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hired gun
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6,113 Posts
Discussion Starter #1
I am having a problem with car popping. Last time at Denton I had a backfire throught the intake and ever since then, The car pops above around 4500 rpm. I have changed the plugs because they were pretty ugly. But it does it on motor and on spray. It pops through the exhaust. any ideas? Bent valve, floating valves? Car is stock block with h/c/i, and a digital 6 with msd dist. and HVC coil
 

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Rebuilding
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2,802 Posts
Hey GRAN86, your 86 still EFI? I can think of a few things that could cause this but need a little more info. I would first check all the vacuum lines to be sure one didn't blow off (or out) when it had the backfire. I would check the easy stuff first before tearing the motor down. How's the idle quality been since the b/f? What exactly did the plugs look like when you changed them?
 

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parts pusher
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21,987 Posts
more than likely...springs went south...
 

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hired gun
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6,113 Posts
Discussion Starter #9
Sonic Blue 2V said:
Hey GRAN86, your 86 still EFI? I can think of a few things that could cause this but need a little more info. I would first check all the vacuum lines to be sure one didn't blow off (or out) when it had the backfire. I would check the easy stuff first before tearing the motor down. How's the idle quality been since the b/f? What exactly did the plugs look like when you changed them?
Okay long story as short as possible. When it back fired it blew everything off the upper intake, the maf tube, and all vacuum lines. I put everything back and tightened them all with holders. 4 of the eight plugs were fouled and a couple of the gaps blown way open. 1 of them had about .100 of a gap. After that I changed all the plugs and tried motor. It popped at first then quit, then started again. On bottle it doesn't make any difference how much timing I retard or leave in it it still pops. could the maf poss have anything to do with it? probably not since it does not read at wot.

The car still idles fine and has fine driveability.
 

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Rebuilding
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Yep, the MAF is still used during WOT, according to my Ford Fuel Injection manual. I just had a buddy with a similar problem on his 89 LX where when he went WOT, it would loose power drastically but idled, cruised and part throttle fine. Replaced the MAF and ran perfect. It is something to check. If you have another to swap, that's the easiest. My manual also has service tests you can run on yours while it's hooked and running with a voltmeter. Let me know if you want the procedure copied from the manual.
Also check the TPS to be sure it's still reading full range and up to at least 4.5 volts at WOT.
Do you have any trouble codes? Maybe the EEC already knows there's a prob?
 

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Premium Member
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3,325 Posts
I would start by borrowing a friends MAF. Because the slightest bend in the MAF meter springs can cause plenty of problems.
 

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hired gun
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6,113 Posts
Discussion Starter #12
slim87GT said:
I would start by borrowing a friends MAF. Because the slightest bend in the MAF meter springs can cause plenty of problems.
Anyone have a 36lb maf I can borrow for a few hours.
 

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in memory of "lil' Roy"
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11,775 Posts
Did you check your canooter valve??????:rolleyes:
 

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gotta love hotties
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1,093 Posts
well if your blinker fluid reservoir leaks onto your transmission belt, it can cause a popping noise as well. LOL!:p
 
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