engine misfire

[Barron]

hey,
My 172 is now running but im currently struggling with it misfiring. The problem is that it is only running on 3 cylinders it seems. The engine management light turns itself on after a while and flashes when driving and building up the rev's. I have changed the coilpack and the spark plugs with no success.

any ideas?

thanks
carl

ps feel free to delete my other post in faults etc

 

[Fred@BTM]

coilpack would be the first port of call

 

[Barron]

yeah thats what i changed first with no success =(

 

[Fred@BTM]

check the HT leads aren't damaged/shorting out, thats common

 

[Barron]

i have two sets of coilpack + HT leads and both are not helping

/carl

 

[skini]

check the injectors

 

[Barron]

check the injectors

how would you check them without a dianostic computer?

/carl

 

[Fred@BTM]

easy (ish) take the plenham chamber off and get a mate to crank the engine, you'll see if the injectors are spraying or not

 

[Barron]

hmm may be worth checking that then, plan for tomorrow is to do a compression test (think that may be a problem?) and then mess around doing other checks. If they fail ill take it to a renault specialist later on the day to get it plugged into the diag computer.

/carl

 

[skini]

take them off (few minutes job) and give them to test their flow on the machine (they all must have same flow) and if necessary they will clean them (ultrasonic cleaning)

 

[Barron]

update: took it to a renault specialist, put it through the clip computer. Only fault showing the misfire. Had a quick check and the guy there sprayed so liquid towards the bottom manifold gasket. the engine would change its tone when cosntantly squirting the liquid towards what seemed to be a small hairline crack in the gasket. He told us that is was possibly a small crack which had expanded in the gasket as i had been driving it fine the first day but the 2nd day it was misfiring.

anyone else had a problem similar or was the guy just stabbing in the dark?

/carl