Mot emissions failure

[hoots]

From the rg screenshot it looks like the ecu is running fuel map 1. From what i understand this is an open loop map - the ecu will ignore any lambda inputs. Standard tvr map for uk car should be 5.

i had exactly the same situstion with my '98 450. Repeated mot probs with emissions. Replaced afm, lots of cataclean pre-mot, and usual faffing around. Finally got sorted with rovergauge and found ecu was running map 1. After much tinkering, and completely by chance, managed to track it down to fuel pump wiring. Previous owner had wired fuel pump to live feed from ignition, bypassing relay, and disconnected the original wiring at the pump. When i put everything back to original the ecu flipped onto map 5 which is the tvr closed loop map where lambda input is used to tune fuel/air mix. No idea why changing the wiring should impact the ecu - lambda heaters are wired on same circuit as the fuel pump, controlled by same relay, so presumably something to do with that. Given up worrying about why - sailed through mot last time round.

[davep]

blitzracing said:

Map one is get you home. That lambda fault could have triggered it although I dont see the MIL light on. An ECU reset should clear it now the probe is working.

I think there are six fuel maps in total, numbered 0 to 5. Fuel Map 0 is the limpHomeMap, and is closed loop. Fuel Maps 1, 2 and 3 are open; 4 and 5 are closed. Fuel maps 1 to 5 are selected by a tune resistor value.

[Chimp871]

Retest today and with lambda correctly wired the results were much better but still failed me.

Fast idle:
Co. 0,35% - fail (limit 0,30)
Hco - 162ppm - pass (limit 200)
Lambda - 1,01 - pass

Natural idle:
Co. 0,30% - pass (limit 0,50)

Think I'll try another garage.

[QBee]

If you are in Herefordshire, try calling Neil Garner (Kemble Airfield, Gloucestershire) and see if he can MOT it. Or get it MOT'd.

[fausTVR]

I seem to recall the TVRs have wider emissions limits because of low volume manufacture or some such? Having said that, looking at my past tests, both on the modern and TVR, the Co max was listed at 0.2%, yours at 0.3%

I take it you gave it a spark plug clean and an 'italian tune up' just before the test?

Edited by fausTVR on Saturday 30th July 18:48

[Chimp871]

Cheers gents.

Its got new sparks and was warmed up appropriately before arriving. If that's the italian prep?

I've booked her in with an indy LR garage for Monday. From speaking to them they seemed to 'get' tvr's rather than the regular garage down the road.

Fwiw- The test print said the parameters were for all chimaera's and griffiths 400 through 500. Just to confuse it more the test engine size said 4200 cc

[blitzracing]

The problem is the catalyst can become fouled if the lambdas dont cycle correctly. Certainly an Italian tune, in so much you thrash the nuts of the car for 20 miles, will get the catalysts nice and hot and burn any crap off so they work properly again. You can get some quite good fuel additives that help the process along as well.

[N7GTX]

With your previous very high hydrocarbon reading the cat is likely to have suffered a little so as Blitz says, a proper thrash (Italian tune up) may help. You will get good results from using Cataclean or a similar product. Available from Halfords etc.

[Chimp871]

Failed at garage number 2, turns out the local indy 4x4 place farms out their mot work.

Threw in some cataclean to a 1/4 tank last night for a 20 mile drive followed by a 20 mile warm up drive today.

Natural idle test passed but both fast idle tests had a fail: test 1 had too high CO and test had too high CO and HC (why would a higher HC have a lower CO?)

On my theory list of possible causes are:
Test MAF
Change air filter
Change extenders/leads
Clean injectors (as in send off)
Coil pack (?) not sure on this one but maybe a misfire even though brain says misfire would have far higher HC content.
Trying my hardest not to the C word as this is proper money and a worst case, 3 cat's! st went and said it.

May switch back OE chip for next test
Sparks were already new

[QBee]

You are still welcome to borrow my catted Y piece if it will help - it passed an MOT on a friend's 4 litre S/C Chim.

[Chimp871]

Cheers Q. Daft thing is all the cat's are in place and jools said the main one has not been tampered with.

[ClassiChimi]

It's an odd one this, could a burnt out catt cause this?
Could changing the chip to a softer power version help I wonder,,

Where are you Chimp?
If your anywhere near Rugby in the midlands I think I can get it ticketed but I would have to check first.
Let me know if your stuck and I'll ask a mate.

[N7GTX]

The first fast idle test is CO 0.44 and the second one is 0.35 the limit being 0.30 so it is only just marginally outside. The fact that the second test is coming down is a good sign. Also the natural idle test is within limits. It seems to be a lazy/contaminated cat.

If it was my car I'd do another Cataclean, thrash and a different MOT station. Or take up Classichimi's offer.

[blitzracing]

If you plug Rovergauge in, are you back on Map 5? DaveP is correct that limp home was map 0 not 1. Map 1 would be very wrong.

[Chimp871]

Just plugged RG in and its saying map 5. Limp home mode from the experience i had stops any power over 2000 rpm.

MAF at idle is 33% at direct setting on RG which I believe from Blitz's g33.co.uk website is where it should be. So MAF crossed off the list.

I've got a free retest so will use cataclean again and maybe some injector cleaner but i feel I'm more guessing things right now. I plan to plug original chip back in being as that was lumpier. The first failure was due to me rewiring lambda incorrectly, it never had a test with original chip and correct wiring.

Meanwhile I'm trying to find the old file that cam ewith the car for previous MOT emissions (if any!), my wife's moved them somewhere.....

Air filter looks like its not been changed in years - possible cause?

Edited by Chimp871 on Tuesday 2nd August 18:20

[QBee]

Are the 400 and 450 chips identical....or different? Does anyone know?

[blitzracing]

No they are not- you need the correct one for your engine size to get the map scalar correct for accurate calibration. It appears the 4.3 and 4.5 are the same however.

http://www.stevesprint.com/remap-14cux/bins

Edited by blitzracing on Tuesday 2nd August 20:23

[QBee]

I ask because I have a spare ECU with 4 litre chip, a spare catted Y piece, a spare cardboard box and a friendly sub-post office.

If any expert thought they would by of any help it would be a pleasure to post them to the OP tomorrow.
If the problem lies elsewhere then there's no point.

[blitzracing]

High HC is un burnt fuel so there could be a misfire there somewhere. ECU wise, as long as the Long term fuel trim is not at 100%, and the short therm is cycling around its mid point at the MOT test RPM, the ECU and lambda probes are working OK. A misfire gets picked up as a lean mixture, so the ECU add fuel which does not help the misfire, just makes the remaining cylinders run rich. You may see this as high levels of Long term trim, or short term not cycling around its mid point. catalyst wise they can melt in extreme conditions, or certain contaminates can foul them like zinc from engine oil (if you use a high zinc oil) that wont burn off, but Ive yet to see a genuine failure.

[QBee]

Suggests you are looking for one misfire, Chimp871. Almost impossible to detect when driving normally, car runs happily on 7 in my experience.

Do you know how to test for one using a cable tie, or an infrared thermometer?

Edited by QBee on Wednesday 3rd August 08:06