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M278. 2012. So to start car is running fine no issues. One stumble and boom, car is in safe mode. Limp it home a few blocks. Codes are Random misfires and fuel rail pressure low circuit . Overall fuel pressure is reading 221 psi at idle and raises up to about 250 when cars off.
my long term fuel trims at idle are bank 1 between 71% and bank 2 14% and when shut off drop between bank 1 46% and bank 2 9%.
Could the sensor cause this? High pressure fuel pump? Possible vacuum leak? Anywhere else to look?
Last edited by Garagebuilt; Aug 19, 2021 at 03:55 PM.
You need something that reads injector cycle. Yeah your engine is adding fuel to compensate. Be careful of running it like that, it could lean out, and boom. Also if the reading of the sensor is incorrect (unlikely but possible) you could flood a cylinder with too much fuel, and hydro lock.
The right tool will tell you what it is right away.
Take it to a reputable Indi if you don't know what it is. You can also run a fuel injector cleaner, and pray for the best.
Last edited by S. Madman; Aug 19, 2021 at 08:56 PM.
ok took it to my buddies shop. They cleared codes and then could not get it to repeat issues after a bunch of driving/key cycles. checked for vacuum/boost leaks. fuel pressure was at 2200 psi. Pick the car up, drive it around for days fine and then boom. one little stumble and the car won't go above 3k rpms. Get the car home and decide to read codes. This time i have an O2 code says it has shifted towards lean bank 1. So now I read. O2 sensor live data voltage since I have a bank 1 code again and I have 1 sensor (bank 2) doing its thing but bank 1 is stuck at .905 V. Im guessing this could cause the car to not allow full throttle to protect itself?
The circular part is a camshaft solenoid, the one above and to the left (of the picture) is a sensor. There are 4 of them. You have to disconnect them by pressing white button towards the button, at the same time you are unplugging.
Look for my post about this to identify them.
Last edited by S. Madman; Aug 30, 2021 at 08:24 AM.
Oh yeah duh. Replaced those as well. A very very small amount on one but wasn’t on pins or in the sensor. Little on outer edge of plug. The other was dry completely.
The next thing is to unplug the ECU, and inspect the pins. If you see no oil then there should be no oil on the connector on the ECU side. Are your STFT moving at all? Also the O2 sensors should be readable. Is the Voltage fluctuating on the O2 sensors?
The next thing is to unplug the ECU, and inspect the pins. If you see no oil then there should be no oil on the connector on the ECU side. Are your STFT moving at all? Also the O2 sensors should be readable. Is the Voltage fluctuating on the O2 sensors?
ecu is clean. Bank 1 (the bank with issues) o2 sensor reads stuck on .905 V. Bank 2 is reading correctly.
Check voltage on the connector side of the of the O2 (may be a pita to get to it. If you have power, swap your dead sensor. O2 sensors can go bad from age, but also from lack of heating (letting the car sit unused too long). And be mindful you are putting too much fuel, which will foul your spark plugs, and possibly hydro lock you engine.
Last edited by S. Madman; Aug 31, 2021 at 12:17 AM.
M278. 2012. So to start car is running fine no issues. One stumble and boom, car is in safe mode. Limp it home a few blocks. Codes are Random misfires and fuel rail pressure low circuit . Overall fuel pressure is reading 221 psi at idle and raises up to about 250 when cars off.
my long term fuel trims at idle are bank 1 between 71% and bank 2 14% and when shut off drop between bank 1 46% and bank 2 9%.
Could the sensor cause this? High pressure fuel pump? Possible vacuum leak? Anywhere else to look?
There is another thread either in this 212 forum or in the 221 forum where an error codes related to the fuel pressures (low and high) are discussed in depth. In one of the posts there is a document explaining how the engine goes to “Limp Home” mode when low pressure in the high pressure side is detected.
This, of course, can be a pump issue but it can also be the pressure sensor issue, i.e. sensor reading wrong.
In your post you mention low pressure and this pressure probably is in the high pressure side so as the car went to what you call “Safe” mode (I think it is the Limp Mode) I would concentrate my attention to the high pressure side sensor and pumps. Sensor I s located I the fuel rail on the right side of the engine. There are two high pressure pumps by the fire wall.
Easiest is to check the pressure sensor first.
Update:
Below is the name of the thread that discuss fuel pressures and sensors in depth. It is in 212 forum.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
