Help! Help! Help! Why Is My Car Doing This ?

[jayripcurl]

hi guys can you help me any idea more than welcome. My car is playing up and its driving me mad.Each time i start the engine in the morning i get a kind of miss fire when she starts and i can not drive away for about 10 mins untill she has warmed up and then it clears and drives fine.
But if i turn the car off after running for a few mins then leave turned off for 1min then start again she run perfect with out no miss fire and i can drive straight away.
Iv had new plugs,leads,coil in the last 3 months and i only had new distributa cap and rotar arm only a year ago so i dont think there is a problem with them.The car has been doing this for about a year now ever time i start her when she is cold.
please help with some ideas as i cant think what it is and iv asked a garage and they had no idea why the car is doing this and they wanted to take her in and no dout rip me off spending hours and hours on end looking
Many many thanks for ur help and ideas

justin

[Munkee_Boy]

First thing I would check would be a bad coolant temp sensor/switch. The coolant sensor seems like it could be it since when the engine warms up it runs fine.

[M3 Mitch]

Yeah, what Mr. Monkey said - if the car runs good when warm, but bad when cold, a good guess is that the coolant temp sensor is bad. Search and you'll find the ohm spec for it in one or more threads. Note that there are 2 sensors, one for the dash gauge and one for the ECU, it's the ECU one that is likely bad.

Do yourself a favor, get a VOM and learn to measure electrical components, don't go around "Easter egging", that is, to change this, change that, till by hit or miss you eventually change the part that was giving the problem. There is nothing wrong with changing out any wear part that's old enough to be suspect, catching up on deferred maintenance is always a good thing. But sensors and etc. can go a long time and if they are working right replacing them only wastes your time and cash. That and if you can't find a shop that really understands the E30 M3, you might as well get used to doing your own work. You will soon be more knowledgable than the local hacks about your car, and the advantage is that "the doctor is always in" if you learn to DIY.

Just my $.02

[Bruce]

It is the blue one. Could be the connections, but most likely it is the actual sensor.

[slow]

I have exactly the same thing on mine: lumpy/slight misfire when cold for the first 1-2 mins, but perfectly fine afterwards and when starting up from warm/hot.

I spoke to another E30 M3 owner and he said they all do that?

If the coolant temp sensor is the fault, how much is the part to replace?

[Dougy Fresh]

maybe o2 sensor

[Bruce]

I have exactly the same thing on mine: lumpy/slight misfire when cold for the first 1-2 mins, but perfectly fine afterwards and when starting up from warm/hot.

I spoke to another E30 M3 owner and he said they all do that?

If the coolant temp sensor is the fault, how much is the part to replace?

They all do that when the blue coolant temp sensor is bad.

Last time I checked it was probably a $20 part.

[Mmark]

How about something different?

1, If you have a Lambda equipped car, the car will be very reluctant to run until the lambda sensor is up to optimum operating temp and can tell the DME what the O2 content is in the exhaust. Then the DME can accurately correct fueling and timing, PLUS the engine is warm enough that the fuel is not falling out of suspension.
This condition is affected somewhat by the amount of carbon deposits in the combustion chambers and on the exhaust valves... The carbon soaks up fuel and messes up the management somewhat.
2, if the car is lambda equipped and the sensor is bad, then the DME has one less input needed to fine tune the fueling, with unpredictable results.

3, If the car is non-cat, it may be a problem with carbon deposits, clogged injectors, clogged fuel filter, sticky airflow sensor, a batch of bad fuel.

IMO, Due to the electrical nature of the coolant temp sensor, you generally see worse running when the car is warm because when it fails, the DME tends to overfuel the car, causing rich misfires. When the car is cold and loses fuel due to the fuel condensation on cold steel and aluminum, and extra fuel required to start, the excess fueling caused by a bad CTS is tolerated.
Once the engine is up to operating temp, it needs less fuel.

m

[Mmark]

One more thing...How old are the ignition leads?

If they are in the original holder and are older than 3 yrs old, you may want to split the holder and see if some of the leads have the insulation damaged or penetrated.
Bad ign leads cause a lot of ignition misfiring when the engine is cold.
If the leads are old, look at the distributor cap and rotor for carbon tracks and damage.

m

[dynospot]

When the car is warming up, the ECU does not use the oxygen sensor for input because until the sensor is reaches a proper operating temp, the sensor has very poor accuracy. O2 sensor heaters are common in many new cars due to this. But, I would say, from cold, it will take about 2-4 minutes before the ECU will begin read the O2 sensor. I would also suggest the CTS.

[jayripcurl]

wow thx for all the info i shall look into all that you guys have sugested and fingers crossed ill sort it out.
the leads are new in the last 3 months but the sensor ill for sure look at,are they the onces that are both together on that cooling pipe near the exaust header (mainfold).i can get a meter to read and test any ideas what it should be.
And does any ones fan on the front allways run as soon as the ignition is on ?

[jayripcurl]

cool i have just orderd a new one with www.C3bmw.co.uk for £13 pounds and i spoke to the guy and he said that it is a commom problem with them.the guys are are realy good and the site is amazing they have so much stock of genuine parts for the hole car,you guys should check the site out
thx again for your help chers

[timsteren]

I believe that on early euro cars eg from 1986 that the electric cooling fan should always run on low speed when the ignition is on and that it switches to high speed when triggered by the temperature sensor on the radiator. On later cars the fan should be off when the ignition is on and there is a dual temperature switch that switches low speed on at a certain temperature (depending on the switch) and then high speed at a higher temperature.
Cheers, Tim.

[jayripcurl]

ar sweet chers mate that makes perfect sense she is an old girl.