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View Full Version : Cyl #3 & #4 running rich... why?



ILikeMy240sx
02-28-2007, 07:19 PM
I pulled my spark plugs out and discovered that #3 and #4 cylinders were running very rich. #1 and #2 looks pretty good.

http://www-personal.umich.edu/%7Etaesoo/pics/Sparkplug/Plug1.jpg

http://www-personal.umich.edu/%7Etaesoo/pics/Sparkplug/Plug2.jpg

http://www-personal.umich.edu/%7Etaesoo/pics/Sparkplug/Plug3.jpg

http://www-personal.umich.edu/%7Etaesoo/pics/Sparkplug/Plug4.jpg

So I thought maybe my #3 and #4 coilpacks were bad. I replaced the plugs with brand new NGK BKR7EIX and swapped #1 and #2 coilpakcs into #3 and #4 sparkplug to see if the problem went away. I drove around for few miles and pulled the plugs again. Once again, #1 and #2 looked brand new where as #3 and #4 plugs were starting to foul up again...

Here are the pictures of the new #3 and #4 plugs after driving for few miles. Notice how it starts to foul up again. #1 and #2 looked brand new. (I apologize for the quality of my cam phone)

http://www-personal.umich.edu/%7Etaesoo/pics/Sparkplug/New%20Plug%20%233.jpg

http://www-personal.umich.edu/%7Etaesoo/pics/Sparkplug/New%20Plug%20%234.jpg

What would cause this? bad injector seals on #3 and #4 injectors? bad ignitor?

jakerps13
02-28-2007, 09:15 PM
Try switching the injectors around to see if it's component related or wiring related.

ItzGenX
03-01-2007, 12:14 AM
I would check the injectors to see if they are leaky on 3 and 4. Simply pop out the fuel rail with injectors still in them and fuel lines still attached. Aim them up and turn the key on but do not crank the engine. This allows the fuel pump to prime the fuel pressure. Now aim all the injectors down and see if any of them drip.

There could also be a problem with the valvetrain due to bad hydraulic lash etc, but you would hear those when they occur. The effect is certain valves won't open as wide as they should compared to other cylinders causing a rich/lean effect.

janders211
03-01-2007, 03:00 PM
82.45% chance it's the 0-rings, injectors or injector clips .
Swap 1 and 2 with 3 and 4 and see = simple

...Unless that's oil buildup. Is it chalky? I can't tell with my bad eyesight + 6 X 4 pixel rez on cam phone

ItzGenX
03-02-2007, 03:54 AM
Just don't kill the O-rings trying to pull out those damned sidefeed injectors with his method :eek: . Check the tips of the injectors too and see if any of the pin holes is rusted over or anything.