Misfire, fail MOT on emissions

lelouis

Hello,

My astra coupe has failed the MOT for the second time today and am in need of some advise.
It has failed on emissions, specifically the lambda reading on 1st and 2nd fast idle.

After failing the MOT the first time I discovered the exhaust manifold had a big crack in it so replaced it thinking that would be the problem, I also had a EGR blanking plate on so put the EGR valve back on, cleaned the throttle body, put some redex in it and gave it a good warm up.

During the second MOT which It failed again (worse emissions than the first time) the mechanic noticed I have a small misfire. I have changed the spark plugs, tried another coil pack and put the egr blanking plate back in but still have the misfire.

My thinking (please tell me if I am wrong) is that the lambda sensor could need changing (but that is rather expensive) or the bad lambda readings could be caused by the misfire.

The first MOT readings were 1.063 fast idle test and 1.224 2nd fast idle test.
The second MOT readings were 1.064 fast idle test and 1.470 2nd fast idle test
I have no fault codes
The misfire is not really noticed unless you hold the revs
it is not lumpy on idle

This is my 3rd z22se engine and really hoping there is nothing seriously wrong with it (timing chain and little end have gone before). It is a re manufactured one with 20000 miles.

Any help would be much appreciated, Thanks, Louis

IDI_AMIN

I have 2 years running failed mot on emissions . To solve this problem an oil flush renew oil and air filter was all that i needed next year i will do this before the mot
This might work for you also(y)

evocarlos

have you replaced the cat ?
you can test the lambdas with opcom and see what they're reading

long run down the motorway in 4th to clear the crap out before the mot ?

lelouis

IDI AMIN said:
I have 2 years running failed mot on emissions . To solve this problem an oil flush renew oil and air filter was all that i needed next year i will do this before the mot
This might work for you also(y)

Forgot to mention that I have just changed the oil and filter.tried clearing out the air filter aswell! Thanks.

lelouis

evocarlos said:
have you replaced the cat ?
you can test the lambdas with opcom and see what they're reading

long run down the motorway in 4th to clear the crap out before the mot ?

evocarlos said:
have you replaced the cat ?
you can test the lambdas with opcom and see what they're reading

long run down the motorway in 4th to clear the crap out before the mot ?

Nope cat is as standard, has done 100k so could need changing? Ahh a friend has opcom so I will test the sensors before buying new ones. Also tried the italian tune before the last MOT :-) .thanks.

IDI_AMIN

Try some redex in the fuel and a good blast on the motorway before a test
mine has always passed with above mentioned methods . did you flush engine also. with mine i could see it quite smokey at exhaust and after oil change noticed less smoke

lelouis

IDI AMIN said:
Try some redex in the fuel and a good blast on the motorway before a test
mine has always passed with above mentioned methods . did you flush engine also. with mine i could see it quite smokey at exhaust and after oil change noticed less smoke

Given redex a go and put my foot downbefore MOT though I didnt flush the oil when I changed it, could this cause problems? Thanks

IDI_AMIN

Worth a try could be the missing ingredient , it has worked for me , could also be cheaper than changing cat or 02 sensors

evocarlos

redex is wank go to your local motor factor and ask for forte specialist injector cleaner 🙂

what are you co2's like ?
mine was off the scale when it failed on emissions ""no cat""

lelouis

The first picture was the first MOT and the other is the second MOT. The difference between the two is I changed the cracked manifold and replaced the EGR valve, fitted an oil catch tank, put some redex in and took it down the motorway and the emissions got worse. I have since found out that the EGR has thrown a P0404 fault up so I have put the EGR cheater back on. Also I have got new spark plugs as they were worn.
Looked at the OBD reader and the lambda sensor seemed to be running between 0.2 and 0.8 volts at 2000 revs which from what I have read suggests it is working ok.
The misfire (if it is a misfire) is like a small pop every 5 seconds.

lelouis

Still not fixed, arghhh. Someone said something about a temperature sensor, any ideas?
Thanks