SRX throwing Code 305
 

Hi everybody,
My SRX is driving me nuts. For some time now (1/2 year) is has been throwing code 305. First, only from time to time, now on a regular basis after start-up.
My garage people put in brand-new NGT spark plugs, swapped the ignition coil banks from one side to the other, de-installed all the injectors, cleaned and tested them, put them back in. To no avail.
When I start the engine it shudders a bit for 3 to 4 seconds, then runs fine. Soon after the engine light comes up. There is no problem with its performance, the engine runs fine and smooth.
The car is 6 years old and has only 63k miles on the odometer.
Thanks for helping me.
Muewi

Code 305
 

I would really check on the fundamentals around the #5 cylinder as in fuel injection, wiring and ignition components. Usually the last number of that code indicates the number cylinder it is.
Hope that helps

Info on P0305 here.

Thanks for helping me, folks.

I got everything inspected so far. Again to no avail.
We put in brand new spark plugs, brand new ignition coil banks, inspected the valves (O.K.), measured compression (O.K.), fuel pressure (O.K.), wiggled the wiring (O.K.), got the injectors cleaned and inspected (O.K.), looked for faulty air inputs, but did not find anything wrong.
Now the computer throws Code 300 "multiple misfires".

What is really weird: The code only comes up when the car is started the first time in the morning after a cold and wet night. Then the engine shudders a bit after start, this stops after 1 minute or so. If I rev it up one or two times just after start the engine runs fine at once.

There are NO problems if the engine has warmed up a bit or when started on a pleasant warm day. No codes then.

May be one or two of the many sensors gone bad? Which one may be the culprit? I am getting desperate!

SRX throwing Code 305
 

Actually your doing well, because you have forced an intermittent problem to be more consistent.

I kinda focused on your quote "wiggled the wiring (O.K.)," inputs, but did not find anything wrong..
Here what I would do to eliminate doubt and not have a meter.
Purchase electrical contact cleaner and:
1) Remove each "one at a time"electrical contact on the injection and ignition. and
2) spray the contact both the male and female connector.
3) Start the car after each connector cleaning and replacement.
4) If the wiring is loose where you disconnect it there's your issue.
Given your components are good it appears you may have a connection that you do not see that is either dirty or an intermittent and loose contact.
Other problems that occur with a 305 code is an oxy sensor. I would do the connector cleaning first because it costs less.

Hope this helps.

Wiggle and check GROUND (usually a Black wire around your engine compartment)
Check and spray those connections with contact cleaner

I did this. No change!
Well, then the weather got warmer and during summer no problems whatsoever. Now the winter is back and promptly the engine runs rough when started in the cold morning (below +5 degrees Celsius).
A friend of mine told me to put one litre of synthetic motor oil into the tank to mix up with the fuel. He said that would clean the valves and the injectors. I did this twice and it seems to ease a bit the rough idle after cold start.
But still the car idles rough for about 20 seconds. Check engine light comes on from time to time (not regularly), now without codes on my OBDII scanner.
Could it be a faulty fuel injector that misfires the first drops of fuel when cold? Any other ideas?
Or the oxy sensor? Which?
Muewi

there is a reflash or calibration with may help but you will need to find a GM service center. I not sure how that works in Europe.