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Engine missing a beat/misfire under load as turbo winds up

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Old Aug 4, 2013 | 05:56 PM
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Thumbs down Engine missing a beat/misfire under load as turbo winds up

Hi iv got a wr1. Its got a decat and has been remaped. Running approx 340 with matched torque.

Its seems to be missing a beat, for example, doing 10mph in 2nd gear and flooring it, as the turbo winds up and gets to full boost it will miss 1 beat for a split second then carry on accelerating as normal and its fine through the rest of the gears whilst flooring it.

Iv seen some posts on here saying it might be the NPS but i replaced that when i had it mapped about 6 month ago.

I put the uprated plugs in it when i first got it, that was a year ago and have covered approx 9-10k miles and also did the fuel filter and put a green cotton air filter in.

Every bit of help will be appreciated

Thanks
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Old Aug 4, 2013 | 07:19 PM
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Have you checked all the vac hoses for splits or perishing ?
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Old Aug 4, 2013 | 07:23 PM
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I shall have a look in 5 mins mate and let you know

Thanks
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Old Aug 4, 2013 | 10:35 PM
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All vacuum pipes seem to be ok
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Old Aug 5, 2013 | 02:30 AM
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coil packs or ht leads....
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Old Aug 5, 2013 | 11:52 AM
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mines doing this at the moment. I was thinking about changing all vacuum hoses...
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Old Aug 5, 2013 | 12:03 PM
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Mine does this on 517hp with a s206, its like a backfire/stutter when winding up I believe its ignition related?
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Old Aug 5, 2013 | 09:24 PM
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Yes id describe it as a stutter aswell, only dus it as turbo gets onto full boost for a split second.

Hopefully we can sort them out guys.

My friends a mechanic and is going to plug his diag machine into it this week and read all the data and logs whilst booting it when it happens, and hopefully itll show up.

Are yours only doing this in the gear you start booting it in? Then as u carry on booting it through the gears its ok?

Annoying.com
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Old Sep 8, 2013 | 09:06 PM
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still having this problem, and the thud that it makes seems to be getting larger!

it feels like its coming form the rear tho, unless it just feels like that cost most power is at the rear wheels?

im thinking its either a fuel/ignition issue?

HELP!
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Old Sep 9, 2013 | 01:44 AM
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long shot but i had this problem in my standard classic, it was the plugs.
have you looked at them?
i put denso iridium plugs in, 10000 miles later had same missfire
took the plugs out one of them had worn out, the point on the electrode had gone, so the gap was huge.
the increasing boost was blowing the spark out, or more accurately the spark was too weak to ignite the mix.
cheap fix none the less
problem is why was it eroding the plugs,
probably a weak mixture in that cylinder, pointed towards a blocked injector,
the plug was getting too hot and wearing down prematurely.
at least the plug wears down before the pistons melt
good and bad news then
good luck lol
andy

Last edited by andyamf; Sep 9, 2013 at 01:48 AM.
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Old Sep 9, 2013 | 06:26 AM
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Could be the problem. I put then pfr7b plugs in approx 8-9k miles ago.

Its wierd because it only does it in the gear that you start off flooring it in, then its fine through the rest!

Annoying
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Old Sep 9, 2013 | 01:46 PM
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get it on a dyno, is it hitting boost cut or summit as it peaks?
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Old Sep 9, 2013 | 02:27 PM
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I wondered if it was sumthing to do with boost cut?

It was on the dyno last week, peaked 21psi boost and held at approx 18-19psi, nothing showed up
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Old Sep 9, 2013 | 06:14 PM
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if it was doing it before may be hitting it when temps are low, run it on a hot day and it wont hit the cut
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Old Oct 8, 2013 | 12:56 PM
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problem fixed! (so far so good!)

rear tyres having 3-4mm less tread than the fronts!
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Old Oct 8, 2013 | 12:58 PM
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eh? it was missing due to tyres being worn?
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Old Oct 8, 2013 | 01:02 PM
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it was the central diff banging (or whatever it does)

3-4mm of difference in tread can cause you to destroy your central diff. over a mile your tyres that are of lowest tread with complete approx. 4-5 more full rotations causing your c diff to work overtime, basically trying to correct the difference.

the way to highlight if this is the problem, is to put your c diff into auto, if it does it in auto and not in manual (set fully to open, all the way at the bottom) it shouldn't do it in manual.

hope this helps a lot of you out there!

it felt like a sudden misfire/bang from the rear area.
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Old Oct 8, 2013 | 01:05 PM
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ah, i thought you ment bang/misfire from the engine.

on a slight side note, launch a classic hard enough and rear dif will smack the sub frame, makes a wicked bang when it does
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Old Oct 8, 2013 | 01:25 PM
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That's why subaru recommend you move your tyres front to back to even out the wear.

I always change all four tyres together on any 4wd car.
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Old Oct 8, 2013 | 01:35 PM
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I do as of now haha
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