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P0303 important (please help)

4K views 14 replies 6 participants last post by  07muranoblue 
#1 ·
I was driving not 30 minutes ago. I was listening to music, going down a hill. About half a mile after I had gotten down the hill I started feeling a little vibration. I pulled to the light, turned on hazard, and turned off the car. I turned that car back on and it was still shaking VERY VIOLENTLY. I pulled into a lot and checked the engine, nothing noticeable. I was able to limp it home. The car had thrown the "service engine soon light" almost instantly after it started. I did the self diagnostic and it gave me the p0303 code. I looked it up and saw "cylinder 3 misfire." I'm almost 99.9% sure the engine is misfiring based on the way it sounds. It doesn't sound bad, it just sounds off by a little bit. I went into all different gears. Park, drive, neutral, 1, and 2. The car shifted fine, and went into all the gears.

Just to mention after I passed 40mph the vibration became much less violent.

If anyone has had this problem please write back about what you did to fix it.
 
#2 ·
Not surprising that the vibration was reduced a bit, because with the engine turning faster, the miss would shake it less.

The question is what happened. Could be plugs, or it could be a plugged fuel injector. I'd suggest that you are up for a fresh set of spark plugs. How many miles on the plugs?

I'd certainly want to pull that plug and see what it looks like. Hopefully it didn't crack or break off, although that's unlikely. I don't recall whether 3 is on the front (accessible) bank, or the rear.
 
#4 ·
That's actually good news. Very good chance that a change of plugs will solve it. Sounds like a Saturday project to me. You can read up on the process. Service manuals are online at Nicoclub. The intake manifold must be removed.
 
#5 ·
Well funny thing... I don't have the tools to do all that. I was watching some videos online and it you're required to take off the air intake boot (already done that once), throttle body, and manifold. Lol. Nissan sure made a great car to work on. Sadly, i'll be having it towed too nissan and pay labor and other B.S fees. I would 100% do it myself if I could but it looks like it's a job for the dealer. :/

Hate having my car worked on by other people I don't know... lol. I like to do it myself.
 
#8 ·
Haha you're 100% right. BTW I had my friend come over with an obd to confirm it was a misfire... and what do ya know, misfire cylinder 3. I'm looking into replacing all the plugs. The parts aren't the expensive thing, it's taking off the intake manifold, and all the other b.s nissan designed to be in the way.
 
#10 ·
Well... I hate to say this. I took the car to a mechanic that built my fathers 2010 iron block mustang engine. The repair will be $1,211. Replacing all the plugs and the coils. Coils in cylinders 1,2,4, and 5 are about to go bad. So there's no way to avoid the repair. It was only going to be about 600$ but adding the coils it jumps up to about $1000.
 
#11 ·
I hate to tell you, but that mechanic is squeezing you. Mechanics will often recommend changing coils along with spark plugs to make more money off the job, but a coil doesn't need to be replaced unless it's actually bad. Did he explain to you how he arrived at the conclusion that the coils in 4 other cylinders "are about to go bad"? No one can tell this for sure although there are some tests one can do on the coils themselves to see if they're out of spec. I doubt this mechanic did that and especially not for the rear cylinder bank since the intake manifold has to come off. My guess is he hooked up his scan tool and checked the misfire counters and saw some random misses for those cylinders. But, such misfires could be explained by the fact that your 10-year old car with 114k miles still has the original spark plugs.

If you were doing the job yourself, I would suggest that along with replacing the spark plugs, you also replace the coil for cylinder #3 just in case it is the reason for the misfire. This is because of the work involved in even getting access to the coils in the rear cylinder bank. But, to suggest replacing all 6 coils when you only have a verified misfire in one cylinder is ridiculous, IMO.
 
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#15 ·
While in there...I'd suggest changing the valve covers. Those rubber boots inside the valve cover that seal the plug area go bad within another 40k miles which means the whole job has to be done over again.Valve covers aren't that expensive, maybe he give you a break on the parts since doing the whole job, but while in there...I would. I didd this job on mine not long ago, took me a week due to various problems. takes a lot of skill imho and tools.

I've never heard of all those coils needing replaced that soon, makes no sense to me, but ok.

sorry to hear. My real answer, buy a good vintage honda or toyota!:)
 
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