Wasatch7 Posted November 13, 2012 Share Posted November 13, 2012 So I am trying to get my 76 280Z running well so that I can drive her to school, but I cant figure out a real reason she keeps running this way. When I start to accelerate or even just push down the pedal while in neutral the rpms will drop and then start going up. As the rpms rise between 1000-2000 it will backfire in the intake. But as soon as it goes over about 2000 rpm it will speed up the way it is supposed to. It is also idling at about 700 rpm and it should be at 800 rpm. I heard that the reason for the backfiring could be because of bad gas or too low of octane rating. I am running cheap 85 or 86 octane from Maverick, but I just put in some octane boost to the remaining fuel, and I also just added a cold air intake with a K&N cone filter. So please if you have any idea what could be causing my car to sputter and then backfire out the intake I would be very thankful. Quote Link to comment Share on other sites More sharing options...
ryanfudger Posted November 13, 2012 Share Posted November 13, 2012 Timing issues or fouled plugs, generally. Check the plugs first. Quote Link to comment Share on other sites More sharing options...
makaofox Posted November 14, 2012 Share Posted November 14, 2012 ^ Agree, also check for an exhaust leak. Check the vacuum hoses, intake and exhaust manifold. If those gaskets are shot, it will give you issues, if you have a tear in you afm boot it will cause issues. But backfire from intake is a timing issue. Make sure you're properly timed, good gas, good plugs and wires, and no air leaks. A good way to check for leaks is using starter fluid, if it jumps in rpm then you have a leak, if nothing happens then your fine in that aspect. Quote Link to comment Share on other sites More sharing options...
AZGhost Posted November 14, 2012 Share Posted November 14, 2012 Does it make a popping sound? It could be your airflow meter, with the flap inside not opening, until there is enough pressure to push that flap down and you typically hear a pop sound (flap hitting the bottom of the air meter). Since you made changes to the air flow meter, is everything hooked back up properly to the unit? Nothing loose? Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 14, 2012 Share Posted November 14, 2012 Has it ever run right? Sounds like it's running lean. Low fuel pressure or bad AFM or vacuum leak. Measure fuel pressure first, it has to be right for the EFI to work correctly. Engine Fuel, 1976 FSM - www.xenons30.comr/reference Quote Link to comment Share on other sites More sharing options...
Wasatch7 Posted November 14, 2012 Author Share Posted November 14, 2012 Yes it does make a slight pop but maybe i am just thinking of the actual backfire. Yes it was running right for a while then I had it sit for about two months and it started doing this. when running it does start to smoke a bit right near where the intake or exhaust bolt to the block. not sure which one its from, but it does start to smoke slightly. Should I just spray the starter fluid into the air filter? From it running lean could that cause the idle rpm to go down a bit? Quote Link to comment Share on other sites More sharing options...
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