1991 316 e30 idle problems

[paddywack]

started my 316 e30 yesterday morning let it idle while i scraped ice off windows after 5min idle dropped to the point of almost cutting out then the revs began jumping from about 750 to 1200 rpm. went for a drive and seemed to run a little rough got car upto normal temp still no diffrence so gave it a bit of a thrash and it wanted to tick over bout 5000 rpm switched it of and restarted it and it seemed to be fine, just wondered if anyone out there had any explination on this... or could car just have been tempramental due to the cold... any help or info would be greatly appriciated thanks

[E30BeemerLad]

is it a 316 or a 316i?

[paddywack]

hi there its a 316i

[E30BeemerLad]

check the usual rubber inlet hoses for any leaks/ splits etc.

Also worth checking the throttle position switch found at the bottom of the throttle body is making a slight click sound when you open the throttle ever so slighty from closed (need the engine off to do this and operate the throttle with your hand on the mechanism at the top of the throttle body). The throttle position switch can get a bit gummed up inside or could have been a little frozen up.

Just guesswork on my behalf and where I would be looking as part of a process of elimination

[paddywack]

thanks for that i shall check the hoses tomorro, as for checking the throttle position switch if it clicks would that mean that its ok?.. you may well be right about it possibly have been a little frozen up as it was realy cold the night before so what your saying makes sense.. thanks again

[E30BeemerLad]

yes if the switch clicks then it would point towards it working rather than not, but is not an absolute guarantee.

[paddywack]

cheers ill check everything out tomorro.. will let you know how i get on thanks once again and and wish you a happy new year all the best

[Dazdabomb]

i had this exact same problem the fault on mine was a small crack where the cps joins on the ht lead, mositure was getting into it while the car was sat overnight, a set of leads and a new sensor solved it for me.

[paddywack]

thanks i was out in the car today never went that far but far enough to get it up to normal temp drove it for a couple of miles and it seemed fine.. so perhaps it was just down to it being cold or the car having a wee tempramental moment. though you could be right about the moisture thing as i stay in a valley next to a river.. but ill check out the leads and sensor tomorro anyway just to be sure. but as i said it seemed ok today... maybe it was just one of those strange freaky things.. thanks