Back firing in intake when accelerating under load

Do a leakdown test (not just a simple compression test) to isolate a cylinder that may have a leaky valve.

If all the cylinders are holding air (passed the leakdown test), then a leaky injector or an ignition issue (coil or plug) is next on the list.
 
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I'm thinking of checking the fuel rail pressure though maybe my fuel pump starting to go I would think I would get a code though if it was low fuel pressure. Everything is untouched.
 
500H V10 said:
The engine idols very smooth and under light acceleration it runs very smooth with no misfire only under heavy acceleration does it randomly backfire in the intake manifold
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Intermittent misfire .. possibly weak or damaged plug or plug wire . I know I had a plug the the electro was bent and off center and cause it to intermittently misfire on mid range acceleration . Plug wire break down in high temperatures or get burned from the exhaust and can send spark to a ground area it’s close to or touching .. try opening the hood in the dark ,, no lights around and see if there is any arcing from the plug wires or coil packs . when my plug was misfiring I did get a code though !
eliminate the easy stuff then move on to the next . Some of the problems that cause that stink ..
 
You can also check using an ohm meter on each plug wire to see if any are broken down on the inside .. yes the wires are a pain in the butt to get to under the intake manifold .
Why the hell did they put the coils there . Still nobody that I know of has relocated the coil packs out from under the manifold ..
 
Michael from the U.K. said:
More fun for us if you put your hand on the wires tho.:D
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Hahaha ,, helps you bounce a bit doing that …
In the old days with customers hanging on the fenders while we worked on cars ,, we always kept a charge ignition condenser sitting on the fender cover .. if they got to nosey we asked them to hand it to us hahahaha ZAP !

years ago I wanted to test out the sparking of my new MSD ignition system .. supposedly fired like 20 times per cylinder revolution .. I believe they were right hahaha ZAP ZAP ZAP ZAP at 40k volts per ZAP hahah
 
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THEWELSHM said:
seen my coil packs 3 times in 3 months, hope I don't see them again for a while. those back inlet bolts suck to get at.

thewelshm
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I’ve heard and read that .. I’ve never had to or even wanted to pull the damn intake ,,,,Stupidest design I’ve ever seen .
 
There is only one bolt that is a bit of a challenge when removing the Intake (#9).

Like everything, once you've done it a few times, there are tips and tricks to make the job easier/faster.

I'm still wondering how grasshoppers and bees (well, what's left of them) end up behind the coil packs.
 
Bees are amazingly resilient!!
 
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