So after a final rush to get the Disco V8 efi 3.9 94 of the drive to the m.o.t center just in time to get the block pathing down on the the drive i thought i was on a winner . Then i got the m.o.t results .... EPIC FAIL

First fast idle test
co -11.9%
HC -3747 ppm

second fast idle test
CO -10.64%
HC -1111 ppm

Have only just bought it and done all the welding work to get it fit for M.O.T , it has a new back box on teh exhaust. It wasn't that well looked after for its llast couple of years so im going to give it a good service and check all the sensor readings are within limits.

The expensive question is shall i replace the Cat and/ or middle box or will i find the improvement i need in tuning the engine . Its running a bit rough so i guess its probably not firing on all cyclinder ect.



Interestingly the readings were exceptionally high could the be down to the car standing for a year causing damage to the cat ?

Any advice is welcome.

That is beyond a cat failure, it sounds like you have an ignition or a mixture issue. First of all I would change all the plugs and leads. Im not up to scratch on the LR's V8's but im guessing the run a dizzy, change the cap/rotor if so and possibly points/condensor if its not electronic. Next check through all the intake pipes for any air leaks, make sure the AFM is working correctly. Reset ignition timing and basically get everything back to where it should be.

Once you have done this get it regassed, this will let you know if your going in the right direction. A failed cat will only add a few % CO and not 10% so hopefully after doing the above it should get you to 1-2% tops. I suspect your cat will be burnt out now but do not just replace this as you will burn out the new one very quickly...

Mine just went through at around 1600ppm HC, can't remember the CO but I think was around 6.0%...

It used to go through around 1.5% and 300ppm, but i set up the MAF correctly a few months back and that sent it richer. It drove better but was obviously very rich.

Mine is a Pre cat model by the way.

Anyway so a recent compression test revealed that the properly set MAF will have caused my very worn engine to run rich. Have recently replaced the engine and at 2000rpm fast idle it runs so cleanly it smells like hot air as it should.

SO, to break it down, CO reading is a telltale of clean or dirty burn, HC reading tells amount of unburnt fuel.

Ie too rich but firing on all 8, high CO low HC, just right but 1 misfire, ok CO but inflated HC, too rich or dirty burn with misfires, both high.

I would start with a compression test so you know where you're at.

Then remove the ignition components. Fit new plugs, NGK only, BPR6ES on my 3.5, Test each ht lead, resistance on a good quality lead is around 5k ohm iirc, ****ty leads around 14k ohm, either way test to see if any are irregular, longest lead gives high resistance and shortest lowest of course...

Dizzy cap and rotor, can play havoc so replace with decent components.

Check the ignition timing with a quality strobe light, set to somewhere between 6 and 12 degrees BTDC.

Remove breather hose between flame arrestor on drivers rocker cover and plenum. Check hose is fully clear. Remove t piece and check fully clear including the pin sized air bleed in the T section. Check the relevant fittings on the plenum body are clear, often blocked. Check the flame arrestor is clear, remove the gauze and wash out in petrol.

Check the little breather at the back of the passenger rocker is clear, mine has a pin size hole under the foam, some are different.

Check the idle control valve at the rear of the plenum is clear.

Basically the engine runs off some off the air from the crankcase so all this needs to be clear and free to get mixture correct.

Once youre sure the top end is cleaned, proceed to check afm adjustment. 5mm Allen key iirc.

Get multimeter on two outside pins of afm plug with ign on engine off. Should be between 0.5 and 1.0 volt, less voltage = leaner. Set to 1.0v and take gear to mot centre.

Non cat limits are 3.0% and 1200ppm, it you can get it decently below here with a good motorway blast and an afm fiddle when connected to gastester then you are safe to try replacement cats.

Should be approaching 1.0% CO for a healthy non cat engine, so see what you can do

Thanks for the advice will follow all the above.

I have purchased new plugs, dizzy cap, rotor arm, ht leads, coil, condenser, sadly new MAF as mine kills the engine when plugged in!

This vehicle hasnt been looked after for the last couple of years by the previous owner so all fluid changes and filters will also get done next weekend.

Hopefully this isn't masking anything more serious but i guess ill find out next week.

again great advice
cheers

Just work through it pal, RIDICULOUSLY easy engine to work on compared to more modern stuff!

Get a good multimeter and then read everything on this following link, it will save your life:

Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting

Cheers

So i manged to make a little progress yesterday and learnt a little more .

I have removed the 14cux so i can follow the workshop manual and previous link, This confirm the MAF was knackered , put the new one on and the engine emmediatly sounded more settled.

I have cleaned and checked all the vent pipes so in theory the misture should be more controlled ! i think. I have check the HT leads and they are about 9k per lead and balanced. I have replaced the dizzy cap, coil and suppressor. Going to replace the rotor arm this morning and put in new plugs, gap and check.

I will be getting a strobe light today and attempt to check/correct the timing.

The exhaust really stinks of rich mixture so im progressing on the basis that either a cyclinder isnt firing correct (engine sounds lumpy) or i need to check my injectors for leaks/faults. Going to concentrate on the timing and ignition first before removing and testing injectors as this requires the removal of the plenum chamber.

I checked the voltage of the lamda sensors yesterday, one was 0.14 v and the other was 0.35 ish , both varied when the teh throttle was pressed maxing out at 1.2 volts each. The lambda test on m.o.t failed at 0.7 pass shoul be 0.95 - 1.09.

Im unsure if the lambda's are working ok but am reluctunt to buy new until im sure. The workshop manual suggest an air leak, misfire or bad injector fault might cause low or high readings.

Oh and the spark plugs where all had heavy carbon deposits, charcoal grey and dry .

So heres my next steps

1. sparks plugs (new)
2. timing check
3. Clean lambda sensors , i assume petrol will do but ill check first
4. Remove plenum to check injectors and check for air leaks ect
5. check injectors for drip leaks and operation
6. And if this doesnt work , by can of petrol , box of matches and claim on the insurance.


As usual , any advice welcome :argue:

Sounds like you've got the job nailed mate so far. You will find the fault, don't lose hope. I've come very close many a time and then it all comes well in the end

Chin up!!

I dont know if this is any sort of indicator , but when i connect the strobe timing to no1 plug the teh light id very inconsitant , i would have though it would be very regular pulsing.

Also the charcoal canister smells of fuel , is this an idicator of saturation ?

Interestingly , when my mass airflow sesnor is disconnected i get a reading of 1.1 on both lambda sensors , when i connect it they operate much lower not exceed .6 . Im hoping this a good thing?

lower reading denotes its running rich ,you probably have several issues ,fuel pressure and injectors are worth checking ,using graduated containers as well as looking for leaks

leclance said:

So i manged to make a little progress yesterday and learnt a little more .

I have removed the 14cux so i can follow the workshop manual and previous link, This confirm the MAF was knackered , put the new one on and the engine emmediatly sounded more settled.

I have cleaned and checked all the vent pipes so in theory the misture should be more controlled ! i think. I have check the HT leads and they are about 9k per lead and balanced. I have replaced the dizzy cap, coil and suppressor. Going to replace the rotor arm this morning and put in new plugs, gap and check.

I will be getting a strobe light today and attempt to check/correct the timing.

The exhaust really stinks of rich mixture so im progressing on the basis that either a cyclinder isnt firing correct (engine sounds lumpy) or i need to check my injectors for leaks/faults. Going to concentrate on the timing and ignition first before removing and testing injectors as this requires the removal of the plenum chamber.

I checked the voltage of the lamda sensors yesterday, one was 0.14 v and the other was 0.35 ish , both varied when the teh throttle was pressed maxing out at 1.2 volts each. The lambda test on m.o.t failed at 0.7 pass shoul be 0.95 - 1.09.

Im unsure if the lambda's are working ok but am reluctunt to buy new until im sure. The workshop manual suggest an air leak, misfire or bad injector fault might cause low or high readings.

Oh and the spark plugs where all had heavy carbon deposits, charcoal grey and dry .

So heres my next steps

1. sparks plugs (new)
2. timing check
3. Clean lambda sensors , i assume petrol will do but ill check first
4. Remove plenum to check injectors and check for air leaks ect
5. check injectors for drip leaks and operation
6. And if this doesnt work , by can of petrol , box of matches and claim on the insurance.


As usual , any advice welcome :argue:

Click to expand...

Put up your location that way anyone who might be local might be able to offer some help.

Have you tried a substitute ECU? Some years ago my ECU stopped reading the MAF although the MAF itself was good. Swapped ECU and not had a problem since. You could also try swapping the tune select resistor to a non-cat one and see if that changes the rich running - if it does it points to iffy lamda sensors.

If there was an air leak you would likely run lean, not rich and also probably have idle issues. Have you done a compression test?

Yep, a full service before an MOT is always a better idea.
All the above, and may have missed it in the posts above, but the obvious replace is to fit a new airfilter....

It's amazing what a difference it makes on a test after just the filter is changed and the engine breather pipes are cleaned out

thanks for all the replies.

I am in northampton town , any local advice would be really welcome.

I have manged to create another issue while ive been doing the tests on the E.C.U , i had been working through tests ok and changing components and was about to go back to the m.o.t place to get the emissions rechecked and i couldn't get it started, when i checked the e.c.u voltages there was no power to the E.C.U on pin 15 which is the ignition off poower supply to the e.c.u.

After a morning trying to work out whats going on i found the 20A fuel injection fuse had blown , i replace this and retried and it has blown again.

Not really sure what my next step is yet as i have run out of fuses until halfords opens. Worryingly this all started when i tried move the wiring loom to teh E.C.U

Anyone had any similair issues ?


No i havn't done a compression test yet as i dont have the kit . Thought id fous on teh ignition system first.

oh and is there any way to get the rotor arm of without brut force as mine seems to be welded on .

leclance said:

when i checked the e.c.u voltages there was no power to the E.C.U on pin 15 which is the ignition off poower supply to the e.c.u.

After a morning trying to work out whats going on i found the 20A fuel injection fuse had blown , i replace this and retried and it has blown again.

Not really sure what my next step is yet as i have run out of fuses until halfords opens. Worryingly this all started when i tried move the wiring loom to teh E.C.U

Anyone had any similair issues ?


No i havn't done a compression test yet as i dont have the kit . Thought id fous on teh ignition system first.

oh and is there any way to get the rotor arm of without brut force as mine seems to be welded on .

Click to expand...

Sounds like a world of pain, we've all been there so chin up and don't quit.

The EFI loom is not that complicated and it is likely you have disturbed something and you now have a dead short, my guess would be carefully check the wiring and relay bases that sit under the drivers seat.

Maybe a bit late but had a quick look at wiring diagram, the the main power relay wiring or the fuel pump circuit look favourite as they share have the same power supply. If I have read the diagram correctly, the main power comes in from the battery, through the ignition switch to the fuel pump relay, after the relay, power is sent to the main EFI power relay (the main power relay also has a permanent live). The only fuse in the EFI circuit is fuse C4 - this is the fuel pump relay and should be 10amp not 20. HTH

Yep, chin up and keep at it. You WILL solve it in the end becuase they are just such a simple system which WILL work again once you have found THE PROBLEM!

Regards compression, dont worry too much just yet, as i have recently found out an engine will run basically perfectly with almost no compression on one cylinder, three around a third of factory spec and the other four just over half what they should be.

Good luck, and find that short

i havnt had a chance to check thsi yet , but first impression suggests either the wiring diagram is incorrect , the fuse that blows is under the bonnet just behing the battery and is called "fuel injection". The fuel pump one is located in the drivers side footwell .

Oddly im getting the 12 volt at the fuel pump relay but not at ecu suggesting maybe a break in the wire, and potentially that break is touching the ground point too. the diagram shows a battery connection remote from the actual battery. Im assuming this will be on the alternator , starter motor or in the fuse box under the bonnet.

anyway ill keep at it , does anyone have the corect electrical diagram ?

Are you looking in Haynes or LR Workshop manuals?

Haynes tend to be simplified, which is good because it helps you get the jist of the system but sometimes duplicated circuits etc are left out for simplicity which doesn't help for finding a fault such as this.

That said I have never used/needed a LR diagram because the Haynes diagrams are simple and accurate and I would say I have done about as much intense wiring diagnosis as a 200 shape allows (hardly any electrics in them to be fair)

Yours is a 200 looking at the carpet so you are already on them home straight in that respect...

Ahhh no, 200 doesn't have an underbonnet fusebox so yours must be a 300 ...

should have read first post

Ooooppps, my bad, forgot this is a Disco so ignore what I said about location of relays and also fuse number and rating.

Anyway, the actual efi circuit should be the same. So fuel pump relay has power, what about the main efi relay? it should have a permanent 12v feed plus an ignition switched feed. What you could do is put the relays in etc then turn the ignition key until the ignition lights come on; at this point you should hear the relays energise. If one does and one doesn't, try swapping the relays around, hopefully this will tell you if the relay is O.K.

The ECU at pin 15 appears to be the main power feed to the ECU and also operates the main power relay, this is a permanent battery live. The ignition switched supply is in pin 19 which comes via the ignition switch. HTH