While driving to work today my 318i started running rough/stalling and blowing black smoke. It was OK for about 2 or 3 minutes after it cooled down but once it warmed up it started doing it all over again. Any ideas why? I'm guessing that it may be the O2 sensor. But I'd rather not guess at the fix.
HELP!! My 318i started running like crap today
- Thread starter 318iguy
- Start date
Its a bad Thermo Time Switch. Had one go out in my '85 318i. The O2 sensor on these cars does very little, just fine tunes the air mixture.
The Thermo Time Switch controls with loop the ECU runs in, closed loop or open loop. Now when this switch goes bad the car will run fine while its warming up but as soon as the engine gets warm the switch is suppose to tell the ECU to start running in "warm engine" mood. Hence the black smoke, your car is running rich when it gets warmed up. Later.
Aaron
The Thermo Time Switch controls with loop the ECU runs in, closed loop or open loop. Now when this switch goes bad the car will run fine while its warming up but as soon as the engine gets warm the switch is suppose to tell the ECU to start running in "warm engine" mood. Hence the black smoke, your car is running rich when it gets warmed up. Later.
Aaron
Dang close on the answer, but here is the deal
The thermal timer controls the cold start valve.
Next to it is a coolant temperature sensor for the ECU.
There is a bad deal on the ECU coolant sensors that can make what you are seeing.
In the 90s BMW did a coolant containment modification.
They added some valves to the heater and the throttle body heater lines.
The used the wires feeding the ECU coolant temperature sensor to power the added valves. So as the valve get older they will affect the sensor and cause exactly what you are seeing.
A specific temperature when the engine will go full rich and cause the engine to sumble, blow black soot, and stall.
Full cold it is alright.
If you can get it past the bad temperature it will also run alright.
I have seen three do this and only figured the fix by luck.
The added valves have a connnector the same as a 30 amp green bladed fuse so unpluging the valve and inserting the 30 amp fuse will bypass the issue.
Later,
The thermal timer controls the cold start valve.
Next to it is a coolant temperature sensor for the ECU.
There is a bad deal on the ECU coolant sensors that can make what you are seeing.
In the 90s BMW did a coolant containment modification.
They added some valves to the heater and the throttle body heater lines.
The used the wires feeding the ECU coolant temperature sensor to power the added valves. So as the valve get older they will affect the sensor and cause exactly what you are seeing.
A specific temperature when the engine will go full rich and cause the engine to sumble, blow black soot, and stall.
Full cold it is alright.
If you can get it past the bad temperature it will also run alright.
I have seen three do this and only figured the fix by luck.
The added valves have a connnector the same as a 30 amp green bladed fuse so unpluging the valve and inserting the 30 amp fuse will bypass the issue.
Later,
My bad, I meant the coolant temp sensor. But yea that I am sure is the problem.
Now IF I remeber correctly one is white and one is brown/reddish. I think the brown/red one is the coolant temp sensor. You can test this buy using an ohm meeter and watching to see if the resistance changes as it warms up. Cannot remember if its supose to decrease or increase, but it should change. Big IF on the colours though.
Later
Now IF I remeber correctly one is white and one is brown/reddish. I think the brown/red one is the coolant temp sensor. You can test this buy using an ohm meeter and watching to see if the resistance changes as it warms up. Cannot remember if its supose to decrease or increase, but it should change. Big IF on the colours though.
Later
Just an update. I checked it out today. It is running rich even at startup. I ran some tests from the service manual. The Idle Control Valve seems fine.The coolant temp switch seems fine.The Cold start system seems fine and the air intake seems fine. Any other ideas? Maybe the fuel injectors are leaking? If I let it idle for a few minutes and then rev the engine a ton of black smoke pours out the tailpipe.If I rev it alot then the smoke thins out considerably.
The problem has been repaired.A local shop messed with the car for 4 days and changed the coolant temp switch and cleaned the fuel injectors. It didn't help. I decided to take the car to the dealership. They had it for 2 days (after telling me that they wouldn't be able to even look at it for a week)They found that the fuel pressure regulator was bad and was pushing the fuel pressure too high causing fuel to bleed constantly from the injectors causing the rich condition. Now the car runs better than ever!! The funky fluctuating idle is gone!! It idles so smoothly now that I can't tell if it's running (that's taking some getting used to.I keep thinking that the car stalled) Of course it cost an arm and a leg but it was worth it to get it fixed properly.
Hey My 325e is doing the same exact thing!!!! I changed the Thermo Time switch and the temp sensoe and the O2 sensor and cleaned the injuctors and cleaned the Cold start valve and messed with the Idle Control valve. However My car only runs rich when it is cold out. Could this be the Fuel Presure reg. Just like 318guy's car? Its been hapening now speraticly for 3-4 months, but only when the temp is lower than 40 deg. Please help!!