So im having periodical misfires and bad hesitation

Sye

New Member
As title says im having a periodical issue with the car hesitating (feels like fuel surges) and occasional misfire on cold idle, doesnt happen all the time only occasional, when it happens the revs bounce about at idle and before the maf was cleaner there was some black smoke coming from exhaust when the problem would happen.

ive changed alot of stuff of the car to try and solve the problem including plugs, leads, dizzy, rotor, fuel filter, fuel pump, had it in having the fuel pump fitted and fueling checked and he said all the fuel pressure, afr's etc are fine, he also cleaned the maf but said it was running a little lean so replace the maf.

I replaced the maf and it didnt cure the problem, i actually tried 3 different mafs and no cure to the problem so it made me think that this is not the issue.

I would like to try and re-earth the maf but im really not sure how to do this and im not too car savvy but i dont know if this will fix anything.

Anyone have any other advice on what to check?

Thanks in advance
 

PobodY

Moderators
Staff member
Try the lambda sensor? - I can't remember if it's on closed-loop at idle or not, but that might explain poor performance at partial throttle positions.

Is the TPS set correctly (i.e. does the ECU know it's supposed to be idling)?
 

mreguest

Member
i'm with you on this one mate!

since the cold weather (maybe coincidence?) my car has been a spluttering pile of shite until warmed up...

sequence of events:
- start car - idle 1500rpm - drive not very far and once the idle starts to come down it begins to cough and splutter on idle at junctions etc - give it some beans and it is as fast as ever - as engine is warming up the idle is lowering and the spluttering gets worse to the point that it cuts out now and again - sometimes the idle falls rapidly to 500rpm and leaps up to 1200rpm and does this randomly and regularly - there comes a point when the engine heats up that idle flatens out at 900rpm and all seems good - as i get closer to work in stop start traffic the engine gets up to full tempterature and my idle will end up high again around 1200rpm - no coughing/spluttering.

holding the car at 2500rpm in any gear at any temperature can deliver a wobbly engine response feeling but as my suspension is harder than chuck norris i wonder if it's just my foot/throttle wobbling...?

i've connected data scan and can see all the parameters are doing something - i cannot tell you if they are correct but they all do move - no error codes - TPS at 0.5V idle states closed TPS - other parameters i cannot remember off top of head.

i have replaced all oil/water/vacuum pipes so i don't think it's this.

my spark plugs get black regularly thus implying over fueling.

dizzy/rotor look good. i've not looked inside MAF but last time that was playing up there was a distinct jolt every now and then when trying to make little boost, doesn't feel like this...

ignition leads i am suspicious cause they look old and battered but connections look clean etc...

but I cannot get my mind around the fact that at a certain temperature everything seems fine!?!? but either side of magic temperature something is wrong.

there are little 'black boxes' on the back of the inlet plenum for cold start and IAC/AAC reasons. i don't know exactly what these things do or how to test them, and i don't have any spares so for the time being i'm just putting up with the madness...

Any ideas from the genius long term owners and tinkerers would be greatly apprechiated?
 

warpspeed

Well-Known Member
check the earths, two onto the plenum first, the main earth strap from thermostat housing to chassis leg and up to battery.
Work you way around the engine bay, pull apart one multi-plug at a time, clean and start engine, that way if you find a fault you'll know exactly where it is....

Nissan used a root type earthing system, this means one earth fault can cause just one item to play up whilst everthing else works fine....
 

Sye

New Member
how do i check the earths? i have a multimeter but i aint got a clue how i should use it lol, sorry im a total noob, and can i clean all the connections with electrical contact cleaner for all the plugs? maybe a stupid question lol

it was also suggested that lambda could be gone so ill replace that asap
 

Sye

New Member
the only issue with this is, the problem isnt there all the time, it can go for days running perfectly fine
 

PobodY

Moderators
Staff member
Have you done any modifications to the car? - I used to have problems with the idle going up and down that turned-out to be the Bailey dump valve.
 

Sye

New Member
yeah its got a few mods and the dump valve is suppose to be leaking slightly so i was told
 

The Doc

Moderators
Staff member
The dump valve is not supposed to be leaking, if it does you will get misfires and poor tick over due to the air leak it is creating, the air flow meter will get a false reading from the air leak and give you the problems you have.
 

PobodY

Moderators
Staff member
Just take the DV off and plug the hole to see if the faults clear .....
Bingo. - You can also try clamping the vacuum/boost line to it. That's how I discovered that mine was at fault because with no vacuum it shut and the idle stabilised.
 

PobodY

Moderators
Staff member
Always start with the simple things first, then move on to the more complex (or possibly more expensive) ones. - I'm often surprised by the difference one small thing can make.
 

campbellju

Moderators
Staff member
there are little 'black boxes' on the back of the inlet plenum for cold start and IAC/AAC reasons. i don't know exactly what these things do or how to test them, and i don't have any spares so for the time being i'm just putting up with the madness...

Any ideas from the genius long term owners and tinkerers would be greatly appreciated?
The IAC/AAC could be an issue they I expect it's more an air leak issue with the high idle. If you can get access to these for removal, they are easy to take apart and clean. IIRC they can get covered in black crud that can cease the solenoids. The car will run without them, I wasn't using them and was using the car every day but they were not leaky.

The problem is there are lots of pipes at the back of the car that could give leaks, I'm not suggesting my extreme option but again it helped lower the idle speed.

http://www.gtiroc.com/forums/showthread.php?46399-Inlet-manifold-tidy-up&highlight=air+leak

Changing the lugs on the earths to the ECU (inlet manifold) and cleaning the contacts helped.

I had a problem once with an inlet manifold gasket that I re-used. This is meant to be okay but it wasn't sealing. A little OTT but now I change them each time the manifold is taken off to avoid issues.

The relationship with temperature makes me think something is sealing as parts expand. The issue at 2500rpm could be where the map leans out and the issue is amplified.

Check all your pipes for good seals between the MAF and the manifold.
 

Sye

New Member
driving home today i noticed my dump valve has a different sound now, it chatters instead of the normal sound a dump valve should make when changing gear, never noticed this before but maybe the dump valve is the issue
 

mreguest

Member
The relationship with temperature makes me think something is sealing as parts expand. The issue at 2500rpm could be where the map leans out and the issue is amplified.
cheers - good shout on this! i totally agree because when i park it at work in multistorey carpark my drive home is nowhere near is spluttery as my way in the morning. thus prooving i think that super cold in morning = rubbish, driving home warmer in evening = better so something is sealing or connecting when hot.

Funny you should mention manifold gasket, i did have that all taken apart not that long ago and i remember getting the gasket to sit right was a pain in the arse! this might be it.

I mean the gasket that sits halfway through the manifold assesmly, basically you could say i lifted the 'lid' off the manifold not the whole manifold assesmbly off the engine. do you know a good place to get the gaskets online or do i need to contact Nissan directly?

Many thanks!

Sye - good luck with your issues, please let us know if/when/what fixes your problems :)
 
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campbellju

Moderators
Staff member
I just got mine from Nissan. Because of the mod I did to my manifold, I can just whizz it off and have a good look at the back of the engine. The last time I think I just bought 3 from Nissan for the price. There may be a blue print equivalent that would be adequate> I'm talking about the gasket that goes between the head and the manifold. Its a metal gasket. You can buy silicon versions too on Ebay etc but they we a lot more expensive than OEM Nissan
 
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