Rough Idle - Have Tried Just About Everything - Stumped!

[Adam]

Don't regap the plugs. What Jet's talking about can happen under load with cars running a higher boost level. Your issue is at idle so the gap won't be a problem.

[MX Dave]

Dumb question, how did you torque your spark plugs?

No offence intended but seen many people crack them before from over tightening. Then refuse to replace them because they are 'new'

Food for thought.

[jas98]

  On 29/12/2012 at 9:01 AM, J@SNOT said:

hold your foot flat to the floor and click the key to start for 2 seconds approx ( it wont start but will crank ) then switch key back to off then foot off then start it as per normal

what does this do? ive been told it does nothing at all

also another thing I did on mine yesterday was check all boost lines and I found the boost pipe under turbo that leads to turbo from intercooler I could do the clamp up about 6-8 turns. im pretty sure it helped allot with mine also found loose spark plugs on mine aswell...

Edited 30/12/12 03:28 AM by jas98

[NickBA-XR6T]

Will check that under car boost hose never thought of that. Plugs I do firm but not too tight. The bad idle was there on the last set of plugs too so doubt it is that.

[MX Dave]

I doubt that would make any difference to idle as its under vacuum so anything leaking before the map sensor shouldn't affect idle.

When you checked for vacuum leaks did you check the brake booster. That often gets overlooked for slight air leaks.

I've had a car before we're the brakes still felt okay but the booster had an air leak causing sh*t idle.

[NickBA-XR6T]

OK so today I ripped the whole thing apart. Tightened everything. Found a dodgy rubber joiner on the turbo inlet and replaced that with a blue silicone joiner. Tightened the upper inlet manifold bolts I could get to. Exhaust manifold bolts are OK. Tightened the turbo nuts. Tightened the spark plus 2 were on the soft side. Checked all hoses. Idles quite a bit better now. Not perfect but better.

[JETURBO]

Semi win then lol

[NickBA-XR6T]

Lol indeed. I think I will send it to Autotech for further diagnosis. Just to be sure.

[gsd112]

  On 31/12/2012 at 8:20 AM, NickBA-XR6T said:

Lol indeed. I think I will send it to Autotech for further diagnosis. Just to be sure.

Good idea, he is a whizz with these cars

[jas98]

  On 30/12/2012 at 6:48 AM, MX Dave said:

I doubt that would make any difference to idle as its under vacuum so anything leaking before the map sensor shouldn't affect idle.

When you checked for vacuum leaks did you check the brake booster. That often gets overlooked for slight air leaks.

I've had a car before we're the brakes still felt okay but the booster had an air leak causing sh*t idle.

hmm been thinking this with mine as not a miss just bad vibration cause of a bad idle. it idles round 700rpm even lower sometimes. but when take foot off brake and go (from lights ) if fine. or when reved slightly it fine

what the best way to check booster?? foot off brake in drive? hand break on?