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5-Series (E12,E28, E34, E39, E60) Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)

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Old 01-20-2007, 05:48 PM   #1 (permalink)
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Car backfires needs help

Folks,

My exhaust is making some poping and cracking every time I let off the gas especially in the lower gears. I heard this symtom is cause by unburnt gas in the exhaust. Does any one know the cause of this? Thank you all for your help.
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Old 01-20-2007, 10:22 PM   #2 (permalink)
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low compression?????hell i dunno
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Old 01-24-2007, 04:55 PM   #3 (permalink)
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Do you have any leaks in the exhaust? Stuff a rag in the rear pipe while idling and see if you can find a leak. Don't leave it in there too long or you may trip a check engine light. The manifolds, cats, pipes everything must be sealed up tight. When you let off the gas cold air can be sucked in to the system at any point that is leaking. When the cold air hits the warm air ...bam a small explosion occurs. Just one possibility out of many.
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Old 01-24-2007, 06:49 PM   #4 (permalink)
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I have done quite a few readings here and there ever since the car started backfires, the majority of people thinks that it is a timing, ignition and fuel. And further reading I learned that BMW came out with VANOS since 1992, my 97 happens to have the single VANOS, and of course VANOS dictates our engine ignition timing. And I just happened to also learned that the VANOS's design is part hydraulic part mechanical and inconjunction with TPS it decides whether to advance or retard the timing, I believe it is capable of rotating +/- 6 degrees.

From the above information, I decided to change my oil to conventional from synthetic and increased the weigh to 15-40. It has been over four days, ten trips and about 200 miles so far without "engine light". I'm crossing my finger right now, and hope that I'm on to some thing here, but time will tell.

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Old 01-24-2007, 07:49 PM   #5 (permalink)
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so your engine light was coming on? How many miles on the engine? What codes were you getting? It would surprise me if an oil change cured this unless your chain is really worn. I would not think 12degrees of timing would make a huge difference, but ya just never know. Hope you have it solved!
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Old 01-24-2007, 09:12 PM   #6 (permalink)
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do u just have a bad muffler.i have heard the after market mufflers make noise
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Old 01-24-2007, 09:41 PM   #7 (permalink)
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Originally Posted by fastshivy
so your engine light was coming on? How many miles on the engine? What codes were you getting? It would surprise me if an oil change cured this unless your chain is really worn. I would not think 12degrees of timing would make a huge difference, but ya just never know. Hope you have it solved!


yes, my engine light was coming ON with " catalyst efficiency below threshold". I replaced all four O2 sensors and Cat, but problem still persist. You will be suprised just a couple of degrees in timing of BWM engine nowadays will throw all kind of codes lol. Well, as I mentioned earlier the Vanos in this engine depends on the weigh of the oil to work properly. My mistake was switching to synthetic. Oh, the engine has 142K miles, but still purrs like a kitten
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Old 01-25-2007, 06:36 AM   #8 (permalink)
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Send the big boys Dirty tool etc.

Hey...This is an interesting thread. I would love to hear from Dirty Tool or some of these super smart guys. What do you think???
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Old 01-25-2007, 06:49 AM   #9 (permalink)
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Hey...This is an interesting thread. I would love to hear from Dirty Tool or some of these super smart guys. What do you think???

Who is Dirty Tool? I haven't a clue. But I kind of know whatyou meant so go for it, Let's hear what they have to say.
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Old 01-25-2007, 11:59 AM   #10 (permalink)
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Quote:
Originally Posted by 16valex
Who is Dirty Tool? I haven't a clue. But I kind of know whatyou meant so go for it, Let's hear what they have to say.

DT, gotKRAUT, BMWJNKY, Starmavin (just to name a few)...any of those guys should be able to help you out. There is quite the broad and deep technical knowledge base of people in this forum, give them time to read about your issues and I'm sure someone will have the right anwer, or at least a really good idea of what's up.


lol..no pressure guys...
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