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My Pug 306 has just failed its MOT on high emissions -mainly CO reading. The mechanic suggested that the lambda may be at fault. Is he right and any other ideas of how I can reduce the emissions -apart from a new Cat?
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More info needed. Values of CO%, Hydrocarbons (HC). CO2% and O2 if possible plus Lambda calculation from emissions printout. Dont throw money at this problem, get it professionally diagnosed, it will cost you less in the long run. The Lambda sensor may well be at fault as may be the cat but I wouldnt dream of changing either on spec!
Andrew
Simplicate and add lightness!!
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Give the car a 30 minute thrash and present it for retest, that *might* just do the trick.
Also known affectionately as an "Italian Tune Up"
--
groups.msn.com/honestjohn - Pictures say a thousand words.....
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Thanks for your reply. Hope this info can help.
Fast Idle Test CO Limits < 0.30 % vol
Actual Value 1.45% FAIL
HC Limits <200ppm
Actual Value 65ppm PASS
Second Fast Idle CO Limits <0.30%vol
Actual Value 0.82%vol FAIL
HC Limits <200ppm vol
Actual Value 26ppm PASS
Natural Idle Test CO: <0.50 % vol 0.07%vol PASS
Pug has 70,000 miles on clock. Recent oil, filter, air filter and spark plug change.
Thanks
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I just wondered if the car was fully warmed up before you took it to be tested, because the readings are close to the limit on the second fast idle. Don't trust the temperature reading on the dash, it needs a 20 minute drive to warm the engine and exhaust properly.
I'd say nothing would be lost by the italian tune up, fully wamred engine, lots of revs, leave it in that lower gear, take it to the red line a couple of times on acceleration. The main aim is to generate lots of cylinder head temperature to burn off any deposits, then give the test another shot.
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My Vectra diesel failed it's test last week on the same thing.So what I did was to put an additive in the tank,(a 1 shot type) take out the air filter and clean it,( I didn't have time to go and get a replacement) and then take it for a good thrash on the motorway.
However,when I returned for the re-test,the guy was out on a breakdown and I had to wait 40 mins until he returned.Result? The car had cooled down.So he had to sit with the revs at abot 4000 for 5 mins to get the oil temp up to the required 88deg,and then did the test.
After 4 or 5 attempts it passed.The original reading was 9.8,and after re-testing it was 3.2.
The reason that it failed the first time is because I now do only 3 miles a day round trip to work,not like the 54 I used to do,so the system becomes clogged up.Not recommended on a diesel.
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Looking at the results it is only just outside on the second fast test so the Italian Tune-Up may do the trick. I suspect that your mech was right and the Lambda sensor may be switching slowly. Characteristically this makes it difficult to hold the fast idle speed as the engine revs will rise and fall rythmically at a steady throttle position. If this is the case then a new one will fix. Insist, by the way, that the oil temperature probe is used during the test to ensure correct engine temp and make sure the engine temp is printed on the results sheet and has not been 'bypassed'.
Good luck
Andrew
Simplicate and add lightness!!
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Thanks for your opinion and fault diagnosis Andrew. A local Pug mechanic says he will put a new lambda sensor in for £40 inclusive. Not bad as main dealer quoted £116 just for the part. I'll also put in some additive and give it a run up the local dual-carriageway
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SWMBO has a secondhand Pug 306 1.8 SR Sedan.
On leafing through the paperwork prior to purchase, I noticed that it had failed a previous MOT on emissions, with readings pretty close to yours.
It passed the following day, but there was no reciept in the otherwise comprehensive pile to say anything had been changed.
I called the servicing garage, who had also supplied the car originally, and who knew the previous owner well, and asked them if they could remember the event. The answer was that they could and the solution was that a mechanic took it for 'a good workout', then immediately performed the emissions test, with excellent results.
So, when this year's MOT was due, I took the Pug for a decent run where the engine could be made to work rather more than if I had just driven the two miles across town. I arrived at the MOT bay bang on time, emissions were the first thing tested, and the result was an easy pass.
Hope your solution is the same!
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astirl - if you do not already regularly use the fuels recommended by HJ (Texaco or Shell), try to use at least two tank-fulls before the next MOT test/retest. Maybe worth trying Shell-Optimax or BP-Ultimate to test if their claimed lower emissions help your MOT.
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check
www.bp.com/ultimate/uk/petrol/reducedemissions.asp
for BP-Ultimate's claimed CO/CO2/THC/NOx reduced emissions.
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