gm 3.1 and 3.4 spark plug order and cylinder location

hello during the spark plug service many people get confused on exactly which cylinders are which and i hope this posts alleviates it here is a picture below for reference.

cylinders 1 3 and 5 are near the back fire wall and cylinders 2 4 and 6 are near the radiator cylinders one and 2 start from the belt side or passenger side of vehicle. hope this helps

many of these questions get asked from my repair video on changing the spark plugs from this engine

testing fuel pressure on a gm truck 1999-2013

a question i get time and time again, "my truck is running rough and dies do i need a fuel pump" this is most certainly a usually easy diagnosis but to start that diagnosis i always consider fuel pressure to be a very liable culprit. from the days of fuel pressure regulators to the more modern fuel pressure control modules in the gm trucks you need that reliable 55-62 psi of fuel pressure to run properly. if its not there than your going to have issues, along with to high of fuel pressure can also cause issues so to check your engine you can follow this video on test port and how to to check if fuel is your issue

2011 buick regal p2135 "reduced engine power" case study

i arrived at the shop today to see the very first thing for me to do is diagnose a 2011 Buick Regal 2.4 liter 4-cylinder. the customer complain of a misfire and check engine light on ( my first thought was its the classic high pressure fuel pump for the direct injection) upon starting the vehicle (verify check engine light illuminated ) it ran fine so i continued to clear the snow off of it.

this is when things turned interesting. the vehicle began to run extremely rough and the foul smell of misfire emitted from the exhaust. i had a reduced engine power notice on the screen in the cluster.
along with the stabilatrak service light ( will come on with reduced engine power, in diagnosing fix the drivability issue first )

upon the arrival of the vehicle in my work area i measured incoming fuel pressure from the fuel pump to verify i had proper fuel pressure. i did this before scanning codes which was me jumping the gun but verifying a factor. it was with in 45 psi to 50 psi plenty of pressure to feed the high pressure pump.

now we get to the fun stuff i scanned the DTC (diagnostic trouble code) to be a P2135 pedal position sensor a and sensor b not plausible. if you look on the internet and identifix it will lead you to just replacing the throttle body , shot gunning the part.

i chose to verify some thing first the pedal position sensors and throttle position sensors should be showing the same voltage to the pcm in your live data. the voltage should range from 1.0v to 4.0 volt

with the vehicle in key on  engine off i witnessed  the pedal at 1.2 volts and the throttle body at 1.6 volts a reasonable difference in % of throttle desired
so i pulled off the air ducting to expose the throttle body ( a little dirty on the throttle plate)
had a helper press the Accelerator pedal with the vehicle with the engine off and the throttle functioned normally. so the position sensor part of the throttle body (not entirely serviceable) could be bad but with the throttle assembly working i though that with the minor difference and the throttle assembly being dirty it could just use a cleaning.

removing the throttle body was pretty easy after removing the ducting its just the connector that need to be removed and the four 10mm head bolts on the body itself. there is a seal on it that can be reused if not damaged.
i used throttle assembly cleaner and a nylon bristle brush to scrub the housing plate and tunnel thoroughly.

with it cleaned to my satisfaction i reassembled the throttle body and cleared DTC's now with the vehicle running the positions match and ran a p2135 verify test (option with my scan tool to do a specific code test)  and no problems being found test drove through a warm up cycle and cool down with no issues or check engine light

usually throttle cleanings don't have that much to do with major drivability issues but in this case it did and i saved he customer about 400 dollars
this isn't always the case but it was a worth while endeavor
With the vehicle running fine i changed the oil to get rid of any fuel wash the vehicle might of had as there was a fuel smell in the oil
CONFIRMED FIX: p2135 performed throttle body cleaning and reassembled