MOT fail emissions

syncroparge · Posted: Fri Jul 31, 2009 5:06 pm Post subject: MOT fail emissions

Posted earlier VSS engine cutting out hunting sort of got this ok by adjusting icv (2.2 my 93 Legacy t25 syncro caravelle ex 2.1 mv)great pulled well. All ok until MOT failed on CO max 3.5 actual 9.97 FAIL HC max1200 ppm actual 458 ppm PASS. I can get the co reading down by turning the icv but then it cuts out on no 1 cylinder and runs really lumpy. I am getting fault codes 24 icv and 49 air flow sensor. I've swaped afm for know good one but makes no difference still get afm fault code. Where next swap icv any ideas tested icv all readings good.Been to see a local subaru man in town said check timing its spot on. cheers...Brian p.s. it goes really well got from Devon to Leicester 210 miles in 3.5 hours with a caravan on the back. help

ElusiveStranger · Posted: Fri Jul 31, 2009 7:39 pm Post subject: Re: MOT fail emissions

syncroparge · Posted: Sat Aug 01, 2009 5:12 am Post subject:

Yes run a lambda. Richards harness I'am totally stumped going to try a icv today I cant get my head round this ,emissions high on tickover, when I move the icv round clockwise revs rise emisions drop but after a couple of seconds no1 cylinder cuts out if I move icv further no2 starts missing as well. Tested coil all ok plugs are new and gapped 1mm leads test ok.Just rembered whilst away when going up steep hills and engine labouring or in top gear at say 40mph if I put throttle down to the floor engine starts to stutter like its over fueling if I back off a bit it pulls alright and accelerates as normal.Thanks...Brian

rjes · Posted: Sun Aug 02, 2009 2:09 am Post subject:

I'd say you need to check the lambda sensor output first of all. See lambdasensor.co.uk for how. A rich mixture suggests a failed lambda sensor or possibly too much fuel pressure, etc. A lean mixture suggests something like a partially blocked injector, etc. Some ECU's can give an IACV error code when they are missing a speed signal, despite there being nothing wrong with the valve. I have no feedback yet about this with your ECU though.

Then I'd check the MAF output to make sure it rises and falls smoothly with rpm. Idealy you need an oscilloscope to do this, but an analogue multimeter or a fast sampling digital one may do. A fairly big induction leak could probably give a MAF error code when the sensor is OK, but I am not aware of any other causes of MAF error codes other than the obvious dodgy sensor or bad connection.

Adjusting the IACV is not a good idea unless you know it's original setting has been lost. The ECU determines the idle rpm, not anythiung mechanical. By adjusting the IACV you'll alter the balance of up and down control the ECU has available to maintian a stable rpm. There is no Subaru procedure for how to set the IACV as they are not supposed to be adjusted. they were supplied preset. For this reason, it is always a very good ides to scribe a line so you can always set it back to exactly how it was set.
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syncroparge · Posted: Sun Aug 02, 2009 3:27 pm Post subject:

Today continuity checked wires from iacv/afm/lambda, all ok changed lambda for new Bosch. Lambda reads 900mv tickover (rich) 3000rpm around 400-500mv. Checked afm with old analogue meter approx 1v tickover rising to 2v at 3000rpm (sweeps freely around). Removed iavc and cleaned moves freeley no inlet leaks. I've got emissions down to 2.8% at tickover by moving iavc (original position paint marked at factory) reading approx 500mv on lambda probe but engine is not happy. So i'am going and try to get it through the mot (hope the HC has not changed) and them investigate further. Thanks for help...Brian

rjes · Posted: Mon Aug 03, 2009 10:09 pm Post subject:

Hello Brian,
Once the engine is up to temperature the lambda sensor voltage should switch from about 0.2 - 0.9V every few seconds at tickover or moderate rpm. Did yours do this?
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Richard,

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syncroparge · Posted: Tue Aug 04, 2009 5:08 am Post subject:

Richard On tickover lambda reads .9v constant if I turn the ivac it will drop to .2v. I have removed injectors and took them for cleaning and testing should get them back tues pm. I will fit them and post results Thank you...Brian

syncroparge · Posted: Wed Aug 05, 2009 6:39 pm Post subject:

Fitted injectors today CO readings same as before or slightly worse. So going to test fuel pressure. Any other ideas ? Cheers...Brian

rjes · Posted: Sat Aug 08, 2009 4:16 pm Post subject:

Helo Brian,
Are you testing the lambda sensor output with the engine at normal running temperature or cold?
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Richard,

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syncroparge · Posted: Sat Aug 08, 2009 6:26 pm Post subject:

Richard Testing lambda sensor at normal running temp. Think I might have found the problem when I bought the donor car the fuel pressure reg was broken (vac pipe snapped) but seller gave me replacement, I've now found they are different types turbo/na. I am now waiting delivery of a na 2.2 Legacy regulator and a fuel pressure test gauge . I'll keep you posted. Cheers...Brian

rjes · Posted: Tue Aug 11, 2009 6:36 pm Post subject:

Hello Brian,
Yes, an incorret fuel pressure regulator is bound to have an effect on the mixture. I bet that fixes it.
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Richard,

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hansend23 · Posted: Tue Aug 18, 2009 5:18 am Post subject:

mine was running so perfict,and then i had everything go wrong.
it flooded a cyl so bad the headgasket blew.well not blew but didnt seal anymore.is still running so rich i cant even drive it. cant get #2 to fire atall.i will try some things on this thread.unless you have magic.
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