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SLR MOT Failure emissions


Sandy

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Hi There,

 

There seems alot in the archives on this subject but I cant find anything relevant to my failure this morning?

 

Car is 2001 bog standard SLR with CAT fitted and ALL emission readings were sky high

CO is the only one I remember at a reading of 8 (0.5 being the max)

The tester reckons an ECU or sensor fault and has suggested I return the car next week and he will try and read the MEMS fault codes and carry out other tests to diagnose and resolve

 

I dont feel the guy is having me on - I saw the readings for myself and then took the car for a good blast which made no difference - He said he though the car had defaulted to 'open loom' which meant nothing to me as Im a mechanical numpty

 

Anyone have any ideas or suggestions please?

 

 

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Check the usual culprits such as making sure the exhaust is sealed fully (particularly the join between the primaries and the cat) and the cat is really hot when he tests it - give it a good hot run then get him to test it immediately.

 

Mine had an emmision reading of 8 also, but having an Emerald fitted meant I could drop it down while he checked it - IIRC he was looking for 3.5 or less not 0.5? If all else fails, can you find someone local who can lend you an Emerald with a suitable map so it can be doctored whilst being tested?

 

Stu.

 


Joint Area Representative MAD Sevens (Merseyside And District)

www.superse7ens.co.uk..........the rebuild 😬

 

 

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3.5 is a non-cat test. 0.5 is the cat test.

 

What throttle bodies does the 2001 SLR use? If it is running on the MEMS then I'm supposing it uses the KV6 TBs on the swan neck manifold.

 

"Open loop" means that the ECU determines the fuelling by looking in a table for the engine speed and load (manifold vacuum). Closed loop is when it uses the lambda sensor to get feedback on the current fuelling and alters it to hit the chemically correct mixture for minimum emissions.

 

Having been here with a number of engines, don't expect too much from plugging into the MEMS. Even the full Testbook diagnostic is of limited use. I agree with Stu. Check the obvious stuff. Air leaks are a disaster for fuelling. Exhaust leaks also.

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Hi Sandy

 

Is this the same SLR as had running problems at altitude in the Alps?

 

With CO so high, could be overfuelling at idle. This could be be due to picking up a wrong parameter from a sensor, for example a temperature reading cold could be causimg a supply of cold start fuel. ( This would also reek havock with running at altidude where mixture needs to leaner do to less oxygen )

 

Also as Peter C says any mechanical issue of air or exhaust leaks must be checked.

 

What were the other emissions readings on the MOT test rig?

 

Did the tester try a fast idle (2500rpm)? Quite often used as a back up test if the car fails the standard idle test.

 

Peter

(Now back from 1000mile AlpenBlatten)

 

 

6SpeedManual *smokin*

*tongue*There's no such thing as too much BHP per Ton 😬

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Peter,

Yes that was my car in the Alps ☹️

I held the revs aty about 3k for the tests

Dont know what the other readings were but they were very very high, all of them

 

Your statement on a faulty sensor is back to back with what the tester said

 

I've whipped the primaries off and from the soot there looks like some leakage and the gasket is beginning to seperate so I will replace, reseal and drop back in for a retest later this week. I'll also seal at the CAT with Permatex

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Hi Sandy

 

Good to hear from you (but not in circumstances of car trouble). Hope you got back ok nursing bad running SLR...

 

If the exh gaskets a bit leaky well worth re-doing them. It is also possible to check for air leaks on the inlet side bay listening for hissing noises at tick-over with a bit of screenwash tube put to your ear, or use a pippet to drip petrol onto any joints or gaskets on the inlet manifold or throttle bodies. If it is sucking in air, when it sucks in the petrol, the engine note will change. (NO SMOKING *nono* *smokin* when doing this!)

 

You may be able to check all the sensors, particularly temp sensors. Do you have an electrical test meter? (£10 at Maplins) It can be possible to check their resistance (ohms) at specific temps or measure the resistance as engine warms or cools to make sure they are actually changing with temp. If they change they are likely to be working. If they are staying at a fixed resistance or are open circuit, it is likely they are goosed.

 

A Rover Haynes manual may give some figures to work from.

 

Alternatively the Rover Testbook may be able to run a test on all the sensors.

 

And of course there's a good chance someone on here has some actual data!

 

Good luck

 

Peter

 

 

 

 

6SpeedManual *smokin*

*tongue*There's no such thing as too much BHP per Ton 😬

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I would suspect the barometric pressure sensor but, as said, it could very well be the temperature sensor. If the car already runs rich at sea level, then it's no surprise it'll get upset at an altitude...

 

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Just second guessing here.

 

Temp sensors never go wrong. If the wiring is intact, the sensors will be working.

 

The fuel system is dead simple. The fuel pressure regulator determines the pressure and the injectors do what the ECU tells them. Not impossible for the fuel pressure to be wrong for the setup though. The setup was never intended. The use of the MEMS to run a throttle bodied car is a bodge and it relies on the fuel pressure and injector sizing just about working out.

 

The vacuum feed to the MAP sensor is prone to leaks. If there are leaks, the MAP reading will be wrong (higher pressure) and the ECU will deliver more fuel to compensate.

 

Has this car ever passed an emissions test?

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Car Passed the MOT at the weekend, the fault being down to a dodgy Lambda sensor

 

Apparently the sensor was discoloured and the tester says it shouldnt be but they saw alot like it after the dodgy Tesco fuel a year or two back?

 

Anyway, I have a new one fitted and 12 months MOT and am looking forward to a loud day at Donnie tomoz 😬

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