Misfire/hunting on part throttle?

[Moog]

Hi,

My 2001 Xsara Picasso 1.6 petrol has been misfiring/hunting/jerking under part throttle. Under full throttle it seems fine and idles smoothlNo DTC codes on my basic OBD scanner.

I replaced the coil pack (with a Delphi brand)which improved it a little, but the problem persists. Exhaust looks a bit sooty too. It's due a service (had new plugs last year though). Anything obvious I'm missing?

Funds are tight so I'm just trying to focus my search. Hoping it's not a failed injector... Could it be a clogged injector and if so, is there any tank additive that might help that? I use Redex occasionally but that doesn't seem to help.

Many thanks!

[GiveMeABreak]

Basic OBD scanners often can't read all the fault codes like manufacturer-specific codes, but how many KMs has the vehicle done?

Without a proper diagnostic it will be hard to pin down and will be guesswork.. It may be an injector or could be a fuel-related issue - so hard to say without further info. When was the fuel filter last changed?

[Moog]

Hi,

Car has done 113k miles. Fuel filter changed 12 months ago, along with spark plugs. I change everything each annual service.

One thing that may be relevant - the MOT emissions are very low - especially HC PPM as it's in single figures out of a maximum of 200ppm. Always wondered if it's running too lean?

I was thinking of investing in one of the Bluetooth OBD scanners that links to a phone app and gives live data - saw one on Chops Garage. Or do old Citroens like mine need something more specific?

Many thanks.

[Rp0thejester]

My first thought was EGR issue if fitted to your vehicle which would be unlikely at the age and being petrol. And that would make the emissions worse. My next thought is air issue, there could be a leak in the air system hence the up/down to much fuel, not enough fuel etc