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Thread: N54 hard starting/ rough idle. Techron complete vs injector cleaner

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    N54 hard starting/ rough idle. Techron complete vs injector cleaner

    Just got a 535i E60 and noticed it is hard starting and running real rough. Pretty much at all times, not just when cold. The long starts arent like 5 seconds long though, maybe like 3. The HPFP was replaced about 8,000 miles ago under warranty so i wanted to try something else before i took it back and they charge me a diag fee because it turns out not to be the HPFP since its out of warranty. Anyway, I tried some Techron Injector cleaner instead of the Techron complete recommended. Does that injector additive also work for our n54 issue?

  2. #2
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    Pelican Parts is offline Senior Member Supporting Vendor
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    The N54 is also notorious for going through plugs and coils and having really high carbon deposits. I would look into that; in addition to pulling the codes so that you have a better idea where to troubleshoot.
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  3. #3
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    Quote Originally Posted by justinp95 View Post
    Just got a 535i E60 and noticed it is hard starting and running real rough. Pretty much at all times, not just when cold. The long starts arent like 5 seconds long though, maybe like 3. The HPFP was replaced about 8,000 miles ago under warranty so i wanted to try something else before i took it back and they charge me a diag fee because it turns out not to be the HPFP since its out of warranty. Anyway, I tried some Techron Injector cleaner instead of the Techron complete recommended. Does that injector additive also work for our n54 issue?
    The N54's are direct injection so fuel additives won't reach the carbon buildup on the valves (i.e. Techron Complete vs. Regular is irrelevant). If it's been more than 50k since your last carbon removal that should be high on your list.

  4. #4
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    I have the "3 second" cold starts on occasion. Runs fine in ~10 seconds or so. I think this rules out carbon buildup in my case. I suspect a leaky fuel injector(s). Check the index number of your injectors. This will give you an idea of how old they are.

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    I really recommend installing some diagnostic software, mine has saved me thousands. You can read off fuel pressure while you start the car, while it is running, and after shutting down. This can tell you if your high pressure fuel pump is going bad, whether fuel pressure is contributing to the rough running, and whether you have a leaking injector. Generic P-codes aren't very helpful on a BMW, you really want the special bmw codes that ISTA can pull. You can get a hacked version of ISTA for free and use an $18 K+DCAN cable.

  6. #6
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    Sorry, I started this thread and forgot all about it. I plan on the plugs and wires first and go from there. If it was the HPPF would it run like crap all the time? Even when warm? Also, How loud are these engines supposed be? Mine is very loud, it sounds like a race car and the noise drops out when the gear changes. Runs like a raped ape though...

    - - - Updated - - -

    Quote Originally Posted by RocketSurgeon View Post
    I really recommend installing some diagnostic software, mine has saved me thousands. You can read off fuel pressure while you start the car, while it is running, and after shutting down. This can tell you if your high pressure fuel pump is going bad, whether fuel pressure is contributing to the rough running, and whether you have a leaking injector. Generic P-codes aren't very helpful on a BMW, you really want the special bmw codes that ISTA can pull. You can get a hacked version of ISTA for free and use an $18 K+DCAN cable.
    Interesting.

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