Engine misfiring

[Dicky]

Following a run out the other day the engine suddenly started to run lumpy. Code reader showed “multiple misfires”. Contacted ZMANALEX who advised I pull each coil pack plug in turn and listen for a change in engine note. I found it difficult to notice a change on any cylinder but eventually thought it might be cylinder 6 (note sure though). I ordered two used coil packs from him just in case.

While waiting delivery read this guide https://my.prostreetonline.com/2019/02/22/p0303-nissan-3-5l-how-to-test-vq35-ignition-coil/  explaining how to measure the resistance between the coil pack 3 pins to determine good/bad. Have to admit I couldn’t quite get my head around how the guy assessed the measurements, so measure the resistance between pins myself. 
First I noticed the the pins are polarity conscious ie placing the red +ve lead on pin 1 and measuring to pin 2 produced a totally different reading to if I placed the black -ve lead on pin 1and measured to pin 2. Completely different to to the written guide above??

Measured all 6 coil packs first with Red multimeter lead then the black lead and all six produced the same readings, so I’m assuming all are ok as the engine wouldn’t run if the were all duff.

 

Anyone gone down this road before and can contribute because I’m beginning to fear it may be injectors or duff plugs or even leaks as raised in the article.

 

[Olly350z]

An intermittent coilpack failure will be near on impossible to diagnose without specific diagnostic equipment, however what Alex has recommended will work providing you get lucky and it decides to misbehave 

 

I had a similar issue back in 2018 on my DE in which a coilpack was failing resulting in a totally random misfire which would come as quickly as it cleared, and I finally bit the bullet when it went into limp mode on a busy roundabout leaving me stranded. 

 

Euro car parts do (did, this was 3 years ago) a OE equivalent coilpack called Bremi. When I pulled all my oem packs these were identical even down to the mould lines. I replaced all 6 and plugs at the same time as I wanted a definitive answer. These packs were around £70 quid each, against Nissan who wanted £120 + VAT each and it worked like a charm. The car never ran so well, increased performance on the butt dyno and improved MPG. Obviously I can't guarantee this is your issue, however most misfires I've seen reported are coilpack / spark plug related. I'd advise checking those as your first response as they can be a relatively cheap fix 

[Kieran O'Quick]

As above. Intermittent failure can happen due to heat. The coil won't show up as dodgy on a multimeter. A clue to this would be if the misfire happens when you're sat in traffic after a run. 

 

[Dicky]

Thanks Olly, it’s been a bit of a sod trying to listen to engine note when it’s running lumpy and hunting all the time.

I was going to order a full set from Alex but he was out of stock. I’ve just rang Euroncar parts and ordered a full set of none budget packs for £30 ea + Vat.

Hears hoping👍 Thanks again

[Dicky]

Thanks Kieran👍

[Dicky]

Thanks Olly,

to be able to get to the coil pack plugs and stand half a chance of removing/replacing them on 2,4&6  I had to remove the air intake pipework (maintaining the maf) the other side was better but not much. Then trying to listen to the engine note when it’s running lumpy and hunting all the time was bordering on impossible.

I was going to order a full set from Alex as it happens but he was out of stock. Rang Euro car parts and they have a decent make for £30+vat so may follow your lead.

[Kieran O'Quick]

If it happens to be heat related you can try to find the broken one by cooling the tops of the coils in turn when it's misfiring. Saves a lot of time and bother for the sake of a can of that freeze-spray stuff used in electronic diagnostics.

[Olly350z]

39 minutes ago, Dicky said:

Thanks Olly,

to be able to get to the coil pack plugs and stand half a chance of removing/replacing them on 2,4&6  I had to remove the air intake pipework (maintaining the maf) the other side was better but not much. Then trying to listen to the engine note when it’s running lumpy and hunting all the time was bordering on impossible.

I was going to order a full set from Alex as it happens but he was out of stock. Rang Euro car parts and they have a decent make for £30+vat so may follow your lead.

 

 

You don't need to remove them to test them, removing the air intake will cause its own set of issues particularly if you disconnected the MAF. You mention the car is hunting, do you mean rev hunting? 

 

To test them, all you need to do is unplug them one at a time at the coilpack. You'll see the engine loom that runs around. 

 

With the car running and everything where it should be, unplug them at the connector one at a time, a long nose screw driver helps here. You will hear the engine note drop noticeably as its essentially dropped a cylinder. If you hear the difference, reconnect and move on. 

 

If you don't hear a note change, that is possibly your culprit coilpack / spark plug 

 

[Dicky]

Hi Olly, 

I tried your suggestion but it seemed the engine note changed on all of them so I was unable to confidently say which one was duff.

I then pull out each coil pack in turn, leaving its plug connected pushed a spare plug into the coil pack, grounded the plug body and turned the car over. Would you believe all 6 produced a spark???. I then bought and fitted a full set of Platinum NGK spark plugs, boxed it all up again and BUGGAR it’s still missing.

Now thinking it may be an injector fault or something more obscure plus I’ve ran out of enthusiasm so it’s off to the garage on Mon where their diagnostic computer will hopefully highlight the fault. It may cost a few quid but I’ll get that back by getting the wife a paper round for a month or two 😂😂😂

Thanks again for your input though.

 

[ZMANALEX]

Injectors are in stock if required. 

[Azurez33]

The garage should be able to at least tell you whether it’s spark or fuel using a diag scan tool and looking at the live data, have you noticed it drinking fuel a bit more of smoking at all? and do you have a standard intake system? 

[monkeybrain1234]

Timing chain stretch? Only say this as on another forum I have been reading about this. (not Z specific) 

[Dicky]

just out of interest, if you pull off the long nose part of the coil pack to reveal the long spring assembly inside, there’s a 20mm ish long item which looks like a fuse inserted in series with the spring. Anyone know what that is and it’s function in life??

 

Might cut one open to see what else I’d involved insde.

[Dicky]

Well poor old Betsey is seriously ill just now. The garage rang to say  one of the cylinders is low on compression and the cause could be one of several things, valves, injector or a piston leak problem. Just waiting for repair estimates now but the service manager did say it will be costly.

Think I’ll remind him I’m just a poor old pensioner with a bad back and a sore leg....it’s worked before😂

[Dicky]

Apparently the exhaust valve is the culprit here. Garage carried out a leak down test and found air was pouring out the exhaust pipe. Cylinder head coming off on Monday but up to now it’s costing circa £3k 😭

Anyway I’ll post exactly what’s been done for future reference 

 

Edited June 12, 2021 by Dicky

[Willsy1980]

Probably cheaper to throw an engine in if its getting to rebuild territory 

[Azurez33]

 message Alex and see what he can sort out for you, as willsy said might be cheaper replacing the engine for a known good one, guess it depends on costs etc 

[ZMANALEX]

26 minutes ago, Azurez33 said:

 message Alex and see what he can sort out for you, as willsy said might be cheaper replacing the engine for a known good one, guess it depends on costs etc 

He already has as I have been advising all the way through the process including emphasising how important a leak down test was compared to just a compression test.

 

My latest bit of advise was just to replace the complete cyl head with a low mileage example complete with valves, buckets and cams.

 

I offered a 10,000 mile complete head which just needs dropped on, with no messy time consuming bench work required.

 

Replacing the head is a 10 hour job and at £50.00 per hour, well I will leave you to do the maths.

[Dicky]

 

The continuing story .....

Well I visited the garage to see how Betsie my sick 350 was doing and nearly fell over when I saw her in the corner of the garage, all forlorn and abused with the front of the car removed, wire looms all over the place disconnected plugs and sockets and air con radiators tied up out of the way etc etc. To be fair they did explain they wouldn’t normally do this but due to the age of the car and the potential for seized  connections and rusted bolts it was the safest option to leave as much connected as possible and tie it out the way, fair enough I thought!

 

The cause of the misfire appears to be down to a burnt out inlet valve on cylinder 4. The edge of the valve had burnt away as had the valve seat. The garage recons this was down to a faulty injector causing a build up of carbon on the valve and seat preventing it from dissipating heat efficiently. Apparently the timing chain had also jumped a link but fortunately hadn’t caused further damage. 

For those like me who didn’t know, and because inspecting the timing chains etc is a major job, apparently you can hear the timing chains “slapping”when the engine is first started up (which disappears after a short while) indicating the chains and tensioner need attention (DON’T IGNOR THIS)

As it happens I had posted a forum question earlier last month asking why cylinder 4 spark plug always looked slightly burnt and sooty when doing the annual service, now I know and here again (DON’T IGNOR THIS).

 

Due to the cost to repair, lack of good engineering companies in the area, plus the additional cost of spares made a replacement low milage engine look the best bet. Unfortunately Zmanalex was out of stock and because I wouldn’t trust anyone else to buy from and because the bottom of the engine looked pristine, I finally decided to buy a low milage cylinder head and injector from Alex and take the hit of any additional expense. Alex is a deep well of knowledge and so helpful when your in the depths of despair (a canny lad in Geordie)

So now I’m waiting for my parts to arrive and hoping that the mechanic building the engine back up again can remember where the multitude of the bits and pieces all go back.

 

[Azurez33]

Hopefully all will get sorted Mate, Alex’s reputation is definitely  well warranted 

[Dicky]

Still waiting for the finished product. Lost a week due to the service manager going on holiday and gaskets etc not being ordered. The mechanic had a little work to do to tidy and check the replacement cylinder head but I’ve been told this would not incur labour costs. Anyway all the parts came in last week so onward and upward.

It’s a bugger though all this hassle and expense

over something I could have spotted had I been more aware. Also, as I mentioned earlier, the timing chain had jumped a link because tensioner was at its fullest wear position. I can’t seem to find any Nissan info suggesting how often the timing chains and tensioners should be changed. I’ve heard 100,000 miles mentioned but I thought they lasted the life of the car. Bugger squared!! 
If I had my time again I would change them at 60 to 70 thousand to be on the safe side especially if the car is driven hard at times.

To be continued....

 

Edited July 20, 2021 by Dicky

[ShortPaul]

11 hours ago, Dicky said:

Still waiting for the finished product. Lost a week due to the service manager going on holiday and gaskets etc not being ordered. The mechanic had a little work to do to tidy and check the replacement cylinder head but I’ve been told this would not incur labour costs. Anyway all the parts came in last week so onward and upward.

It’s a bugger though all this hassle and expense

over something I could have spotted had I been more aware. Also, as I mentioned earlier, the timing chain had jumped a link because tensioner was at its fullest wear position. I can’t seem to find any Nissan info suggesting how often the timing chains and tensioners should be changed. I’ve heard 100,000 miles mentioned but I thought they lasted the life of the car. Bugger squared!! 
If I had my time again I would change them at 60 to 70 thousand to be on the safe side especially if the car is driven hard at times.

To be continued....

 

Zedmanalex will be able to advise when a timing chain should be changed 

[Azurez33]

I know more about hondas than the ol Z, they usually recommend 100k valve clearances and 200k replacement of the chain because I guess they see life of the car being around there, I imagine similar for most cars, apart from BMWs/minis and range rovers they’re about 100k 😂😂 but the same as everything, regular servicing should see it last as long as possible 

[Dicky]

The final chapter.

Got the car back from Vic Youngs garage in South Shields who have saved my old car Betsy’s  life (I recommend them). She’s sitting in my garage now with blankets and a hot water bottle to recuperate after 4months of waiting hindered by Covid staff shortages, Holidays and sourcing parts. 
The final bill £3200 which seems fair considering the parts cost circa £1200.

Shes had new timing chain and tensioner, water pump, a low milage cylinder head and injectors from ZmanAlex and gaskets etc etc.

All this because of a faulty injector on cylinder 4. How on earth can you tell if an injector is functioning 100%? 
As it happens I had noticed a dirty cylinder 4 spark plug over the last 3 services but couldn’t understand why, even posted the question but no positive solution.

All I can recommend after all this aggravation is 1) be weary of dirty plugs when doing your servicing, possibly do a leak down test on the cylinder if your not sure and 2) listen for timing chain slap after a couple of seconds after starting and be sure to change it well before 100K miles especially if you give your car the beans a little to often. 
 

 

 

 

 

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