Author Topic: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected  (Read 304 times)

paul_jj

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P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected

Any idea where to look and what to replace? The ignition wires?
I replaced a lot of parts on another cars, but it's my first Honda, so any advice would be appreciated.


Thank you.
Paul

John Ratsey

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #1 on: January 13, 2019, 08:30:57 AM »
Check if the back row of spark plugs are long overdue for replacement. A lot of people don't know they are there.

culzean

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #2 on: January 13, 2019, 09:38:11 AM »
Modern cars don't have ignition leads as such,  each plug has a coil pack fed with 12volt signals from the ECU,  the Jazz iDSi 8 valve twin spark has two spark plugs per cylinder one plug at the front the other at the rear. As John Ratsey says the rear plugs never get changed and just basically the gap gets too big and either this blows the coil pack up or just causes misfires as the system struggles to get a spark to jump a 2mm gap ( should be just over 1mm).  Just search for rear spark plugs and misfire on the forum.  plenty of information and plugs are not expensive but get NGK or Denso - some Japanese cars don't like non OEM specified plugs like Bosch.
« Last Edit: January 13, 2019, 09:44:58 AM by culzean »
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Jocko

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #3 on: January 13, 2019, 09:39:41 AM »
If not the rear plug it could be a faulty coil. Front and rear coils are different, and Hitachi are reckoned to be the best.

Jocko

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #4 on: January 13, 2019, 09:44:50 AM »
I fitted 8 off NKG BKR6E-11 (cost me 15), 15,000 miles ago and they have been great. I'll replace them when it gets its next service in the summer.

sparky Paul

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #5 on: January 13, 2019, 10:03:34 AM »
As above, change all 8 plugs has to be your first port of call.

As Jocko says, go for NGK.

paul_jj

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #6 on: January 13, 2019, 06:44:01 PM »
Great, thank you guys.

Are they all the same 8 spark plugs or the rear ones are different?

Does anyone know which torque they have to be set? A lot will argue, but it's very important to set the correct torque for the spark plugs. Professional mechanics would set the torque even for the wheel nuts.

I didn't know that it's 8 spark plugs, probably going for Iridium ones would be rather expensive.
If it's not the spark plugs, can this coil pack be changed individually for just a single cylinder or is it all in one?

What other things would you do if you just bought a Honda Jazz and weren't sure about the previous service history?


Thank you.
Paul

culzean

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #7 on: January 13, 2019, 07:59:55 PM »
All 8 plugs the same but front and rear coil packs not interchangeable ( rear are shorter ) change the plugs first before getting too complicated as this usually clears the problem,  I have changed 100's of spark plugs over the years and never used a torque wrench, with new plug just hand tight and whatever part of a turn it says on the box ( 1/2 to 2/3 turn) to crush the washer the right amount, if you refit an old plug with a washer already crushed ( why would you do that ? ) it is just hand tight and eight of a turn. 

If you use copper grease on thread of standard plugs you need to reduce torque 20% anyway, I never use copper grease on iridium plugs as they have a special tri-valent coating on the thread that does not bond with aluminium head.  Standard plugs have a passivated zinc coating that can stick if left in too long, if the old plugs don't want to come out I use the two steps forward one step back with some penetrating oil allowed to soak in ( not WD40) turn forward a bit and then back a bit and easy does it, the steel wall of a plug is surprisingly thin where thread meets main body and you do not want to sheer it off...

I always remove plugs when engine is warm as the aluminium of cylinder head expands more than steel of plug body and this eases the side pressure on the thread, and if you need penetrating oil the heat helps it to get into thread.

http://www.ngk-sparkplugs.jp/english/techinfo/qa/q18/index.html


Other than that, change all oil and filters and coolant, replace brake fluid and inspect brake pads, discs and callipers the rear callipers are especially prone to sticking on the slide pins especially if gaiters split or not fitted properly. Don't use normal petroleum based grease on slide pins as there are seals on them that will swell and will also attack rubber gaiters, I have used TRW PFG110 for quite a while now and apart from a quick check and another smear when I change pads or discs never had a calliper go tight or seize.

https://www.amazon.co.uk/TRW-PFG110-Grease/dp/B00H8ZX4F8

Gearbox oil ( manual transmission ) is every 70,000 miles use a good quality synthetic oil, have you got any whining noises from gearbox in lower gears when accelerating ? There is a bearing in there that is prone to getting noisy, plenty of info on forum about it.

Rear brake pipes prone to rust where they go unto rear torsion beam, worth a check as MOT failure ( but better an MOT failure than a brake failure).
« Last Edit: January 13, 2019, 08:32:31 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

paul_jj

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #8 on: January 14, 2019, 12:53:11 AM »
Great reply. Thank you.

The car has 168K miles on the clock. The brakes are very good and it looks like Suspension has been replaced as well. No noise of any kind, very quiet, my little boy is sleeping in this car much better than in my noisy JDM 250BHP Subaru Forester P reg.

It's great car as a first car, my missus likes it and the insurance is very cheap.

I will look in to spark plugs, but if someone has any kind of manual the torque for the plugs would be very beneficial, this is something I learnt from the engine tuners.

Jocko

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #9 on: January 14, 2019, 08:08:24 AM »
According to the Haynes manual the torque setting for the spark plugs is 18 Nm/13lbf ft.

springswood

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #10 on: January 14, 2019, 08:34:53 AM »
By the way each spark plug has its own coil.
Indecision is a terrible thing.
Or is it? What do you think?

culzean

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #11 on: January 14, 2019, 05:25:37 PM »
According to the Haynes manual the torque setting for the spark plugs is 18 Nm/13lbf ft.

Once you lubricate a thread the torque value changes by an unknown amount between 15 and 30% anyway.  Torque values are only good for a dry thread.  ( This remark is for OP not you Jocko as I am sure you already know this ).

I always start the plugs without using the wrench to make sure they don't get cross threaded and then screw  them hand tight without the wrench.
« Last Edit: January 14, 2019, 08:09:16 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Jocko

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Re: P0304 Powertrain - Cylinder 4 Misfire Detected - Random Misfire Detected
« Reply #12 on: January 14, 2019, 06:27:08 PM »
I never torque plugs, mind you, now my mechanic son-in-law does all my work, and he doesn't torque them either!

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