My car would get the occasional cold rough start and SES with P0171 & P0174 during cruise only after some time (though increasingly frequent). Also, the heat was getting cold at idle, so the thermostat was going. Car has 139,000 miles.
This is not a DYI, just some observations.
The fuel pump died last fall, I already had a new one and the relay, popped it in in 30 minutes, occasional rough cold starts fixed.
I decided to tackle a bunch of things while I was under the hood. None of these had been done before except for the Belts & Tensioners, as the hydraulic tensioner failed at 65,000 miles.
Pre-Cat O2 sensors
Cooling System Refresh
Belts, Tensioners & Pulleys
Fuel Filter
Intake Boots
DISA Rebuild (GAS upgrade)
Clean ICV
Pre-Cat O2 sensors were easy, make sure you get a proper socket, the only thing that required any thought was getting the wires back in the clips (this is a recurring theme, I have large hands).
Cooling System Refresh, also very straight forward. I use Dow DC-4 to lube all of the O-Rings before assembly, makes everything slide together nicely. The radiator drain screw was brittle and snapped, so I had to order a new one, no big deal. I don't see why people struggle so much with filling and bleeding the system. It's just not that difficult. I used the ECS kit, it came with everything. I inspected the radiator and it looks fine, so no reason to replace it.
Having done the Belts, Pulleys and Tensioners before, I knew the only pain was getting the serpentine belt back on. I still don't see a way to get the tensioner pulled back by using the bolt to torque the tensioner, without stripping the stupid Torx bolt. I used a motorcycle tire iron to lever the tensioner, not ideal, but still works. What you really need is a helper, which I didn't have.
Fuel Filter was a slight pain, but I see no need to pull fuses, empty the fuel tank or clamp lines. I relieved the fuel pressure at the Schraeder valve on the fuel rail, had a quart plastic bowl handy and basically only drained what the filter held with a slow dribble from the line to the fuel tank. Get new hose clamps for the lines, the stupid BMW ones can be loosened but not tightened. I didn't have new ones, so I figured out a way to tighten them anyway.
Intake Boots, what a pain in the ass. The lower boot clamps are positioned so you can't access the screws. I resorted to cutting the boot off with a utility knife and still had to curse at the screws to get them off. What is irritating is that it was quite easy to position the clamps to put the screws where they could be accessed, so I have no idea why BMW puts them where they do. Both boots had multiple holes in the inner radius of where they bend, I was quite surprised they were such bad shape.
DISA valve was slight dirty, but 100% intact and operating correctly, I already had the GAS kit so I put it on. The GAS kit is very well made, so I don't see any reason to pull the DISA again.
The ICV was just a little dirty, but operating correctly, I cleaned it up and put it back in.
I inspected all of the vacuum lines and they were fine.
Everything buttoned back up, moment of truth, started right up. I cleared the codes. went on a short drive, let it cool off, topped up the coolant, went for a longer drive, let it cool again. topped up about 2 more ounces of coolant. At this point only the EVAP readiness monitor was not ready, so I went for the emission inspection. Passed no problem. On the way home, the EVAP readiness cleared too. No more codes so far, so I'm sure the intake boots were most of the problem, though I suspect the O2 sensors were getting lazy too.
I also did an oil service and changed the aFe conical filter and cabin filter while I was in there.
Now the bad news. The car was running fine before and runs the same now. No increased performance or improvement in efficiency. Not that I expected any. I was averaging 28.3 MPG before and the car was still accelerating like it always did before the work. But it's nice to see that SES light out.
This is not a DYI, just some observations.
The fuel pump died last fall, I already had a new one and the relay, popped it in in 30 minutes, occasional rough cold starts fixed.
I decided to tackle a bunch of things while I was under the hood. None of these had been done before except for the Belts & Tensioners, as the hydraulic tensioner failed at 65,000 miles.
Pre-Cat O2 sensors
Cooling System Refresh
Belts, Tensioners & Pulleys
Fuel Filter
Intake Boots
DISA Rebuild (GAS upgrade)
Clean ICV
Pre-Cat O2 sensors were easy, make sure you get a proper socket, the only thing that required any thought was getting the wires back in the clips (this is a recurring theme, I have large hands).
Cooling System Refresh, also very straight forward. I use Dow DC-4 to lube all of the O-Rings before assembly, makes everything slide together nicely. The radiator drain screw was brittle and snapped, so I had to order a new one, no big deal. I don't see why people struggle so much with filling and bleeding the system. It's just not that difficult. I used the ECS kit, it came with everything. I inspected the radiator and it looks fine, so no reason to replace it.
Having done the Belts, Pulleys and Tensioners before, I knew the only pain was getting the serpentine belt back on. I still don't see a way to get the tensioner pulled back by using the bolt to torque the tensioner, without stripping the stupid Torx bolt. I used a motorcycle tire iron to lever the tensioner, not ideal, but still works. What you really need is a helper, which I didn't have.
Fuel Filter was a slight pain, but I see no need to pull fuses, empty the fuel tank or clamp lines. I relieved the fuel pressure at the Schraeder valve on the fuel rail, had a quart plastic bowl handy and basically only drained what the filter held with a slow dribble from the line to the fuel tank. Get new hose clamps for the lines, the stupid BMW ones can be loosened but not tightened. I didn't have new ones, so I figured out a way to tighten them anyway.
Intake Boots, what a pain in the ass. The lower boot clamps are positioned so you can't access the screws. I resorted to cutting the boot off with a utility knife and still had to curse at the screws to get them off. What is irritating is that it was quite easy to position the clamps to put the screws where they could be accessed, so I have no idea why BMW puts them where they do. Both boots had multiple holes in the inner radius of where they bend, I was quite surprised they were such bad shape.
DISA valve was slight dirty, but 100% intact and operating correctly, I already had the GAS kit so I put it on. The GAS kit is very well made, so I don't see any reason to pull the DISA again.
The ICV was just a little dirty, but operating correctly, I cleaned it up and put it back in.
I inspected all of the vacuum lines and they were fine.
Everything buttoned back up, moment of truth, started right up. I cleared the codes. went on a short drive, let it cool off, topped up the coolant, went for a longer drive, let it cool again. topped up about 2 more ounces of coolant. At this point only the EVAP readiness monitor was not ready, so I went for the emission inspection. Passed no problem. On the way home, the EVAP readiness cleared too. No more codes so far, so I'm sure the intake boots were most of the problem, though I suspect the O2 sensors were getting lazy too.
I also did an oil service and changed the aFe conical filter and cabin filter while I was in there.
Now the bad news. The car was running fine before and runs the same now. No increased performance or improvement in efficiency. Not that I expected any. I was averaging 28.3 MPG before and the car was still accelerating like it always did before the work. But it's nice to see that SES light out.
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