Technical Missfire on one cylinder

[jb88]

i was wondering if someone could help me
my cinquecento failed its MOT yesterday :bang:

as you can imagine i was not pleased...
the main problem that i am having is that the MOT inspector said that it was running on only three cylinders. because of this it had very high monoxide and hydrocarbons.

ive tried everything that i could think of.

ill list what i have tried

1. New Spark Plugs
2. HT leads
3. Ignition Coil packs both replaced
4. Had Head Gasket off - looks OK

apart from these any ideas why it is not working would be apreciated

jb88

edit: forgot to say its a 95ish bog standard 899 cc

 

[FIREsporting]

A cylinder may misfire due to loss of compression, check the compression pressure of each cylinder

 

[jb88]

A cylinder may misfire due to loss of compression, check the compression pressure of each cylinder

yes i have done that the compression is ok

forgot to put that in my first post

jb88

 

[randomizered]

Check for spark on all of the plugs.

Just because the tester said it's runnining on 3 doesn't mean he's actually right though


What were your reading? any idea?


Kristian

 

[jb88]

Check for spark on all of the plugs.

Just because the tester said it's runnining on 3 doesn't mean he's actually right though


What were your reading? any idea?


Kristian

My dad stuck his finger over each spark plug hole in turn whilst i turned the engine over. i do trust him because in a previous job he worked in a garage

jb88

 

[fingers99]

My dad stuck his finger over each spark plug hole in turn whilst i turned the engine over. i do trust him because in a previous job he worked in a garage

jb88

You have to be joking! :bang:

Get a guage and use it, throttle fully open.

 

[randomizered]

:yeahthat:

I also meant the emissions readings, not the compression readings. Both of them may be useful

Kristian

 

[jb88]

Standard idol speed:
Co2 should be less than 0.300
actually is 0.476

hydrocarbons should be max of 300
my car is 467

and on the faster idol speed
Co2 should be 0.300
actually is 0.492
hydrocarbons should be max of 200
my car is 236


once again thanks for help given and a thanks in advance for any other help
jb88

 

[randomizered]

Bah, thats nothing

Get yourself to Halfords, buy a bottle of Wynns Emissions reducer (purple bottle), stick it all in. Rag it for 20 mins before test to let it work through. Bet it goes through.

If not, then i'd look at the lambda. A missfire will not cause higher CO levels by that much, but with a missfire HC would be a lot higher. Looks like it may just be riching the mix too much imho.

Kristian

 

[jb88]

Well the thing is not only that it is that my car has a loss of power

i think this happened when i was driving, i stopped to go into a junction, clutch down, brake on, then stalled???? since then it has not been running correctly. it bounces a little when the accelerator is pressed down a bit and not sounding 100%

its just that its runable but it drinks the petrol like it's going out of fassion. its using about half as much petrol than it did before.

jb88

 

[fingers99]

If it is running on 3, that would explain why it's down on power.

Compression test!

You might like to pop off the cam cover and see if there's anything out of the ordinary there.

 

[jb88]

Well after a bit of tinkling we have my car running on all 4 almost
now it is a misfire
after 3 MOT Failures thats what we have decided
the emissions are still in the red
I have three options
1. Scrap it
2. Replace engine
3. a cylinder valve has been burned out
what are the chances of no 3???
if so how expencive would a new valve be and how hard would it be to replace the valve

this is because i don't want to spend out money on a new engine
and i don't really want to scrap it

the emissions are about the same as mentioned before except the hydrocarbons are over 500!!

any other possible solutions are welcome!

thanks for everyones help so far

jb88

 

[rallycinq]

Compression test dry, compession test wet, then, if the results work out, change the head.

Cheers

D

 

[jb88]

On tuesday its goin into the guy who is in charge of the MOT center and he is gona do a compression test.

 

[rallycinq]

Make sure he does both, wet and dry.

Cheers

D

 

[Gav F]

On tuesday its goin into the guy who is in charge of the MOT center and he is gona do a compression test.

compression test is easy though
takes us 5miuntes to do a wet and dry compression test at college

 

[rallycinq]

compression test is easy though
takes us 5miuntes to do a wet and dry compression test at college

Ah, but you'd still charge the full hour.

Cheers

D

 

[jb88]

Well Thanks to all of you.
i got through the MOT yesterday.
i found the problem



it was a blown exhaust valve

£12.50 for a replacement and sailed through emissions test

once again thanks to everyone

jb88

 

[ycming]

hmmm.. this could possibly be my problem ......

going to change the leads tonight heop it fixes it !!!!

Well done on getting the car back on the road

Ming

 

[Vic20]

Hmmm, I wonder what could have caused that?

An overly weak mixture is generally the cause of exhaust valves burning. Did the other valves look ok and was the head seat of that valve ok?