Ka-t runs rough and back fires.

[1WheelWonder]

Today after replacing my brake booster vac line and checking a few things, my car started to run rough. Before today it ran abosulteyl perfect. It runs rough at idle and low rpm under light throttle, and during deceleration it will back fire. I have already checked for boost/vac leaks and I checked the plugs but could not find any problems. I am currently running stock ignition besides wires and a stock maf for now. Any help with my problem will be appreciated.

[1WheelWonder]

Do you all think my deceleration settings on the safcII could cause this?

[uncle_louie83]

no...its not your dec. air settings

how much boost are you running...are you on stock injectors...used upgraded injectors...i need to know your fuel system...also like about your fuel pump too...which one is it and is it new or used...im also thinking that its lack of fuel somewhere...and may be due to a weak pump or a bad injector...ive had injectors fail on me before and costed me a whole motor before....the backfiring is from detonation....dont get into it if you have to drive.....its prolly running rough because your ringlands on your pistons took a **** on you and now your getting low compression...i would do a compression test and list your fuel setup...and we can go from there.

lewis

[1WheelWonder]

For fuel i have got a set of used 370cc injectors with new o-rings installed and I am using a walbro 255lph pump. As far as boost goes im running like 5psi. I've been into boost three times since the car has been running. I will do a compression test as soon as I can.

[Craving4Boost]

what are you using as fuel management?

[Craving4Boost]

oh nm i didnt see that you said the safc...

is this after a full warm up? a cold start with a SAFC can idle very sh*tty.. what are your dec. air settings because it COULD be part of the problem

whats your airflow % at idle? after warm up...do you have a wideband? if so whats your afr

[1WheelWonder]

I'm no where close to my car so I cannot be 100% sure of the settings I give but if I remeber correctly my dec settings are 1.0,1.4,1.0. Which where set during cold start up like the manual says but at the time I set them my idle was off partially due to my vac leak. And the problem continues to happen after warm up. I will check airflow at idle, and wideband is on it's way, just ordered it the other day.

[WDRacing]

If its backfiring on decel, it's not detonation...

If it runs rough, there are 2 million other things it could be aside from ring lands...

When you say, Checked a few things, what exactly does that mean? Cause if it ran great before hand, then it was somthing you just did that has it running different.

WD

[nissanfanatic]

[quote=""WDRacing""]If it runs rough, there are 2 million other things it could be aside from ring lands...[/quote]lol

Try a cylinder drop test. Pull plug wires one by one and try to narrow it down to a cylinder. Chances are, if you find that taking spark away from one cylinder helps considerably, its an injector O ring which causes very crappy idle, bad cruising, and drive-by like backfires.

Pull the plugs and see what they look like too.

[Jookmasta]

i say check i/c piping for leaks and check all couplers.........backfiring will be normal on deceleration.

[1WheelWonder]

As far as checking things go I checked for vac leaks, boost leaks as best as I could, I pulled the plugs and checked them, and there are no exhaust leaks. I have suspected a leaky lower o-ring due to my car hesitating upon start up. It acts like it's flooded, which is my fault because after supposedly installing all the new o-rings there was still a new one in the package. I had no way of knowing which one I forgot to give a new o-ring.

[1WheelWonder]

Well before heading to Home Depot to create my boost leak tester I figured I check a few things again. I went ahead and started it and my car was nearly pouring gas out of the exhaust it was running so rich. I got under the hood and did the ole wiggle wires test, but to no success. So I decided to unplugged my injectors one at a time. When I unplugged the first and second one it made no difference in the way my car ran, but unplugging the last two caused it to run even worse which leads me to believe the lower o-rings are faulty. Would anyone agree with me?

[hysteria]

seriously as has been said before check and recheck for any air being able to enter without going through the mafs... which means the leak could be in the space between the mafs and the turbo. check the mafs out. make sure there are no bad connections. i have had this exact same thing happen to me DOZENS of times and every time it has been caused by air getting through somewhere other than through the mafs... i am willing to bet this is the problem. if you can't find anything by visual inspection take your plumbing apart and try to find tears in the couplers or things like that... a lot of times the pipes will come apart in a way that you will miss by visual inspection but when you take it apart it's obvious...

[WDRacing]

When you unplug an injector or spark plug the car should run worse, if it doesn't it means that particular injector/plug is broken. Understand??

WD

[1WheelWonder]

I got ya WD, thanks for the help everyone.