1100 rpm idle when hot! mot co2 fail!

[thealchemyst]

right then chaps time to tax your little grey cells if i may?
after a couple of weeks layed up (with battery disconnected) due to gearbox swap ive noticed that the idle has been running slightly fast when warm 1100rpm as opposed to 850-900rpm as it used to, add to that the fact it failed the mot on emissions yesterday, im guessing something is wrong with it!
other than the slightly fast idle and failing the emmisions the car runs faultlessly from tickover to vmax no probs
have read a few similar old posts after a search but none of the posters have comeback to say what was the cure/fault or if they ever fixed the problem.

so any ideas?

oh yeah! mot man recons it might be that the exhaust clamps need tightening!
cant see that cureing it myself but ill do it anyway!

[rippedoffagain]

Originally Posted by thealchemyst

so any ideas?

oh yeah! mot man recons it might be that the exhaust clamps need tightening!
cant see that cureing it myself but ill do it anyway!

Plausible. If air can get in before the lambda sensor(s) then you're ECU might be thinking the mixture is too lean and increasing the fueling.

Other than that, vacuum leak in an air hose somewhere perhaps?

[thealchemyst]

could be an air leak so many damn hoses on these things! i guess one could have come loose or split whilst ive been doing the gearbox swaps guess i'll start checking the hoses in the morning.

[Rnash2002]

You have probably seen one of my old posts,mine does the same only once warm,when i turn off the engine and then turn on again its fine untill i go for a drive.
Havent found the problem yet,ive done most things,no codes comming up.
If you find anything out let me know,it still pee's me off lol but got used to it now aswell.

[thealchemyst]

doesnt bother me other than it failing the mot! got a month to sort it im gonna replace all the small vac/boost lines and clean out any larger breather pipes see if it helps!

[pigpott]

hi all mine is the same so would love to no why this is but i do have a hole it my back box was just thinking it was that. mot in march so will try to sort it for that. if i can get the bonnet open by then snapped cable on sunday after fitting dump valve only wanted to ajust the waste gate after a run around the block

[thealchemyst]

read codes tonight and one was fuel trim out of range and another was faulty or missing maf sensor output, so after id come home from work i left it idleing and disconnected the maf sensor plug and it kept right on running exactly as it had been before! and didnt change when i plugged it in again. im thinking that this is pretty strong evidence the maf sensor is bow loxed as im sure the car is supposed to stuter and even stall if you disconnect the maf sensor when its normally working but if its faulty the ecu uses a base setting and ignores the sensor alltogether!
does this make sense?
if your maf sensor has gone did it have no effect when unplugged?
cheers for any feedback

[Rnash2002]

I tryed this also with my maf and run alittle more lumpy but didnt stall,tryed another and made no difference.
Least your getting codes to work from,mine has none come up.

[Matthews 855 T5]

Originally Posted by Rnash2002

I tryed this also with my maf and run alittle more lumpy but didnt stall,tryed another and made no difference.
Least your getting codes to work from,mine has none come up.

Thats because your MAF is working as it should. Its only when you disconnect it and there is no difference to running then you know your maf is bad.

Matt

[thealchemyst]

Originally Posted by Matthews 855 T5

Thats because your MAF is working as it should. Its only when you disconnect it and there is no difference to running then you know your maf is bad.

Matt

so that means mines dead then! as mine just carries on regardless of wether its in or not!