Popping Sound And Car Shaking

[Wacky Dee]

Just got the car back from a big-ish service incl all oils changed, fuel filters, gapped spark plugs etc and noticed that if I rev the engine and hold rpm somewhere between 1500 and 2500 rpm (I didn't try higher because I didn't want to attract attention to myself..) while the car is sitting idle in neutral, there's a muffled popping sound followed by a small shake (drive seat shakes noticably) every few seconds ..sometimes more than one in a row.

Like popcorn starting to pop ..just more muffled sound, and each pop shakes the car a bit. Is this just the exhaust note or should I be worried ? Detonation? Car's ecu was tuned before the service and it was NOT pinging/detonating...

The car's an R34 GTT with a turbo-back exhaust with a 3" catback (HKS SilentPower)

I never noticed this before but then again I never held the engine at 1500rpm for a few seconds before either..

[Wacky Dee]

could it be that the car is just running a bit rich in the lower revs and its dumping the excess fuel in the exhaust ?

[trel]

It's a misfire, what gaps are the plugs set to?

[Wacky Dee]

0.75 I think they said the new plugs are ... the car never missfired according to my tuner (different guy to those who changed the plugs)

[Wacky Dee]

hm are you sure this is missfire? I searched for "Popping" last night and read a lot of older discussions and a lot of people seem to be under the impression that these popping sounds are normal on skylines and a few said it's probably due to running rich in that rev range .. no mentions of missfire anywhere.

[bubba]

Could be sh!t plugs or wrong heat range.. do you know what plugs were put in?

[Wacky Dee]

I have no idea which plugs they put in ... I'm taking the car back to unigroup to have a listen to this. Could it be due to old fuel? car's been at the shop for was 2 weeks and only 1/4 of tank of fuel sitting in it

Edited August 6, 2008 by Delta Force

[BHDave]

mine runs rough in the same situation. though in mine i put it down to section of the map thats never been tuned.

It's just a rich miss and nothing to be overly concerned about. It's something tune related and i wouldn't expect it's a result of a service. I'm pretty sure unigroup will tell you the same thing but it doesn't hurt to have it looked at if you are concerned.

[Wacky Dee]

Took it back to unigroup and as soon as Yavuz heard the popping at idle and low revs he said "yep it's misfiring" .. and that it's due to the small gap (0.75mm) so they regapped the spark plugs to 1mm and no more misfire/popping sounds ;-) Best of all ..they did it all for free! That's good service. Cheers.

[adzR34]

Took it back to unigroup and as soon as Yavuz heard the popping at idle and low revs he said "yep it's misfiring" .. and that it's due to the small gap (0.75mm) so they regapped the spark plugs to 1mm and no more misfire/popping sounds ;-) Best of all ..they did it all for free! That's good service. Cheers.

Hey mate was yours the black r34 there? I was there about a week ago also.. had a safc tune. Mine is doing the same thing and yavuz said its normal with running small gapped plugs.. Funny i also hear it pop every now and then only on idle

[Wacky Dee]

yep black r34 .. if it's misfiring at idle and up to 3000rpms (popcorn sounds and vibrations with each pop) get them to increase the gap to 0.9 or 1mm (1mm worked for me .. its perfect now)

[Wacky Dee]

just one thing ... Yav also mentioned that the car may misfire at higher rpms with bigger gap (and non stock boost). But for me that's not really an issue as a very rarely go above 4000rpm anyway (daily driver)

[369]

sorry to bring up an old thread but i think my input is relevant and not worth starting a new thread.......

i have been experiencing the same muffled popping/rumble sound then shaking when car is idling after cold start. i noticed the rumble and shaking start to settle down after the engine oil had warmed up to about 90 degrees.

couldn't figure out what was wrong, then 2 weeks later the check engine light came. it turned out an exhaust leak at the rear muffler was causing the rumble and shake while idling.

the leak was at the weld joints along the exhaust pipe that had started to rust. this was probably making the car run a little too rich as well, but i could be wrong.

cheers!!!

[PaulosECR33]

mine does it too at idle, is normal. atm mine has a dump pipe like 6 inches long and is running Super rich so it sounds worse, gaps are .8. is perfect when you apply any throttle though all the way to 7000rpm

[SargeRX8]

Rich miss or a lean pop. Mine developed the same thing. Get your afr checked and go from there.

Edited September 21, 2011 by SargeRX8

[PaulosECR33]

mine does it too at idle, is not dangerous. atm mine has a dump pipe like 6 inches long and is running Super rich so it sounds worse, gaps are .8. is perfect when you apply any throttle though all the way to 7000rpm

ah crap that effort to edit a post was ABSOLUTE FAIL

Edited September 21, 2011 by PaulosECR33

[369]

one other thing i just found out is that the fuel filter is gone, so it's causing a "lean pop" at idle.