Mystery of the Check Engine Light

[slysuby]

Hello all. I have a 99 Forrester L that I bought 3 years ago at 32K miles and it now has 137000K miles. I drive quite a bit and love this car. Never gave me any problems, aside from the regular maintenance type stuff. A few months ago, the CEL came on. No change in performance - so i took it to the dealer. Codes read were engine misfires 3 and 4. So they changed the coil pack, plugs and wires. CEL came back on in 1 day. Took it back to the dealer, where they proposed starting with a valve adjustement, then replacement of the fuel injectors, so on and so on. Make a long story short, don't have a fortune to spend. Took it to my local mechanic, tried replaceing the wires and plugs again, but still have the light. It sometimes will go off and stay off, until i get on the highway for my 40 mile one way trip to work. Once on, it flashes while driving at highway speeds. All the codes that have been generated were engine misfires cylinder 3 and 4. My mechanic is now suggesting that we try and replace the coil pack again and if that doesn't work, then he believes it could be the head gasket going. Just seems like spending lots of dough for replacements that may not be needed because we can't figure out what the actual issue is. VERY FRUSTRATED!! Anyway, just wondering if any of you out there have had or are having a similar experience. I'd love to pinpoint this down even if it this the infamous head gasket.

 

Thanks in advance for your help/advice/etc.

[SuBrat84]

I've had this happen a few times in my 98 Legacy 2.5 GT ... 1st time it was fouled plugs... then two or three months later it was bad wires. Every research I could find about it indicated flashing CEL is an emission problem... (Plugs, Wires, O2 Sensor, Etc.) It could also be caused by a loose gas cap!!! Best of luck... let us know what it is when you get it resolved... I hope it's not that gasket!!!

[erikm]

I own a 2000 Forrester and had a very similar situation. In my case the CEL was coming on for #2 only. This was also after I just changed the O2 Sensor and the Oxygen Fuel Ratio sensor. Then the CEL was coming on for #2 misfire. I changed all 4 plugs only, and I went with Bosch High End plugs. Did not fix it. Then I found out that the #2 plug wire was having a hard time staying on to the plug. I pinched it and other stuff and finally got fed up.

 

So, I went back to the store and got the import NGK plugs and paid twice as much for them as the high end Bosch. I also got a set of plug wires. This cleared it up, and the new wires made really good snap-in connections.

 

I guess the point to all of this is, are you using American plugs? I think it really makes a difference to use the NGK original equipment plugs. It is possible too that the bad O2/Fuel Mix sensor is sending a bad mixture causing the misfire. What about running a heavy duty engine cleaner. There is a certain brand that is all petrolium products and only costs about $3.

 

It is possible that the dealer or repair shop is correct, however I tend to agree with you that it sounds like they are fishing.

[BulletRide]

ive learned to ignore my CEL

[shimonmor]

Check out these two posts:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=32962

 

http://www.ultimatesubaru.org/forum/showthread.php?t=32863

[ron2368]

Both my sube's and another Honda all have the CEL go off when I fill the gas tank. At some point as the gas gets lower they light up.

 

On a 99 Forester where do these codes some from, do you need a special reader?

[DWM650]

Had the same issue, did all of the simple stuff first.

1. replaced coil pack
   
2. wires
   
3. NGK lazer tips @ $12.00 a plug
   
   
4. Rear O2 sensor
   
5. seafomed the IACV
   

Then adjusted the Vavles, 7 out of 8 ex. Way over tight this at 102000 mi. No more CEL po301 & po303, + 25mpg.

[boysoccer3]

I have had the CEL light go off and on for over two years now. I have had it checked and these are the diagnostics:

1. Bad cat converter

2. Bad cat converter

3. Bad 02 sensor

4. Bad Coil and wires

5. Bad cat convterter

 

I don't know what to do either but I am sick of paying $45 to get someone to check the codes over and over. I think I will just leave the light on since the "professionals" can't figure it out.

 

Good luck to you though!

[Sweet82]

My CEL went on and we were able to trouble shoot it to the gas cap

[Brick]

Got my "new-to-me" 01 Forester home from the dealer on Friday, and by Sunday the CEL had come on (had a little engine stutter releasing the clutch on Sun AM, light came on after that).

 

Hope this doesn't turn out to be too big a pain in the rear....

[slysuby]

Thanks for all the good info.

 

The CEL went off over the weekend, and on my way to work monday morning, it flashed a few times and would go off - then flash a few times and go off. It stayed off for a while and was flashing and off for 2 days, until today when it came back on. CRAZY!!

I've noticed that it only starts acting up at speeds in excess of 60mph if its been off.

I pretty confident that its not the gas cap issue. Put NGK plugs and new wires, changed out a bunch of sensors. The phantom theory makes sense though. Can someone please enlighten me as to what SEAFOAM THE IACV stands for? THanks again.