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Slight misfire - any help appreciated


RobPhoboS

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I had the same issue with mine minor miss fire unplugging the coil packs one at a time didn't help I just changed mine one at a time for a known good one until I found the right one the other problem with testing modern coil packs (not sure about the 350) is lots of them have a transistor driver in them so you can't just measure the resistance of the windings at best you only have access to the secondary coil (the one connected to the spark plug) :)

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Rob, do remember you also have the camshaft/crankshaft position sensors that can cause "random" misfires.

 

Of course your process of elimination seems rational atm.

 

But from experience you could be spending a lot of time on coils when the issue could lie somewhere else.

 

PS: had a remap done a @ Abbey few months back, had fresh spark plugs fittted before tune, and the plugs that came out looks similar colour and shades to yours, and Mark did state "They look fine".

 

Good luck.

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Hopefully one day I'll get to the bottom of this, hah.

Right just to recap.

 

Cleaned injectors.

New lower injector o-rings (as I damaged them last week).

New spark plugs.

New cam sensors.

Checked for air leak.

Contact cleaner on all of the harnesses that I could see as well as the maf and throttle body (didn't touch flappy).

Tested coil packs (all 'seem' ok).

2 new coil packs (spares to test with).

 

I might just get another 4 new coil packs to at least replace all and see if that helps.

I'll order a crank sensor too, just in case.

Lastly I've seen that people can have an issue with the knock sensor and harness, so I may get one of those to try.

Lastly, as mentioned earlier it might be worth sending the injectors off to get tested and cleaned professionally.

 

I have torque pro if any settings I can report, let me know.

 

Otherwise I'm at a loss, the car was mapped about 4 years ago by Jez, might be worth heading up to get it looked at again.

 

 

Last thing...

It's now taking its sweet time to fire up after the car is warm.

(I re-did idle air volume learning too)

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Last thing...

It's now taking its sweet time to fire up after the car is warm.

(I re-did idle air volume learning too)

 

Defo sounds like Camshaft/Crankshaft Positon Sensor by that symptom, generally the 2 ontop of the engine.. Dont get aftermarket will do exactly the same.

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Last thing...

It's now taking its sweet time to fire up after the car is warm.

(I re-did idle air volume learning too)

 

Defo sounds like Camshaft/Crankshaft Positon Sensor by that symptom, generally the 2 ontop of the engine.. Dont get aftermarket will do exactly the same.

 

Ah ok, I kept the original ones so I'll test one at a time.

 

How come the oem copies aren't the same?

Cheers for clarifying this!

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Last thing...

It's now taking its sweet time to fire up after the car is warm.

(I re-did idle air volume learning too)

 

Defo sounds like Camshaft/Crankshaft Positon Sensor by that symptom, generally the 2 ontop of the engine.. Dont get aftermarket will do exactly the same.

 

Ah ok, I kept the original ones so I'll test one at a time.

 

How come the oem copies aren't the same?

Cheers for clarifying this!

 

I think its the programming/hardware used,

 

I brought the £20-£25/each jobbies on fleebay (Both the top engine ones) and done exactly as you explained.

 

Exactly same size etc, after 10mins when warmed up all went to hell. Turned out my sensors was fine (touch wood).

 

It seems Aftermarket Coil Packs are fine, but CPS no chance.

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I used a cheap sensor when one of mine was playing up it's still in there 3 years later no probs also the error code for the other sensor came in a month later this was the angled sensor not the straight one when i took it out to have a look at it i noticed their was some corrosion on the contacts 5 minutes with some switch cleaner and a cotton wool bud and it's worked ever since must be 3 yrs now but that's just my experiance with them. :)

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Heh, good to hear, I shall pop the old ones on to see what happens one at a time, if that sorts it out they can go back :)

 

A couple more things I shall try out too.

Test out someone else's working Maf, my one has been removed and cleaned but you never know.

 

I'm going to do a smoke test for the vacuum leak, I don't think just spraying around with the carb cleaner is really ideal as you can't get into every nook and cranny.

 

Something like this will do, I'll either use a hand pump or my electric tyre pump for pressure:

https://www.youtube.com/watch?v=rumgJ5UBpCw

:teeth:

I also found this which could be a good alternative:

http://www.atmospher...ducts/uk-europe

ingredients include propane (45%), butane (45%), and mineral oil (10%) - I think it's safe enough -

OBVIOUSLY no engine running on these tests :lol:

 

Lastly I've got one of these to see what the spark is like from coil packs:

http://amzn.eu/6szs6TL

Does this:

 

The hunt continues!

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Arrrrrrrrgh I was hoping today would give me a clue!

 

I put the original cam sensors back on, no hard hot starts now, so yep off they go for a refund.

 

I did a smoke leak test, the can of smoke didn't work for me as it shoots out very cold if it's going into a hose. If you have a big opening to spray it into first before pressurising it, then it'll work.

I just did it the same way the guys did in the above video.

The smoke only came out of the intake.

 

Next I tried my coil pack spark tester, tonight I'll upload a video of them so you can see what it does.

They all seemed to be the same, slightly pink/blue spark.

 

Next I tried a new maf, and no change yet although I haven't driven properly yet.

 

I'll chat to Jez at Horsham Developments on Monday.

 

Just to clarify, no lack of power or hesitation.

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