hi guys,
my car was doing some strange stuff today . firstly it was running fine but when i turned it off it kept running for about 4 seconds while making a strange kind of gear grinding diesely engine grr sound followed by a big puff of smoke coming out from under the bonnet . now its done this before maybe 1 or 2 times before. why does it do this and what is it doing to make the noise and smoke??? after doing this it started and shut off again normally . now the other question i have is..... when these cars have problems and fault codes are stored on the ecu memory does the ecu continue to try and compensate for a now repaired and non existing problem?? do you need to wipe these old codes off the ecu for it to run ok again or not??? you see i adjusted my afm because i had a 1300 rpm idle which i got down to 1000 which i was happy with, but now the bugger is back up to around 1300 on tick over when cold or hot.
The problem you describe is raer on EFi cars, think it was pre ignitioning and was quite common on poorly adjusted carb models, it is also called over run.
Basically the engine continues to run after the ignition is turned off and the fuel vapours comust making it run and make the pinking type noise.
Not really sure what would cause this on an EFi car quite possibly an air leak on the inlet side.
AFAIK the ecu is pretty thick by todays standards so if a fault occurs it will most likely just do its best to keep running but I may be wrong.
Cheers
Luke
Please call me Luke
1989 BX 16valve White 70k almost up to scratch
hi guys
aha well it did do this when iw as in the middle of messing with the afm so was probally running really rich at the time. i put 20 quid of premium unleaded in and got about 4 hours ticking over and it was gone i have been quite blindly adjusting the afm to try to get it to tick over and run properly.
could someone clear something up for me please.!! now with the top off the afm i can see there are two parts you can adjust. you can tighten or loosen the spring flap and also you can loosen the wee screw and move the pointy arm about a bit. now can someone tell me for sure, ..... which richens and which weakens the fuel mix when you tighten/loosen the flap spring. and also moving the little arm which direction left /right does what to the cars running.
Chances are you have buggere your AFM if you have been messing with the spring tension.
If you move the small arm left or right that basically just changes the part of the carbon track that it runs on so doesn't affect the mixture directly.
To adjust the mixture you can rotate the plastic cog tyoe thing on the top of the flap, the stronger the tension the weaker the mixture as you wil need more flow of air to move the flap.
Cheers
Luke
Last edited by Toddman on Tue Oct 10, 2006 6:52 pm, edited 1 time in total.
Please call me Luke
1989 BX 16valve White 70k almost up to scratch
hi luke,
ok so that makes sense now. more tension less fuel. though i have found moving the arm does slightly adjust the idle rpm, i found going more to the left lowers the rpm and to the right brings it up considerably, i had it ticking over at 2000rpm then back to 1300 when i re-adjusted it. i will play around more now i know how to weaken it and get back to you guys on this one.
hi there,
throttle switch sticks a little sometimes on startup but only if i dont push the gas a few times before turning the key, so its not that. im not sure what you mean about the 2 inlet valves? i hear my idle control valve making noises occasionally so i think that works.
sorry, i mean the throttle valve! is that correctly adjusted? That cause normaly a high rpm idling. adjustmentscrew just touching the metal, and then + 1/8 of a turn. after that adjust the throttle switch, that you can hear a click when you give a little bit throttle.
Adjusting the AFM at idle is really not a great idea, as idle mixture can be adjusted separetely anyway! only under load do the changes feel any different...
If it can't be driven then wait till it can before trying to tune it.
Also idling a car for 4 hrs is very bad for it indeed and that much overfuelling has prob washed half the oil from the insides of the engine....
As for tyhe fault codes it is very very thick, it will keep the engine running on guessed setting for some sensors and thats about it, if major ones like AFM fail it just stops as it has no backup information. Most major faults are intermittent when it looses vital info like TDC or AFM momentarily through poor connections, a soon as the info is back it uses it immediately if within parameters. If a fault resets itself - like we plug its sensor back in! it does remove the fault itself so no need to clear them manually.
Fault codes on this system are fairly useless as the real fault is more often going to need a multimeter or Osciloscope to fix, and an operator with time, experience and the tools to understand it.
hi there,
dont worry ive never let it idle that long i normally switch it off to cool before the cooling fan comes on. my afm is a re-con one fitted last year. it does work. the only sensor i know isnt working is the oil temp sensor cos it doesn't work/isnt connected. i haven't adjusted the new throttle body tps since i fitted it so maybe thats the problem. but i know now how to adjust the idle mix through the afm cos luke explained it to me so i will give that a shot later.
. firstly it was running fine but when i turned it off it kept running for about 4 seconds while making a strange kind of gear grinding diesely engine grr sound followed by a big puff of smoke coming out from under the bonnet 
. now its done this before maybe 1 or 2 times before. why does it do this and what is it doing to make the noise and smoke??? after doing this it started and shut off again normally 
. now the other question i have is..... when these cars have problems and fault codes are stored on the ecu memory does the ecu continue to try and compensate for a now repaired and non existing problem?? do you need to wipe these old codes off the ecu for it to run ok again or not??? you see i adjusted my afm because i had a 1300 rpm idle which i got down to 1000 which i was happy with, but now the bugger is back up to around 1300 on tick over when cold or hot.
