting to burn and fail. Usually they last a very long time. See image below.

The Mass Air Flow sensor, EGR valve and Injectors get their supply voltage from the Main Relay. Check the voltage and see how in compares to battery voltage. On the MAF and Injectors the wire color is Yellow with a green stripe.

You might have to hook up a wire and bring it inside so you can watch the voltage as you drive. Battery is 12 volt, but with the engine running the alternator increases the voltage.

Replacing the Main Relay might be easier.

[milty60]

I will look into it. 

Thank, 

Milty 

[milty60]

I looked under the hood at big fuse box - I see relays but not the main relay - also checked fuse box under dash driver side - only see fuses - where do I find the main relay? I will probably just swap it out. Assume its a Subaru dealer part. 

Thanks,

Milty

[Rampage]

In the diagram below, connector B220 located at Row B Coulomb 4. Looks like a block to hold relays.

[el_freddo]

Have you got one of those IACVs that has the little rubber O ring like rubber gasket in the shape of two rectangles (from memory, I haven’t had much to do with this IACV setup)? 

If so, check that it’s not cracked. If it is, replace it. 

Cheers 

Bennie

[milty60]

I'll try to use the diagram to locate relays and check to see if I have a IACV with a crack 

Thanks, 

Milty

[milty60]

I need to investigate further but I see a very small puddle of coolant sitting in indents in the engine block around the back right area of the intake manifold. I don’t know if it’s a manifold gasket leak or some other hose/pipe in that area that may be leaking. The radiator level and overflow tank are right on the mark – so it’s a slow leak – I need to dry up the small puddle and see how quickly it fills in and/or rent a pressure tester this weekend and look for a leak. I had previously sprayed carb cleaner around the entire intake manifold to see if I had any vacuum leaks – no increase in idle occurred – so I’m assuming no cracks in the manifold. Until I investigate further do you guys know of anything else that may be leaking in that area? Do you think this is a separate issue entirely or could be related to all those check engine codes and/or low idle? Please advise.

Thanks,

Milty

[heartless]

9 hours ago, milty60 said:

I need to investigate further but I see a very small puddle of coolant sitting in indents in the engine block around the back right area of the intake manifold. I don’t know if it’s a manifold gasket leak or some other hose/pipe in that area that may be leaking. The radiator level and overflow tank are right on the mark – so it’s a slow leak – I need to dry up the small puddle and see how quickly it fills in and/or rent a pressure tester this weekend and look for a leak. I had previously sprayed carb cleaner around the entire intake manifold to see if I had any vacuum leaks – no increase in idle occurred – so I’m assuming no cracks in the manifold. Until I investigate further do you guys know of anything else that may be leaking in that area? Do you think this is a separate issue entirely or could be related to all those check engine codes and/or low idle? Please advise.

Thanks,

Milty

when you say "back right" are you referring to the passenger side of the car, or the right as you are looking in the engine bay (drivers side)?

If it is on the drivers side, yes, there are a couple of coolant lines in that area that can leak. I actually had to replace the one on my 2002 due to rust causing problems. Kind of a pain in the rump but it can be done without pulling the engine out.

There is a main cast crossover line that runs from passenger front to drivers rear, then there is another metal tube that runs solely on the drivers side - from the water pump area, up the front of the block to the top rear of the block called the "bypass pipe" - this is the one that likes to rust out. It has a couple of rubber hose connections toward the rear... one small one that goes to the throttle body, and a larger one that runs to the heater core

[1 Lucky Texan]

maybe a pinhole is spraying coolant on a cracked spark plug wire?

[milty60]

Sure could be.  Once I replace hose I'll see how car behaves. 

Update - I found a small coolant host that goes from the throttle body down to engine block – it has the OEM squeeze clamps on it – I can move clamp around with my fingers – looks like original hose too - I ran my finger on the bottom of the hose by the throttle body and its wet – coolant runs along the hose and drips around the intake manifold in the back right and pools in depressions in the engine block – going to get a new hose and screw type hose clamps this weekend. Thank God I wasn’t facing a manifold gasket replacement this weekend.

Thanks,

Milty

[milty60]

Still trying to determine the location of the "Main Relay" to see what condition it is in and/or replace it. I spoke to a Subaru dealer parts guy - he said Subaru is a pain in the butt when it comes to identifying any relays. Parts do not list a "Main relay" I told him what is hooked to it - maf, egr, fuel inj - he said he cannot locate it but look for the biggest relay with the biggest prongs closest to the passenger side under hood in the fuse box - the biggest one in that location has written on the lid diagram - main fan relay. So, I hate to take it to Subaru and have them charge me labor to point it out to me - unless they would do it as a courtesy to help out the parts guy. Thoughts? 

Thanks, 

Milty 

 

[Rampage]

All that wiring harness in the photo is behind the dash. The holder for the relay looks like it would be behind the glovebox right below a wire that goes through the firewall. I don't know if it is mounted to the firewall or on a bracket.

These two pics say the Main Relay is located in the upper righthand corner of the relay block. In the wiring harness above it shows the 4 fuses on the bottom of the block.

[milty60]

Appreciate it - I will check it out over the weekend. 

Thanks, 

Milty