VS ecotec flatspot, any ideas?

[Shambo]

Hi all,

The problem I am trying to solve is when I rev the car in neutral there is a hesitation, then a slight miss and the revs take up ok.

The more repeated bursts in quick succession the worse it gets. Like its not responsive enough...



Other info:

If you do it slowly its not so bad.

The car drives fine, it accelorates evenly and changes gears with no problem. Although the other night it ran rough for a while (this now seems to of corrected itself).

I changed the plugs about 3 months ago. I would think they should be ok.

I have no error code messages.

I checked the IAC sensor with a multi meter (ohms were correct) and cleaned the pintal tip. It idles fine, nice and even and doesnt
miss at all on idle.

The TPS seems ok. It has the right ohms resistance. Ohms goes up evenly when the throttle is opening with the engine switched off. I wasnt sure what wires on the TPS to use to check the voltage. I know it should be 5v when the throttle is wide open and about .65v when shut.

The injectors seem ok. Ohms resistance is correct @ 12.1 on each and they seem to be working. I did the "listen to a long screw driver test" on each one with the engine running as well. They have a bit of weaping around them but not wet puddles, kinda black dust if you know what i mean.

Car has done 110000kms

Any thoughts on what to do now to fix it? Is it normal for it to hold back when you rev in neutral and then take off?


Tommorrow I am going to remove the plugs, clean and check the gaps and check the resisance on the leads and the resistances of the coil packs, but I'm thinking it maybe a fuel related problem....

Cheers

[hako]

I'd throw a tin of injector cleaner in next time the tank gets filled - don't use the cheaper ones. I've got rid of a similar hesitation before by decreasing the spark plug gap - recommended is 1.5mm but I found I had no problems with 1.0mm and got rid of the hesitation.
Good Luck.

[paytons_dady]

have u put a pod filter on it? mine did that when i put the pod filter on its not resposive in neutral but drives ok..but now gone back to the standard box..cheers

[Shambo]

I dropped the gap to 1.25mm and checked the leads at the same time and still the same problem.

Turned out to be poor spark leads. I did a resistance check pretty much per the Checking Ignition Leads post and found 2 of them had no resistance at all.

Chucked a new set on and she seems as good as gold.

I left the gaps at 1.25mm not sure if that matters, its going well now and im over it

Cheers



P.S. no pod fitted

[immortality]

open the plug gap back upto 1.5mm it'll effect your fuel economy and check this out Clean your MAF

[Shambo]

OK.

At least they will be easy to get out now.

I only do them finger tight then say 1/8 of a turn just to nip em up tight.

I am amazed at the info on this site.

Cheers