Hello all,
I have owned a 2002 '52' Omega 2.2 Petrol Z22XE CDX Saloon now for 4 years, from 63,000 miles to its current 105,000 and for the most part it has served me very well. I service it regularly myself and for the bigger jobs (bushes, wishbones, timing belts (because the latter scares me), full new exhaust and cat) I put to a reliable local garage.
Before that, I owned 4 Carltons (H - L reg) and knew them like the back of my hand, including the famous gauze under the rocker cover clogging up issue and also the idle valves. But I digress.
I have read great help articles from OOF previously (thank you everyone!) which has helped me out with my Omega in the past, especially with the oil in spark plug wells and water dripping through the bottom windscreen rubber, through the scuttle and into the oil wells. Great design Vauxhall! Winner!
Anyway, joking aside and getting to the issue, over the past 2 or 3 months, my Omega has been getting grumpy, then even more grumpy in that it runs reasonably well for the first mile or so from cold, then really starts to run rough from there on, until I let the engine go cold again.
So in my mind, it is temperature (air / fuel mixture - or clogging up - or faulty sensor that should kick in at a point in temperature?) related. Maybe.
If I rev the engine at a steady pace up to lets say 2-3000 revs whilst the car is at a standstill, it seems relatively happy, but running under load (driving) it runs a bit rough. If I let it idle (it should idle around 700) it bobbles around 200 to 600 rpm and chugs and splutters.
I have had a good rummage around the forums and on the net in general and it seems to be a common (but perhaps many causes of) issue / symptoms.
Here is what I have done already:
Cleared oil and water out of spark plug wells.
Sealed windscreen.
Replaced rocker cover gasket and gasket sealant sealed it 2 months ago. Checked wells this morning, still bone dry (yay!). Scuttle foam still bone dry. (Yay!)
Replaced spark plugs with new plugs.
Replaced throttle body (together with new gasket) with one bought "working" from ebay - yesterday - hoping it would resolve the issue. But sadly no.
Bought MAF sensor on ebay at same time as buying a throttle body but it is now going back as it has 5 pins, not 4 pins, so MAF sensor still as suspect (I suppose as is throttle body I got - but I've gotta be very unlucky here right?).
Cleared oily gunk out of the throttle body fat pipe and thin pipe (thin pipe was especially very blocked with hardened oil gunk).
I think the small pipe is the "vaccuum pipe" - question - are you able to blow into the pipe in the throttle body that this small hose connects into - is it naturally resistant or is it "blocked" inside the throttle body? (As both my throttle bodies I cannot blow through the pipe.
When connecting my computer to the ECU, the accelerator pedal readings respond as I would (assumedly) expect in the numbers change when I press the accelerator pedal.
I do not know where the coolant temp sensor is on my engine so unable to check this at the moment. Does anyone know where it is on a Z22XE?
I have connected my computer to the ECU and (after resetting any old fault codes 2 months ago, these fault codes have been seen since then ...
2 MONTHS AGO RESET CODES ... SINCE THEN ...
P1555 - Throttle Position Sensor (TPS) Load Signal not Plausible with Engine Load
(00) - Not present
P0170 - Lean Exhaust
(02) - Not present
CLEARED FAULT CODES 2 DAYS AGO - THE NEXT CODES ARE FROM 2 DAYS RUNNING
P0303 - Cylinder 3 Misfire Detected
(01) - Not present
P0302 - Cylinder 2 Misfire Detected
(01) - Not present
P0420 - <Unknown DTC>
(00) - Present
P1525 - Limp Home Position Error
(00) - Not present
P1550 - Electronic Throttle Control Engine Stop
(08) - Not present
P1526 - Throttle Position Adaption Error
(04) - Not present
CLEARED FAULT CODES, THEN FIRED ENGINE UP AGAIN TODAY TO RUN ON IDLE FOR 2 MINUTES:
P0303 - Cylinder 3 Misfire Detected
(02) - Not present
So, there you have it, I think I've given some healthy detail there and have tried many things, but the car still runs rough. I am determined to get to the bottom of it, especially after spending £1000 in the past year on it including bushes, springs, timing belt and full new exhaust and a promise to the missus that all it needs is a little poke to get it going again. I just need to know where to poke it as this has me stumped.
Any help greatly appreciated. I live in Wigan, Lancashire by the way
Oh, and as an aside, as I cant seem to find any anywhere. Does anyone know where I may buy spark plug silicon covers from? Part code 1 220 703 018 ( 1220703018 ) as mine are pretty shot and perhaps this could be the issue arching to the body? Not sure, but there are burn marks on at least one of them where it has been happening in the past. 
