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Mass air conv. backfires

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Old Oct 16, 2018 | 08:29 PM
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Mass air conv. backfires
I have a 94 F 250 7.5 with a mass air conversion that started to miss, low power and backfires in intake. Any ideas?
 
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Old Oct 16, 2018 | 08:58 PM
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Air leak after the maf would be a classic cause...

t
 
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Old Oct 16, 2018 | 10:17 PM
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I have checked for leaks can't find any. This started with out warning, drove fine one day and like crap the next.
 
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Old Oct 16, 2018 | 10:18 PM
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Very bad under load.
 
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Old Oct 16, 2018 | 10:58 PM
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Check the basics... fuel pressure and for codes.
 
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Old Oct 17, 2018 | 07:57 AM
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#1, Timing with a bullet. Timed to 10* with the spout plug removed, right?

There's no fuel (EFI) in the intake.

Can only backfire in the intake if valve is open or there's a chunk missing in the valve face.
 
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Old Oct 17, 2018 | 11:43 AM
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Originally Posted by Scndsin
#1, Timing with a bullet. Timed to 10* with the spout plug removed, right?

There's no fuel (EFI) in the intake.

Can only backfire in the intake if valve is open or there's a chunk missing in the valve face.
Timing is correct, yes with spout out. This is a new engine only 800 miles nd compression is 150 across the board. I fixed a nasty exhaust leak and the issue has gotten bad.
 
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Old Oct 17, 2018 | 11:47 AM
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No codes for issue, only vss and air valve (disconnected) and fuel pressure to spec two new pumps and regulator.
 
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Old Oct 17, 2018 | 01:23 PM
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Originally Posted by Frank C
No codes for issue, only vss and air valve (disconnected)...
Idle air control valve???
 
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Old Oct 17, 2018 | 03:49 PM
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New valve has been installed
 
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Old Oct 18, 2018 | 12:59 PM
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If it were me I would pull the plugs and have a look at them. A dead cylinder will cause the backfire as you describe and the plugs will tell you if you have fuel AND spark.
 
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Old Oct 21, 2018 | 06:15 PM
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Have you clean mass air. are truck was doing tne same mass air was very dirty
 
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Old Oct 22, 2018 | 06:52 PM
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All look good
 
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Old Oct 22, 2018 | 06:52 PM
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Brand new mass air
 
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Old Oct 22, 2018 | 07:32 PM
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Was the MAF conversion done at the same time as the engine swap or was it in and working fine on another engine before that?
Is it a 460 specfic conversion or one built for a windsor? if it's not 460 specific what PCM and MAF meter are being used?

Have you looked for crossfiring between plug wires or from the wires to metal engine parts?
 
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