e55igor1

Hello, everyone!

I having problem with my AMG, the check engine light is ON and white smoke from exhaust pipes when I start the car in the morning (no smoke when the engine is warm).
STAR diagnostic fault code is:

*3699, P0191 Fuel pressure control:the upper limit value is reached*

Tried erase fault code: check engine light came on every time after second engine start when I accelerating on highway
Checked the voltage from ECU to Fuel pressure sensor: OK (4.9V);
Replaced Fuel pressure sensor: did not fix the problem;
Checked coolant level: OK;
Checked engine oil: no milky stuff.

The white smoke just started week ago, before it was just Check engine light on. No missing performance from the engine, idling good, a lot of power, maybe some "farts" in the exhaust pipes when braking (not sure if it is normal).

Guessing:
1) Stuck open fuel injector. Any idea how to detect one? No misfire in cylinders...
2) Faulty fuel pressure regulator? (not sure how it looks, maybe somebody know the part #?)
3) your opinion???????????????
Please help me to detect this problem. Thank you for your time!

roadtalontsi

possible tune problem. The fuel pump control modules controls the fuel pump output. Id imagine its probably got a dead one. Either that or a software fault.

justthebest

White smoke usually indicates coolant is being burned. Probably a pretty big issue lurking. I'd guess that whatever leak / crack is small though - as the metal expands, the crack could close, leading to no smoke.

Ingenieur

have you been adding collant?
monitor the level closely

before starting when cold open the reservoir and start the engine, see if any bubbles are present

e55igor1

Did not add any coolant, no bubbles, collant is clear, engine oil is not milky.

AMG 17GT

White is water.

Could be head bolt problem or head gasket.

alrasheed1991

it happen to me white smoke from exhaust but i dont remember check engine light was on or off, i toke to the dealer they said bad fuel they cleaned the fuel tank and never came back again.

e55igor1

Wondering why is STAR showing that fuel pressure is too high, what can cause it? STAR suggesting to replace fuel pressure sensor, I did it. Fuel pressure sensor is brand new OEM, maybe leaking injector that delivering fuel to the cylinder even the engine is off. When I start the car, too much fuel causing white smoke. Wondering how to check the injector valve and how to detect the bad one?

roadtalontsi

is it always smoking white or just at cold start? is your car stock? did you check restistance of the wires from the sensor to the m.e.? check pin tension/tightness? check for wire chafing? Did you actually check the fuel pressure to see if its what the sensor is reading?

e55igor1

White smoke only after cold start, after 1min no smoke at all, even when accelerating, also no missfire. My car is stock. Voltage from ECU to fuel pressure sensor is 4.9V(normal is 4.8V.....5.2V). Fuel pressure sensor reading 6=6(normal if you will follow WIS and STAR). Connection to fuel pressure sensor is good, no rust, have voltage ( checked many times). The guy with e63 had white smoke after cold start up, problem was in purge valve and PCV valve, but my car do not have P0444 fault code and no whistling sound from the engine.....

e55igor1

Car problem is: white smoke when cold start up, check engine light is on, P0191 fault code and sometimes fault code 374a (the internal data could not be stored in control unit)

e55igor1

Also, my oil dipstick popped out one time, that was caused check engine light and many fault codes: P0451, P02187, P0191. Pushed dipstick back in place, no more malfunctions for 3 month. Can it be related?

e55igor1

Thank you for taking some of your time to answer my question.

Ingenieur

fuel pressure too high: the sensor is most likely reading properly since you replaced it

do our cars have a diaphram type regulator in the fuel filter?
most are regulated by engine vacuum

PVC valve: oil stick popping out is an indicator of high crankcase pressure
perhaps it is the PVC valve and the high pressure is due to no vacuum to control the regulator?

roadtalontsi

some white smoke at start up is going to be normal its condensation/water in the exhausts which these cars have alot since good combustion forms water so i wouldnt worry about that and it is unrelated to your fuel pressure codes. Like i mentioned probably a bad fuel pump. The pressure is regulated via the fuel pump control module which sends pwm signals to the pump for output and pressure. The filter module on the left side of the fuel tank saddle is has an over pressure release and part of the syphon jet pump system to swap fuel from side to side. The pump is on the right side of the tank. you really need to check your fuel pressure from a true gauge see what it looks like. You also need to do a volume test. Your pumps are probably fine at low output but running out on highload/top end which is causing the sensor to read low pressure intermittantly.

e55igor1

Thank you. Just checked and I found engine oil on the PCV valve, looks wet to me. It is the symptom of bad PCV valve? How to test PCV valve? Thank you very much for your time!

DuaneC63

Read the sticky on head gasket failures before you drive the car anymore.

e55igor1

Update: replaced PCV Valve/Breather hose. The check engine light comes back on after second engine start when the speed of 50 MPH is reached (just like it did before). Coolant is clear and level still the same. Can be the ECU software? Left and Right fuel pumps does not have any fault codes. What 374A fault code means? No information about it in WIS and STAR, just I know the internal data could not be stored in control unit....??? Thank you for your time.

e55igor1

What can cause high fuel pressure (higher than limited) during acceleration? Thank you

khaloof

White smoke means your engine is burning oil, if you see black smoke then theres too much fuel to burn or spark plugs are bad.
I'm guessing the piston rings need to be replaced,if its white smoke, or you can just ignore it and let it burn oil, but dont forget to check oil level and add as needed.
Unless theres a lot of white smoke that is very noticeable, then i would suggest you take it to the dealer to check it out.

roadtalontsi

sounds like its time to review the tune...

lots of thoughts on the white smoke, which isnt there when its warm. Have ya'll never looked at your car start in the morning?

Youngin

had the same code p0191 and also p2187 just last week took it in the benz and they changed the purge valve. no cel since

e55igor1

Thank you. This is what I am going to change next. Does your car had any symptomps of bad purge valve except CEL?

e55igor1

Finally, I found and resolved the problem with "Check Engine Light". In my case it was bad PCV Valve / Breather hose (part of emission system), part# A156 010 03 70 ($90.00). In regular maintenance routine, it needs to be changed every 70,000 miles.

Maybe this information will be helpful to someone who has similar problem with M156 6.2 engine
Symptoms:
If the faults codes P0191 P2187 P0451 present, CEL is ON, could be white smoke from exhaust after cold start, no misfiring, engine oil around the PCV Valve, engine oil dipstick popping out, part# A156 010 03 70 must be replaced.

In some cases, it can be the Purge Valve, fault code P0444. Check if it pulsing by holding it, you will fill the vibration if it working good.

Thank you everyone for help!!!

NCBob

White smoke on a cold start? I don't believe it is smoke. Condensation in the exhaust system evaporates and turns to steam which goes away once the engine warms up.
All IC engines do it. Totally unrelated to the PCV issue.