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        General >> Give/Need advice to/from others >> Lambda sensors
        
(Message started by: tlundkvi on Dec 6^th, 2008, 3:58pm)

Title: Lambda sensors
Post by tlundkvi on Dec 6^th, 2008, 3:58pm

Hi,

My scorpio failed the emission test, it has CO 0.7, and HC 280 ppm on idle, and HC 80 ppm on revs, so I suspect the lambda sensors are due for replacement. Since the 24V has potentially four failing sensors, and replacing all att once is quite expensive, will a failing rear sensor have any affect on the emissions?

Title: Re: Lambda sensors
Post by scorpio_man on Dec 6^th, 2008, 4:25pm

hi there

no, the rear sensors are just cat monitors.

hth

Title: Re: Lambda sensors
Post by tlundkvi on Dec 6^th, 2008, 6:25pm

on 12/06/08 at 16:25:50, scorpio_man wrote:

hi there

no, the rear sensors are just cat monitors.

hth

Sounds good then, I'm a bit on a budget, the Finnish customs just billed me on 880 euros for registration tax (based on a hypothetical value of 3800 euros the customs assumes it has, ridiculous system), have only a week to fix it until the temp plates expire. Will keep my fingers crossed it isn't the cats. I'll have the values checked in any case, but I can replace the rear ones with less hurry should they have failed as well. Cleaned the MAF, but it had no effect on the emissions, but the car felt more responsive, so definitely worth the trouble.

Otherwise, no serious issues except the rh headlight leveller didn't work.

Title: Re: Lambda sensors
Post by martin_rowe on Dec 7^th, 2008, 11:39am

what was your Llambda vaue on the emission test, if it was close to 1.000 (higher than 1.000 is lean mixture, lower than 1.000 is rich mixture, with or without a cat fitted) then emissions are ok, probably a cat problem, more info needed. rear sensors are just for monitoring purposes, its the front ones that control emissions (together with many other sensors.

Title: Re: Lambda sensors
Post by Highlander on Dec 7^th, 2008, 11:49am

on 12/06/08 at 18:25:07, tlundkvi wrote:

Otherwise, no serious issues except the rh headlight leveller didn't work.

Got a spare leveller unit if you need one ;)

Title: Re: Lambda sensors
Post by tlundkvi on Dec 7^th, 2008, 6:00pm

on 12/07/08 at 11:49:43, Highlander wrote:

Got a spare leveller unit if you need one ;)

Good to know, thanks, will have to take the car to a garage to get the emissions tested and (likely) to replace the sensors, we'll check at the same time the leveller. Highlander, if the "stopper thingies" inside the road springs have nothing to do with self levelling, would you have an extra pair of those as well? I will put the picture of how it looks when I take it to a garage, but the failed MOT for registration has kept me occupied (mentally at least).

The lamdba value was not printed on the certificate, cleaning the MAF changed the CO to 0,9 (0,5 allowed) and the HC to 325 (100 allowed) on idle when tested in a garage. AFAIK a dirty MAF causes a too lean mixture. The last german MOT was made in march this year, but the test values are not available anymore. The values would have been useful, to see if a sudden drop has occurred.

Title: Re: Lambda sensors
Post by Highlander on Dec 7^th, 2008, 6:45pm

The rubber things? no sorry, they seem to perish fairly badly, rarely see a good one :)

Title: Re: Lambda sensors
Post by tlundkvi on Dec 8^th, 2008, 2:41pm

Small update, the garage I visited (friends) didn't have any advanced ODB scanning equipment, so testing the values of the sensors was not possible.

We added the "normal" Forte treatment, ran it in first gear at 6krpm for 30 minutes, effect CO dropped to 0,6 and HC to 180 on idle. Lambda value 1,01-1,03 during the test. On revs, CO was unchanged but HC dropped to 60 at best. Funny observation was that when running idle, we pulled the MAF plug out, but it didn't change the emissions remarkably, neither did the engine stop or warning lights come on. But spraying CRC-MAF on it while running affected engine sound, the idle revs fell to around 400-500 for a few secs. Have a bottle of special Forte Fuel System Cleaner to run through, and after that the ODB specialist will test all sensors if the emission test still fails. Both garages doubted cat failure, they both believed the cats should rattle and warning lights come on if this was the case + the emissions should be a lot worse.

Title: Re: Lambda sensors
Post by martin_rowe on Dec 8^th, 2008, 5:02pm

Unfortunatly Llambda value of 1.01 - 1.03 means emissions are correct, (Llambda value will not change if the cat is good or bad) with that Llambda reading, but still high CO means the cats are not 'burning' off the CO and HC's, they only rattle when the 'brick' breaks up, how long have you owned the car ?, the catsare expensive, many people remove the 'brick'. sorry, with out further data looks like a cat problem, try comparing Llambda sensor readings (electrical) of pre & post cat sensors, a post cat sensor with a fluctuating reading (between 0.2 -0.8v) usually points to a failed cat, post cat sensor usually provides little variance, constant 0.5v if everything is good.

Title: Re: Lambda sensors
Post by tlundkvi on Dec 8^th, 2008, 5:28pm

on 12/08/08 at 17:02:31, martin_rowe wrote:

Car has been with me since 3 months. Luckily, I found a place in Germany that sells the pair for about 400 euro delivered (175€/pc.+sh). But I'll run through the Forte anyway and have the ODB test, and then see.

Title: Re: Lambda sensors
Post by scorpio_man on Dec 8^th, 2008, 6:28pm

on 12/08/08 at 17:28:19, tlundkvi wrote:

hi there

you can get patterned cats from http://www.cats-direct-shop.co.uk/ for about 170 euros + VAT + delivery.

*WARNING*

they're not the best fit. you may need to 'help' them to fit, but cheaper than you've been quoted.

hth
andrew

Title: Re: Lambda sensors
Post by tlundkvi on Dec 8^th, 2008, 6:54pm

on 12/08/08 at 18:28:07, scorpio_man wrote:

http://www.cats-direct-shop.co.uk/two-year-catalytic-converter.php?recordID=633
http://www.cats-direct-shop.co.uk/two-year-catalytic-converter.php?recordID=632

Seems ceramic direct fit is about the same price (thanks for the tip!), is there a substantial difference in quality between ceramic and steel cats? Need still to check shipping to Finland.

Update: Seems my local discount part dealer sells a universal model for only 99 euros (VAT incl.) pipe diameter 51-57mm, weldable. It says max 2.5 litre engines, but doesn't the cats in the 24V count for 1.45 litres a piece, since each block has one? Will the diameter of the original pipes be within the range?

Title: Re: Lambda sensors
Post by martin_rowe on Dec 9^th, 2008, 8:56am

I looked at universal cats some time back, you could 'weld' in 2 at the side of the g/box, but bit of a compromise on ground clearance, though you can get the exact same cat that is used as a weld in unit, just has no pipe or flange on it, you could do it that way, just a lot of time & a welder needed.

Title: Re: Lambda sensors
Post by tlundkvi on Dec 10^th, 2008, 12:23pm

Problem seems to have been identified. A T-connector for the vacuum hose had broken off. Irritating enouch, but very, very hard to reach without taking the bullhorn out (sorry, I'm not native English nor a mechanic to say what the part is called). Are all connectors in the joint inner diameter 6 mm?

Thanks for all the help!

Title: Re: Lambda sensors
Post by tlundkvi on Dec 11^th, 2008, 5:03pm

on 12/10/08 at 12:23:18, tlundkvi wrote:

Problem seems to have been identified. A T-connector for the vacuum hose had broken off.

Or then not. Runs slightly uneven on low revs, cables are checked and plugs run 2000km. probably a cat problem then.

Title: Re: Lambda sensors
Post by martin_rowe on Dec 11^th, 2008, 5:12pm

yes the 'T' under the inlet manifold is very problematic, you can extend the pipes to outside the manifold & make up a 'T' that works ok, another place to check is the EGR system, they come loose causing erratic idle. a squirt round with 'cold start' or wd40 would find it, or a propper 4 gas emission test would show high oxygen, Llambda sensors would try to compensate. fuel trims would also indicate problem.

Title: Re: Lambda sensors
Post by tlundkvi on Dec 12^th, 2008, 5:12pm

Hi,

Martin was right from the start. The right cat is dead, the left one almost dead. Lamda sensors were all in order, switching quick. Same for the MAF. The heat sensor in the injection system was dead and replaced, but the effect of this is minimal compared to dead cats (except for that the lambda value in emissions test improved to 1.00-1.01.

Title: Re: Lambda sensors
Post by tlundkvi on Dec 12^th, 2008, 6:52pm

on 12/11/08 at 17:12:36, martin_rowe wrote:

... or a propper 4 gas emission test would show high oxygen, Llambda sensors would try to compensate. fuel trims would also indicate problem.

The HC didn't go down on idle to less than 160ppm. Oxygen at 0.8, CO at 0.7%. CO2 at best 14.1. On revs the HC went down to 20ppm, but CO remained at 0.7. But that'll go away with new cats.

In Finland the limits are (idle/2500rpm) HC 100/100, CO 0.5/0.3, O2 5.0/5.0.

Title: Re: Lambda sensors
Post by tlundkvi on Dec 15^th, 2008, 7:30pm

New cats ordered. The pound is low compared to the euro right now, now UK is the place to buy car parts. £152 + 40 P&P to Finland including VAT (both cats, ready-to-fit). In Finland its not possible to get ready-to-fit cats for the scorpio for a reasonable price (e.g. Mondeo cats are here around 300 euros a piece from others than the main dealer, a piece, it seems I saved big time).