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TerryTibbs

518i running issue, back firing

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I bought the car with the running problem amongst other problems,

the car would tick over very lumpy , misfire and cut out, when revved it would sound even worse and struggle to get rpm up, ordered new cam pos sensor n fitted this evening, the car now idles perfectly and sounds much healthier, the revs can be raised high now but only when it’s throttled steadily to get it there, if I open the throttle quickly it dies back and back fires into the inlet manifold and air box, I’ve just ordered the obd adapter so  hopefully I can use my diagnostic tool and get some data, but til that comes I’m not buying any parts, unless any of you guys have any pearls of wisdom?

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Unfortunately it may be, had a look on my diagnostics and it does have the e34s on from 92 so should give me all data available including live data, ordered adapter for less than a tenner, 

at least the cam sensor wasn’t a waste of money tho 

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How old is it? Does it start up ok from cold and then develop fault or always present?  Possible Lambda sensor failed 

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Obd adapter arrives Monday so will have some data all being well,

first job is look at afm values, my diagnostics usually show actual values and desired values,

.... on the whole tho the engine sounds sweet on Tick over and is quiet for a high miler, and not a puff of smoke from cold or when warm, 

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Well been thru logged faults and cleared them, only fault that comes back is o2 control fault, looking at the live data all seems ok, apart from the o2 voltage which is sat still at 0.2v which is showing it running lean??? Tomorrow I shall replace fuel filter and might pull the pump out of the tank to rule out contamination in the tank, the car doesn’t have a fuel flap and when I bought it, it was the roughest car on the street, it’s just the right height to take a p@ss in :huh: 

should have new crank sensor in the post in next few days too

Edited by TerryTibbs

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So why are you not chucking in a new lambda sensor?

 

if it's not feeding back to ecu that might explain why when you crack the throttle it's not seeing it go lean and upping the fuel and why perhaps gentle increase in throttle isn't confusing it as it's thinking mix is right. 

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@duncan-uk if it’s struggling to get fuel like a weak pump or contaminated fuel or some blockage at the injectors then that would show as running lean, I’m about to start going thru the fuel system now, starting with the tank,

before the car went back on the road it had been stood for a few years and has had fuel lines replaced, quite shoddily tbh and I need to see what comes out of the fuel rail when flushed for my piece of mind, I suspect rust from the old fuel lines

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Lambda has had a good clean and a rinse out with electrical contact cleaner and now shows voltage rise and fall to match rpm, been thru fuel lines all clean n good, fuel pump is a little noisy, I could do with testing fuel pressure now, I nipped the return pipe closed and still the same issue, It’s starting to annoy me now:mellow:

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So no faults are being shown with diagnostics but when blipping the throttle it won't rev? But you can gently increase revs?

 

sounds then like an air leak after the afm/ maf? As engine is getting air but unmeasured so not adding fuel? Hence running lean?

 

have you had a good look at pioework?

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Yes been thru it all and been over everything with brake cleaner listening for slight rise in rpm and nothing?? Going to take the whole inlet manifold off tomorrow and hopefully I’ll find something a miss

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Well I’ve ordered a fuel pump today as it’s the only part left that could cause this problem imo, if this doesn’t cure it I’ll break the effing thing!! 

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