Page 1 of Need to lower emissions on an L-Reg astra

Poor bugger failed its MOT, mainly on emissions (Tyre and a bulb need replacing, but that`s easy - and cheap). The engine has misfire, which the garage reckons is the cause of the high CO readings

The garage we took it to knows we`re on a budget, so they didn`t start tinkering with the engine as it`s done 125K and the high emissions could simply be a sign of a knackered engine, and didn`t want us to incur any further costs unnecessarily.

I`ve just hoiked out the spark plugs, there`s a brownish deposit on the points, which apparently is normal, however 2 of the threads had oil on them, but this might be deliberate to assist in putting the plugs in in the forst place.

The HT leads are the originals, but being Vauxhall, they`re the awkward ones with the metal spring-loaded contacts. There`s a breakers in the area that I should be also get a cheap replacement pair from.

Anything else I can check myself? We`ve got about 6 days before the MOT expires

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I`d do a DIY basic service on it oil & filter change, air filter, plugs, leads, distributor cap & rotor arm, then check the timing as if the ignition isn`t right you are exhausting unburned fuel.

A trick you can do is lean the mixture right out just before the test, to pass the test, once you have the certificate, richen it up again. Removing the airfilter may have the same result IIRC.



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This item was edited on Saturday, 3rd October 2009, 18:09

A good long run before the test is worthwhile too.....a good 10 miles at 70 mph to blow all the crap out.

why take life so seriously..its not like you are going to make it out alive

depending on the engine you have?

I had a 1.4l petrol OHC cnz there was a small vacuum connected to the elec ignition that effected combustion. I had a small tear in the rubber seal that sent my emitions up the chute might be worth checking if thats ok.

Plus Id defo change the air filter as that makes a huge difference with a clean one fitted.

Air filter deffo.
Timing deffo as if it`s misfiring there`s a high chance the timing is out.
(timing is reasonably easy if you have access to a strobe light and a wee bit of know how but also shouldn`t cost a fortune if you need to get it done by a garage or one of those tune-up services)

Thent he mixture. Again, reasonably easy to adjust with a bit of know how etc and something to show what the mixture is. I have a gas tester (cost £100 years ago from Halfords) which gives a reasonably decent indication of how the emissions are sitting but somewhere I also have a thing called a Colourtune which fits into one of the plug sockets with the plug lead attaching to it and the colour changes as per the mixture... bit like looking at a gas flame and trying to get it a nice pale blue. Again, quite cheap to buy.

Plug leads: don`t get them from the scrappy.
Don`t change one or two, change the set and buy them new. If you use older leads or replacements they could also have problems or shorts and cause more grief than they are worth.
Doesn`t sound like the leads are causing the misfires though and a way to check is to remove the plug, have it resting against an earth (the bottom of the plug where you said it was brown) and crank the engine. If it sparks it`s generally ok.

Clean the plugs with some emery paper, shouldn`t need to go nuts just a quick rub to take away the brown deposits and wipe the outsides. Plugs are also relatively cheap and come pre gapped these days so dependant on how much of the budget is available it also might be worth changing them.

If I think of anything else I`ll let ya know. If you need any specifics on the car lemme know engine size, year etc as I can get access to the Autodata program which is pretty darned good too.

Jimbo : oÞ

"Making Teenagers depressed is like shooting fish inna barrel"

Cleaning up the throttle air in take and the EGR valve (if fitted) with Carb cleaner makes a big difference to emissions too and only cost about a fiver to do.

The throttle buterflly is a forged metal piece that the air filter box hose will be connected to, it is usually then boltes on to the inlet manifold. The butterfly is the round metal spring loaded disk within.

The EGR valve is usually the same type of metal, located near the butterfly, looks like a flying saucer with a vaccum hose or 2 connected to it.

Take them both off the can and give them a through clean with carb cleaner, you can buy from local motor factors normally about £5.00 or so.

The butterfly usually has a small pin hole in it or a bypass hole around it, make sure both of these are clear.

It is also suprising how much of a difference a bottle of injector cleaner can do.

I would suggest giving it a good service, don`t use 2nd hand parts, put some injector cleaner in the petrol, about a double strength dose if have not used it before, it is normally 1 bottle per tank of fuel, so add 1 bottle to half a tank, leave the car ticking over for about half hour then taking it for a good belt up the motorway for at least half an hour.

No need to speed along, just use lower gears, eg using 4th instead of 5th at 60 MPH. We usually make a day of it and aim for somewhere to go, taking the Mrs shopping to Bristol or similar, give the car a good run there, a rest for a few hours while shopping, then another good run back again.

I did all of this to a freinds M reg Cavalier when it failed the emissions and it did the trick.

Don`t worry about grey `smoke` coming from the exhaust, if it is grey then it is most likely steam where the exhaust and cat are having a thorough warm up and drying out.

All the best

Gerald.



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Good luck on teh EGR Valve thing, had to get one for the missus Tacuma (General Motors), could only get manufacturer original, and that cost £240 + Vat, then fitting...

Also try a bottle of Redex or similar, and make sure engine is nice an warm when you take it in!



`i am going to live forever or die trying`

cheers for the advice guys. We actually had the car serviced about 6 months ago (new filters and plugs fitted, apparently). For it to deteriorate that rapidly is telling us it`s more than past it.

We do have another car (Rover 214), and as we were thinking of selling one of them after Christmas (when annie goes on mat` leave) We`re going to say farewell to the astra this weekend. Can`t really complain, only cost us £100 in the first place (used to belong to Annie`s aunt)

Cheers again. I`ve picked up a lot of tips

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An easy way to look for the cause of a misfire is to pop the bonnet in the dark while the engine`s running , doesn`t always work but sometimes you might see a blue spark around one of the plug leads or distributor cap etc showing where the misfire is.

If you see a spark then check it out the day later , unless you have access to a lit garage etc.

yep, tried that one. no sparky

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