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1999 forester Auto
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5 Posts
Discussion Starter · #1 ·
So, I bought my 1999 Forester with 130K miles 4 months ago, the previous owner reset the ECU just before I bought it to hide the P0420 CEL that it threw at me 2 days later. The car is currently running rich, I can smell it, I can feel it in my wallet with the bad MPG, and Torque is telling me the same. Other than this issue, I must say the car runs really good. It's an auto tranny, it shifts smoothly, has plenty of power climbing hills or passing on the highway. This being my first Forester, I have noticed how touchy the gas pedal is. Just barely touching it and the car wants to rocket off the line.


I'm at wits end when it comes to fixing it. Since July, this is everything I've done to it.

Parts Replaced:
  • New O2 Sensors, front and rear.
  • New Catalytic Converter
  • New Knock Sensor
  • New K&N Filters
  • New Double Plat NGK Plugs
  • New Plug Wire Set
  • New PCV and Cleaned Hoses
  • New Radiator and Cap

I've also seafoamed the engine. When I did that I did a visual inspection for exhaust leaks and found none. Currently, I am running 91 Octane fuel. No matter what I do I can't seem to get MPG better than 18MPG. When my wife is driving it, it gets about 16 MPG. Really love the car, but it's going to break me getting mileage like that. Along with the terrible mileage, When I hook up Torque and run a "Test Scan" I get a test flagged:

TID:$01 CID:$01
- Rich to Lean sensor threshold voltage(constant)
- Max 1, Current (35 - 101 ususlly)
- Test Failed


Here's a capture of the Torque Screen.


I was told to check the EGR Valve and clean it, but this EJ25 doesn't seem to have one, otherwise I would have.

So, What have I missed that could be causing this? Here is a list of suspects I still have:

  • Mis adjusted/bad TPS
  • Bad Temperature Sensor ( Torque says it is 188F when warm though)
  • Clogged Vacuum Hose somewhere.

Any help would be much appreciated. I've lurked here a while getting ideas for things to try. This is a great forum with lots of really smart folks and I'm hoping someone will give me some insight I haven't thought of yet!


Oh, and my 3 yo son, who is "hell-ping" me write this says i need to add these:

:Banane35:
:starwars:
:Banane36:
:bananapartyhat:
:icon_cool:
:icon_biggrin:
 

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Administrator
2007 Forester Sports XT 4EAT
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40,529 Posts
Welcome to the forum from another Oregon member! :biggrin:

I have a couple questions: :confused:
  • Have you cleaned the MAF sensor?
  • Is the front O2 sensor a factory/OEM part?
Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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1999 forester Auto
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5 Posts
Discussion Starter · #3 ·
Thanks for the welcome Sleeper, I've followed a lot of your posts for a while, since you are only a few miles south of me :)

As to your questions:
MAF has been clean less than a tank of gas ago.

The O2 Sensors were replaced with Bosch, not Denso :-( I didn't realize they were not the OEM as the car already had Bosch sensors and I just replaced with the same part number as was on the sensor. Bosch 15732 and Bosch 15726. Imagine my surprise when I realize they where universal fit sensors and I just couldn't see the splice until I pulled them.
 

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From my years of experience and limited data I can see I'd suspect leaking fuel injector(s) Undetonated fuel causes premature cat failure.

Spark plugs can give a hint of this cylinder to cylinder.

Easy way of finding out is to simply remove them and pressurize the system by simply cycling the key. If one drips, its failed.

Another way is with a fuel pressure gauge if available. Pressure drop off with return and feed blocked. Check fuel pressure regulator as well.

Last way is to graph on a oscilloscope, which I find is more work and less conclusive sometimes on higher mileage cars.

My 2c could very well be wrong, just a suggestion.

Also do you have access to fuel trim on a data steam or freeze frame of a code?
 

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Administrator
2007 Forester Sports XT 4EAT
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40,529 Posts
Most members here will tell you Subaru prefers Denso factory/OEM or direct fit O2 sensors. :wink:

More questions: :confused:
  • Have you checked for exhaust leaks ahead of the front O2 sensor?
  • Was the replacement CAT(s) factory/OEM, or muffler shop weld on?
  • How did the old spark plugs look... oily or sooty?
  • Are you having to add engine oil?
  • Any oil in the coolant?
Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2006 FXT 6MT
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2,699 Posts
If all of Bobby's questions check out, I would first change the front o2 sensor to a Denso piece. The Bosch ones are notorious for not pairing well to these cars. They have made a lot of good parts, but o2 sensors are not among them...
 

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1999 forester Auto
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5 Posts
Discussion Starter · #7 ·
@Burnwood69:
When spark plugs were changes they were a tad on the rich side (sooty), but not unreasonable from what I have seen before. With the degraded mileage I would not be surprised if all, Injectors were leaking.

I have run through probably 3 bottles of Lucas Tune Up since I bought the car, and it does delay the CEL and code from being thrown.

I'll pull the injectors, and do the drip test on them, thanks!.

@2.5x_sleeper
  • I did a visual inspection for exhaust leaks when I seafoamed the engine, no leaks found.
  • The cat was replaced with an OEM subaru, exact fit cat.
  • Plugs were slightly sooty.
  • No engine oil consumption, HG's were done 3K ago.
  • No oil in coolant or vice versa.
 

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1999 forester Auto
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Discussion Starter · #8 ·
[SOLUTION] found, it's not what you'd think.

After changing just about every sensor I could find, having the injectors tested, (spray was within tolerance), the issue was finally resolved.

Turns out it was...

THE ALTERNATOR.

This one for whatever reason really threw me for a loop. The car had always had a squeaking sound coming from the alternator. I never really paid it any mind because it was still working fine. Meaning the bat light never came on. At least until it finally did. When I pulled the alternator out the bearings were so shot it was difficult to turn by hand although it did turn. I took it into a local shop to have it rebuilt. Based on the amount of force it was taking to turn the alternator the shop said that it was probably using 2x the amount of force that was needed to turn the A/C compressor when active.

New alternator has been in for 2.5 weeks now. 2 tanks of gas later, 1st tank 80% hwy driving yielded 23.7 mpg. 2nd tank 80% city driving yielded 20.9mpg. To boot, Torque app now reads no errors on a scan. Since the running rich problem has resolved itself as well, I'm guessing this issue was part mechanical failure and part electrical failure. Either way I'm a happy Suby owner again!
 

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2015 Highlander AWD XLE 6AT
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4,255 Posts
Thanks for posting the fix!

Regards,
Jim / crewzer
 

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Administrator
2004 Forester XT Premium 4EAT
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29,432 Posts
Wow! Thanks for the update - the alternator is definitely not one of the usual suspects with those symptoms!
 

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2014 Forester XT
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38 Posts
I've been down this road.

Replace your ground cable immediately even if it looks good. For good measure replace the starter supply cable too.

The alternator likely went screwy when the ground started getting bad. The ground being bad causes all of the sensors to have additional noise.

I added an additional ground cable from each head to the battery - as well.

Car has never worked better. (98)
 

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2003 FXS Auto
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107 Posts
When I changed my belts I noticed my alternator seemed to be binding. My Foz has 162K and still has original alternator...I am thinking it may be failing.

How much did you pay for alternator rebuild?
 

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1999 Forester 5 speed manual
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1 Posts
P0420 code, running rich

My car, 1999 Forester was giving me fits, running well most of the time, but it started setting the dreaded P0420 code and I noticed that it was running rich, gas mileage dropped to 17 where it usually gets 29 to 31 mpg highway. Also, the idle was wild at times, either idling at 1800, or bouncing between 500 and 1000 rpm. At 254,000 miles were the catalytic converters possibly defective? The car has fresh oxygen sensors. At one of the rich running events I pulled all the spark plugs, all the plugs had porcelain that was jet black. Fuel pressure was 36 and 46 psi like it should be. Just by chance I checked the ground wire that is next to the ignition coil electrical connector. This double terminal has 4 wires going to it, has an 8mm bolt attaching it. I found that the bolt was loose, terminals dirty. I cleaned the terminals and re-tightened the bolt. That was 1500 miles ago, no check engine light, the idle is a rock steady 800 rpm and the fuel mileage is back to normal. This may be an isolated case, but it's simple to check, clean and re-tighten that ground terminal.:icon_biggrin:
 

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1999 forester Auto
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5 Posts
Discussion Starter · #15 ·
4 Month Update

I'm happy to report that after 4 months the car is doing great, I had 2 recent trips. One from Portland to Eugene 212 miles round trip and one from Portland to Lincoln City 300 miles round trip. The Eugene trip which is a straight shot up and down I5 with very little elevation change, I averaged 27.1 mpg. On the trip to Lincoln City which is coastal mountains with plenty of ups and downs going over the passes I averaged 23.6 mpg. It may not be as good as I hear others are getting, but I feel it is perfectly acceptable.

And as a side note, after reading the new responses, I'm going to go and throw some new grounds on tomorrow. It can't hurt anything.
 

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1999 L 4AT
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1,216 Posts
Wow! Thanks for the update - the alternator is definitely not one of the usual suspects with those symptoms!
You can say that again!

However, that squeak coming from the front end is always a tell-tale sign of something failing or binding though ... never a good sound.
 

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2000 Forester Automatic
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29 Posts
I'm glad I found this thread. I just got my first P0420 code yesterday and was figuring on sensors and a cat. Now I'm going to try the alternator first since it is already on my list of things to take care of because of squealing. Hope this will solve the problem. If it doesn't, still needed to change the alternator. I've been looking at local auto part stores and right now the least expensive is a 90 amp at advance auto. Most of the others are 65 to 75 amps and cost more. Is there a problem or advantage with using a 90 amp?
 

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1999 L 4AT
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1,216 Posts
it'll work

also, shop online with their coupon code TRT30 and then pick-up in store ...
 

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2009 forester XT L auto
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58 Posts
Same problem here. squeaking and the code. Just put in a new alternator on my 00' and the code has not come back in 200+ miles. Fingers still crossed. And also no more squeaking.
 
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