Weird missing issue. Any ideas???

[iSOARu]

Hi all,
I have a 7mgte. Now if I drive my car everyday it runs perfect. But when I don't drive it for a couple of days it starts missing most of the time when I do drive it. Weird thing is that when that happens and I'll drive it for 2 days or so straight (if I don't boost it's fine also) it'll start running perfect again. If I continue driving it again very day after that it'll stay fine until I don't drive it again for a couple of days.
I have changed the spark plugs, leads, fuel filter and even tried the nulon injector cleaner but all with no luck. Which now makes me think it might be my coil pack/s... maybe. What do you guys think??? Is this weird or what?

Thanks all

Any help is greatly appreciated.

p.s. sorry I'm not very good at explaining things, hope you can understand what I mean.

[Devils]

I'm not familiar with the 7M, but typically coil packs can get moister in the contacts or even inside them though small cracks which will cause them to short out until they dry out and run fine again. If they run a coil-on-plug setup like some of the Nissans this is also the case with moister down inside the rubber boot that covers the contact between the plug and the coil.

What you could try, once they are dried out and the car is running fine and your about to park it up for a couple of days, spray some water dispersant spray into the contact areas and around the coil/s. See how that goes.

When you first start it up after it's been sat for a while and immediately starts missing, are there any signs of what it could be causing the problem? Ie. Smoke, if so, how much & what colour. Fuel smell?

Quite often this problem can be due to a leaky injector but i dont think it would cause a problem to the extent your making it sound like.

When you took the spark plugs out, what did they look like? No cracks on their casings or anything like that. How were the tips? Wet? Black? White? Or a browny-black on the base going to a whitey on the tip?

Do you loose any water?

Have you had a compression test done?

[EldarO]

sounds like somethings straining your battery, might need a new one.

alternator might be a bit sus too, charging, but slowly.

[iSOARu]

Yeah I'll give the spray a go. Would using contact spray help at all? Or just utterly useless?
Ok, no smoke, no fuel smell, no cracks on the plugs, as for their colour if I can remember correctly black can't remember if there was a white tip, they weren't wet and no loss of water in the radiator. I haven't had a compression test done yet but I will if that's going to help. Honestly haven't thought of doing that as of yet.

I'm not familiar with the 7M, but typically coil packs can get moister in the contacts or even inside them though small cracks which will cause them to short out until they dry out and run fine again. If they run a coil-on-plug setup like some of the Nissans this is also the case with moister down inside the rubber boot that covers the contact between the plug and the coil.

What you could try, once they are dried out and the car is running fine and your about to park it up for a couple of days, spray some water dispersant spray into the contact areas and around the coil/s. See how that goes.

When you first start it up after it's been sat for a while and immediately starts missing, are there any signs of what it could be causing the problem? Ie. Smoke, if so, how much & what colour. Fuel smell?

Quite often this problem can be due to a leaky injector but i dont think it would cause a problem to the extent your making it sound like.

When you took the spark plugs out, what did they look like? No cracks on their casings or anything like that. How were the tips? Wet? Black? White? Or a browny-black on the base going to a whitey on the tip?

Do you loose any water?

Have you had a compression test done?

[iSOARu]

Interesting... I would have never thought of something being wrong with the battery nor the altermator. How did you come up with that theory?

sounds like somethings straining your battery, might need a new one.

alternator might be a bit sus too, charging, but slowly.

[EldarO]

as pressure in cylinder goes up, the spark has a harder time jumping across the plug gap.

thus miss on boost

if there isnt enough power in the battery, this can also cause spark breakdown, hence miss in general.

leaving the car for a while = battery not retaining charge, either something draining it, or dodgy battery

driving car, clears up after two days = alternator charging battery up to point where it has enough power to not break down on boost.

this is just one of the possible things that could be wrong, but it'd be the first thing i check, as well as all your earths, make sure they're in good nick and nice and clean, main ones being between battery and block, and battery and chassis.

[iSOARu]

Just a thought. What if when I don't drive the car for a couple of days, I check the voltage of the battery using a multimeter and see if there is a voltage drop? Could that be an easier/ cheaper way to check without having to actually change the battery?

[EldarO]

well, ideally you want to test the battery.

best way to do this would be to drive down to supacheap, take your battery out, and ask politely if they could spare a few mins to chuck their tester on for you.

as for the alternator, start the car, and pull the terminals off the battery (obviously dont drop the positive onto the body )


if the car stalls, the alt needs a reco, if it still runs, it still could need a reco, but at least is working somewhat (as is evident that its charging the battery over a couple of days)

but all this should be evident when you go to start it etc.

if the battery's low enough on charge to drop spark under high boost, it should be struggling to crank over, or at least be doing so slowly.

[Devils]

hhmmm thats a good point... might have to check that out on my parents pulsar before i go swapping injectors over. As it's got a similar problem to iSOARu.

Hope you get yours sorted mate!

[Cruiser97_80]

as for the alternator, start the car, and pull the terminals off the battery (obviously dont drop the positive onto the body ).

wtf
please don't do this!! test it with a multimeter they are cheap now days.
ECU's aren't cheap, you could cause a voltage spike doing this.

[lexsmaz]

I second what Cruiser97 80 says, Do not disconnect the battery with the engine runing, Just check the voltage at the battery with the engine runing ideally should be around 13.8 to low 14 volts, maybe a bit lower at idle but not much, bring the revs up, & turn lights on etc, should still be around 14 volts, ( ideally it takes 2.3 volts per 2 volt battery cell to charge up the battery, hence 2.3 x 6 cells = 13.8 volts ) if it starts up under its own power after sitting for the couple of days ie, no jump starting required & cranks over well, i personally believe the battery etc should be ok .. Doesnt help fix your problem though ...

[Kyosho]

You do realise the ECUs have voltage regulators in them and only run internally at 5V anyway right?

[Kedderz]

checked all intercooler and intake piping to make sure its all tight and secure? unmeasured air could be causing the issue. I know you say it goes away if u drive it for 2 days straight but that could all just be coincidence.

[iSOARu]

I strongly believe that it's not down to coinsidence because I've been having this problem for 6 months plus, but thanks anyway.

I know you say it goes away if u drive it for 2 days straight but that could all just be coincidence.

[iSOARu]

I'll be using one of those hand held battery check machine things but that wont be till Saturday. The car doesn't need a jump start after a couple of days and it cranks over fine. Still thinking it might be a coil pack issue, although I have no idea how to check them.

I second what Cruiser97 80 says, Do not disconnect the battery with the engine runing, Just check the voltage at the battery with the engine runing ideally should be around 13.8 to low 14 volts, maybe a bit lower at idle but not much, bring the revs up, & turn lights on etc, should still be around 14 volts, ( ideally it takes 2.3 volts per 2 volt battery cell to charge up the battery, hence 2.3 x 6 cells = 13.8 volts ) if it starts up under its own power after sitting for the couple of days ie, no jump starting required & cranks over well, i personally believe the battery etc should be ok .. Doesnt help fix your problem though ...