mot .Emmissions help please v8 1986
Discussion
Hi all.Car failed its mot today.After a long lay up of 6 years .one year in my ownership.The car has only covered 8 miles since its last mot .Passed on emmissions then .now sky high.Ithink there must be a sensor stuck.Car does not want to idle at all.tryed adjusting idle no joy.Can you be of any help please..............Failed on a couple of minor details.but emmisions the biggest problem................ Thanks for your time Mike 350i s2 1986
Did you get a printout from the MOT station ? We may be able to help a bit more if knew which part of the test it failed on. Plainly as a starting point you need to fix the idle problem, if the engine is not happy it is fairly likely the emissions will be less than ideal.
Just a thought, if it has been out of use for 6 years you have drained the fuel and put some fresh in haven’t you ?
Just a thought, if it has been out of use for 6 years you have drained the fuel and put some fresh in haven’t you ?
Had this as well (by the way '86 built 350i) and idle was as in your case not adjustable in the end. And every year it became more difficult to pass MOT on emissions.
Top tip here on pistonheads saved me when I couldn't get it below 7-8 CO%: take out the CO-adjuster from the AFM, clean it (it gets gunked up) and put it back. After this I was able to adjust idle and and CO to what ever I liked. This year without adjustments during MOT it was on 2.5-3.0 CO%! Didn't know it could be this low
If this doesn't work many other causes are of course possible, worst a worn engine. But too high fuel pressure and ignition not ok (timing or parts) would be the first things I would start to look at.
Rob
Top tip here on pistonheads saved me when I couldn't get it below 7-8 CO%: take out the CO-adjuster from the AFM, clean it (it gets gunked up) and put it back. After this I was able to adjust idle and and CO to what ever I liked. This year without adjustments during MOT it was on 2.5-3.0 CO%! Didn't know it could be this low
If this doesn't work many other causes are of course possible, worst a worn engine. But too high fuel pressure and ignition not ok (timing or parts) would be the first things I would start to look at.
Rob
It is a metal piece so no worries, probably a cloth will do it. Otherwise a bit of petrol, wd40 or something like that.
After putting it back it is preferred that you are able to set CO (use a gunson myself) as a minimum to avoid running lean (it influences the whole rev-range on a flapper). Idle will be necessary to be adjusted on the plenum as well due to the interaction between the two.
Rob
After putting it back it is preferred that you are able to set CO (use a gunson myself) as a minimum to avoid running lean (it influences the whole rev-range on a flapper). Idle will be necessary to be adjusted on the plenum as well due to the interaction between the two.
Rob
If that doesn't work I have in the past put an extra bypass. This is how:
- get a piece of copper pipe or even plastic pipe, about 10mm o.d. (between 8 and 12mm)
- if it's copper squish one end till it's almost shut but not quite
- get a bit of sponge
- undo the big jubilee clip at the air meter
- slip the pipe and sponge under the big air pipe
- put the jubilee clip back on and trap the pipe and sponge in place.
- if it's too lean squish the open end a bit to reduce the bypass
Yes this is a bit of a bodge-up but can get you through the MOT until you can solve it properly.
- get a piece of copper pipe or even plastic pipe, about 10mm o.d. (between 8 and 12mm)
- if it's copper squish one end till it's almost shut but not quite
- get a bit of sponge
- undo the big jubilee clip at the air meter
- slip the pipe and sponge under the big air pipe
- put the jubilee clip back on and trap the pipe and sponge in place.
- if it's too lean squish the open end a bit to reduce the bypass
Yes this is a bit of a bodge-up but can get you through the MOT until you can solve it properly.
For the sake of 12 quid it'd be worth dropping in a new coolant temperature sensor (the smaller of two together, front top of the inlet manifold).
It could also be ECU related - the good old dry joints scenario. See if you can borrow a known good ECU - but bear in mind that no two ECUs are the same so can appear to run better OR worse! Alternatively plug your ECU into a known running V8 (TVR, Rangey, as long as it's a 3.5 it should be somewhere near).
There is a ton of diagnostics you could run but it'll probably be something stupid. It's almost certainly overfuelling so I'd be checking the injectors (including the cold start injector) to see whether any of them are stuck open. It's more usual for them to stick closed after long periods of disuse (ask Hotty and Uglymug) so whilst that might explain the poor idle I'm not sure it would explain the emissions results. It's easy to check if you can find a small pressure guage (0-5Bar would do) that you can install in place of the cold start injector.
The other thing to check would be the flap in the airflow meter: is it sticking if you move it round with your fingers? It should move smoothly with the same resistance across its travel and no scraping noises.
It could also be ECU related - the good old dry joints scenario. See if you can borrow a known good ECU - but bear in mind that no two ECUs are the same so can appear to run better OR worse! Alternatively plug your ECU into a known running V8 (TVR, Rangey, as long as it's a 3.5 it should be somewhere near).
There is a ton of diagnostics you could run but it'll probably be something stupid. It's almost certainly overfuelling so I'd be checking the injectors (including the cold start injector) to see whether any of them are stuck open. It's more usual for them to stick closed after long periods of disuse (ask Hotty and Uglymug) so whilst that might explain the poor idle I'm not sure it would explain the emissions results. It's easy to check if you can find a small pressure guage (0-5Bar would do) that you can install in place of the cold start injector.
The other thing to check would be the flap in the airflow meter: is it sticking if you move it round with your fingers? It should move smoothly with the same resistance across its travel and no scraping noises.
One thing that is always worth a try......4x the normal dose of REDEX (in the petrol) and take it for a "blast" (high throttle but not overly high revs, 4000+ should be sufficient?) that will often get rid of any residue/deposits that may have built up from the years of laying up, especially if its only ever been started and left to tick over during that period?
Using 4x the recommended does is a kin to being able to put it neat into the cylinders, but also gives the injectors etc a good clean trhough, a dirty injector can make mixture less than ideal for combustion and cause emmission problems.
Might not be the solution but certainly won't do it any harm?
I assume you have changed oil/filter/plugs/fuel filter etc when you put it back on the road?
Using 4x the recommended does is a kin to being able to put it neat into the cylinders, but also gives the injectors etc a good clean trhough, a dirty injector can make mixture less than ideal for combustion and cause emmission problems.
Might not be the solution but certainly won't do it any harm?
I assume you have changed oil/filter/plugs/fuel filter etc when you put it back on the road?
wedgeinald said:
One thing that is always worth a try......4x the normal dose of REDEX (in the petrol) and take it for a "blast" (high throttle but not overly high revs, 4000+ should be sufficient?) that will often get rid of any residue/deposits that may have built up from the years of laying up, especially if its only ever been started and left to tick over during that period?
Good plan but a bit risky if the car has no MOT.It failed on both being to high .The car was serviced when laid up new oil and filter flushed cooling system by previous owner.Going to have a look over the weekend .With a friend who knows his stuff.Also going to buy a new collant temapture sensor .Where is the best place to buy from rimmers maybe?.Thankyou all very much for your help.As i said looking foreward to driving the car.........................Cheers Mike
A few weeks ago my car (86 350i) started running like the choke was fully out; incredibly rich. Turned out to be a poor connection in the main ECU plug under the dash; I simply disconnected and reconnected the ECU and now all's well. Try the easy things first; disconnect and reconnect all the sensors too.
Hello Mike glad to hear you are so close to getting the car back on the road. The emissions were never an issue all the times I had the car tested as the old MOT sheets should show. Have you taken out the spark plugs and cleaned them like I suggested some time back? It really is worth it before you start spending time and money elsewhere. As the car has only been started and run for numerous short periods in the garage the plugs are almost certain to be sooted up, a quick wire brush costs nothing but a bit of time and could make a huge difference. Regards. Steve.
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