Iridium Plugs / Idle Issue???

[iamawookie]

Hi, I’ve seen that not everyone is overly happy with Iridium plugs and was just wondering if any one who’s had issues with them could tell me of their problems? I have a set and an annoying idling issue at the mo, don’t know why but have got it into my head that the problem lies with these!
Currently when the car idles it will start off at about 1300rpm and then after about 5 seconds drop down (although it doesn’t always drop) to about 700rpm / 800rpm (where it usually sits), I’m pretty sure that the revs don’t drop quite as quickly as they use to when I change gear too. I’ve done quite a bit to the car recently so it’s even harder to try and remember when the issue first occurred!
A bit of recent history...
*BSR Optiflow (I do remember this issue not happening for quite a while after this being fitted)
*Last service the fuel filter was replaced
*Stage 1 chip (I do remember this issue not happening for quite a while after this)
* Jetex Cat-Back system
*Throttle Body and ICV cleaned
*HT Leads replaced
I always try and use V-Power and the strange thing is that this problem doesn’t always happen, however I would say that 4 uses out of 5 it does. Any other suggestions apart from the plugs would be welcome, cheers for your time!

[Baffler]

Sometimes mine idles high after a spirted run but I assume it's due to extra fuel in the exhaust. Short runs can effect the idle too if I don't allow the fuel gases in the exhaust to burn off. I just let it idle for several minutes and it returns to normal. Although I don't know if this effects your cat back exhaust system.

For peace of mind clean the ICV again. I'd also pop in some OEM sparks plugs.

[iamawookie]

Originally Posted by Baffler

For peace of mind clean the ICV again. I'd also pop in some OEM sparks plugs.

I only did the ICV about 3 weeks ago, so can't really see it being that, I was thinking that I would go down the route of sticking some OEM spark plugs back in again (I just wish I wouldn't have thrown the old ones away so I could test with them again).

[Baffler]

I cleaned my ICV when I got the car but I noticed it was still a little lumpy on idle and gear changes. A second clean did the trick. I probably didn't get all the crap out first time. Original Volvo plugs are highly recomended! (lots of threads on this topic)

[thebigv]

Iridium plugs are a little funny in my T4, they work better at full chat but as they keep the internal temps down slightly they do run a little lumpy at idle. Check your iridium plugs have the correct temp rating to them. Some people do not realise they have temperature ratings on spark plugs.

[Enigma666]

OEM all the way for the X40's
Many people have tried the iridiums and they just dont work as well.
I guess at least Volvo got something right when making the 40's lol

[manoman48]

and they last 30,000 miles...

[Jocksuper7]

OEM plugs the engines hate anything else, especially the T4s i had bosh platies in and it ran like a dog, wouldn't idle and lost power so they got the elbow back to oem and there is no problems, oh yeah give the MAF a carefull clean though frowned apon in some schools of thought, but if your do it carefully with a proper maf cleaner or a carb cleaner it get rid of the road scum, i found since the K and N has been in mine that it gets coated up quicker

[alistairk24]

Hi has anyone experienced starting problems as well with non OEM plugs?

[Dandle]

My T4 runs and has run perfectly on NGK Iridium IXs for the past 15k miles.