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Missfire under hard acceleration 

 

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 Post subject: Missfire under hard acceleration
Posted: Sun Mar 06, 2005 3:44 pm 
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Hi,
My 1980 fairlane 302c is having a problem with missfiring, it only happens when you give the accelrater a hard stab.
It will happily rev to high revs if you steadily increase power.
I have changed plugs, was going to change the leads in the next couple of days, but wasnt sure if it had anything to do with them as it only happens when u give a hard stab on the gas pedal?!

Thanks in advance
Steve
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Posted: Sun Mar 06, 2005 3:47 pm 
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well if its only doing it under heavy load then it will start to get worse, check all the ignition system starting with leads dizzy ect. the more the load on the engine the high the compression in the engine which means the ignition needs to make a higher voltage spark
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Posted: Mon Mar 07, 2005 9:49 am 
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Sounds like lean condition...Check accelerator pump is working...Take air cleaner off open throttle and there should be fuel sprayed into inlet..Check for inlet leaks...Restrictive fuel filters... etc....

 

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Posted: Mon Mar 07, 2005 11:13 am 
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Leads can break down under load.

 

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Posted: Thu Mar 10, 2005 12:16 pm 
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Thanks for the help so far....

I changed my leads but still a large missfire, and fuel is being sprayed into the inlet, however a small amount of fuel seems to leak out the bottom of the carby when the engine is not on?!? Could this have something to do with the problem?.... I dont think the car is fitted with a fuel filter, not one i could find anyway. Its a 1980 zj fairlane with a holley carb.
Steven
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Posted: Thu Mar 10, 2005 4:19 pm 
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No fuel filter ?????? So your jets are probably full of s**t.

Take the carby off and get it overhauled. The last holley I had rebuilt cost me $80. That was a square bore 450 vacuum secondaries.

While your under the hood fit a fuel filter so it doesn't happen again.

 

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Posted: Thu Mar 10, 2005 7:47 pm 
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just a small thing but check the vacuum advance is all working correctly, it might be only advancing via the weights and not quick enough for quick reving.

 

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Posted: Fri Mar 11, 2005 3:15 pm 
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How do i check the vacum advance?
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Posted: Sat Mar 12, 2005 12:13 am 
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newbie wrote:
How do i check the vacum advance?


Put your finger in spark plug lead while engine is running...
When you rev it you'll notice it..

 

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As in ZOOM 126 edition
331 Dart block,3.25/ 4340 steel crank, Oliver rods,TFS ported track heat heads, TFS track heat inlet Twin SC61 turbo's
Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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Posted: Sun Mar 13, 2005 8:42 pm 
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what an answer , i love it
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Posted: Sun Mar 13, 2005 8:56 pm 
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ha ha ha, if that doesnt work you could try getting the lead that runs from the vacuum advance to the carby or manifold, take the dissy cap off and suck on the tube, if its working you will see the plate in the dissy moving around as you suck on it, if it doesnt move then good chance its not working.

 

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I dont own a Landcruiser, it's a Maverick recovery vehicle!!!!

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