I am not discouraged because every wrong attempt discarded is a step forward. A little Experiment When my idle got soo bad it was making the car rev up and down, it made me aware that this became a sensor problem. I unplugged my Air mass sensor to see what would happen. Lo and Behold the idle smoothed out, I still had an odd hesitation. A new fuel pressure regulator solved this, please remember to use a BMW FPR, an aftermarket will not work and will most likely cause an engine code. Digging Deeper With the occasional idle fluctuation and slight rough idle, I seem to have gotten it to a reasonable idle. I decided to remove the spider injector hosing for the air shroud system going to the fuel injectors. I went to Advance Auto and bought Vacuum line caps and capped off the 4 small injectors and 1 large hose fitting. This seemed to pretty much smooth out the idle to a very passable one. After doing this I put in a spare set of injectors, this was a mistake because it cause a weird acceleration lag where the car would be super slow and then kick in at full force acceleration. This was annoying and so i decided to go back to the original injectors with the air shroud reattached; this fixed all acceleration issues, but caused massive cold rough idle. I did this along with changing the oil to 5w30 castrol edge full synthetic. I believe the oil had a bit to do with the idle, so i may be trying 5w40. Future plans I will be Removing the air shroud system with the original injectors (as a side note, please remember to lube all fuel components with a little Vaseline when installing) I will be switching to 5w40 or something else (will be noted)
Eventually i will replace the Air mass sensor and most like the throttle position sensor. On a side note, I noticed a slight leak from my coolant reservoir during my last oil change. This makes me wonder if lack of coolant system pressure may be causing issues. I will most likely be replacing the O-ring gasket associated with the base of this tank. I also cannot seem to get the heat in my car to come out warm. perhaps a clog
3 Comments
martin
12/22/2012 23:30:21
hi, im from poland. i have z3 1.9 m44 and same issues with engine as you. after 2 years reading forums and changing parts i found that rough idle, power loss, missfiring on m44 engine is coused by not fully closing valves. valve guides are the problem. even bmw issued service note describing this problem (in late 90's). in next month i will change head gasket and rebuild head. i saw your youtube clip with rough idle exactly runs like my engine. my friend in poland solved all the issues with his m44 this way. sorry for my bad english. greeting from poland :)
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12/23/2012 00:16:54
Hello Martin,
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Mike
12/26/2012 16:35:06
The water pumps on the Z3 are not strong enough to push coolant into the heater core at idle. The heat only works above ~2000 rpm. I would have your head gasket checked. I had a small leak in my coolant system that ended up blowing out the plastic side of my radiator. I replaced the radiator. Ended up with a leak at the rear of the engine. Had that replaced. Then the leak moved to the radiator cap. Replaced it and it still leaked. I found out the head gaskets on the Z3 are made out of a cheap material. Mine developed a small leak which allowed the cylinder to pressurize the coolant system causing the problems. It could also be the source of your idle issues. My car has an idle issue but no where near as bad as yours that I am trying to fix. I only occasionally get rpm revving but only when the car is hot. I will let you know if I figure it out.
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