Low rev jerky/misfire? no pulling power

[starcar]

Hi All
2002 1.6 Petrol 16V runs fine... except recently noticed a bit jerky at low revs pulling away.
Long journey today so managed to work out that if revs are below about 2000 in any gear any heavy acceleration causes jerky possible misfire problem, at higher revs and/or slow acceleration no problems at all, motorway travel at 90ish mph pulls great.

We have two 206CC cars in the family so I can swap parts to try and fix this.
Have PP2000 which comes up with no faults at all.
No petrol smell, (leaking injector- had that on old 206 hatchback)
Temperatures all normal (head gasket ok- had this before as well)

Any ideas where I should start?

[Capncol]

How many miles and when was it last serviced?

[IanL]

Mmm...yes. Maybe start with a new set of plugs?

[starcar]

Hi
Thanks for your quick replies.
96000 miles, recent service, plugs all good.
Just to add:- no squeeks, rattles or anything unusual. Both lambdas operating ok. Starts first time even on a frosty morning, tickover stable.

[IanL]

Well, if it's not ignition, I suspect mixture, which is determined by inlet air temperature and pressure. This is measured by a combined sensor. See the 4th post in this thread.

You could try cleaning the plug/socket first.

[starcar]

Hi IanL, good idea, but alas not the problem, going to try coil pack next as its also quite easy to swap over. Have a sneaky suspicion it might be an injector, they all work ok when using the PP2000 injector test and with no error codes its going to be a 1 out of 4 chance of getting it first time.

[Capncol]

Doubt it's the coil pack.
If you have planet, what's the IAT & coolant temp compared to what's expected?

[Artermis]

I agree this sounds like it's related to air metering / intake. A misfire as a result of a coil pack tends to be coupled with a fault code as it can detect the electrical abnormality.

[Capncol]

Exactly, whereas metering sensors can be wildly inaccurate but still show no faults

[starcar]

Hi All, thanks for your replies.
I also doubted the coil pack and nearly didn't bother trying it, but as it was an easy test I fitted the coil pack from the other 206cc and the problem was gone!!

Comparing the two, identical part numbers, identical extensions but the spring contacts on the working one were around 0.75cm longer, see photo.

PICT2760.JPG

Not sure if they changed these at some point, the second one was off a 2004 allure, or someone, in the know, has stretched them. I did notice I had to push down as I fitted it, pressing against the springs,
So I stretched the spring contacts on the original one refitted as it also worked fine!
I had not touched anything else and had previously had the pack off when I checked the plugs.
I assume there was a poor contact causing a weak spark on one or more of the plugs.

Pleased it was a simple fix, didn't fancy too much tinkering in the current freezing fog conditions.
Cheers.

[GrandadMonkey]

Odd that. I can't see that they'd have shrunk but clearly they did need stretching to make proper contact.

Well done, nice to hear of a really cheap fix.