Misfire at low RPM

[rowanxx]

Bought a Ford Ka about a month ago, little service history so decided to service it. Whilst replacing the spark plugs, I damaged the HT lead, so decided to replace all of them. Now, (wasn't present before), I have a misfire when accelerating hard, from low RPM. This only happens when there is a high load, not at high revs. Any ideas?

[Krikkit]

Coilpack. I had the same with a couple of packs for my 106, a subtle misfire at low RPM and wide throttle openings, cured immediately with a new coil.

[rowanxx]

Would this start straight after fitting new plugs/leads? It wasn't happening before....

[DocArbathnot]

Maybe a coincidence maybe faulty or incorrectly fitted parts. Did you keep the old stuff? Try refitting (one item at a time) and see if the fault is still there.

[rowanxx]

Might be the crap eurocarparts leads I bought, will replace once I get home!

[TameScrapman]

Try spraying inside the ends of the leads with some WD40. My money is on the coil pack though. IIRC it's up the back of the engine and a real PITA to change.

[Spangles]

rowanxx said:

Might be the crap eurocarparts leads I bought, will replace once I get home!

I would suspect that'll be your problem. They're cheap for a reason.

[Convert]

Make sure the ignition leads are separated properly, and that they aren't shorting out on any other wires.

[Rich1973]

Plug gaps OK?

[rowanxx]

Plugs are standard replacements, havent checked the gaps as i thought they came pre-gapped!

[kambites]

Check in the ECU to see which cylinder is misfiring, swap the leads and plugs around, then try again and see if the misfire follows the leads, the plugs, or the cylinder.

ETA: Obviously I don't mean just to swap the spark-plug end of the lead around, or you'll end up with a decidedly worse misfire.

[Sonic]

kambites said:

Check in the ECU to see which cylinder is misfiring, swap the leads and plugs around, then try again and see if the misfire follows the leads, the plugs, or the cylinder.

^^ This.

Will be the plug, lead or coilpack for that cylinder.

[DocArbathnot]

Another very easy check. Open the bonnet at night in a low light area. Watch for the "blue sparks" of stray electrickery.

[rowanxx]

Diagnosed! (Not solved) Spark plug 4 isn' firing at all, no output from the distributer.... Off to the scrappy to save me £60.

[Rickyy]

Don't these use coil packs?

http://www.directcarparts.co.uk/product/1556/tc05/...

[rowanxx]

Yeah they do, just got mixed up :P