Car Failed Mot

[ablister 31]

Just put my cat through the mot yesterday and failed on emissions

 

It came out at 8%, where it should be about 3% i think.

 

What can cause it, the guy said it might be needing a service, plugs, filter, or a new sensor etc but it smokes alot so i'm guessing it's valve stem oil seals or worse piston rings.

 

How can i tell what it is and how easy will it be to put right, i have a week to get it sorted.

 

Any help is appreciated

 

ali

[woodsy 0]

if it was me i would give it a bit of service (oil change,plugs and air filter) and clean breathers out.Then adjust mixture on airflowmeter if tester will allow that when he does it again

[ablister 31]

in what way do i adjust the air flow meter?

 

ie what way should i turn the screw?

[AndyR 0]

It smokes alot? Does your car use alot of oil? Towards the end my 1.6 used to burn about a litre a week!

 

It badly needed stem seals doing and the piston rings were probably knackered too.

 

You could see if the engine is running rich by looking at the spark plugs. If they are black its likely the engine is too rich and running sooty..making plugs black.

 

Then you would adjust the AFM with the hex (allen) bolt. I cant remember which way is lean out. If you do a search it may turn up.

 

Other than previously suggested you might have to have a head rebuild or new rings.

 

But then youd have a nice healthy engine again with good compression.

[pug_ham 242 3 Cars]

Try giving the whole of the intake system & breather pipes a good clean out with carb cleaner, including a good scrub inside the AFM & throttle body before you go adjusting it randomly but iirc the Haynes manual does tell you what direction to turn the screw for adjusting mixture.

 

When was it last fully serviced with a new air filter etc as well though as an old clogged air filter can cause the emissions to rise quite a bit.

 

(You could also pull the breather pipe that goes to the inlet system from the oil filler cap off if needed to lower the emissions a bit. )

 

Graham.

[christopher 5 1 Cars]

Try giving the whole of the intake system & breather pipes a good clean out with carb cleaner, including a good scrub inside the AFM & throttle body before you go adjusting it randomly but iirc the Haynes manual does tell you what direction to turn the screw for adjusting mixture.

 

You turn it out to make it leaner

 

if you have new plugs, dizzy & rotor, oil and you turn the AFM out as much as you can...and no joy then you either need a new one AFM or repair it maybe...

Edited August 14, 2004 by christopher

[Ahl 4]

I didn't think MI16's had a lean screw on the AFM?

[christopher 5 1 Cars]

I didn't think MI16's had a lean screw on the AFM?

 

 

daaam i forget most you boys are on Mi's.....right Ahl

[Alastairh 47]

Do a compression test, that should tell you the truth about your piston rings.

[mi16nut 0]

To be honest, you're better off taking it somewhere with diagnostics.

 

Mine failed last year on 3.56% CO2 (pass is 3.5%). I took it to my usual rolling road where he tweaked it properly & ensured fuelling was correct at high revs also.

 

Cost: £20 including power run, so well worth it. You wouldn't want to ruin the engine by running it too lean.

[christopher 5 1 Cars]

Do a compression test, that should tell you the truth about your piston rings.

 

I have had a light skim...will a compression test tell me the true compression ratio?

Edited August 14, 2004 by christopher

[pug_ham 242 3 Cars]

I have had a light skim...will a compression test tell me the true compression ratio?

Not straight away, I think you need some formula to calculate it from you bore & stroke & psi etc compared to a standard healthy engine but I'm not sure.

 

Graham.

[eddie_1.9 1]

mi16nut or anyone else where did u get it tuned? any ideas where i can get mine rolling road tuned near guildford or within a 30 mile radius? i had my mixture tweaked at the MOT to get to pass too it was 3.58 but now 2.5. But i am a bit worried about it running too lean. for £20 i'd get it setup if i knew where to go.

cheers guys.

[Rob_the_Sparky 9]

mi16nut or anyone else where did u get it tuned? any ideas where i can get mine rolling road tuned near guildford or within a 30 mile radius? i had my mixture tweaked at the MOT to get to pass too it was 3.58 but now 2.5. But i am a bit worried about it running too lean. for £20 i'd get it setup if i knew where to go.

cheers guys.

on a 1.9 8v the adjustment is for tickover only and should be 1 to 1.5% for a healthy 1.9. You are not going to damage anything by runing lean (even if you were) as it is only tick-over mixture that is adjusted.

 

Rob

[Guest birdii]

You cannot adjust the mixture on a CAT car, believe me, i have tried.

 

The ecu is running closed loop, so the lambda sensor will feed back to the ECU when the mixture is tweaked and then alter the fuel back to how it was.

 

It might be worth trying a new lambda probe, doesn't cost much from gsf, 4 wire citroen universal probe, about £30.

 

Other possible cause is a failing CAT, expensive!

 

Of course if you have oil burning problems then that can cause both mentioned items to fail!

Edited August 16, 2004 by birdii

[Minsc 0]

I have the same problem in my gti 1.9 cat, the CO emissions are about 8%, but my car hasn't cat because I taked out. In my car the mixture is not adjustable, I'm sure that the problem is the lambda probe or the airflowmeter. What AFM could I use in my 205? From what cars? Maybe 405 1.9, BX GTI?

[pugpete1108 62 1 Cars]

my hc levels were sky high on my last mot but the tester is a top bloke who elt it through anywy turns out it was a leak in the manfiold that did it