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Miss firing between 2000 and 3000 rpm
https://www.ausmini.com/forums/viewtopic.php?f=2&t=65996		 Page 1 of 1
Author:  Booglie [ Wed Sep 29, 2010 6:46 pm ]
Post subject:  Miss firing between 2000 and 3000 rpm
I am having a strange problem where in every gear except 1st my mini miss fires when I have the accelerator past half way and it is reving between 2000 and 3000 rpm but then works perfectly throughout the rest of the rev range. What is going on?
Author:  Lillee [ Wed Sep 29, 2010 7:10 pm ]
Post subject: 
Check your dissy points. When you say missing do you mean the engine hesitates? if so it means the carb is running lean. Have you changed any carb/air filter configuration lately? if it's breathing better then you need to give it more fuel.

SU carbs or weber?

Could also be fuel pump on it's way out
Author:  niceboy1275 [ Wed Sep 29, 2010 7:16 pm ]
Post subject: 
my clubman was doing that, turns out the piston in the carby was sticking.
Author:  Drexxle [ Wed Sep 29, 2010 11:57 pm ]
Post subject: 
using to thick oil in the dash pot piston can do that too. it will rise to late and drop to late. use dashpot oil, or sewing machine oil. not engine oil.

also had this problem once because had the wrong rotor arm in the dizzy, it was just to short and as the revs went up it didnt spark properley.
Author:  pristic [ Thu Sep 30, 2010 9:20 am ]
Post subject: 
Does it just miss or backfire?
One thing to try is to put it in a higher gear (3rd, 4th) at a low speed (40km/h) and floor it, if it does it alot more, your leads could be arcing or breaking down...

You cant feel it much in first usually because of the load, etc.

Cheers,
Pete
Author:  Booglie [ Thu Sep 30, 2010 9:20 pm ]
Post subject: 
I have a megajolt in this one so no dizzy problems, I also have light machine oil in dashpot. It misses worst in 3rd and 4th while in 2nd only slightly, it is missing not backfiring, it misses so bad that the whole car shakes and the engine sounds like it is trying to rip itself from the car, I find it quite strange that once it gets to 3100 it feels like it gets a massive power surge and will pull perfectly all the way to 6000
Author:  BALLISTIC [ Thu Sep 30, 2010 10:13 pm ]
Post subject: 
Since you have the megajolt fitted do you have the program and a computer/laptop etc . . . . so are you able to show/see the live data or record the data/snapshot of when the fault is happening and what the megajolt components are doing?

Is the a vaccuum leak at the manifold or in the pipe from the manifold to the ECU not allowing it to advance properly causing it to misfire.

It could also be something simple like a lead breaking down, poor electrical connection, the oil in the dash pot could be to light, spring in the carb could be to soft or the needle could be incorrect for the application, worn throttle shaft or jet . . . .

hope these ideas point you in the right direction.
Author:  pristic [ Sat Oct 02, 2010 8:15 pm ]
Post subject: 
Yep, good test, like I said its leads failing.
Can you borrow another set to test it all ?

What leads do you have? The MJ setup uses the single coil pack and its meant to have a spark plug boot that clips onto the coil... (well 4 actually lol)

I have mine just pushed on (shoved) and its fine... know of a couple others the same... I would test with another set of leads by throwing it into high gear at low speed/rpm again ... if it doesnt miss anymore... just keep the leads and tell whoever you borrowed them from too bad :-)

Peter
Author:  Booglie [ Thu Oct 07, 2010 11:14 pm ]
Post subject: 
I have changed all the plug leads, still missing. I have ordered some new manifolds and a carb kit as I had to do a carb needle and seat unblocking on the side of the road the other day it was missbehaving before that but after it is worse and it now back fires as if it is running lean on decelleration
Author:  pristic [ Mon Oct 11, 2010 7:40 am ]
Post subject: 
Wait, you said you had NO backfire before... now you changed the leads, cleaned the needle/seat and its now backfiring??
How did you clean it?
Is it backfiring through the carby or through exhaust?
Does it still miss then pull through strong after 3000rpm or has that changed?
Does it miss now or only backfire when you hit the go pedal...

What do you mean by missbehaving??
Im a little confused. All you had originally was the miss right, then we talked about this and that and you changed leads.
Did you do needle and seat cleaning BEFORE leads or after? Was is running fine after you changed leads? Then after that the needle seat problem or?

Give me a bit of a timeline and when it did something and what you did... If you said backfiring or stuck needle and seat before it makes me think about carb, fueling, etc more than electrical.

The way I see it now...
When you accellerate - misses
When you decelerate - backfires through exhaust

Is that right?

Pete
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