Misfire

[Guest nick jc]

hi all, the number three cylinder has a missfire on my 16 gti, ive changed the plugs leads and dizzy cap but still no change, all the plugs are sparking and under laod the engine runs fine its just when its ticking over, ive been told it could be early signs of the head gasket going, does anyone have any ideas, thanks nick.

[kyepan 291]

if you're suspecting head gasket, it might be worth doing a compression test, and check the coolant for hydrocarbons. A compression tester costs a tenner, and the hydrocarbon thingy tester is about 20 quid.

 

 

 

if it's missing at idle, it could also just as easily be an air leak, try taking the air filter off, get a long wooden spoon or some such other implement and carefully deflect the flap in the afm to see if you can get it to run right... if you can it's an air leak after the afm that is screwing up the mixture, which will explain why it goes away at higher revs.

 

Cheers

 

J

[Tom Fenton 1,542]

I'd also try a compression test and see what result you get.

[DamirGTI 342]

Might be bad injector check the connector/wiring on this the No. 3 injector .. if theres everything fine one the connector/wiring side try to swap the injectors over (mix them a bit/swap them over the cylinders but mark this 3-rd one first) then you'll see if this misfiring appearance will move on the another cylinder ... if so , then it's bad injector ..

 

Damir

[Guest nick jc]

thanks for the advise guys, i wil start with the injectors and see if that makes sense of things.

[Guest nick jc]

had a compresion test done today and the 3rd cylinder is only raeding 20 psi, all the others are reading around 130 psi, the guy said it could be head gasket or even worse a cracked head, what do you guys think.

[EdCherry 34 1 Cars]

130 psi isnt very high!

 

Id get it stripped down, only way your gonna find out really.

[Guest nick jc]

what psi should it be?.

[EdCherry 34 1 Cars]

150-200 psi for a healthy engine so i've been told. Its not really a case of the psi being really accurate, its the difference between the cylinders you want to watch.

[Tom Fenton 1,542]

130psi is fine if all equal across cylinders. Absolute reading is not important, especially as most compression testers are not the most accurate instrument in the world. It is the difference that matters, the 20psi points to a definite problem, and for the comp to be that bad it should be something obvious.