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High Compression on 1 cylinder



  Clio 182
Hi all, im in a bit of a pickle with this. So i recently done a cambelt change on my 182 and everything has gone smoothly apart from cylinder 4 is now misfiring... i thought it could be the coil leads at first as they weren't in great condition so i have change those out for genuine ones and still no luck. i started to get worried thinking that the timing was out so went back and checked it multiple times and it all seems perfect.

I ran a compression test on the car today and noticed that cylinder 4 was up on compression by around 10-15 psi so its reading around 210 compared to the other pistons which are all reading around 200 psi.

can anyone suggest why one cylinder would have higher compression than the others? and how i may resolve this?

Thanks
 

Brigsy

ClioSport Club Member
  Kangoo 172cup
Compression is within 10% by the sounds of it so not an issue, its decent overall and generally you would need a big drop in compression on a cylinder to get it to misfire.

If the timing is correct, id say its injector fault or ign related, resistance check the injectors.

Next step for me would be to swap cyl 4 injector, then spark plug to a different cylinder and see if the misfire follows suit, give you an idea whats playing up
 
  Clio 182
Compression is within 10% by the sounds of it so not an issue, its decent overall and generally you would need a big drop in compression on a cylinder to get it to misfire.

If the timing is correct, id say its injector fault or ign related, resistance check the injectors.

Next step for me would be to swap cyl 4 injector, then spark plug to a different cylinder and see if the misfire follows suit, give you an idea whats playing up
How do you restart check the injectors mate?
 
  Clio 182
Compression is within 10% by the sounds of it so not an issue, its decent overall and generally you would need a big drop in compression on a cylinder to get it to misfire.

If the timing is correct, id say its injector fault or ign related, resistance check the injectors.

Next step for me would be to swap cyl 4 injector, then spark plug to a different cylinder and see if the misfire follows suit, give you an idea whats playing up
sorry auto correct there...

how do you resistance check the injectors?
 
  Clio 182
No worries :)

Failing that, pull the rail off with the injectors in, stick a sheet of cardboard in and crank the car a few times and look at the spray pattern and volume of petrol :)
Cheers mate. There is good resistance on the injectors so that next up then!
 

Martin_172

ClioSport Club Member
  182 RaceVan
A lead trapped under the inlet manifold, I've cured a miss fire when I found that before
 
Leads, plugs, coilpack & injectors are all things to check

Easiest thing to do is just to swap plugs from one cylinder to the next, then injectors and if you have a spare HT lead then keep moving them around and see if you get any changes
 
  Clio 182
Leads, plugs, coilpack & injectors are all things to check

Easiest thing to do is just to swap plugs from one cylinder to the next, then injectors and if you have a spare HT lead then keep moving them around and see if you get any changes
Yes I think I’ve found the problem! Cylinder 4 injector is not outing any fuel out! All other injectors are working...
 
  Clio 182
Anything over 190 is decent really.

Yours is probably better than factory 😂
Lol not sure how it’s managed that 😂 maybe my excellent ability to time the engine 🤔

in all honesty the car is in Vee good condition mechanical and is actually better than my past Clio’s that had half the mileage
 

JamesBryan

ClioSport Club Member
  Titanium 182
Lol not sure how it’s managed that 😂 maybe my excellent ability to time the engine 🤔

in all honesty the car is in Vee good condition mechanical and is actually better than my past Clio’s that had half the mileage
Some engines just are.

Good valve seating and piston rings.
 

Brigsy

ClioSport Club Member
  Kangoo 172cup
Probably thrashed from new and the rings bedded in really well;)

I would bosh a new set of injectors in at 130k. I replaced all of mine after one failed and it ran great after, miles better than with the old injectors.
 

JamesBryan

ClioSport Club Member
  Titanium 182
Probably thrashed from new and the rings bedded in really well;)

I would bosh a new set of injectors in at 130k. I replaced all of mine after one failed and it ran great after, miles better than with the old injectors.
This.

Keep the 3 working ones as spares.
 
  Clio 182
Probably thrashed from new and the rings bedded in really well;)

I would bosh a new set of injectors in at 130k. I replaced all of mine after one failed and it ran great after, miles better than with the old injectors.
Well after finding one to have randomly stop working this will be the next thing to replace.

it still baffles me as to how it stopped working while I was changing the cam belt... then again it’s French 😂
 
  Clio 182
You moved the injector to make sure that its the injector and not a loom/signal issue
I did try this straight away and it wasn’t the loom thankfully! I managed to get an injector from someone local who was turboing their Clio so had one spare to give me 👍🏼

Car is no running perfectly
 

Brigsy

ClioSport Club Member
  Kangoo 172cup
The injectors are fragile if original. I knocked one of mine when changing the oil filter and the plastic connector part simply fell off as brittle and old.
 
  Clio 182
The injectors are fragile if original. I knocked one of mine when changing the oil filter and the plastic connector part simply fell off as brittle and old.
lol. the connector for the injector that failed was wobbling and could move back and forth but it was definitely still working but just blocked up... you need to be super careful when pulling them out. as you say its very easy to break them
 
  182, E46 M3, 1000RR
I just fitted a set of new injectors after one failed - bought from Autodoc on one of their discount days and paid £123 for all four, might be worth checking them out rather than ecp.
 


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