I have e60 535xi (N54) For a few months my car has had a rhythmic intermittent misfire for around 30 seconds to 1.5 minutes on startup -- then it went away and car runs perfectly fine. All signs pointed towards a leaky injector as is common. I have index 7 injectors with 106k miles on the car. I ended up getting a check engine light once on startup indicating cylinder #2 was the culprit.

I replaced the injector with a used eBay one in addition to new spark plugs and ignition coils. Car ran solid, but still had the misfiring issue. After a week, the car took about 5-7 seconds of cranking and ran poorly. Cylinder #2 misfire code returned and was constant and did not go away. Unplugged the ignition coil, and the engine did not run any different. So I swapped the original injector back in and it is running as it was before again - misfiring on startup but clears after a minute or so.

While doing some diagnostics on this, I also noticed a 29F3 engine code and realized my fuel pressure sensor was reading a constant 94.3 psi - so it was replaced and the issue has remained unchanged.

With the injector replaced (then unreplaced), ignition coils and spark plugs new, and fuel sensor replaced, what other causes are possible for this misfire that only happens on startup??? The HPFP is outputting 700-800 psi per ProTool. I feel as though I've addressed nearly all the possible issues... has anyone had any experiences like this and what ended up fixing it? Thanks in advance guys - I really appreciate any help I can get on this one

 

Why did you start changing parts before troubleshooting? Should have at least swapped parts from cylinders before buying more. Did you perform a smoke test yet? If not done I would perform one. Have you checked to make sure there's no carbon buildup? Also, in your vehicle you have a MSD80 so don't ever want to skip over a bad MOSFET. Being that you're not having any additional codes I doubt it's your issue. What brand sensor did you install. If it's not OEM then you may be just chasing your tail. Always OEM for parts like this (sensors).

 

I did complete troubleshooting. There was no lights being thrown so I was unable to tell which cylinder(s) were causing the issue. Replacing the spark plugs and ignition coils was an easy step given I had FCP Euros warranty. Nothing changed after that. Still misfired for a minute on startup but ran fine after. Then, I finally ended up getting a check engine light ONCE for a brief period which linked me to cylinder #2. I replaced the injector and the misfire remained. The injector not working a week later I think was a coincidence that the eBay part had failed me. Likewise with the fuel pressure sensor. I put the old injector back in and I'm back where I started...

I cleaned the intake valves about a year ago and there was carbon buildup at the time. While the engine used to idle a little rough before that, this misfire is different and began a few months later. I can confirm this is not the cause as it goes away after 1-2 minutes.

The fuel pressure sensor is not OEM because BMW wants $247 for a brass fitting with a resistor. I bought an aftermarket one, but confirmed using ProTool the sensor is functioning equal to OEM. I've read many people go without this sensor functioning without even noticing and I've heard for others it causes issues. In my case, nothing changed when I replaced it (and again it is working).

The only answer that makes any sense is that the other injectors on the car are possibly leaking - not just cylinder #2. Without the check engine light being thrown it is almost impossible to know which cylinder it is isolated to. If it throws a code again, I will be sure to swap with another cylinder to see if it follows, but between the new ignition coils and plugs - injectors are all that is left (or some other electronic issue). Thing is, I don't have or want to spend $2500 on new index 12 injectors to potentially solve a misfire on startup when the car is otherwise running perfectly fine, but unsure what else to check.

 

Ok maybe our definitions of troubleshooting is different. You need to get rid of PT because reading a code doesn't help if you don't have a tool to run tests. You need ISTA so you can run a couple ABLs and test your combustion system from there you perform manual tests. Never replace parts until you find the root cause. You'll spend unnecessary money.

 

I was able to return the parts free of charge + ISTA is a big chunk of money to spend in an attempt to maintain a car that is stock...

The point is that the injector #2 is not the issue, the fuel sensor is not the issue, and sparks + plugs are not the issue. I'm still seeking possible answers that are not injector related as I don't have the thousands to spend on that. Thank you again for your input and let me know if you have any other ideas. Until then, I will continue living with it unfortunately

 

ISTA does not take a substantial amount of money to obtain. All you need is a laptop and a K/DCAN cable and you can Diag it with the tools the dealership would use maybe cost you $20 at most if you have a laptop already.

The suggestions/steps is all I have to give without a diagnosis. Anything more would also be just guessing