Rough idle after spark plug change!

PeteZ3

PeteZ3

Zorg Legend
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Joined
Jun 18, 2015
Points
75
Model of Z
1998 Manual 2.8
I have just changed my spark plugs and after the car has warmed up it is idling rough with a lumpy feeling to the engine. its also dropping slightly in RPM when idle (upon the lump). the engine was fine before i change them but as i didn't know when they were changed last i thought i would change them for new ones. it is fine when running though! and its just as responsive as it has been.

The car sometimes doesn't want to start easily.

I have checked that all the coil packs are screwed down correctly and they are in good condition too, the Leads are connected correctly and the clips are tight. so what have i done wrong? could it be the tightness of the plugs? or do they need setting to specific gap?

I used NGK plugs from euro car parts http://www.eurocarparts.com/ecp/c/B...ular-service/spark-plugs/?408110050&1&&000301

This has happened as a result of me changing the plugs as it was perfect before! so annoyed with myself, hopefully someone can help me! :(
 
You need to code read it and it may point you at the bad plug.
A few guys have posted recently about rough idle and after re seating things over swapping over coils etc have rectified the issue.
Hopefully a bad plug but with out a read it may be difficult to pin point.
 
What engine is it. As i know the 3.0 have platinum plugs.
 
Ignore that as just noticed its a 2.8
 
yeah 2.8. i have swapped the coil packs over a few times and its just the same. i dont have a torque wrench, so i dont know what guage i tightened them to. could this be a potential problem? i think your right though, i might need some professional diagnostic tools to see whats wrong :(
 
Antm72 said:
Have you tried just refitting the old plugs ?
Click to expand...

stupidly i threw them away. i would have though if i hadn't. reason being, i didnt notice the roughness until a few days after as it only idles rough when it warms up a bit, and since it was fine upon start up and a quick spin i just left it for a couplle of days and by the time i used the car propperly and found the fault, the plugs were long gone :/
 
do you know if you should be setting the gap for these plugs?
 
Shame not sure if anyone is close to you to give it a quick read only other thing would be to get another plug and when it runs lumpy swap one plug out at a time till you remove it.But it could be a coil this would show on a read though.
 
Are they not the four Electrode plug they are set but it would not be a bad thing to check them if they are single .
 
they are single, its in myorigional post the link to the plugs

yeah i know if anybody is close that has a reader i woud be very grateful if we could have a look!

i suppose i could just get another plug!
 
they are part number 408110050 from euro car parts, they looked exactly the same as my old plugs
 
i checked the coils with a ohms reader and they are all reading 1.0 which i believe is what they are supposed to be reading
 
Standard plug i believe .032 gap should be present but think they come gapped.
Info i found says that they are none adjustable though so they should be ok.
I still think plug as its all that has been swapped and a break down with heat seems likely.
 
Antm72 said:
Standard plug i believe .032 gap should be present but think they come gapped.
Info i found says that they are none adjustable though so they should be ok.
I still think plug as its all that has been swapped and a break down with heat seems likely.
Click to expand...

Cheers mate, right, I'll have a look on Thursday as its my day off, I'll see what's what then I'll get another plug and swap them over one by one. Gonna take me ages, but at least it's only six cylinders not 12 hah
 
Thanks for the help, I'll report back on thurs
 
You should always check plug gaps if only by eye. If not it's possible one could have been dropped and nipped the gap up. Very easily done.

Tony.
 
t-tony said:
You should always check plug gaps if only by eye. If not it's possible one could have been dropped and nipped the gap up. Very easily done.

Tony.
Click to expand...
I will check them all on Thursday, to see if any of them are different from each other. I've got another car so she's just sitting on the drive way until then :)

I wish I knew this prior to changing them, I don't know if I could have done any damage by running the car? Hopefully not!
 
This should not have caused any damage Pete, so don't worry. Plugs do come pre set at a certain electrode gap but it best to check them before fitting.

Tony.
 
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