Trying to Diagnose a P0304 Problem

[saturn rings]

This is a '97 SL1. A few days ago while driving, started to get a sputtering from the engine and the SES light came on. Had the code pulled and it was the P0304 misfire code I have read on here about. Now i'm trying to figure out what the problem is. On these forums i'm hearing it could be coils, ignition module, spark plugs & wires (already replaced those). My question is the tech at the parts store said to check the coils, remove the plugs from either end and check for spark. CHECK! both sides have spark. He also told me that the ignition module would not be the problem if i'm getting sparks from the coils. When i start it it sounds like it doesn't want to start almost like a dying battery trying to crank. but on the second or third try it starts. But it's still misfiring.... BADLY, especially when put in drive. So what do you guys think should be a next step for solving this? Should i still replace the coils? the ignition module? anything else to try or check? Help guys.

[madpogue]

If the ignition checks out as it apparently does, and esp. if it's on just one cylinder, check everything with that cylinder that's NOT ignition related:

* vacuum leak (intake manifold gasket, albeit unlikely at #4)
* fuel injector
* compression

[saturn rings]

Uh....... To do the compression test: Disconnect ALL spark plug wires at both ends? or just from the spark plugs? Remove ALL spark plugs and connect the gauge and crank for 10 revolution at each cylinder and check the reading. YES/NO? RIGHT/WRONG? Did I Miss Anything?

[madpogue]

Close. HOT engine. No need to mess with the coil ends of the spark plug wires, just remove the PCM I fuse to disable spark. Push throttle WIDE open for each test. Wait until engine is COLD before re-installing spark plugs. Re-install PCM I fuse when done.

[yupper]

skipped timing belt causes misfire on 1 3 5 if out 1 tooth with no valve damage

[yupper]

skipped timing belt would also explain hard cranking

[mattelderca]

Originally Posted by yupper

skipped timing belt causes misfire on 1 3 5 if out 1 tooth with no valve damage

Saturns do not have timing BELTS and certainly do not have a 5th cylinder.
Timing CHAIN failures involving skipping one tooth are near impossible on these cars.

[yupper]

sorry misread first post as an L series

[madpogue]

Originally Posted by yupper

sorry misread first post as an L series

You misread this entire SECTION as having anything to do with the L-Series. How hard is it not to get the model, the site section, or even the CENTURY (there were no L-series in '97) right?

[yupper]

i guess sorry doesn't cut it with some people

[saturn rings]

Ha Ha Ha! You guys are too funny.
Hey, since the worst case scenario i would hope for is maybe one of my injectors are bad, is there a separate test just for the injectors or is the compression test the only way. Cause I just saw Richpin's injector removal video and it's do-able (eventhough it is for 98 and up and mine is a '97) guess not much of a difference right? Anyway, anything to check injectors wise before OR after removal? Thanks guys....... and play nice.

[fdryer]

While y'all (my bestest southern drawl) are bickering, no one has mentioned the infamous engine coolant temperature sensor! (ECTS)

If yours has the original two-wire coolant sensor, replace it ASAP. The plastic ones fail and allows rich mixtures all the time. A whole host of problems have been posted about this one sensor, all the way to affecting transmission shifts. Replace it from any auto store with the brass one and check to be sure the connector isn't corroded otherwise it needs replacing too.

You've also inherited the weak fuel pump check valve issue of the pressure bleeding off. Search '97's about it for the simple work around.

You'll have to excuse the bickering. We're a small family here..................

[saturn rings]

The ECTS has been replaced already, (had a little oil on the wire and connector though) cleaned it all up and all looks good on that. But one thing has been bugging me and i'm gonna ask AGAIN only because i'm basically stuck at home in my driveway trying (HOPING) to get this thing fixed, is.... Why is it that on cold starts when I turn the key it would act like no power or electricity is going through it, but after the second try it cranks 3-4 times then turns over (with the misfiring of course). Any ideas on that while i remove the Coils and check for corrosion would be great and i'll check for posts in an hour. Understand guys that i'm trying to narrow down the problem so i don't have to keep asking friends/neighbors for a ride to get parts and such. Damn wish i hide my old BMX bicycle about now!

[fdryer]

Originally Posted by saturn rings

.... Why is it that on cold starts when I turn the key it would act like no power or electricity is going through it, but after the second try it cranks 3-4 times then turns over (with the misfiring of course). .....

You are describing at least two different issues and this last one is about starting and the starting circuit. This can either be related to the ignition switch wiring (control circuit) or the starting circuit (power wiring). Have you at least looked over the battery (over 4yrs old and it may be on its last legs), the battery cables for obvious signs of corrosion, and lastly the starter? If its the original starter it may be on its last legs too.

And, of course, there's the built in faulty fuel pump check valve that may not have been mentioned. It bleeds off fuel pressure so starting is difficult. The easiest work around is to allow the ignition key to stay in the ON position for 2-3 seconds, long enough for the fuel pump to cycle, then try starting. This works for everyone having the same '97 check valve issue. Better than replacing a perfectly good pump just because the check valve is faulty.

[saturn rings]

Battery and starter are both 2 years old and had them checked at autozone. They are good, and I know exactly what you mean on the fuel pump. I Always wait until i hear the fuel pump kick in (wait for the humming sound to stop, then turn the key). But, hey I got my coil packs off, question what should i clean the ignition module off with and do I need to use any dielectric grease or anything on them? the coil contacts? should clean the base of the engine block where the Ignition module gets attached?

[saturn rings]

O.K.! Just replaced and tested the coil pack and it was still misfiring. At the same time my neighbor was passing by and told me to lightly tap on the injectors and listen for change in idle, and sure enough when I tapped on the last injector (cylinder #4, On the driver's side....Right?) the engine started convulsing violently. So should I replace this injector now or do more testing? If replace, where should I buy from? Buy New or Used?

[fdryer]

Originally Posted by saturn rings

.... Why is it that on cold starts when I turn the key it would act like no power or electricity is going through it, but after the second try it cranks 3-4 times then turns over (with the misfiring of course). .....

If no sounds occur from turning the ignition key to START (starting circuit), something is wrong. Keep that in mind.

Scrubbing the ignition module with Scotch Brite synthetic sanding pads is one method to cleaning off corrosion while polishing metal. A wirebrush is another way. Wirebrush the mounting bolts and the area as the bolts ground the ignition system. Dielectric grease on the plug boots/coil towers provides corrosion protection and lube for ease of removal. Light grease on everything else for some corrosion prevention can help.

Before jumping to conclusions about a faulty injector, there's wiring to consider. Separating a wiring problem from an injector failure is what you need to think about. Although tedious, removing the fuel rail and injectors to lay them out and wired up may tell you what's going on. Cycling the ignition key will pressurize the fuel lines all the way to each injector. Any leaks will show up. Cranking the engine briefly and observing the injectors spraying into jars (for safety) may also reveal anything out of the ordinary. If you're going to replace an injector or two, you might as well verify it before replacement. There is another recommended method of sending all four injectors someplace (like witchhunter.com?) for cleaning and testing.

[saturn rings]

fdryer I understand your instructions completly, but once i get the procedure done what exactly am I looking for exactly to determine if it is a wiring problem or an injector problem?

[fdryer]

An injector failure would be easy to find; just swap two injectors around and you'll find the failed one never sprays or sprays phunny as its moved from one connector to another. Wiring is isolated in similar fashion; swap injectors and if one connector or wire is broken/intermittent, injectors won't work on the failed/intermittent connection. Think about it until its clear in your mind.

[saturn rings]

Madpogue, fdryer and anyone who's helped me so far. I have isolated the problem to a faulty or clogged injector. I just rotated all 4 injectors back and forth then restarted the car and low and behold MISFIRE GONE! Drove it round the block, fast, slow hard acceleration and all. All was fine. Great right? Well after cleaning up my driveway I remembered that I didn't put any dielectric grease on the boots for the COILS. After applying some, when I turned the key to "ON" I have dash lights/radio etc. I hear the fuel pump working but when I turn the Key to start the car I lose all power and get one click sound. DEAD. NO dash lights/radio, nothing. Then have to wait maybe two minutes before I can get power again but the same thing happens again when trying to start. What did I do wrong now? Man, I thought I had this thing licked. HELP guys! (again).