is this sound detonation? please help.

[kevsstang]

Under heavy acceleration in 4th (3/4 to WOT) I heard a pop sound. Is that sound detonation. I should also mention when i heard it pop i let off immediately. Also earlier when in 3rd it sounded like it was popping. I filled the tank today with Sunoco 94 about 9.5 gallons. thank you.

kev

 

[kevsstang]

TTT

 

[mackey]

Sounds like marbles in a jar? What timing are you using?

 

[kevsstang]

Timing is at 16*. and i run sunoco 93 or 94. I took the car for a ride again and got on it and again it seems to be sputtering under full throttle. Maybe a miss it just started to do it. I just put new plugs in the other day auto 3924 and gapped them at .054. new cap, rotor, plug wires, and cleaned IAC.

 

[HISSIN50]

what kind of revs were you turning when you heard this? what were the engine temps?

good luck.

 

[5spd GT]

I got a pop the other day when I revved it up...possible bad injector? Maybe causing to run lean on one cylinder?

I think the popping and detonation are different sounds...

I have AFR 165's and have my 3924's gapped at .045...

 

[houstonstangguy]

yep thats detonation unless it doesn't sound like a bunch of marbles, then it could be an intake backfire. if det., then back the timing down a degree or two.

did it do it before the tune up? my 3924's are gapped to .42

 

[5spd GT]

My pop happened once and was a sharp yet deep pop from the engine bay...it wasn't a constant sound...I don't think mine was detonation...no marbles or nothing...

 

[kevsstang]

No it did not do it before the tune up.
I had a fouled plug on the drivers side 3rd one back. That is when i did the tune up.
The car was revving around 5000 in 3rd and 4th. Temps where low between the A and L in Normal. the car always runs cool.
Should i regap at .045?
I had like a popping sound 2 times. and the other time was a louder POP as soon as i heard the popping and the pop i immediately let off.

I had the car at the dyno in april and he set the timing at 16* and the A/F Ratio was good between 3000 and 6000 it was between 12 and 13.

Other than full throttle the car runs great. thanks for the continued help.

kev

 

[HISSIN50]

Kev, that sounds like a plan to me (regap). what was your old gap at?

near 5K RPM is one of the hardest times on an ignition - if you were gonna have spark break-up, i would expect it then.

i might close the gap a smidge and see how you do.

good luck.

 

[bluevenom867]

through some 100 octane unleaded in there and see if it keeps poping, if thats stops it you need a little less timing or run higher octane.Also a .054 gap is a little large maybe try to gap it down some?And try adjusting your fuel pressure.

 

[5spd GT]

Those 30lb injectors seem a bit big for your setup which could contribute to the fouled plug...it probably occured more at the lower rpms...and evened out nicely in the WOT stages (3k-6k)...

My spark plug gap is .45...it seems you gapped your plugs for the stock gap...yours ain't stock

 

[kevsstang]

Well regapped plugs to .045 and all is well . Took the car out for a blast and no popping, sputtering or other nonsense. Thanks for all the info guys.

kev