Question about BMW 525

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Car runs rough when hot

Black smoke srart great when cold then goes funny at running tempature changed fuel pump main one in engine still doing same this is a 525tds m reg 1994

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Mixture control black smoke is rich mixture ,but sorry not sure what or where the control is weither its a sensor or a ECU fault. most likely cause is the autochoke staying can only sugest the main agent or a decent garage who have some test equipment .if you see any sensors in or around the top of the engine try disconnecting them one at a time and see what happens if it stops,and engine will not start when its cold then you have found the problem .

Posted on Nov 11, 2008

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STARTING PROBLEM, WONT IDLE,BLACK SMOKE, ONCE STARTED IT SOUNDS ROGUTH


This problem is a bit more difficult to diagnose because half of your symptoms rule out half of the solutions. I would think the ISC control could be dirty or not working or your fuel injectors are sticking open.

With black exhaust smoke you are running rich. Often the "Cold start sequence" is at fault for poor starts making the engine too lean when the sequence fails. An intake air leak can cause the engine to run Rich, causing the black smoke, rough idle, rough running conditions. This is still a possibility, but the on-board computer usually sets a Code saying you are running "Lean" and then enriches the fuel ratio and floods the engine by itself.

Now the fuel injectors can cause several of your problems. For start-up problems, the remaining fuel pressure can dump fuel into the engine as the car sits because the injectors are sticking open. Someone would need to perform a fuel pressure bleed-down test to see if you have this problem.

Another way to verify this problem is to capture the oil during an oil change and smell it for gasoline fumes. The dilution of the oil will destroy the engine. If the injectors are found to be the problem, a new oil filter and change are needed.

Mar 17, 2014 | Ford Escort Cars & Trucks

2 Answers

Occasionally runs rough


This is usually caused by a bad crankshaft postion sensor.

Oct 02, 2008 | 1991 Mazda 626

1 Answer

1990 Jeep Wrangler 2.5l idles rough/ black smoke/ fuel odor


You could pay a garage to diagnose the problem cheaper than throwing more parts at it.
The problems may be connected or they may be different issues.
Yes I would change the oil and filter, but first I would make sure the fuel system is not dumping too much fuel into the cylinders.
The O2 sensor helps the computer decide on how much fuel the engine needs, along with the other sensors. And you said you have already replaced the O2 sensor.
A mechanic would take a scanner and "read" the sensors and look for something out of normal range.
The fuel pump and fuel filter are off the list as far as causing a rich mixture goes.
I would start with the rich mixture and then see if fixing that issue takes care of the no start when hot issue.
Change the oil and filter first, and see if the injector is on too much.
You can watch the spray and tell - at idle it should be very light.
Also look at the engine temp - is it warming up to normal 195 degrees? Can you tell if the fuel pressure regulator is blown and pouring fuel into the throttle body ?
Without a scanner its going to be more difficult, but not impossible to diagnose.
Let me know what you find out.

Jul 23, 2012 | 1990 Jeep Wrangler

2 Answers

Black smoke>fuel consumption>rough idle


Hi there:
Black smoke is caused by excess fuel that has entered the cylinder area and cannot be burned completely. Another term for excess fuel is "running rich." Poor fuel mileage is also a common complaint when black smoke comes out of the tailpipe. Black smoke out the tailpipe is the least cause for alarm. Excess fuel will usually effect engine performance, reduce fuel economy, and produce a fuel odor.

How did the fuel get into the cylinder in the first place? Some of the causes of excess fuel are a carburetor that is out of adjustment, a faulty fuel pump, a leaky fuel injector, or a faulty engine computer or computer sensor. If black smoke is present, check the engine oil as in the white smoke example to make sure excess fuel has not contaminated it. Do not start the engine if a heavy, raw fuel smell can be detected in the engine oil. Call your mechanic and advise him of what you have found.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Mar 04, 2012 | Cars & Trucks

1 Answer

1998 GMC Savana 3500 5.7L. Truck starts ok when cold. After running, very difficult to start have to pump the pedal and hold to the floor. Fuel pressure jumps to 62psi when pump runs, drops to 58 and holds...


HOW MANY MILES ALOT IT REALLY SOUNDS LIKE YOUR O2 SENSOR OK LOCATED ON THE EXAUST PIPE CLOSE TO ENGINE UNDER THE HOOD THEY CONTROL YOUR FUEL MIXTUER FOR HOT AND COLD LIKE A CHOKE . IF ITS BAD THE ITS FLOODING IT OUT WHEN HOT AND YOU GET ROTTEN GAS MILAGE BECAUSE YOUR FUEL PRESSURES ARE FINE REGULATORS EITHER WORK OR THEY DON'T AND IT THEY DON'T YOUR TRUCK WON'T RUN O2 SENSORS GOING BAD DON'T ALWAYS GIVE A CODE OR A DASH LIGHT BECAUSE OF THE BAD GAS MILAGE AND BLACK SMOKE WHEN IT IS WARM ITS PRETTY OBVIOUS WHAT IT IS OK GOOD LUCK POHLCAT

May 03, 2011 | 1998 GMC Savana

2 Answers

86 Ranger 4X4 2.9 fuel inj runs rough when warmed up


1988 ranger 2.9 runs great cold then after a few minutes when warmed up hesitates with intermittent black smoke from the tail pipe until i hit the the throttle then clears and will repeat this behavior...

Jan 26, 2010 | 1986 Ford Ranger 2WD

3 Answers

Runs good when it's cold, warm it chokes and dies


sound like the catalytic converter is going bad or is bad,take out the oxygen sensor before the converter and see if it runs better. if you need more help get back to me please rate my fix

Jul 24, 2009 | 1989 Oldsmobile Cutlass Ciera

1 Answer

Running hot coolent is fine...


check for a blown head gasket it will sometimes pump air into the heads and make the coolant levels seem fine but in truth they are not and check the water pump for rusted fins make shure the water level sucks down during sharp throtteling of the motor if so the cooling system is fine as far as that goes but where to start

1.) tempature switch located on the motor it tells the ecu when to kick on the cooling fan

2.) fans spin freely without taking force

3.) thermostat it could be stuck closed due to someone at sometime only running water without antifreez and causing the pressure pin to rust and freeze the gate shut

4.) monitor the water levels if they go down suddenly as 1 gallon of water a week or 2 weeks its a bad head gasket you can see this on spark plugs as well

and for most your water pump make shure you get good heat from the heater at low running tempatures and start the car and monitor what the water in the radiator does (while its cold) the water in a car is over 195% and can easily do harm if the car is just warmed up not even close to over heating so you can imagine what it could do at an over heated state



but get the problem fixed or else you can result in blown head gaskets water in the oil piston breakdown do to rust in the piston walls and even worse complete engine failure

Jul 16, 2009 | 2002 Chevrolet Impala

1 Answer

Only runs rough after running and fully warmed up


when it is cold there is extra fuel going to the plenum chamber its like pulling a choke on a carby that is why it is running smooth but when engine gets hot it is back to normal supply of fuel and yours is not normal.one reason might be not enough pressure in the fuel rail due to defective fuel pump or pressure regulator or blocked fuel filter. it is best to check your fuel pressure first.

Apr 25, 2009 | 2002 Daewoo Lanos

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