Dodgy/rough idle - common causes?

[Jimi137]

Hi every1. I have had my car for a few months and have done 4.5k in it. Over the last few days the idle has been getting progressively worse and is now juddering a lot and the revs keep varying from about 600 to 1000 rpm like its missfiring or something. I have also noticed a slight drop in power and a few flatspots on the rev range.

Now i have just had my middle box of my exhaust removed a few days b4 this problem started but i was told it wont cause any problems. Is that true or is there sumthin the garage didnt tell me?

Also it is 10 months and like 9 or 10 k miles since the last time the spark plugs were changed so could this be the cause? It seems pretty bad for just spark plugs but i really dont know how much they effect this. The oil has been changed in the last 2k miles though as it was getting a bit thin

So basically is it one of these things causing it or something more worrying like a head gasket on the way out?

[roperstun]

most proberly your idle control valve

[aimable455]

yeh it most prob is ur idle valve mate because im having all the same trouble you can get one on ebay for 25 quid mate so easy fix

steve

[Jimi137]

I thought that would cause a high idle (like 2 - 3k revs) not a low one though? And if i did buy one how do i fit it?

[roperstun]

it courses any irrecular idle

it might just need cleaning so id find it first and remove it and clean it off and try it back in

[Jimi137]

I just went out into it and it seems to have stopped??? The idle is perfect on 800 rpm now and there is no flat spots on the rev range in any of the gears. Very strange. I have a suspicion it is cuz i used quite a lot of supermarket petrol last week instead of my usual esso or shell. Anyway if it comes back yeh i'll try cleaning that idle control valve out and see if that solves it

[roperstun]

you mite av just had sum poo in ur exhasut system thats was restricing it but urv managed to dis lodge it.

try putting sum redex in it jst incase

[Jimi137]

Yeh i was thinkin of doing that as well. Probably go halves with my m8 and get a bottle between us lol