Mk3 Cavalier Owners Club | Vauxhall Cavalier Dot Com

Ok, another MOT another bodge pass for the emissions. High Lambda and CO at 3k revs, HC ok at 3k revs. I'm thinking next step is go for an original lambda sensor, but cheaper option first would be blank off EGR valve. Trouble is I don't have an emissions tester I can plug in and work away at the car trying different things without paying a garage and a mechanic to do it.

Wow gas testers have gone expensive...
Well not really - I bought a Gunsons Gas Tester 2 professional in about 1990 for £80.

Just looking now, the cheapest I can find start at £99 for a standard model.

There are a few used Gas-Tester 2s for sale on ebay... currently about £50 each.

Robsey wrote:Wow gas testers have gone expensive...
Well not really - I bought a Gunsons Gas Tester 2 professional in about 1990 for £80.

Just looking now, the cheapest I can find start at £99 for a standard model.

There are a few used Gas-Tester 2s for sale on ebay... currently about £50 each.

I was thinking along the lines of getting one of those, would be interesting for tuning purposes as well with my collection of cars!

Only thing is it looks like the Gunson ones, and ones around 100 quid mark only check for CO, need one that does lambda and HC as well. Think that would be one of those around the £1K mark, or at the very least 5-600 min.

I suspect you are correct.

The sub-£150 units will do CO, RPM, Dwell angle and Voltage.

That is what the Gastester 2 Pro does.
Quite nifty 20 -odd years ago.
But not enough by modern standards.

Just a thought, because I'm having similar problems... could it be due to a naff fuel pressure regulator? If the springs become weak, wouldn't is allow too much fuel to be burnt for the volume of air it's taking in, leading to incomplete combustion and increased CO readings? I had that particular flash yesterday, I'm going to have a look-see at the vac line to it to start with, and see if it has any effect. But maybe replacing the whole thing might yield better results, if they're not too expensive?

Apologies if it brings back bad memories but my 8v 2.0 Cavalier is having emission problems.

Did you ever resolve it?

Any thoughts would be great fully received.

Regards,

Dave

I had an emission high comment with my 8 valver a few years ago and discovered an adjustment screw.
On the airflow meter was a blue plug inserted into the electrical part of the unit, near the connector, if it's encouraged out beneath can be found a screw adjuster, can't remember which way did what but adjustment is possible.

Alan

Thanks Alan, l will go hunting.
My car has only covered 47000 miles and is regularly serviced. On a careful run down to the south of France it turned in 45+ mpg.It was heavily loaded as well. I associate poor emissions with poor fuel consumption. I must be wrong.

My fuel consumption has always been good it was just that it showed up on the idle test - still in spec but notably higher than previous.
I wondered if the air flow meter was a bit 'gummy' down that end of its working range?

Alan

The early pre-cat air flow meters were adjustable. Later meters are sealed with resin to prevent inexperienced tampering.

It is possible that it is either the air flow meter or the fuel pressure regulator.

I replaced both of mine about a week ago.
The fuel consumption didn't appear to change, but the emissions must have improved, as the car did not fail it's MOT due to emissions.

Beware though... if you are talking an 8 valve 2 litre engine, then the fuel pressure regulator is about £80.

And air flow meters are anywhere between £130 and £350 depending who you buy from.
Avoid genuine parts search and any German ebay sellers. They all charge silly money.

I seem to remember a post where an air flow meter was taken apart for cleaning and/or repositioning of the carbon wiper on its track?.
Mine didn't fail the idle emissions test but I did notice from the figures it was higher than previous tests.
Not much can be done to the pressure regulator I guess!

Alan

Not really, no.
It is a sealed unit with a spring and diaphragm mechanism inside.

Usual culpret is a weak spring.

If the emissions are still within spec, then do not fuss too much - unless of course it is just below max permissible value.

The problem with these cars is that you can become almost paranoid about stuff.

I am one of the most guilty of that trait.
And it has cost me a lot of un-necessary worry, work and expense.

There are two "new old stock" AFMs on ebay for about £70 plus postage.

They look like they have been used for test purposes.

I got mine from the same place, and internally it was spotless.

I used "vauxhall 90272153" for my search on ebay.

As regards my own emissions, I will let you know when I get the car back.

Are those Genuine GM? I would imagine that they would be as most of these types of parts aren't usually replicated.

Yes original Bosch parts.

As said, mine was externally a bit mucky from storage, but internally it was spotless.
Even had paper wadding in the orifaces to keep any muck out.

Nice friendly seller.
Not the fastest but amazingly well packed.

You can get intermotor parts, but I don't trust them as much. And they are as dear as original bosch parts.
I used to find intermotor ignition amplifiers on my mk2 cavalier did not last as long as original parts, so that dis-trust still lingers at the back of my mind some 25 years later.

Well it appears that the emissions is going to continue to tease us with that ever elusive cure.
Even with all new parts my car is still mis-behaving.
The CO is far too high - over rich mixture.
The HC was quite normal so no valve gear concerns.
So further investigation is required.
Refer to my WIP

I was really hoping that I had found the solution - pah.

I've now fitted a genuine exhaust sensor and gave plugs and dizzy cap a clean. I also double checked for air leaks. I suppose i could also count exhaust fix a couple of weeks ago, as back box was patchy and the clamp was too big, and it wasn't secure. meaning it swung about and was leaking.

Dizzy cap looked past it, so have ordered a new bosch one 50 bucks cheapest i could find, will get new rotor, and am goint to flush and change oil as it's black. Goin to do cts as well while im there.

I will also get it on ramp and check for any exhaust leaks however small.

Currently seems to be running better, but i need to get emission check soon to see if it makes and difference. I also replaced the little idle solenoid last year, which seemed to improve things too and at same time new gm leads.

The oil is changed and have checked for exhaust leaks, I thought I might have heard an ever so slight leak somewhere but I couldn't find anything, and it was probably just my imagination.

Just thinking about rotor arm and dizzy. I don't think they have ever been changed since I got car in 2008, and probably never changed before that as it only had 55k on it when I got it.

Will also be getting a new air filter as it is manky.

Defo seems to be running better, even a bit more so after the oil change and wee service.

Time to finally blank off egr i think, been meaning to do it for years! I'll make up a plate myself, drill two holes in it and seal with blank gunk. I think it still plays havoc with tickover and so many report better running with it blanked. Makes me wonder why it was ever fitted, i think to comply with emission laws or something. Also got new air intake pipe winging its way to me.

Correct EGR valves were fitted to allow manufacturers to meet ever tightening emissions levels at the manufacturing stage.

The C18NZ was also Vauxhall's so called economy engine, although to be honest the older C20NE has very similar emissions output levels and mpg figures but with 25 more bhp.

Another Vauxhall EPIC fail.

Hopefully blanking the EGR port and the new hose will finally sort it for you.

Robsey wrote:Correct EGR valves were fitted to allow manufacturers to meet ever tightening emissions levels at the manufacturing stage.

The C18NZ was also Vauxhall's so called economy engine, although to be honest the older C20NE has very similar emissions output levels and mpg figures but with 25 more bhp.

Another Vauxhall EPIC fail.

Hopefully blanking the EGR port and the new hose will finally sort it for you.

Hopefully it should. On subject of mpg, i once got 59.9, whisker off 60 mpg on a run down south in my old pre-cat 2.0, you are right the c18nz is an epic fail for emissions and mpg. I reckon i get about 45-50 mpg on a motorway run, about 35 in town, it should be better than a 2.0 but isnt, and performance is markedly less.

Something i was wondering about was the drain hole in the back box, i've had gen back boxes with and without this so im thinking maybe the one with drain is for pre-cat model. The reason i say this is because i read an emissions bible thing and it said any leaks in exhaust will introduce air into exhaust and cause high lambda. This is what i had at idle.

This would make sense as i think lambda is more readable at idle and is less noticed at higher revs.

Recommendation was to block this drain with a small screw or bolt when goin for test. My old back box had this drain and the new one does. Both my last back boxes didn't have the drain so i drilled a small hole in it thinking it is a good idea to let water drain out, not realising of course!

I've also done it to the 3 Boxes on my omega, all post cat though.
, so need to bung them at mot time.

That is a new one on me...
Exhaust boxes with holes in ?
(Apart from inlet and outlet stubs of course - ha ha).

None of the exhausts on any of my cars had drain holes in them.
At least I don't think so.
Only when they were blowing, which I thought was an MOT fail.

Hmm and surely that only affects back pressure and to a small degree timing (cacuum advance).
As for mixture, I would have said any induction leak after the air flow meter upto wherever the lambda probe is located.

I have had a car with a purposed hole in the silencer box to disperse condensate but I seem to remember the first place it started to corrode was from the hole!
Not really sure if it's a good idea.

59.9mpg, that's brilliant! Best I have achieved was 54.

Alan