Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: JasonH on 19 May 2007, 16:52:54

Title: Lumpy idle when hot
Post by: JasonH on 19 May 2007, 16:52:54

Any ideas where to look for this one.

No oil in plug wells
New DIS pack
Well serviced: oil, air filter, fuel filter, etc.
MAF clean
No obvious air leaks
EGR can be heard opening and closing with Tech 2
No fault codes
ICV clean

Car runs very well otherwise. No missing under hard acceleration (so I'm inclined to think the HT leads are OK although they are old).

Idle isn't perfect but after a good run down the motorway i.e. engine full up to temp, idle is lumpy. Not fluctuating more than 50 rpm but just vibey at around 550rpm. Enough to shake the gear stick and to feel it through the seat.

Where should I look?

Title: Re: Lumpy idle when hot
Post by: Auto Addict on 19 May 2007, 17:07:59

Breathers clean?

Title: Re: Lumpy idle when hot
Post by: Chopsdad on 19 May 2007, 20:32:23

Change of fuel - treat it to a dose of Optimax of BP Ultimate.

Although it does sound like mine last year, which tuned out to be faulty MAF - but these are rare to fail and I had emissions light on and fault codes too.

Title: Re: Lumpy idle when hot
Post by: JasonH on 19 May 2007, 20:39:18

The breathers are clean.

A good does of redex does appear to have improved the MPG but the idle is the same.

Title: Re: Lumpy idle when hot
Post by: Darth Loo-knee on 19 May 2007, 22:08:11

Could it be a breaking down Plug or lead?

Title: Re: Lumpy idle when hot
Post by: Marks DTM Calib on 19 May 2007, 22:10:05

Do a vac test.....a vac gauge is the single most useful bit of DIY test kit (non electronic) you can get....

I suspect an air leak somewhere....

Title: Re: Lumpy idle when hot
Post by: JamesV6CDX on 19 May 2007, 22:42:12

Quote

Any ideas where to look for this one.

No oil in plug wells
New DIS pack
Well serviced: oil, air filter, fuel filter, etc.
MAF clean
No obvious air leaks
EGR can be heard opening and closing with Tech 2
No fault codes
ICV clean

Car runs very well otherwise. No missing under hard acceleration (so I'm inclined to think the HT leads are OK although they are old).

Idle isn't perfect but after a good run down the motorway i.e. engine full up to temp, idle is lumpy. Not fluctuating more than 50 rpm but just vibey at around 550rpm. Enough to shake the gear stick and to feel it through the seat.

Where should I look?

What's it like through the rev range?
Potential blocked exhaust?

Title: Re: Lumpy idle when hot
Post by: JasonH on 20 May 2007, 10:37:31

It runs very well and has a new Vx exhaust cat back.

Mark - air leak feels right to me as well but I can't find one.

How would I find it with a vacuum gauge?