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Discussion Starter #1 (Edited)
Hiya,

Just wondering if anyone has experienced a similiar problem to me in either a skyline or any other car they have owned...

My cars always driven perfectly, until recently when pulling of a sliproad at about 50mph it started 'juddering'.. almost felt like someone was tapping the brakes as I was driving. Only happened a couple of times on that journey, however today it wouldn't go more than 10 seconds without doing it - feels like a slight misfire

Unfortunately last week I was forced to fill up with crappy supermarket fuel - being an NA I thought it wouldn't cause any damage, though I'm thinking this could possibly be the cause of the problem?

Only things I can think of doing to sort it is replace the fuel filter & change the spark plugs as this wasn't done on the last service (& put decent fuel in!)

Anyway - if anyone has any advice or know what the cause could be please let me know!
Cheers, Vicki
 

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I've owned my NA 2.5 for 4 years, filled up on all sorts of petrol including supermarket 95, never had an issue like that. As above, i would start with AFM, Fuel pump, fuel filter and possibly injectors?

Daz
 

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Discussion Starter #4
I've owned my NA 2.5 for 4 years, filled up on all sorts of petrol including supermarket 95, never had an issue like that. As above, i would start with AFM, Fuel pump, fuel filter and possibly injectors?

Daz
Cheers - have changed the sparks and fuel filter and seems to have done the trick! Fingers crossed it won't come back!
 

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Discussion Starter #5
So the problem still isn't fixed - had 3 days of it driving perfectly before it started juddering again
So far have tried changing the spark plugs, checking the AFM, changing the fuel filter, and draining the fuel tank and replacing with new fuel. Also checked the fuel lines which don't appear to be blocked.
Just took it for a short spin and it drove fine but doesn't idle well, revs seem to drop and rise every now and again. Have put some injector cleaner in with the fuel as thinking maybe they're just blocked

Next step will be replacing the injectors and possibly the fuel line just to be safe. If anyone else knows of anything worth a try before I admit defeat and take it to a garage if appreciate the advice!
 

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Before you go to the expense of replacing injectors, try and borrow an AFM form somebody, could easily be the old problem of dry internal joints in it.
 

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Discussion Starter #9
Anyone have an AFM from an RB20 or RB25?? Doesn't matter whether its from a turbo or NA
Need to get my skyline back on the road!!
 

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Discussion Starter #11
ah possibly... if my old one hasn't been thrown away you can have it. I'll have to check if it has been binned or not, but if you pay for delivery (or collect from Apple County) it's yours.
Thanks that'd be great if you still have it - am happy to arrange a courier etc
 

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Just some basic diagnostics

In my experience this is almost always caused by a faulty coil pack.

Unplug the MAF and start the engine, does it idle properly?
(note that with the maf unplugged the engine will not rev up, but should idle)
if yes, replace the maf

if no plug the maf back in
With the engine running
Unplug coil number 1, does the engine idle worse or the same/better
plug number 1 back in
Unplug coil number 2, does the engine idle worse or the same/better
plug number 2 back in
Unplug coil number 3, does the engine idle worse or the same/better
plug number 3 back in

etc

If it idles worse when you unplug it then the cylinder is firing
if it idles the same/better then the cylinder isnt firing

When you find a cylinder that isnt firing, take out the coil pack and swap it with one of the ones that is firing

Is it now missing on the same cylinder or the one you put the coil pack in?
If its the one you put the coil pack in it is a faulty coil pack

If its the same cylinder as before its the spark plug or fuel
If this is the case remove the spark plug
Switch the ignition on so that the dash lights come on but do not start the engine
remove the crank angle sensor (cas)
with the cas plugged in but remove from the engine, turn the wheel on the back clockwise (looking at the back of the cas, this is actually turning it backwards and pulses all injectors at once) and look down the spark plug hole
do you see fuel?
if yes, its the spark plug or potentially an electrical issue
take the spark plug out, connect it to the coil, touch the bottom of the spark plug to the rocker cover and hold it there, then turn the cas in the opposite direction to before, do you see a spark?
if no, swap the spark plug with another one you have and try again, do you see spark?
if no then your issue is most likely ecu

if you dont see fuel
at this point youre looking at a faulty injector or an electrical issue
try another ecu, if that doesnt fix the issue then
this is where it starts to become a pain in the arse to fix as you may well have to take the top half of the intake manifold off to diagnose further

it may be worth plugging someone elses ecu in to see if it runs properly, doesnt matter if its a 25det or why, just dont drive on it, idling is fine

also make sure your ecu plug is clean, this can cause major issues if its not. (like free from oil, not like sparkly clean)

I am fairly confident if you do all these things you will find your problem
If you need help, feel free to pm me, I'll do what I can
 

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Discussion Starter #15
Hi - thanks for your help
Had already checked coilpacks and they were all working fine
Turns out it was the AFM - have upgraded to the newer one as the green ones have a reputation for failing! Since then no issues, just hope it stays that way
 
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