Engine help needed please!

[PicklesSE8]

Hi all, my Nova is a 1993 K reg 1.2 Merit+ 3dr and I'm having a bit of engine trouble. I've only just bought it and noticed the heater wasn't working so replaced the thermostat. Now the heater's fine but it won't go through an emissions test. Also the EML light comes on now and then, the fault code is for the oxygen sensor. But although it is injected and has a cat, there is no oxygen sensor, just a loose wire where it should be and nowhere in the manifold to put one! The engine code on the block is 12ST which having read some old threads, i thought was carbed :confused: I'm wondering if I can fit a manifold from a C12NZ Corsa which will have an oxygen sensor?

[Rage]

if you have the engine management light up and it's injected with a cat then it should have a lambda/oxygen sensor so if there is nowhere to put the sensor before the cat then you have the wrong exhaust manifold or downpipe and due to you not having a sensor with a cat you may find that it still won't go through the emissions test due to your cat being destroyed because the sensor has not been controlling the fueling to protect the cat. putting a corsa manifold on with the hole for the lambda sensor will work so long as it fits you engine (that i can't say as i don't know) then you may need the engine management light turned out and the fault cleared to allow the lambda sensor to do it's job.

hope this helps

[marc69]

If it's a 1.2 ST I would see about going back to carb. If you don't mind a choke you are looking at an immediate increase from 45 to 55 bhp. Whilst it doesn't make it a Subaru, it does make it a better drive.

Just a thought?

Otherwise, look out for a Nova 1.2i manifold, will probably have a sensor in it but, I don't know how the ecu etc wll adapt for a different block?

[PicklesSE8]

Thanks for your advice, not sure if going back to carbs is an option though as due to the age of it (January 1993) it needs to go through a cat test for MOT. I bought a new downpipe today but still doesn't have anywhere for a sensor to go, I've found a Corsa manifold with lambda sensor so thinking I might have to give this a go. Good point on the cat being destroyed due to overfueling, I guess that will be the next thing to look at once this problem is sorted. Everyone at work is saying get rid of it before I spend a fortune on it, never that simple though! :)

[Rage]

hold on i'll check the mot regs for you

[marc69]

I may be wong...but think it depends on age of engine, an ST was non cat I think? An mot tester will know for certain.

Where are you based? I broke my 1.2i in the summer and have all the running gear including manifold and engine, but postage would be extortionate if your nowhere near the frozen north(aberdeen).

[Rage]

If you can prove the engine is older than 31st july 1992 then it will be able to be tested as a pre-cat engine. as for the emissions with a carb so long as the carb is good and setup right emissions shouldn't be a problem. the problem you have with the emissions at the minute is the lambda reading everything after 31st july 1992 has a 'BET' emissions test that includes lambda reading. have you had a print out shown to you of the emissions test as this should be available to you. i would guess that getting the lambda put back into the system would sort your test problems as it would then have the ecu reading what the exhaust is like and adjusting the fueling. the cat is only in the exhaust as an extra way of dealing with cleaning the exhaust gasses it's not always the reason a car fails the mot on emissions but it can be damaged by excessive heat, overfuelling, under fuelling etc this is usually a fault with the engine. the cat can only clean so much of the exhaust gasses so if there is no lambda readings and the engine is overfuelling then your HC reading will be high and this could cause damage to your cat. the high HC reading won't be the fault of your cat though so don't get lead to believe that a new cat will always drop your emissions into spec.

[PicklesSE8]

Interesting, I'll give them a call tomorrow, not sure how I can prove that its an older engine though! Been reading through a few old threads on here, one said that the engine can only be tested if its listed on the MOT computer, the 12ST isn't listed so they were testing it as a C12NZ. Can't remember what the rest of the emissions readings were, I've got the printout from the last test and there's no mention of lambda or a cat test, just CO and HC. Thanks again both of you for your help, will update tomorrow

[jimbob-mcgrew]

this sounds dodgy to me. sounds like the engine is half and half carb and spi.
how could he tell ? rectangle shaped inlets and and blanked mechanical fuel pump on the head ? i wonder if its a complete carb engine ?

when you bought the new downpipe, did they source the part by car reg ? or did you ask for an SPI version

an N rated ecu wouldnt fuel so well, paired with an S rated block would it guys ?

are you in deptford pickles (SE8) ?

[mowgli]

my money is on a 12st bottom end & c12nz top end.

the manifold for a c12nz should have a lambda hole. fitting one should clean up the emissions too.

[Rage]

shouldn't matter wheather the engine is listed it's done by date of first use then it selects the tolerance of the emissions that need to be read from the car. hence why i say try to prove the engine is older then you get the slacker emissions test. if you have the print out can you scan it onto here i'll take a look and see if there is anything i can help with as i'm damn near completed the mot course so it'll give me good pratice and you up to date info aswell

[PicklesSE8]

Right, think I might be getting somewhere, Rage you're quite right about saying it's done on the date of first use of the engine, but apparently I don't even need to prove that the engine is older, if I write a letter to the testing station telling them that the engine is a 12ST from an earlier car, they have to basically take my word for it and test it as such, as you say the test will be more lenient for an older engine. So getting it retested tomorrow and hopefully it'll go through ok!

[PicklesSE8]

OK, quick update, got it retested today using the more lenient test and it went straight through :) So just need to get a couple of other bits done and it'll be back on the road, thanks for your help people!

[Rage]

no problem mate glad to help. good to hear it went through

[jimbob-mcgrew]

cool, an mot'd rustbucket lives for another year :)

now that thats all out the way, when youve got time, id look into the engine specs if i were you. (if your bothered obviously, leave it otherwise)
but if its running an spi head, you could get 10 horse power by converting the top end to carb