poping through intake at 12lbs of boost

[eddiedellz]

poping through intake at 12lbs of boost, ive had a poping sometimes under load but allways once i hit around 12 - 13lbs of boost i was running fine i changed my plugs and now this started happing but anything like cruse and idle car runs fine exept for the occasinal pop under load same as when the boost .. i pulled the cap off the cam sensor to check it was good and tight not hitting the window.. . no faults blms at 128 at idle.. dont know where to go now or what to do .. can you guys give some suggestions. thanks!

 

[Russ Merritt]

Ignition. Wires, coil, or module. My money is on the pack.

 

[eddiedellz]

why the pack if its good all exept load ? could i have made a wire that was on its last leg go worse from when i changed the plugs and not the wires but agin .. not affected untill under loads? or quick throtle.

 

[Wheezy]

Valve springs maybe?

 

[turbolou]

Originally posted by eddiedellz
poping through intake at 12lbs of boost, ive had a poping sometimes under load but allways once i hit around 12 - 13lbs of boost i was running fine i changed my plugs and now this started happing but anything like cruse and idle car runs fine exept for the occasinal pop under load same as when the boost .. i pulled the cap off the cam sensor to check it was good and tight not hitting the window.. . no faults blms at 128 at idle.. dont know where to go now or what to do .. can you guys give some suggestions. thanks!

Sounds like a valve train problem or worn cam lobe

 

[Blown&Injected]

it was a loose spark plug when my car had the induction backfire under slight/moderate load.

 

[Mr.Buick]

Popping back

If you are popping back through the intake it's almost got to be an intake valve issue. Do a leak down check on the engine and it will tell you which valves are good or bad. If you have never done a leak down check it puts air pressure on the cylinder at top dead center with the piston at top of stroke and if you have valves or rings leaking you will hear it in the intake, exhaust, or valve cover breather

 

[eddiedellz]

a valve train problem would show up istantly like that ? before it was fine now it happens all the time .the valve springs where done about a year and a half ago at rons coustom auto. right before i bought the car

 

[eddiedellz]

well its started getting worse now it does it around 7 psi :T i swaped out new wires checked how tight the plugs where . just to backtrack because thats when it started happening i couldent find anything so now i swaped out the maf sensor and the map sensor no luck. i know i should do the leak down check but other then then under boost thing it runs strong and idles really nice .. is there anythign els i can do before i go out and do the leak down check. =/

 

[MARINES185]

my car started backfiring when under just a few pounds of
boost. it turned out to be the coil pack. one day it was fine,
and the next day it just happened. the coil pack can be
check with an ignition scope. some local garage should have
one.

 

[TurboShane]

Mine does the same thing only get's worse and happened over night. Had a broken rod on the #1 cylinder. Been like that for the last 1 1/2 in the next two weeks finally going to get around to fixing it. By the way it has been parked in my garage for the whole time.

 

[eddiedellz]

ok more info! doesnt really happen when its cold i could get it past 10 psi and hold it and it wont pop but after that it will do it. i swaped out a coil pack today and no luck but i dono maby its my imagination it does feel a lil stronger my car allways felt weeker compared to my brother in laws ive been smelling fuel out the tailpipe a lil before it happend and today too anyone els have suggestions

so far new plugs , wires , coil pack , maf , map check cam sensor for damage. maby ill do a run on the turbo link but ive been haveing problems saveing what i record :/

 

[BM Computer Src]

check for a flat cam lobe, its easy. Just rotate the engine and watch the rockers move. My bet is #3.

 

[eddiedellz]

but why would a flat cam lobe not affect it when its cold on the first run and then after that be bad.. allso sometimes after it pops if i stay on the gas it could pas the point where it pops and dont pop anymore this is when its not under load

 

[BM Computer Src]

I dont know, but I have seen it more times than I can count. Its an easy check. Good luck!

 

[rsmith]

I would check the plugs (that was the one obvious variable that you changed). Sometime they come bad. Especially them damn bosh platinum pieces of crap.

Start the car and turn out the lights (be careful not to put your arms/fingers/privates into anything) look for any sparking around the plugs/coils/wires.

 

[jastrckl]

this is about guaranteed not to be a valvetrain issue if it's heat related, could be a goofy hydraulic lifter though. My money (lots of it) is on it being an ignition issue. Check the coilpack, module, and wires first. After that it might be plugs themselves. gap them at .035"

 

[slipstick]

I had a similar symptom that turned out to be caused by 500 mile AC 43RTS spark plugs. I have always used AC plugs with no problems. Now I am trying Autolight 23 and so far they are performing fine.

 

[Jimn8or]

I'd start a little more basic...
The coil-pak numbers, as viewed from the 'rad' looking down on it are:
1 5 3
4 2 6

Same view, the engine numbers:
6 5
4 3
2 1

When you changed the coil-pak did you re-connect the ground wire that attaches to the coil-pak hoop bracket at the rear, center??? Is this tight on the intake?
HTH
Jim

 

[eddiedellz]

Originally posted by Jimn8or
I'd start a little more basic...
The coil-pak numbers, as viewed from the 'rad' looking down on it are:
1 5 3
4 2 6

Same view, the engine numbers:
6 5
4 3
2 1

When you changed the coil-pak did you re-connect the ground wire that attaches to the coil-pak hoop bracket at the rear, center??? Is this tight on the intake?
HTH
Jim

we might have something here the hoop? heh ive seen no hoop at the back of the coil pack.. =/