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Re: car runs rough when hot
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 .
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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.
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.
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.
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
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...
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
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.