Missing once warms up CODE P0301 - cylinder 1 misfire detected

Checked the compression on that cyl ?

Pressure not checked, have noticed that once EML starts flashing if engin is given a little rev for few seconds then light goes off.

The 1.2 3cylinder polos have a comon fault with the valve guides wearing. VW replace the clylinder head if the car is under waranty but a cheaper alternative is to lap in the valves. this fault can be determined after a compression test. compression should be above 175 psi. if the compression is low then the cylinder head will need to be removed and that will mean one of the 2 fixes mentioned earlier in this post. and lods of bolts and seals will also need replaced as they are only to be used once.

This previous reply explains why I asked if you had checked compressions . "delboy_11 " suggestion of lapping in valves is wrong and wont cure fault .The valve sticks in valve guide resulting in burnt valve / seat .


Volkswagen Polo low pressure cylinder 1?
The Problem
Car Volkswagen Polo 1.2 55psi 3cylinder
Year 2006
Owner mark coyle
Posted 29 03 2010

Ref#:
4535
The Problem

suspected stuck valve in cylinder 1. how can this be fixed without taking off cylinder head


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Solution 1
whittingehame
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Since: Oct 2009
Posts: 415 | Fixes: 5418
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Posted on 2010 03 29

More than likely if sticking , valve / seat will be burnt , meaning head off.




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Solution 2
seat tech
Driver

Since: May 2010
Posts: 0 | Fixes: 3
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Posted on 2010 05 16

Hi this sounds the same problem as the Seat 12 3 cylinder and the only fix is a new cylinder head as these heads cant be reworked. The problem is burnt valve seats you will usually get the engine warning light on and when you have the fault memory read it says misfire on cylinder ?.

i currently work with VW and tha is a solution we present to customers that cant afford a new cylinder head. Valves had been lapped in on mny polos and there has been no further customer complaints. VW technical also say this solution will work and have authorised use to carry out this repair.

How can cutting / lapping in clear tight valve stems ?

the vavle stems dont actually go tight on the 1.2s. the valve guides wear causing a little extra movement in the vavle. VW have a tollerance for the free play in the vavles which is 1mm each way. the misfire will be caused by carbon build up on the valve seats and on the valve. and lapping in the vavles will clean the carbon off them and provide a a beter seal if done right than the origional manufactured heads from VW

It's because the valve stems are too tight and causing them to stick , hence carbon build up and also burnt valves .It not just VW's it has happened with . Could go on all day about this with you but will finish now .

Hi

Compression checked and is fine.

Going to swap ECU with one from a car thats running right (if same engine code).

Will post back once done.

In the meantime any further advice most welcome.

I have a VW polo 1.4 4 cylinder 57 plate where this issue has arisen twice. The car has done 33,000 miles! First time March 09 under warranty 11,000 miles VW replaced cylinder head - clearly does not resolve the underlying defect as now the same problem has mainfested and they want to charge us £2,500 to replace the cylinder head and an (apparently failed injector). We were told that "without taking the cylinder head off they cannot identify the exact fault" this is apparently at least 6 hours work which they expect us to pay for. We have had an independent mechanic look at it and he asked a specialist as could not detect any issue with the injectors or even low compression. The specialist said something about the alignment of the valves which I assume is what is being said on this thread (I'm no mechanic!). I have also taken legal advice and think I have a pretty good case against VW and their service team who did the warranty work.

Timing Chain is fine, just ordered Fuel Filter so that can be eliminated as well.

(ECU not changed yet)

hi i had a polo with a missfire 3 times and no one could fix it so i fixed it my self i am the missfire king if you want your car to be fixed im the only one in the uk call me on 07943293843