Loss of power, 2002 Forester

[ThosL]

I had two jobs I contracted for today.  They involved driving down from New Canaan, CT to New Rochelle, NY.  On the way to NY the Subaru lost power.  I noticed a gas smell out of the exhaust previously.   It bogs down when you put your foot on the gas pedal.  Gas is burning excessively, 10 mpg at best.  I ran a computer check on it and it showed cylinder #3 and #4 misfire.   Also codes for O2 and evaporative came up.  I disconnected the O2 censor into the main engine thinking that might effect improvement which it didn't.

My older brother warned about doing work with a car with problems such as towing a work unit if the car breaks down being very costly.  I was able to get the work done without car breakdown.  Is this likely electrical?

Edited October 8, 2022 by ThosL

[Turbone]

2 things to check - the coilpack and the catalytic converter

[ThosL]

I replaced the ignition coil nearly a year ago and I was thinking of that too.  The previous owner said that he had replaced his a year before.  But when mine failed power loss was greater and the unit broke down physically.   I replaced the cat converter last winter.  I'm assuming running the car with gas not burning even for 50 miles puts an undo load on the cat converter.

[heartless]

3 hours ago, ThosL said:

I replaced the ignition coil nearly a year ago

with what? aftermarket or used Subaru OEM?
did you change the wires, too? also with what?
what about spark plugs? again, with what?

on all of those it DOES matter what you use..

having owned a 2002 Forester, i am sure that it takes basic copper core NGK spark plugs (owner's manual lists BKR5E-11, or BKR6E-11 (the 6 being colder than the 5) with a gap of 0.039-0.043 (i generally set mine at 0.040 for simplicity)
Wires should be OE or NGK ONLY for reliability - anything else is a waste of your money.. parts store brands almost always cause firing problems.

for the coil pack.. i would honestly go with a used OE unit over anything aftermarket.. aftermarket is more likely to fail prematurely than OE will..   If you are concerned about corrosion issues, then order one from a JY out of your area.. like Colorado, Idaho, or something.. someplace that does not use salt or other chemicals on the roads.  car-part.com is your friend here. Or check with lmdew.. he lives in CO and can probably help you out.

beyond that, when is the last time it got a fresh air filter? have you checked/cleaned the air flow sensor? (a dirty air flow sensor can cause issues, too... )

and yes, raw gas thru the cat convertor can spell trouble..

[ThosL]

Thanks for the recommendations; the last ignition coil was replaced on last October 15, so I went to the mechanic he emailed proof of the receipt/transaction and they reluctantly backed up their guarantee.  Problem solved.

FYI the diagnostic on it was to remove coil wires while vehicle is running, two had no spark.  

[heartless]

21 hours ago, ThosL said:

Problem solved.

for now.... but hey, glad you got it replaced under guarantee

21 hours ago, ThosL said:

.....reluctantly backed up their guarantee

this does not bode well for the next time there is a failure.  Hopefully you dont have one,

[ThosL]

I'll look for a used Bosch unit at the junkyard, not worth taking the chance of a breakdown on the road.

With other cars other problems, as one friend said:  Compression check? Dirty injectors, bad coil, spark plug, fuel pump/filter, pvc valve, egr valve...

[heartless]

21 hours ago, ThosL said:

I'll look for a used Bosch unit at the junkyard,

i believe the OE supplier is Diamond, not Bosch.

generally speaking, a misfire is usually caused by:

a) bad coil
b) bad plug wires
c) bad plugs

not always, but usually...

 

[1 Lucky Texan]

if the codes are consistently in pairs like ; 1 & 2, OR, 3 & 4, that points to a possible coil problem because of 'waste spark' sharing of coil output.

cetrainly oil on plugs or cable ends or bad wires, etc. could be an issue.

[ThosL]

I liked the way the mechanic loosened and pulled the plug wires while running for confirmation which I had not thought of.

What damage does running a Subaru with a bad coil, do?  I ordered some fuel injector cleaner.

[heartless]

3 hours ago, ThosL said:

I ordered some fuel injector cleaner.

ordered? you can buy injector cleaner just about anywhere - even Walmart. Regardless, injector cleaner is not going to help you with this issue.

your misfire is not a fuel delivery problem, it is a spark problem - or lack thereof. Lack of spark is one of (or a combination of) 3 things... coil, wires or plugs. (fuel injectors have absolutely nothing to do with lack of spark.)

how much damage depends on how bad things are, and how long it stays that way..
long term, you can do a lot of damage - to pistons, valves, and cat converter..

 

[1 Lucky Texan]

consistent misfires will often cause the CEL to flash. Your manual probably says not to drive the car if the CEL is flashing. Too much unburned fuel going into the cat. conv. can ruin it.

highly unlikely to be this pair of clogged injectors - though occasional use of injector cleaner shouldn't hurt anything.

[jonathan909]

On 10/11/2022 at 6:06 PM, 1 Lucky Texan said:

consistent misfires will often cause the CEL to flash. Your manual probably says not to drive the car if the CEL is flashing. Too much unburned fuel going into the cat. conv. can ruin it.

Fwiw, years back when my '95 OBW's EJ22 chipped a valve, it was at the beginning of a nasty winter and I knew I wasn't going to be able to do anything about it until spring, but needed to keep the car running.  I wasn't even thinking of what the unburned gas would do to the cat; I just didn't want to waste gas by pumping it into a cylinder that I knew wasn't going to be burning it.  So I unplugged the injector and ran 'er on three until the weather turned.

Edited October 13, 2022 by jonathan909

[ThosL]

After replacing the coil, the car started running normally again.

 

The fuel injector cleaner was to get a cleaner burn, hopefully do something to help the catalytic converter.  There are dedicated products for the cat converter, doubt they do a lot of good.

 

Looks like NGK is the OE on the coil, around $130 online.  All the franchise auto stores sell a coil knock off for around $100, probably not much better than the China imports on ebay for $25 delivered.

[ThosL]

I checked with a mechanic today after my brother said the unburned gas smell was noticeable like the 60s cars.  He said the plugs should be checked may have been fouled by the 10 or less mpg I was getting.

[1 Lucky Texan]

is the car producing a fuel smell at the tailpipe now?

[ThosL]

Seems to be ok now.