Any suggestions re this P0300 engine light??

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jham66
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Joined: July 2nd, 2011, 8:41 pm

Any suggestions re this P0300 engine light??

Unread post by jham66 » November 18th, 2013, 4:01 pm

Hi,

I am having trouble with ah an engine light. I keep on getting a P0300, which is a random engine misfire.

The story is; the car went in to have the engine gaskets replaced in a recall. I got the car back and first drive the car threw the P0300 code. I took the car back and they started replacing parts under warranty. So far it has new plug leads, coil pack and plugs. I also replaced the crank angle sensor for good measure. They (dealer mechanics) don't believe it is anything that they have done (I disagree).

There is no misfire that you can feel or hear when driving.

I have a phone app to record the OBD parameters but am having trouble. Looks to me like it is running rich and compensating by trimming the long term fuel trim...... but no idea as to why.

Can anyone offer suggestions?

Two examples of the OBD information:

#1
Freeze Frame
P0300: Random/Multiple Cylinder Misfire Detected (Powertrain, Generic)
Fuel system status: Fuel system 1: Closed loop (1)
Fuel system status: Fuel system 2: NA
Calculated engine load: 56.5 %
Engine Coolant Temperature: 90 °C
Short Term Fuel Trim - Bank 1: 2.3 %
Long Term Fuel Trim - Bank 1: -10.2 %
Intake Manifold Absolute Pressure: 55.0 kPa
Engine RPM: 2581 RPM
Vehicle Speed Sensor: 100 km/h
Intake Air Temperature: 47 °C
Absolute Throttle Position: 14.9 %

#2
Freeze Frame
P0300: Random/Multiple Cylinder Misfire Detected (Powertrain, Generic)
Fuel system status: Fuel system 1: Closed loop (1)
Fuel system status: Fuel system 2: NA
Calculated engine load: 36.5 %
Engine Coolant Temperature: 89 °C
Short Term Fuel Trim - Bank 1: -0.8 %
Long Term Fuel Trim - Bank 1: -10.2 %
Intake Manifold Absolute Pressure: 46.0 kPa
Engine RPM: 2158 RPM
Vehicle Speed Sensor: 53 km/h

JRD
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Posts: 113
Joined: April 3rd, 2009, 8:10 am

Re: P0300 engine light

Unread post by JRD » November 18th, 2013, 4:33 pm

Take it to an auto electrician who can graph data ! That's the only way to see what is really being affected.

jham66
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Posts: 5
Joined: July 2nd, 2011, 8:41 pm

Re: Any suggestions re this P0300 engine light??

Unread post by jham66 » November 19th, 2013, 11:45 am

Was hoping someone might shed some light on it using the numbers. The car is still under warranty, I am just trying to help get the problem solved, hopefully a bit more quickly..... Although I don't mind them throwing parts at the car!

mydmax
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Joined: August 4th, 2011, 10:43 pm

Re: Any suggestions re this P0300 engine light??

Unread post by mydmax » November 19th, 2013, 12:45 pm

jham66

If they are just replacing parts willy nilly as you have indicated they are doing , it indicates they haven't a clue and will try anything.
Depending on what was done and who did it, ie, replacing gaskets, which gaskets? because the degree of disassembly would mean different amounts of electrical wiring disconnection.
Since many vehicle faults are induced by Humanoids it IS reasonable to assume they, dun sumfink. Maybe a plug to a component is not connected correctly or it is dirty and shows up with certain harmonic vibrations or road bumps when driving. Not there constantly but happening all the same.It may not do it in the THE WORKSHOP.

I would go over all plugs in the engine bay and see if the pins in each connector are in the correct position and not pulled back/receeded slightly in the plug and also that they are clean and when connected are fully engaged.

Having them replacing parts more and more is likely to cause more trouble as the more they touch the more room for error.

Worker come in two types, one is diligent and others can be a gent but also a dill.

jham66
I'm new, be nice!
Posts: 5
Joined: July 2nd, 2011, 8:41 pm

Re: Any suggestions re this P0300 engine light??

Unread post by jham66 » November 19th, 2013, 9:15 pm

The motor was completely removed from the car. I have re-plugged everything I can reach.

It has never done it in the workshop or with them driving. Usually takes a decent drive, sometimes only when at highway speed. If it does go off at highway speed, it will usually go off many more times in the same drive (after resetting each time).

I have just put metho in the tank at the request of the service dept. I hope it doesn't void my warranty since it says clearly in the manual not to use e10. It is about e15 at the moment.....

I mapped the long term fuel trim this afternoon. It is nearly always negative, down to -16. The only time out hits 0 is when the MIL comes on.

mydmax
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Joined: August 4th, 2011, 10:43 pm

Re: Any suggestions re this P0300 engine light??

Unread post by mydmax » November 19th, 2013, 9:55 pm

jham66
I'm not sure of this but from what you say the trim is going negative. Does that mean the oxy sensor is feeling too rich and is it spark plug/s which may be under stress. have they put a scope on it to find out the firing voltages so they can see any differences likely to cause misfiring, ie too wide a gap and then misses under certain situations and delivering raw fuel to oxy sensor.

High speed may be heating a dodgy plug to fail point.

Is there crap on the porcelain of one of the plugs and spark voltage leaks/jumps to ground? Seen Mitsubishi V6 do it.

jham66
I'm new, be nice!
Posts: 5
Joined: July 2nd, 2011, 8:41 pm

Re: Any suggestions re this P0300 engine light??

Unread post by jham66 » November 20th, 2013, 6:18 am

The plugs, leads and coil are all brand new to attempt to fix the problem. The original coil was a bit dodgy. One side measured 0.5ohm the other 1.2ohm. Replacing it made no difference

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