P0304 has me confused?

[3500srw]

First a little background: I bought the car in March this year. It had 4 DTCs EGR and mis-firing #4 cylinder codes. I tried to clean the Egr but ended up buying a new one. I put on new plug wires and new plugs. I carefully cleaned the Ignition module and coil packs used corrosion preventive dressing and all. All codes were gone and all has been well for the past 2 months. I've even used a couple bottles of Chevron Techron fuel cleaner in that time and have logged 7000 miles. The last bottle was about 3 tanks ago. The car has been getting 40-42 mpg highway. All was fine until today!!

I started the car and immediately noticed unusual vibs coming from the engine. I got out the drive way and drove a little bit and turned around and parked it. P0304 is the only code present which is "mis-firing of #4 cylinder" I took the ignition coil packs apart from the ign. module again and cleaned it again. I have lightly cleaned the throttle body(sprayed a 1/8 of a can while it was running). I switched the coil packs to see if the location of the mis-fire would change, nada! I check for spark and it has spark. Anyone have any ideas?

Thanks in advance

[tech360]

Try swapping the #4 injector with another one and see if the misfire follows it. Otherwise, you need to take a compression test.

[fdryer]

Have you done the campaign for the infamous engine coolant temperature sensor (ECTS) replacement? The original fails and leaves the engine running rich all the time; fouling plugs, wasting gas, creating odd running problems, messing up the EGR valve with excess carbon, misfiring, etc.. Look in the How-to library's first two posts about the coolant sensor and its two-wire connector. Its a must read!

[3500srw]

I swapped #3 and #4 spark plugs to see if it was a bad plug. It runs a little better but still has mis-fire on #4. The #3 plug looked perfectly normal but the #4 plug looked fouled. Problem stayed on #4 cylinder. I will try swapping injectors now.

Coolant temp sensor seems to read correctly according to my scan tool. The dash gauge is reading normal as well.

[3500srw]

After removing the fuel rail, it was very clear why # 4 was mis-firing.... about an 1/8" of white crud covering the orfices in the injector. I cleaned it but only one orfice appeared to be clear. I put it back together hoping it would clean it self out the rest of the way(wishful think), it ran a little better but still not normal. The other 3 injectors were very clean and clear. I ordered a new injector and fuel filter today.
Thanks all, I'll let you know what happens next.

[nivlem7]

Originally Posted by 3500srw

Coolant temp sensor seems to read correctly according to my scan tool. The dash gauge is reading normal as well.

If it hasn't been replaced, it needs a new brass-tipped one that will last for the rest of the life of the car. Less than $15 at Advance or Autozone.

It may be working o.k. NOW, but when it leaks, it could ruin the ECTS connector as well. It's time well spent (about 10 minutes - you sound like the handy type) to replace it now.

[OldNuc]

Originally Posted by 3500srw

After removing the fuel rail, it was very clear why # 4 was mis-firing.... about an 1/8" of white crud covering the orfices in the injector. I cleaned it but only one orfice appeared to be clear. I put it back together hoping it would clean it self out the rest of the way(wishful think), it ran a little better but still not normal. The other 3 injectors were very clean and clear. I ordered a new injector and fuel filter today.
Thanks all, I'll let you know what happens next.

You might want to consider spending the $75.00 + shipping to get them cleaned and rebuilt. Growing mushrooms on the ends is not a good sign that all is OK inside.

[rc1488]

First: Post your vitals!!! Having this in the beginning of your thread is unbelievably important!

According to your profile you have a '99 SL. Im going to assume this is the car your thread is about.

Check your intake manifold gasket. Tho its more common on 3rd gen SOHC cars, it hasnt been limited to those years and i would suspect you have the issues especially if you have a late '99. Spray some carb cleaner around the gasket at each cylinder and see if the idle changes. If it does...you found your issue. Good luck!

[3500srw]

Originally Posted by nivlem7

If it hasn't been replaced, it needs a new brass-tipped one that will last for the rest of the life of the car. Less than $15 at Advance or Autozone.

It may be working o.k. NOW, but when it leaks, it could ruin the ECTS connector as well. It's time well spent (about 10 minutes - you sound like the handy type) to replace it now.

It has a brass tipped one now. I doubt it has ever been changed, nothing else has been on this car I will get a new one! Thanks for the tip.

Originally Posted by OldNuc

You might want to consider spending the $75.00 + shipping to get them cleaned and rebuilt. Growing mushrooms on the ends is not a good sign that all is OK inside.

Where can I get them cleaned and rebuilt?

Originally Posted by rc1488

First: Post your vitals!!! Having this in the beginning of your thread is unbelievably important!

According to your profile you have a '99 SL. Im going to assume this is the car your thread is about.

Check your intake manifold gasket. Tho its more common on 3rd gen SOHC cars, it hasnt been limited to those years and i would suspect you have the issues especially if you have a late '99. Spray some carb cleaner around the gasket at each cylinder and see if the idle changes. If it does...you found your issue. Good luck!

Your assumption is correct. The problem car is a 1999 Saturn SL 1.9L SOHC 5 Speed. I will check the intake gasket in the AM. Thanks

My BIGGEST problem now is getting to work...My truck is in the body shop getting fixed from a deer running into the drivers side front and rear door. I have no wheels, relying on friends now. What a time to break down

[OldNuc]

No matter how large the personal motor pool they will all quit working at the same time.


Injectors. These are the sources for both new and clean and flowtest/refurbish service.
Brand new BOSH injectors.
http://www.fiveomotorsport.com/Injector_SetsSATURN.asp

Clean and flow test.
http://www.witchhunter.com/

[madpogue]

Originally Posted by 3500srw

It has a brass tipped one now. I doubt it has ever been changed, nothing else has been on this car I will get a new one! Thanks for the tip.

If it has a brass-tipped one now, it has, by definition, been changed. Your 1999 Saturn came from the factory with a resin-tipped ECTS. Brass-tipped replacement should last the life of the car; no need to go out and get another one.

[3500srw]

I removed the fuel rail again today and tried to clean the injector again, This time I soaked the injector in carb cleaner for an hour. Only fuel in/out were immersed, not the electrical part. When I put it back together I switched #1 and #4 injectors...now #1 cylinder is mis-firing. So now, I positively know it is the injector.

OldNuc,
I need to get it up and running asap. I like the cleaning/testing injector service, but don't have the time now. I am still going to replace just the one injector for now. If I have injector problems again I will be sending them to be cleaned. Should I keep the bad oem injector in case(so I have a matched set) or turn it in for the core($25) on the replacement I'm getting? (reman. 1 year warranty $55)

I did spray carb cleaner around the intake gasket, while I had it running, there are no leaks there.

madpogue,
Thanks for the info.