Hello again,
This is doing my head in.
Many weeks have passed and I am still no nearer to solving this emissions problem on the 1998 Omega 3.0 Elite saloon.
Here are the MOT test results (video):
https://youtu.be/2Zhv0ReIUDQHere is the summary of what we have done over this period and to date.
Car arrived for repair with engine in poor condition having overheated, head gaskets gone, engine block u/s due to rust in bores having been standing for months with water in the bores.
Good replacement block selected, bores measured etc and honed. Cylinder head mating faces lightly skimmed. Cylinder heads refurbished and skimmed. Engine rebuilt, using new piston rings on good used standard pistons. New big ends shells and main bearings, on good standard crankshaft.
Engine built up with great care using new parts where needed. Graphogen paste used when assembling pistons, cams etc.
Fuel injectors refurbished by Bosch specialist.
Problem: passed MOT on 3rd November 2022, including emissions, although tester remarked that engine seemed a bit smoky (possibly due to Graphogen being burned away?) CO at idle 0.07 pass is 0.50, at fast idle .03 pass is 0.30
Needed welding so time passed waiting for this to be done, so during December and January the car was parked outside in the wet and cold. After the welding was done we took it for MOT on 7th March 2023. It was all OK except for the emissions, with engine showing 8% CO at idle and fast idle.
After some headscratching, decided to replace both cats and lambda sensors with new. Also a new idle valve. Checked all vacuum pipes and potential air leaks. Nothing found.
Took for MOT again 31st March. Still failed on emissions. (!!!)
CO at idle 0.95, at fast idle 8.87
HC at fast idle 425, pass is 200
Further work carried out:
New temp sensor 1.
Checked air intake temperature and air mass sensor by replacing with known good ones.
Checked compressions. Two cylinders found down a bit possibly due to sticky rings, poured small amount of ATF into bores to free up, this restored compressions to normal
Checked spark plugs and combustion with Gunsons Colortune , appeared good (blue flame)
Took down to MOT tester (PT Autos) for informal check on the gas analyser. Still no change in excessive emissions.
Checked fuel pressure. Gauge still attached to fuel line by fuel tank.
Decided to try a different engine management ECU, so swapped it for another but only had a 2.5 one. No obvious difference in engine running.
Decided to buy a proper MOT spec gas analyser (Tecalamit) so that I could do my own emissions checks. Seems to show readings although it cannot be used properly as it needs a subscription for calibration and the fully functioning software (calibration ran out in 2021). Checked readings on other vehicles where CO is known from previous MOTs etc. and it seems to be in the right range For the Omega it shows CO as around 6% at fast idle.
At the moment I am stumped.
Here are videos just done showing engine readings on Snap-on Ethos and Tech 2 (engine warmed up)
I note that the engine air intake temperatures seem a bit high at the end of my testing, eg 30 or 40 degrees, is this normal? Maybe because engine bay is hot? Ambient temperature today is about 17 degrees C. See
https://youtu.be/ujypQ0lDMAM https://youtu.be/yt6Bs451xnUhttps://youtu.be/LN1AvCNbRtIHere is a video of the engine bay:
https://youtu.be/Owk_leL0E14If anybody on here has a lightbulb moment I would really appreciate the advice, as the car cannot be returned to the customer with no MOT!
(Apologies for not acknowledging last couple of posts, I had not logged back on here for a bit)