Hesitation when cold and lowish RPMs

[wintertidenz]

Okay, after all the work I've done on my car lately I thought it was sorted... seems it isn't :(

Driving up the road after the pod was put in the bumper I noticed the car hesitating at random times and quite badly. Put the old pod back in - no problems.
Okay, I thought, I'll put in some air ducting under the bumper to aid air flow to the pod - done. Reinstalled the piping to the MAF - still same issue!

The one thing that puzzles me is that this does not really happen after the car warms up, and it boosts just fine. Fuel economy is excellent with the pod in the bumper (9-9.5l/100km highway) but the hesitation issue is a bit worrying.

I'm suspecting that it might be plugs, as I haven't done them yet, however it looks like the previous owner might have. There are iridiums in the front from memory, heat range 6. Will pull the front ones out in the morning and take pictures of them to confirm.

Does anyone else have any other ideas as to what the hesitation might be? To give you an idea, it feels like fuel or speed cut.

[Davezj]

it is quite common for the front plug to be OK and the rears to be warn out. the rear of the engine run much hotter than the front due to no air flow over the rear bank of cylinders compared to the front bank .
the other thing is the rear plugs are a pain in the arse to change so some people (stupidly) don't bother. so the rear plugs might just be old.

[bradc]

Possibly related to the length of the pipe or some funny harmonics down the tubes?

[wintertidenz]

Brad - could be related to the pipes, considering how they are positioned and the amount of bends in them... it's also 3" pipe so it could be restricting. Funnily enough the car pulls harder with the pod in the bumper!

Dave - I can get to the front plugs easily enough so I will check them first, if they are stuffed I will also do the rear. There is red gasket stuff around the plenum so I know it's been pulled off at some stage, and they probably last did the plugs at cambelt time, so the plugs are near the end of their life.

However - why would this issue happen with the new pipes, and not the old? If the plugs were dying, wouldn't I have the issue throughout the rev range especially up high?

[wintertidenz]

This morning I whipped out the front three plugs on the car to check them and got a nice surprise.

http://i100.photobucket.com/albums/m23/wintertide/Legnum/IMG_0051-resize.jpg

http://i100.photobucket.com/albums/m23/wintertide/Legnum/IMG_0050-resize.jpg

All three plugs look exactly the same so I only photographed one.

So it looks like the plugs aren't the issue. I've also pulled out the oil catch can now and reverted back to the factory PCV system, will see if this makes a difference (although I doubt it would?).

[swinks]

Oil catch can doesn't make a difference at all to performance. I'm bit concerned with that red silicone sealant used to fit intake plenum. Shouldn't be that way. It should go metal crushed gasket (stock Mitsi one is quite cheap), and no sealant at all, otherwise you gonna squeeze sealant into plenum chamber, and intake plenum won't sit properly onto head whilst tightening bolts.
Just spent few quid and do it right in your time.