We have a 2005 GMC Canyon. The check engine light has been on so we had it checked and cylinder 2 was misfiring. It was suggested that we change the spark plug for that cylinder. We ended up changing all 5 spark plugs, but the problem is that the truck in now running worse. The check engine light is now flashing. What do we do?

The engine compartment fuse block is located on the driver's side of the engine compartment

Check fuses 21 and 42.
https://my.gmc.com/content/dam/gmownercenter/gmna/dynamic/manuals/2005/gmc/canyon/2005_gmc_canyon_owners.pdf

Park the Canyon on a flat stretch of road or driveway and open the hood.

2 Remove the master cylinder cap located near the firewall on the right side of the GMC's engine. Remove half of the brake fluid in the reservoir with a turkey baster. Lay the cap over the container.

Read more: How to Change Rotors on a 2005 GMC Canyon ' eHow.com http://www.ehow.com/how_6717490_change-rotors-gmc-canyan.html#ixzz29JfCwiDq

Hi there:

Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.


A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.

Symptoms may include:
the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be present

A code P0300 may mean that one or more of the following has happened:
Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer


Possible Solutions: If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.


If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.


Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.


Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

A misfire means the a particular or several cylinders failed to effectively produce work. The engine may feel shaky and sluggish. Ultimately this could cause further damage such as catalytic converter.

Sorry to say that vehicle has had electrical issues
over the years & I would like to get one, before they start
coming from Brazil next year ,with no frame under them,
starting in 2013 possibly. I'm not going any where near that
5 cylinder engine. It is a V8 etc or I'm out

The dealer is your only hope there.

Forget me & the other guy

The dealer has all the resources & factory field
support to resolve the problem

The most common cause for a misfire is a bad igntion coil - each cylinder has a coil. I would find a different repair shop.

Try to clean the throttle body out. Its not getting enough air going through. The five cylinders create a lot of carbon build up. Is your check engine light on?

How do i remove the cover on the engine to get to the spark plugs & were is the purge throttle valve located?

From http://www.obd-codes.com/trouble_codes/
The P0300 is a misfire and P0506 indicates low RPM at idle.

A misfire can be caused by poor ignition (spark plug, plug wire, coil, ignition module/engine control module).
OR
Poor air/fuel (air filter, fuel injector, fuel pressure, fuel filter, fuel pump, bad gas, or engine control module).

Check your maintenance requirements and see if any of these items are due for replacement first.