Coolant temp sensor

[Ryan12345d]

Ive got a 91 535i that runs very rough when it is started cold in the mornings. i replaced the headgasket on it about 100km ago. I have read up on what could cause this, and one thing is it could be the coolant temp sensor. i just measured it then and it got a reading of 3.57K. this was taken with the motor stone cold (hasnt been started for a few days) and it was only a max of 14degrees celcius today. i do not think it is anything to do with the headgasket, as when i rev it it blows a dask colour smoke (not white steam).if i rev it and keep it at about 1500rpm for about 30secs it will then idle fine. i have had it upto its proper operating temperature and the system was pressurized as normal, i then parked the car and felt the hoses 2 days later and they were still sort of hard so i dont beleive there is a leak of any sort. If anyone could help me it would be appreciated.

[Paul in NZ]

i am very interested in this,because this is the exact trouble i am having with my car...however my hoses are very soft the next day.I was thinking today that it could be the temp sensor,quite a petrol smell when starting although i thought the exhaust was normal when the car was hot....I am gooing to try to clean the sensor connections for a start

[Ross]

Temp sensor seems within normal range. Definately too rich if black smoke.
It may be injector(s) leaking down after shut off or maybe a pressure regulator gone south.

[Ryan12345d]

one thing i have noticed, is that if i start the car and leave it in neutral it will idle fine, but if i start it and put it straight into drive, it really starts idling rough and shakes and almost stalls at times.however after a while it comes good.i tried the "stomp" test but my car doesnt seem to have an engine light?is there any way to check the pressure regulator without a fuel pressure gauge?ive got a hand vacuum pump so i can check for whether it holds vacuum i suppose?

[tim eh?]

one thing i have noticed, is that if i start the car and leave it in neutral it will idle fine, but if i start it and put it straight into drive, it really starts idling rough and shakes and almost stalls at times.however after a while it comes good.i tried the "stomp" test but my car doesnt seem to have an engine light?is there any way to check the pressure regulator without a fuel pressure gauge?ive got a hand vacuum pump so i can check for whether it holds vacuum i suppose?

that stomp test is really handy, it diagnosed an oxygen sensor problem for me. not sure about australian models, the european models don't have it i believe. but if it's just the bulb i'd be borrowing the dash parking brake light bulb to try it out, it might pinpoint your problem right away. when i bought my car the CE bulb had just been removed for obvious reasons.

there is a good photo of the back of the cluster on bruno's wiki site (http://www.bmwe34.net/Wiki/tiki-index.php?page=Dashboard+capacitors). you should be able to reach the bulbs without taking out the steering wheel, but put a cloth on the steering column so you don't scratch the cluster face.