2000 3.5L Cylinder 4 misfire

steffenk · #1 12-28-2009, 01:09 PM

Hi,
This morning, I had a misfire problem that caused the service engine light to flash. The car started fine (cold start) but was running a little rough at low speeds (some vibration / not smooth). As I was getting on the highway at ~40mph, the SEL started to flash. During the time it took to turnaround and return home (about 5 minutes), the light stopped flashing and resumed flashing twice (seems to flash when engine is under more load). When I got home, the SES light was off, and a reader shows the stored, pending code as P0304. I filled up the fuel tank 1.5 days ago and drove approx. 125 miles since then; the first sign of the misfire condition was this morning. The car has 68,000 miles, and the spark plugs have never been changed.

Does anyone have recommendations on what to check first? I was planning to pull Plug#4 and inspect both it and the boot/coil pack. I know that a flashing SEL is severe enough misfire to damage the catalytic converter so I was going to avoid driving the car.

Thanks for any advice.

Steffen.
2000 V63.5L Olds Intrigue

danielsatur · #2 12-28-2009, 02:19 PM

4cylinders - 1 = 25% hp gone!

Caution - Keep an eye on your Temp guage.
If your Catalytic converter is plugged, the temp will rise, misfires on random cylinders, and choke your engine out.

1) Get your DTC's pulled for free @ any local Auto parts store.

LittleHoov · #3 12-28-2009, 11:02 PM

His engine has 6 cylinders, so your math is a tad skewed haha.

As for advice, you could get a can of something designed to remove water from your gasoline, something like HEET. I also believe that Seafoam will remove water.

You can also swap coil packs and see if your error code "moves" I cant remember how the numbers go in the 3.5, but the new code would be the opposite side know what I mean?

But yeah, checking the plugs and boots cant hurt anything. Also if you do happen to find its your coil, I have a spare one sitting around than Ill sell you.

You can also crawl underneath the car and give your catalytic converter a good whack with something pretty solid (jack handle, breaker bar, etc) and see if you hear anything rattling around on the inside of it. The idea is to jostle it around a bit, not to rip it off

steffenk · #4 12-29-2009, 08:30 PM

Thanks. It seems the misfire depends somewhat on the outside temp. I drove the car for a few minutes when it was above 40F It was running smoother, and the check engine light did not come on - the pending DTC code went away. However, this morning it was below freezing, and the misfire was noticeable at idle. I drove for 5 minutes, and the flashing check engine light came back followed by a solid check engine light. The code is again P0304 so it seems the issue is specific to cylinder 4. I pulled the front coil pack and plugs 2 & 4 this evening. Everything looked good visually. I will try replacing plugs 2/4/6 to see if that fixes the problem. If not, I may try the coil pack swap test (good idea LittleHoov). I really wish this happened in Spring/Summer/Fall -- it's 15 deg. F out there now!

krivasauto · #5 12-31-2009, 10:02 PM

Quote:

Originally Posted by steffenk

Thanks. It seems the misfire depends somewhat on the outside temp. I drove the car for a few minutes when it was above 40F It was running smoother, and the check engine light did not come on - the pending DTC code went away. However, this morning it was below freezing, and the misfire was noticeable at idle. I drove for 5 minutes, and the flashing check engine light came back followed by a solid check engine light. The code is again P0304 so it seems the issue is specific to cylinder 4. I pulled the front coil pack and plugs 2 & 4 this evening. Everything looked good visually. I will try replacing plugs 2/4/6 to see if that fixes the problem. If not, I may try the coil pack swap test (good idea LittleHoov). I really wish this happened in Spring/Summer/Fall -- it's 15 deg. F out there now!

Not losing water, are you? I picked up a misfire on No 2 - at same time my crossover water leak seemed to go away but was still having to add coolant. No overheating and the miss improved once warm. Pulled the plugs today - had water in the cylinder. Oh, well, time for a head gasket.

steffenk · #6 12-31-2009, 11:14 PM

Thanks. I do have a coolant leak, but it appears to be external - see it on the ground. It's been a very slow leak and I've been adding coolant (approx a liter every 600-700 miles). When I pulled cylinder 4, it was completely dry. I stopped in to Autozone today, and they said they are able to test the ignition coil pack so I will have that done.

steffenk · #7 01-02-2010, 04:56 PM

The problem turned out to be a bad spark plug in cylinder # 4. I swapped plugs 2 & 4, and the misfire moved from cylinder 4 to 2. I'm pleasantly surprised that this was an easy fix. The plugs were original with 68,000 miles on them. After reading other threads encouraging the use of OE ACDelco/NGK plugs, I went with the ACDelco 41-980 (labeled NGK). I replaced plugs 2, 4, 6 and will wait on 1, 3, 5 until Spring is here. The misfire and DTC code are gone. Thanks for the replies to my post.

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