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Steve, BMW Expert
Category: BMW
Satisfied Customers: 24007
Experience:  BMW Expert
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2003 BMW 525i old code

Customer Question

2003 BMW 525i old code 1343,p01313,0300,1345,p1083,,1085,p0171,p0174
Cranks runs smooth, then when take of no power sometimes backfires, but if I turn off and back on will run smooth for few minutes then the same problem... Almost like it resets itself.... I have seen that with oil pressure in GM trucks but nothing like this problem on a BMW.... We checked for
vacuum leak...please advise
Submitted: 9 months ago.
Category: BMW
Expert:  Steve replied 9 months ago.
Hello and welcome,
My name is ***** ***** it will be my pleasure to assist you today.
What has been checked other than vac leaks?
Customer: replied 9 months ago.
Coils and plugs ...vvt
Expert:  Steve replied 9 months ago.
what do you mean that you checked the vvt?
how did you check for vacuum leaks?
Customer: replied 9 months ago.
Sprayed down engine with brake cleaner like I did to find hole in the original valve cover. oil on coil boots either...recently had 02 sensor bank 1 sensor bnk 2 sensor 1....checked while running took oil cap off didn't affect car running either
Customer: replied 9 months ago.
Confused about why no power after set after run good at start...leaning toward clogged catalytic converter just never seen a clogged cat clear up once you turn car off and on instantly
Customer: replied 9 months ago.
At one point in time today it drove perfect opened her up to 80mph then came to a light and she took off slow again like only running on 4cyl
Customer: replied 9 months ago.
Will check plugs but don't think it's them or the coils. ...Because it clear up as soon as you turn car off so I'm not not sure if ecm or catalytic converter it may be partial moving clog
Expert:  Steve replied 9 months ago.

I would suspect it is in fact a bad maf. a bad cat would not reset. you would need to live-diag the vehicle with a factory bmw scan tool or equivalent to verify.

Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.

Customer: replied 9 months ago.
Will try that but what about the minor backfiring
Expert:  Steve replied 9 months ago.

this would cause backfiring because of poor fuel/air mix. Please do not forget to click on a positive rating