Toledo V5. Loss of power when cold and misfire

[armitagemark]

I have '99 V5 (150bhp) with 73K on clock. I've had a number of problems recently with intermitent fast idle, which was fixed by new temp sensor. Now I have an intermitent cold start problem. The engine always starts first kick, and idles fine but when you you drive off, it's very low on power and the motor will misfire badly - pops and bangs. After a few hundred yards it'll clear itself and drive normally. It does feel a little down on power though. Feels like its lost it edge. Incidentally this only happens when engine under load. It revs cleanly on cold start when parked.

It's been to SEAT and they've run the usual diagnostics and given it a "software upgrade". Also, fuel econ is down a bit. SEAT have compression tested so they say head gasket is OK. Recent oil change didn't show any water in oil.

Any ideas?

[towcestervag]

early v5s suffered from cam chains wearing
does it sound rattly at back of engine (gearbox end)
this will cause loss of power the missfire could be down to plug leads

[armitagemark]

Thanks TOWCESTERVAG, however no rattle evident from engine. If it were the plug leads would the low power and misfire clear after a few hundred yards/mins?

[towcestervag]

depends the v5 and v6 engines suffered from either leads/coils and individual coil packs
good news about no rattle at back of engine as this is a big job
as your car got individual coils? or has it got coil pack
if its got a coil pack look for arcing between coil posts/leads and whrer leads go to plugs

[motechmike]

If its the 150hp car then there on plug's! Change them over and new leads should run like new.. ! Make sure you use o.e ones tho.

Mike

[armitagemark]

If its the 150hp car then there on plug's! Change them over and new leads should run like new.. ! Make sure you use o.e ones tho.

Mike

OK Mike and Towcestervag - i'll see if that does the trick.....! Thanks for help thus far. I may be back....!!

[hnh5]

MAF sensor i would say. Sounds exactly like my first V5 and a new MAF sensor cured the problem straight away. Mine used to start fine and tick over/rev fine too, but i had real problems pulling away at a main road junction about 20 yards down the road after starting it - it would miss and hick badly then after a few moments would pick up normally. It also had issues at high revs if i was having a bit of fun in it, the only way i can describe it is it felt restricted somehow and wasn't pulling like it should.