At wits end, pls help! Misfiring!

[impreshark]

Hi all, I am new to driving a used golf mk5 gti TFSI. Got this misfiring problem for months which is killing me. when part throttle the car shutters all the time. Idling can sense slight misfiring and boost meter factuate a little. On long journey or when the weathers hot, throttle will definitely trigger CEL flash and then stays there. Diagnosed P0300 random mutiple cylinder misfire detected P0304 Cylinder 4: misfire detect Had changed countless spark plugs / ignition coil. went to lots of workshop without success. Any suggestion or remedy is deeply appreciated.

[sparky68]

i had almost the same problem on my vectra it turned out to be a HT lead although no obvious shorts visible ie sparks, it was breaking up inside the lead which couldn't be seen or detected very well.

[impreshark]

i believe ht lead is the ignition coil equivalent in gti5. yea change those, 2 sets to be exact but the problem keeps coming back.

[sparky68]

got this from google, you might have have already seen this ?


What does that mean?

Basically this means that the ecu has detected that not all of the cylinders are firing properly.
A P0300 OBD 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

Symptoms may include:

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

Causes

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
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, 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 , 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.

[sparky68]

got this from google, you might have have already seen this ?

http://www.aa1car.com/random-misfire/

[impreshark]

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
Defective computer


Thanks Sparky for your input, will have my mech check these. Hope it works.