Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: Markie on 08 September 2007, 13:21:00

Title: "Misfire" only when engine heats up! Why?
Post by: Markie on 08 September 2007, 13:21:00: Yep this misfire again.

Plugs new
rockers fine - no oil and done with gnuine parts recently
new dispack
new leads
both multi rams kicking in at appropriate range.
breathers and iacv spotless

Car unlike before now idles fairly okay. Starting sometimes requires a turn or two with an occasional pop noise from under bonnet...

Car then drives fine - 2 mile run to the tip was fine but i get impression its lacking power.
2 mile trip back sees car with less power, very heistant and lurching in all gears when pushing it. By this time engine temperatur at norm. No verheating issues.

Got to last turn at the house and gently increased my speed in second gear at low down revs and got that pop noise again from under bonnet.

Cricket? well im stumped now :-/
Title: Re: "Misfire" only when engine heats up! Why?
Post by: CaptainZok on 08 September 2007, 13:28:04: Dodgy temp sensor confusing ECU with wrong engine temp data, leading to overfuelling.
Dunno really just a guess. I'm sure the all knowing ones will be here soon enough.
Title: Re: "Misfire" only when engine heats up! Why?
Post by: Paul M on 08 September 2007, 13:59:30: Definitely sounds like a sensor problem, as the ECU will be in open loop mode when cold due to the lambda sensors not producing a usable reading when cold. Might actually be the lamda sensor(s) themselves, no guarantees of a fault code. I assume you've checked the codes and found none.
Title: Re: "Misfire" only when engine heats up! Why?
Post by: Markie on 08 September 2007, 14:06:50: im confused by this one.....been back out to the beer shop and its shuddering and juddering - clearly a low down rev issue again i wonder if twhen it was run with misfire before that it may have damaged cats etc....

no fault codes by the way - nver has been :-/
Title: Re: "Misfire" only when engine heats up! Why?
Post by: CaptainZok on 08 September 2007, 14:13:03: Its not blowing through the SAI rubbers is it? Mine did when the cats were blocked.
Title: Re: "Misfire" only when engine heats up! Why?
Post by: Markie on 08 September 2007, 14:22:03: Quote
Its not blowing through the SAI rubbers is it? Mine did when the cats were blocked.

nope - all fine there too..and consumption and idle is fine, no fuel smells either,

Intrestingly when i went out along a favoured section of road it was doing its normal acceleration by the time i got to the end....just feels sluggish and it kangerood through all gears and every rev..
Title: Re: "Misfire" only when engine heats up! Why?
Post by: CaptainZok on 08 September 2007, 14:26:25: If your thinking maybe cats blocked try disconnecting the SAI rubbers, then try a quick run.
It will vent the back pressure in the case of cat/exhaust blockage and shouldn't feel as sluggish just a bit noisy.
Title: Re: "Misfire" only when engine heats up! Why?
Post by: JasonH on 08 September 2007, 14:29:55: Perhaps a blocked exhaust. One of my centre boxes clogged up and just knocked the power right down with no other symptoms.