We have a 98 Forester with 190,700 miles. Yesterday the CEL started blinking. I dropped by the O'Reilley Car Parts store and discovered they will use their OBD II code scanner to read your DTC. The only code was Misfire on Cylinder 2.

 

I've recently replace all spark plugs with those iridium plugs, all the plug wires, and fuel injectors. The car runs fine, but every once in a while it misses a beat--I guess a misfire.

 

Anyway, I've heard a blinking CEL is some sort of bad news about the Catalytic converter.

 

The gas mileage is terrible. I haven't had the chance to measure the miles per gallon, but at the rate the gas gauge needle is dropping, the mileage is very low.

 

Could this perhaps be a bad oxygen sensor (before the catalytic converter) even though no code is being thrown?

You put in the wrong plugs. You also probably used the wrong wires.

 

NGK Laser Platinum plugs, OE wires.

We've been using the Iridium plugs all along without any problems. That is what the mechanic used and we just replaced what was in there.

We've been using the Iridium plugs all along without any problems. That is what the mechanic used and we just replaced what was in there.

 

OK. The OE plugs are the NGK Laser Platinum. I had misfires even using the Bosch Platinum. They all went away when I got the NGK plugs and OE wires.

Have you ever adjusted the valves? Might be a burnt valve. A compression test may be in order.

yes, an o2 sensor can be old and working poorly and not throw a code. bad fuel mileage can be caused by that or a bad knock sensor.

 

i would re-do the wires first, they are easier. but plugs and wires are probably the cause of the misfire. move the #2 wire, driver side front, to the passenger rear, #3. see if the misfire moves with it.

 

a flashing CEL is an indicator of a condition that could 'potentially' damage the cats. especailly if it goes on for a long time and is not addressed.

Edited November 9, 201114 yr by johnceggleston

We had a compression test done and a leak down test. Valves passed the leak down test. But eventually the problem turned out to be that the timing belt had slipped a couple teeth. So we replaced timing belt and belt tensioner. While we were driving it with the teeth slipped, could the valves have gotten burned?

If your front 02 sensor has not been replaced in the last 40k miles, replace that also. Was that your original timing belt?

Front Oxygen sensor was replaced about 40,000 miles ago I think. This was not the original timing belt. Last timing belt change was maybe 40,000 miles ago.

it is doubtful the valves burned while the belt was a couple of teeth off. but if it was out of time far enough, you could have bent valves.

 

what was the compression after you reset the timing.? if it is good, then no valve damage.

Well, I think if valves were bent the symptoms would be obvious. I would still do a compression test. I just can't imagine the timing belt being a couple of teeth off and no valve damage. I hope I'm wrong.

yes, an o2 sensor can be old and working poorly and not throw a code. bad fuel mileage can be caused by that or a bad knock sensor.

 

i would re-do the wires first, they are easier. but plugs and wires are probably the cause of the misfire. move the #2 wire, driver side front, to the passenger rear, #3. see if the misfire moves with it.

 

a flashing CEL is an indicator of a condition that could 'potentially' damage the cats. especailly if it goes on for a long time and is not addressed.

 

Since the oxygen sensor was so old I decided to replace the front one. I had cleared the misfire code for cylinder 2 on Monday at O'Reilly auto parts and the next day it came back on the same way by flashing first. I dropped by O'reilley again tonight and it was the same code: Misfire cylinder 2.

 

I changed the front O2 sensor this evening and then started looking at the spark plug wires. I immediately discovered the number 2 cylinder spark plug wire was not attached to the spark plug. I just sent an email to my mechanic about this. I wonder if the plug got damaged from the sparks arcing to the spark plug. Seems the spark plug was able to fire enough of the time that the engine ran very smooth except for the occasional mis.

The car is running great now. No more misfiring and has normal power again. Next time we fill up the gas tank I'll post the miles per gallon we are getting.

The car is running great now. No more misfiring and has normal power again. Next time we fill up the gas tank I'll post the miles per gallon we are getting.

 

 

:clap: