P0304 cyl 4 misfire detected

[97sl2DOHCaut1.9]

Hi, I got a 97sl2 with 205,000 on it, here's what happened earlier today...

I started the car this morning and noticed it was running a little rough. As I pulled away the engine sounded like it was misfiring and the "service engine soon light" flashed on and off for around 5 seconds then it stayed on for the rest of the short trip. When I got back i plugged a scanner in and got a
"P0304 cyl 4 misfire detected" code and I did not clear it. Then after driving around to a few different places the light finally turned off.

The car runs good otherwise and just about everything has been replaced in the past year or two thanks to this website and everyone. I have not ever gotten around to cleaning under the coil packs or cleaning/replacing the fuel injectors though ...

[adventureoflink]

Then that would be the first place to start. (and by that I mean do a spark plugs/wire exchange, as well as a coil pack/ignition module inspection/cleaning. save the injector swap for when the tune-up doesn't fix it)

http://www.saturnfans.com/forums/sho...d.php?t=163654 -- look under the spark plugs/wires bit for everything you need to do.

FYI, SES flashing = a misfire bad enough to destroy the cataclyctic converter.

[97sl2DOHCaut1.9]

FYI, SES flashing = a misfire bad enough to destroy the cataclyctic converter.

Is that right ? Can you elaborate? ...

So sometimes the light will flash and other times it will stay on ???

[OldNuc]

Yes, if you get a backfire it will gut the CAT. The SES will flash when it detects a hard misfire. The PCM does not detect a backfire, all it does is assume a hard misfire means excess fuel into the exhaust system.

If you have never dealt with an older car that you could backfire anytime you wanted it to you have missed one of those little fun automotive things. You have to have a real carburetter to do it though. It will make quite a blue flash and impressive bang. You can blow the entire exhaust system off and/or blow out the head gasket.

Try the ignition cleaning and new NGK plugs and new mid priced direct fit wires. If that does not fix it then run a compression check.

[adventureoflink]

Originally Posted by 97sl2DOHCaut1.9

FYI, SES flashing = a misfire bad enough to destroy the cataclyctic converter.

Is that right ? Can you elaborate? ...

So sometimes the light will flash and other times it will stay on ???

Yep. When the SES flashes meaning a catcon destroying miss, you're basically dumping LOADS of raw fuel into the cat, causing it to get destroyed pretty damn quick.

The light ONLY flashes when there's a misfire bad enough to destroy the catcon, like in your car. Otherwise, you should be good for a little while with it on solid.

[97sl2DOHCaut1.9]

Did the job now have 2 questions

(pic 1) - Was that dirty enough to cause a misfire?

(pic 2) - the paint or plastic along the top of the left coil peeled off and rust is there, Is that a problem ?

[OldNuc]

The rust is not a problem yet. Give it a coat of black brush on gloss Rust-Olium before it is. Wire brush under the heads of those bolts. That is an RFI-EMI ground path. The base is probably not a problem but the bolts might be.

Running a compression check on #4 is not a real bad idea either.

[97sl2DOHCaut1.9]

Hey Oldnuc

I plan to do a compression check; i'll have the plugs out anyway when I replace them. I have a que about a tester I got @ Harbor Freight: do I use the extension piece (in the pic) that the tester comes with?

[OldNuc]

No, just screw the end of the tester into the spark plug hole until that small o ring contacts the head. Don't crank down on it, very light pressure is all it takes. Sometimes those things leak so if you get goofy numbers check the tester for leaks. Be sure to completely open the throttle and remove the PCM B fuse from the UHJB, engine compartment fuse box, to turn of the spark and injectors. Crank the engine until the gauge quits increasing and keep a count of the compression cycles to max reading. The number of compression cycles and max pressure should be close between all cylinders.

[adventureoflink]

Originally Posted by OldNuc

No, just screw the end of the tester into the spark plug hole until that small o ring contacts the head. Don't crank down on it, very light pressure is all it takes. Sometimes those things leak so if you get goofy numbers check the tester for leaks. Be sure to completely open the throttle and remove the PCM B fuse from the UHJB, engine compartment fuse box, to turn of the spark and injectors. Crank the engine until the gauge quits increasing and keep a count of the compression cycles to max reading. The number of compression cycles and max pressure should be close between all cylinders.

Question: what is meant by a compression cycle? Just curious.

[Guy in WNY]

i used to backfire my 350 w/headers on it. While slowing down, you just turn off the ignition, stomp the gas a few times, and turn the ignition back on. it would cut loose like an M80 thru the header muffs!
Another good trick was to fill the secondaries on the 4bbl with oil. Idle thru your local park until you are just about to where you want to lay down the smoke, and just blip the throttle. The oil dumps in to the intake and you lay down a smoke screen like a battleship!
Good times!

[OldNuc]

Originally Posted by adventureoflink

Question: what is meant by a compression cycle? Just curious.

The compression cycle or, correctly compression stroke is when the piston comes up with all valves closed. This is what builds the pressure you see indicated on the gauge. As there will be multiple strokes to reach a peak reading I just refer to it as compression cycles.

[OldNuc]

Originally Posted by Guy in WNY

i used to backfire my 350 w/headers on it. While slowing down, you just turn off the ignition, stomp the gas a few times, and turn the ignition back on. it would cut loose like an M80 thru the header muffs!
Another good trick was to fill the secondaries on the 4bbl with oil. Idle thru your local park until you are just about to where you want to lay down the smoke, and just blip the throttle. The oil dumps in to the intake and you lay down a smoke screen like a battleship!
Good times!

Install a 18mm O2 sensor bung on the exhaust several feet back of the manifold outlet flange. Requires a non cat equipped exhaust and preferably a cherry bomb muffler. Then install a spark plug and a old Ford coil with a push button in the primary side. Hook up a fitting to inject gasoline into the exhaust stream on demand. Inject a shot of gas followed by pressing the button on the coil.

[97sl2DOHCaut1.9]

The same thing happened again yesterday ...

This time I got a "P0301 - Cylinder 1 Misfire Detected"

I have done two things to the car since the original P0304; I cleaned the coil packs and ICM (I guess I could have swapped them not sure though), and ran a bottle of Techron.

Could the two be related somehow??

[OldNuc]

The possibility exists that the events are related. I would go to the pick and pull yard and obtain a nice looking ICM with 2 coils from a newer, low mileage Saturn. The coils and ICM will swap 96 - 02. A defective 1-4 coil will do this.

[97sl2DOHCaut1.9]

I will check out the local yard, my packs and ICM don't look to be in too good of shape. Which coil is the "1-4 coil"? The Saturn coil is confusing to me; a 1/3 and 2/4 is on both of them

[OldNuc]

The one that feeds the #1 and #4 plugs is the 1-4 coil, the one on your left as you look at it. The issue could be the coil or the ICM. As the used units are usually low price, $40.00 at the non pick an pull yards and 10 to 15 at the pick and pull here there is not much point in fiddling with it to prove it is failing when just substituting another unit will do the same thing for much less labor and fiddling.

[97sl2DOHCaut1.9]

Originally Posted by OldNuc

The one that feeds the #1 and #4 plugs is the 1-4 coil, the one on your left as you look at it. The issue could be the coil or the ICM. As the used units are usually low price, $40.00 at the non pick an pull yards and 10 to 15 at the pick and pull here there is not much point in fiddling with it to prove it is failing when just substituting another unit will do the same thing for much less labor and fiddling.

Ok that sounds good. My plan for now is to try to find one @ pic/pull.

I have this one question though: are all the 96-02 ICM's the same? I live in California and when I got one for an old Ford many years ago the CA type are different (apparently) and a lot more expensive: around 2 to 3 times the price!

[OldNuc]

You are in luck, they are all the same. The 2000+ have extra clips to hold the wires that are nice, be sure to grab the longer bolts for them also. Look for coils that do not have exposed laminations on the coil core.

[97sl2DOHCaut1.9]

Oldnuc

I finally got a chance to test the compression and here is what happen:

(From left to right facing engine and as I cranked the engine until the gauge quit increasing and counted cycles)

Cyl 1 - 218psi and 8 cycles
Cyl 2 - 218psi and 8 cycles
Cyl 3 - 210psi and 10 cycles
Cyl 4 - 212psi and 11 cycles

Any thoughts on the test or the pics of the plugs etc ??????????

Also, I did get a set of good quality OE coils from a yard but I have not installed them yet maybe that will help with the misfire too ?????