Backfire/Pop Exhaust Leak?

[Khronik]

Car runs fine, no noticable hestitation, sluggishness, etc etc

.... but if I shift over 3k rpm's it seems to backfire/pop once, does not continually pop just the one and then no more

sounds like it just may be the exhaust but im not sure, would an exhaust leak do this?

i have not found a leak, but im sure there might be one. on a cold start, cold day, i get vapors out of ONLY my passenger side exhaust until it heats up

[xclusivez32]

I have the same problem, my car is also an N/A with headers deleted egr, deleted aiv (welded shut) and catback.

[xclusivez32]

any insight?

[spenka]

Im having the same issue too with my zx. i have a 1990 300zx with non-oem exhaust from headers down.

[Khronik]

well... 3 people so far anyone else? nah really does anyone have any idea wtf is causing this?

not sure if im doing any damage here or if its normal

[FlogWaffle]

wow small world. call me #4 haha. i get the same thing sometimes... i got headers to 2.5 inch all the way back w/ hi-flow cats....(this is when it was running like a peach)

now im battling a MEAN hesitation...its popping quite a bit..haha but thats another story..

[Khronik]

damn... who else?

[xclusivez32]

does everyone dd their car with this pop? does it happen in every gear? and how long has it been doing this? my car is a project car so i dont get it out much to drive

[FlogWaffle]

does everyone dd their car with this pop? does it happen in every gear? and how long has it been doing this? my car is a project car so i dont get it out much to drive

I dd mine, but come to think of it i am no longer quite sure it was running right when i finished my exhaust up. Once i get my new vtc springs to stop my rattle...and figure out my hesitation ill report back and let you know if im still popping haha

[es.biggs]

flogwaffle - check your timing with a timing light. I would put money on it that your CAS needs to be adjusted.

It wouldn't hurt for everyone else in here to check ignition timing as well.

Does anybody have signs of either a lean or rich fuel/air mixture? An engine running rich might make a little black smoke, and the exhaust pipes will blacken faster than normal. Another good way to tell if its rich is checking the spark plugs - http://www.ngksparkplugs.com/tech_suppo ... aqread.asp

Lean mixture could be caused by low fuel pressure, an old fuel filter, clogged injectors, or other fuel system issues.

[Khronik]

im guessing there is no way to check timing without removing anything?

[es.biggs]

it's actually very simple all you need is a timing light. No need to remove anything.

There's tons of info about it...try searching

[Khronik]

it's actually very simple all you need is a timing light. No need to remove anything.

There's tons of info about it...try searching

nevermind i got it

[DCaff300ZX]

I also get the "pop" when shifting over 3000RPM, which began shortly after my 2.5" custom exhaust was added just before my 5-speed swap.
My personal thought is a problem with my old auto ECU being used with the 5-speed, since swap info I've seem recommends the ECU from a 5-speed model be swapped in- but my Z guy did not do this, and wants me to go to a Nistune setup where he says he can tune this issue away. To me it seems that with an auto you don't get the RPM drops when shifting gears associated with no throttle during manual trans shifts, and this seems to be true since if I hold throttle on while shifting, no pop.
He says it will not cause a problem but I am not so sure (no problems to date- about a year since) and would love to delete this issue without the $1,000 Nistune price tag for a simple NA.
Any thoughts marty, or anyone else?