My EF Falcon was missing under load in the mid range and got worse so I replaced the coil pack last night but after driving for about 30min it started doing it again, only under load at high rpm. It also had a slight mis at idle which is still there with the new coil pack.

I replaced the plugs 5000km ago and ive checked them, they look ok, I got the coil packs from a trusted wrecker so I just want to eliminate all other possibilities before I take them back.

I will replace the plugs and leads (which are also not that old), is there anything else which could be causing this problem?

Thanks

I changed my plugs to NGK and had an immediate response in smoothness/fuel economy, so it could be your plugs; I'm not saying that it was an NGK plug that made the difference, but the other plugs were the cheaper variety.
Did the missing start after you changed the plugs/leads?
If so, you might have a dodgy plug or lead.
I guess if it is a plug, one way would be to get a new plug, and replace it in each pot to see if it makes any difference. A bit of a hassle, I know.
Then maybe the same with the leads (if it can be done).
There has been a few posts about this in the last few months....including a lengthy one about my car...so go back through the posts and start reading. There are a lot more qualified people here than I, and they gave me some great advice.
Good luck!

new plugs and leads then, also check where the leads go and make sure they dont touch metal on the car, even though they are insulated, small chance of some leakage

get a new OEM coil pack! just because its a trusted wrecker dont mean it wont be faulty!


also thought about injectors and fuel system?

the slight miss on idle might be the ISC.
Id try the fuel system if a new coil pack doesnt change anything. Check your pump for correct operation, check your fuel filter, then check your fuel reg and then injectors. Try a Nulon injector cleaner and see if it changes anything. If there is any difference with the Nulon s**t in your tank then it might be fuel related and the Nulon s**t is under $15, so that might be a good eliminator before you replace the coil maybe.

By checking the fuel pump I mean check for weird sounds you might miss if your not listening for them i.e tired pump etc. If you havent changed your fuel filter in a while it would be best to do it anyway for the sake of $20.

i had simular issues in my sisters nf fairlane.. did the usual leads, plugs, ecu, isc. (injectors-good ones out of my old eb)

put the code reader on it and her oxy sensor was rooted along with the cas sensor. it only ever missed at idle or when you gave it some wot

i should of just done a scan first but i hadn't unpacked it from when i last moved house at that stage.
there is little point swapping stuff over for it might fix it.. get the codes read and fix the actual issue. as it can work out cheaper replacing the one part thats dead instead of everything before you figure out what is actually the fault

her leads were arcking out badly and her plugs were just as old so it was on the to do list to replace them anyways so she did them at the time.

that being said it hasnt skipped a beat since.. only issue now is i have to find time to help her replace a broken engine mount rubber

Is there only one rubber seal on the connection of the harness to the coilpack?
Sometimes they get stuck in the socket other times the plug, if there is one seal on both, there will be a poor connection.

Worth a check.

I replaced the plugs 5000km ago with Bosch Platimum series plugs which have always lasted well in my other falcons. Thanks i will have a look back.

I have a new set of leads to put in the car, so will try that tonight along with new plugs, OEM coil packs are very expensive in Nz compared to Australia so will try and steer clear of buying a new one. Otherwise I will look at the fuel system.

http://www.ebay.com.au/itm/NEW-BOSCH-FO ... 256b840a0a
Thats cheaper ( even with postage) than what I paid 12 months ago from Bursons

Email these guys for a quote:
http://www.fordpartslive.co.nz/sp.aspx?contacts
They have the best prices I have found on new Falcon parts, and their service is fantastic.

I replaced the Coil Pack and the leads and the car run really well for a week or so but now the miss is back, probably worse than before. I'm thinking maybe the problem was with the leads in the beginning so i could change back to my old coil pack first and try that? It definately feels like it's an ignition problem and not a fuel filter etc as it doesn't happen much at high revvs mainly at low revs under load and at idle is misses a bit......

A few months ago I was chasing two issues on my EF as well - one was a very noticeable miss / cut at idle once the engine was warm (ie. it didn't do it for the first few minutes when started cold) - often accompanied by stumbling when accelerating from standstill - and the second was a random serious engine miss at various speeds and loads - ie. the engine would suddenly make a very loud "BUH-BUH-BUH-BUH-BUH" noise for a few seconds (frequency dependent on the revs at the time - ie. at high speed it would be more like "BBBBBBBBB" ) - during which there was no response to even flooring the accelerator. Was really frightening as it sounded like a dropped valve!! First time it happened I thought I'd blown the engine. It would happen sometimes not at all in a whole day of various driving and other times be happening every 10 minutes or so - mostly tho it would happen maybe only once or twice during the course of the day.

The idle miss ended up being injectors - replacement set fixed it completely - and the random engine choppiness has been fixed by disconnecting the cam phase sensor.

I hadn't seriously considered that the cam phase sensor itself might have been faulty as it's one I fitted new only 6 months before these issues showed up - but after confirming the sensor drive is all fitted up correctly I'm thinking that "new" sensor might well be the issue. She's running sweet tho without it connected at all so I'm in no panic about it (kicking myself I threw out the old one!!!).

Just thought I'd share that recent experience in case it helps. Problem with these sorts of things is they can be from so many possible causes you can burn up huge amounts of time and dollars chasing your tail As has been suggested, pulling codes might be well worth doing - ie. perhaps approach EFI workshops to see if they have the gear and might be willing to do it for a few bucks.

If you have a multimeter, you can pull the codes yourself quite easily. You will need 3 small jumper leads from Jaycar, d**k Smith, etc. I can scan through the page from the service manual if you need it. Let me know.

Tip: make sure the alligator clips on the jumpers are contacting only one connector each. If they are not covered in plastic, wrapping in electrical tape does the trick nicely.

Here are the instructions for pulling codes (from my Gregorys manual):