Code po300

[tophammer]

2008 ford focus 1.4 petrol hatchback

Cylinder 4

Is weak 

Car cutting out 

When I go to stop in traffic 

Code po300

 

 

 

Edited October 13, 2021 by tophammer

[isetta]

How have you established cylinder 4 is weak? Eg compression test   Or    Listening to the effect of disconnecting each plug lead one at a time.   Or….    P0300 means misfire on more than one cylinder I believe. If it was only cylinder 4 I think the code would be p0304.

[DaveT70]

26 minutes ago, isetta said:

How have you established cylinder 4 is weak? Eg compression test   Or    Listening to the effect of disconnecting each plug lead one at a time.   Or….    P0300 means misfire on more than one cylinder I believe. If it was only cylinder 4 I think the code would be p0304.

 

26 minutes ago, isetta said:

If it was only cylinder 4 I think the code would be p0304.

Exactly.

First point would be plugs and leads.

Then coil pack

Then compression test

[tophammer]

Ahh TK for reply true what u said 

Tryed everything

Even swapped

All coyle packplugs leads 

From other 08 focus 

Still hunting

Then  done compression test 

4 slynder little bit weak cleared all faults with high spec computer

Drove on motorway

Not hunting as much 

But when I slow down 

Car cuts out 

Apart from tht 

Driving as new 

Just fully serviced and

T belt and water pump 

Last week

As u said it's cylinder 4 

My mechanic

Says drive for the weekend

See how it goes

But he did say might

Be head gasket

Or the brain

Or valve 

Any way I can sort this 

Or will I have to replace

With 2 ND 

Engine

What u think tk again for reply

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[F0CUE]

P0300 Causes

(* = Most Common)

• Faulty or worn spark plugs *
• Faulty spark plug wires or coils *
• Distributor failure *
• Faulty fuel injector 
• Vacuum leak
• Low fuel pressure
• Camshaft sensor defective
• Crankshaft sensor defective
• Engine timing off
• Leaking head gasket
• Low engine compression
• Poor quality fuel

[tophammer]

Many thanks for your help

Car cutting out

When I go to stop or slow down

No reading on the crankshaft

Etc however done compression test

Cylinder 4 is week

Is it fair to say I could

Put spoon full of oil.down cylinder 4.was told to try slick 50.oil.car is driving fine other than.that like.engine light is staying of.so no fault s .as my friend cleared with.computer .iv done air test etc all is good.

 

 

 

 

[Tizer]

6 minutes ago, tophammer said:

Many thanks for your help

Car cutting out

When I go to stop or slow down

No reading on the crankshaft

Etc however done compression test

Cylinder 4 is week

Is it fair to say I could

Put spoon full of oil.down cylinder 4.was told to try slick 50.oil.car is driving fine other than.that like.engine light is staying of.so no fault s .as my friend cleared with.computer .iv done air test etc all is good.

 

 

 

 

The idea of putting oil into the cylinder is that if you do a compression test and one or more cylinders is lower than it should be then you put some oil in that cylinder and do another compression test right away. Do not start the engine though because the oil will burn off.

If the compression in the low cylinder then rises a lot to a near normal level then the problem will be with the piston rings/cylinder bores rather than the valves or cylinder head gasket.

I wouldn't waste my money on slick 50.

Your cutting out problem is unlikely to be anything to do with low compression unless they very low. As for what it could be then it is impossible to say from here.

[tophammer]

What would you say problem is by car cutting out.just as I'm about to.stop just cuts out like

 

[tophammer]

Idle What would you say problem is by car cutting out.just as I'm about to.stop just cuts out like.

U tube video

Idle speed control valve.replacment .might stop from cutting.out .