Engine runs Rough when Cold

[BeemaBoy]

Hi

I have just joined this website forum after it being highly recommended by a friend of mine. First impressions are great, so keep up the good work!

To jump straight into my problem, I have a 1987 E30 320i (Oh yea, E30's rule. This is my first car as Iam 19 year old student. She takes nearly every bit of money I have but hell she's worth it!) that for the past 4 months has a very annoying problem. When I first start the engine in the morning, there is no problem. She starts straight away and idles perfectly. The problem starts as soon as I pull out of the driveway and get onto the road. When I accelerate in any gear, the engine feels very rough and tends to jerk and shudder(almost like it the engine is missing or something). I will have to floor the accelerator to get it to move forward. It also seems to chuck out a lot of white smoke aswell. All of this will last until the car is almost off the blue zone on the temp guage and then everything is ok. She accelerates smoothly with plenty of power and no smoke. It is actually quite embarresing when you pull away from someones house and the car jerks and smokes away .The car has just come back from a quick service that had the mixture and idling adjusted but that service has not fixed the problem. Can anyone suggest a fix for this??? The engine is the Vacuum type engine with fairly new spark plugs and cleaned out fuel injectors. Could this mean that the Air Flow meter or cold start injector is stuffed? Any suggestions would be great

Thanks
BeemaBoy

[Simon]

First thing I would change is the blue temp sensor, located on the thermostat housing, change the brown one when you're there, the blue one is for the ECU, and the brown one is for the temp guage.

[Simon]

Ohh yeah, and welcome to the zone!!

[BeemaBoy]

Hi

Thanks for the welcome and the very quick response. I have just looked at my engine and I do not seem to have a blue plug. I only seem to have a dirty brown one and a dark red one. The dark red one is the one furthest from the radiator. Just to ask, do you think that the temp sensor would be lying to the ECU and getting it to inject too little fuel into the mixture?

Thanks
BeemaBoy

[Simon]

Hi

Thanks for the welcome and the very quick response. I have just looked at my engine and I do not seem to have a blue plug. I only seem to have a dirty brown one and a dark red one. The dark red one is the one furthest from the radiator. Just to ask, do you think that the temp sensor would be lying to the ECU and getting it to inject too little fuel into the mixture?

Thanks
BeemaBoy

Hi yes, the temp sensor will over fuel the engine and hence the rough running when cold, sounds like the sensor that's fitted may be incorrect, or aftermarket, it would be a good idea to get a new one from the main dealers, (not too expensive) and change it, let us know how you get on!

[BeemaBoy]

Cool thanks.
I will order the new sensors and fit them tomorrow. I will get back to you as soon as possible with the results.

Thanks
BeemaBoy

[Andy_magic]

do you think that the temp sensor would be lying to the ECU and getting it to inject too little fuel into the mixture

Thats pretty much exactly what happens, the sensors age aswell, a film of oxidisation builds up on them so the don't read the temp of the water properly.

Another possible is that the ECU was re-set with a warm engine, the engine then re-learns its setting thinking that luke warm is actually cold, when the engine does get cold it over-fuels badly until warmed slightly.

I reckon you plan of action should be get a genuine temp sensor and fit it with the engine cold, then bleed the cooling system properly and disconnect the ECU (With the ignition off) leave it for 5 minutes and then re connect, go for a nice drive somewhere and drive like you normally do.

This should reset the ECU parameters and it will drive better, you might need to get the CO checked again as it can change.

Is your car the L jetronic or the motronic one as I think 87 was the changover year. The above tips are aimed at the motronic cars.

Good luck and welcome to the zone

[PeteE30Tourer]

I have the exact same symptoms on my 325 Tourer, but after asking around lots of people, both on here and at BMW, the concensus is that either the head gasket has gone, or more likely, the head is cracked. What's happening is that when the car is left for any period of time, the pressurised cooling system allows water to escape either through the gasket or the crack in the head into one of the cylinders. Then, when you start the engine, that cylinder wont fire because the plug is wet. Then you get loads of water vapour blasting out of the exhaust for the first few miles until all the water is gone, the spark plug can do it's job again and all is fine once more.

I really hope for your sake that it is something as simple as the temp sender - i dont think it is in my case as i have replaced them in the past 12 months. I'm already resolved to the worst case though - head is coming off and being replaced.

Keep us posted as to how you get on though - it's good to share the results as well as the advice.

Oh - and welcome to the zone too - you'll never go wrong on here!

[BeemaBoy]

Hi all

Hey man, sorry to hear about you're problem with the head gasket as I know it is expensive to replace as I had it replaced as part of the deal when I took the car after I discovered the mine was cracked. So I hope mine has not gone again!

I finally got around to taking out the temp sender and testing and cleaning it out. My Haynes manual states that the resistance in ohms should be between 2400 and 2800 when cold and the sensor only seems to be at about 800 when cold until I discovered an interesting thing. Earlier in the post it was mentioned that the temp sender to the ECU had a blue cover on it and that the other one sent the temp to the guage on the dash. Funnily enough I found that the cover cap to the sensor had faded to white and that the actual colour of the sensor under the cap was infact blue. The only problem is that according to my BMW Haynes manual, this is suppost to be where the sensor that sends the signal to the temp guage is. Is it possible that some time in the cars life that a mechanic or the owner has been confussed about the location of the sensors and has put them back in the wrong locations. And, just to ask has the one that connects to the dash temp guage got 2 terminals inside the cap or just one. I ask this as the sensor with the blue cap has got 2 terminals where as the sensor that has a red cap on it has only one terminal. I have tested the sensor with the blue cap and the reading gets to about 1700ohms and then fades and goes back to 1ohm on the multimeter Iam using. Could this mean that the blue sensor is shot. I got a price from BMW that was about R271 which is about 23pounds. Does this price sound right for the sensor?

Thanks
BeemaBoy

[Simon]

The blue temp (ecu) sensor has 2 connections, while the brown temp (guage) sensor has one connection.
The brown sensor is mounted first inline and is easier to get to than the blue one is mounted further down, the connections should be colour coded too.
The price for the sensor from the dealers sounds about right, you can pick them up cheaper from ECP/GSF, but for a part that plays a big part in the way the car runs, I would get the dealer version.

[Andy_magic]

1 ohm is almost a dead short, it should be around 300-400 when running at 80 degrees C (Check your thermostat)

I'm guessing that the shipping from ECP/GSF might be a little more expensive than a dealer part. Does the R stand for rand???

I bought one a few weeks ago and it was Ԛ£18. Worth every penny, thermostats are Ԛ£20, again worth the money as a car running too cool will cause running problems/bad MPG.

[PeteE30Tourer]

I dont mean to question anyone's responses here, but can someone please explain why the temperature sensor would cause the problems originally detailed in this thread. I dont think the same applies to my problem, but for the sake of a better understanding and a few measurements, i'd like that peace of mind before going spending hundreds of pounds replacing my head.

Apologies for hijacking the thread slightly.

[Andy325i]

I dont mean to question anyone's responses here, but can someone please explain why the temperature sensor would cause the problems originally detailed in this thread. I dont think the same applies to my problem, but for the sake of a better understanding and a few measurements, i'd like that peace of mind before going spending hundreds of pounds replacing my head.

Apologies for hijacking the thread slightly.

Here goes for the blue senser:

It has three states (cold/warm/operating temp) The value from this is read by the ECU which then decides how much to richen the engine by (a lot/alittle/none) when they play up they normally tell the engine it is colder than it is. Thus the engine has too much fuel and runs like a shed until it reaches warms up.

Is this right?

Pete, how much water are you loosing?

[Andy_magic]

The engines fuel delivery and metering is pretty much dependant on the information given to the ECU, if the ECU is beign told the engine is -30 degrees C it will fuel accordingly, likewise if its being told it is 42 degrees C it will fuel accordingly.

If the ECU reckons the engine is at -30c it will over fuel to the point of bore wash, this is where the amount of petrol being injected into the cyliders is so great that it washes the thin film of lubricating oil off the bores and burns it, leading to blue smoke, quite a lot of it. (and lots of engine wear due to no oil in the bores)

As the original post was about smoking and rough running, rather than just say "Get a recon head" at Ԛ£400-500 and given the information from the original post an Ԛ£18 sender is a good place to start.

Given that these sensors do age/breakdown and could probably do with changing every 4 years or so.

They age as they are in a pretty harsh environment, not only does the temp go up and down every time the engine is ran they also suffer from oxidisation, leading to incorrect values beinf fed to the ECU. Another form of damage comes from osmosis (spelling?) This is caused by poor earthing of the engine, it's a huge topic that I'm not going into here.

Hope that answers your question

[BeemaBoy]

Hi All

I did finally manage to get to the blue temp sensor after removing half a dozen other things! After I removed it, i cleaned it because it was thick with rust (I think the prevous owner let the Anti-Freeze level get too low). I managed to get it back to a nice shiny brass colour. I then whipped out my multimeter and gave it a test. Too my suprise it was giving a reading of about 1600 ohms after I had held it in my hand. Following what info I could get from my manual and you guys I tried my best to test it through different temperatures (From 2400ohms to about 400ohms).
Basically held the brass bit it the kettle as it was heating up and tracked that the ohms change as it heats up, getting to about 540ohms when the water was hot. Guess there is no problem there. I then tried hanging the sensor in my deep freeze fridge and checking the ohms then. They rose to about 1970ohms and then nothing. The multimeter went back to 1ohm. I then took it out of the freezer and slowly heated it up again. As i was checking it suddenly at about 1990ohms came back to life and began changing resistance as it heated up.
To get to what Andy_magic was saying about the resistance being 300-400ohms when at 80C, the mutimeter is showing 1ohm when the engine is stone cold. I dont think it is the thermostat as the engine seems to get to about 2/5th of the way, just under the half way line on the temp guage. As I said earlier, everything clears up after about 3 minutes of driving.
Iam also pretty worried about what you said about the engine wear caused by the oil being burned off. As today is a pulic holiday in South Africa I will have to wait till tomorrow to get the sensor (If it is in stock).
I will replace it as soon as the engine cools down and get back to you guys with the verdict,

I also forgot to mention earlier that my car is infact the L-Jetronic. It was one of the last made before the switch to Motronic.

Thanks
BeemaBoy

[Andy_magic]

I think the L-jet system has a thermo-time switch to control cold start fuel enrichment, I don't know the procedure for checking this out as it's been a few years since I had an Ljet powered car.

I'm sure someone can help.

[krazypaul]

My 320i (March '87) suffers from exactly the same symptoms as you, so I will be interested to see if replacing those sensors improves the situation!

I have also been told that my exhaust manifold is blowing when cold, could this contribute to the poor response when the temp is cool?



kp

[BeemaBoy]

Hi all

Sorry to take so long to get back to you. Hey Krazypaul, nice to hear someone is battling through this damn annoying problem aswell.

Here is the latest. I have finally got the 2 sensors from BMW (The blue and brown one) and I installed them today when the car cooled down. I have not been able to test the results yet as I want to leave the car overnight so that it is stone cold in the morning. Will give the results when I get to work .
Funny thing, about what I suggested earlier that maybe the cap of the blue switch(Temperature Sensor) had faded to white and thats why I incorrectly identified it. As my car is a L-Jetronic is it possible that this car has something called a Temperature Switch mentioned earlier in the thread??? I mean, if the guy I bought the car from thought he could save some money by putting this sensor inplace of the other, this would cause serous problems, noh? And this could easily be done as www.realoemparts.com/bmw states that these 2 sensors are interchangable in the same hole . Does anyone have a L-Jetronic whith a white sensor that can confirm this for me . I have had a look in varous websites and they all say that the L-Jetronic has no blue temp sensor. Could the prevous owner be that careless??? My hayness manual also tells you to probe the black/yellow wires on the sensor cap, and guess what, I seem to have a black/yellow wire going to the white cap . I don't.......Just don't know anymore!!!

Thanks
BeemaBoy

[BeemaBoy]

Hi

To get to results: Started car up this morning, with the outside temp being pretty cold and she started first time with no smoke or mist at all. But now the real test, accelerating with engine cold in 1st gear upto 3000RPM. And guess what----No smoking or jerking of the engine at all. And I have noticed that the engine seems to REV a lot smoother than it used to. Guess I was splitting hairs in the last thread . So I would say that this has solved my problem even without having to reset the ECU. BTW did have the ECU system adjusted not too long ago so that may help. The only thing I can think is that the rate that the older sensor use to change in resistance in no longer preportional with the actual engine temp. So if you have the same problem, it is probably worth replacing this part even if it seems to be working. It is one of the cheaper parts I have had to buy!

So thanks a lot people for all the help as I would have never in a million years think that it was the Temperature Sensor. I thought it was a bad injector .

Thanks
BeemaBoy

[hogweed]

The Haynes Book of Jokes has the WRONG temp sensor arrowed in its picture, ie the brown one is identified as the ECU sensor.

Do yourself a favour, and use the Haynes book for lighting the fire.

[TouringMatt]

Hence the fact i call it "The Haynes Book Of Bullshit"

Pleased you sorted it out BeemaBoy, im having similar problems and after reading this thread will change those sensors too

Matt