E30 Zone

as it say in the title iv had the blue temp sensor changed to a brand new genuine BMW one brought from Cotswold....
my car is a 1989 m20b25 cab preface lift factory engine not an upgrade.......no silly cone filters etc all standard except a straight through exhaust from manifold....
now im noticing these problems fuel efficiency hasn't got better due to this behaviour of my engine

my car seems to idle just above 1000rpm when it should be about 500-750rpm, other times it revs slightly by itself, in the mornings i assume these cars have an auto choke it comes on when i drive the car it revs slightly higher then as i come to a stop it drops in revs... if i just blip the accelerator when its revving by itself the revs come down to 500-750 rpm but then creep up slightly,
i have a reasonable mechanical mind and i think i can tackle this problem my self, im thinking possible t.p.s or air leak or maybe a good clean of the inlet and attachments etc but please put me on the right path so i can diagnose this problem as its annoying when you sit in traffic and revs by itself....


t.ia

might not be the same problem but i had the same symtoms and worse after a year of trying to find out what it was it was the earth to the blue temp sensor had broken down not the sensor its self but yeah sounds like air leak of some sort

cheers ross all info appreciated, so the connector that fits the blue temp sensor where does it lead back to? so i can diagnose this earth

i really dont know mate i just cut the wire and put a new earth in to just under the inlet

ali50ferrari wrote:cheers ross all info appreciated, so the connector that fits the blue temp sensor where does it lead back to? so i can diagnose this earth

Won't be a completely honest test, but you could just check continuity from the wire in the plug to the frame or anywhere else something earths. Might give a false reading of amount of continuity, but you will at least be able to see if there is any or not.

(until someone comes along and says where the earth runs to)

Bump for a cure please

The temp sensor wiring passes through C191,the round plug thingy located on a metal bracket underneath the inlet manifold.I would suggest that you split this connector and check for water ingress and corroded terminals.

Ok will look on friday on my day off and report back any other hints or tips?

any more info out there

To me it sounds like a vacuum leak, very common on these motors. If you can get access to a smoke machine that is the best test. Check the attachments to the throttle body, esp the ones to the booster.

Also there is a way to rebuild/repair your idle valve:

http://socale30.com/theforum/viewtopic.php?f=1&t=6029

I just did this and wow, I have a smooth idle now (and adjustable)

Still no luck man