intermittent issues starting, low idle and stalling

1991 BMW 735
220,000 MILES • 3.5L • 6 CYL • 2WD
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PALOSBB40
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When pressing gas pedal engine backfires. did find filter from fuel pump strainer floating in gas tank. Did replace with new fuel pump and fuel filter. Did also replace spark plug wires and distributor cap. The spark plugs are less then two years old and looked good. Did clean the ignition rotor because it was black. i also cleaned the EGR valve and air flow mass sensor and throttle body. What do you think the problem could be? Thanks.
Jun 7, 2020 at 7:47 AM
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AL514
  • ✓ASE Certified Mechanic
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Hello, thanks for using 2CarPros. have you had a timing belt done recently or at all that you know of? That's a high mileage car and if the oil is changed regularly it will gunk up the hydraulic tensioners causing slack in the chain. Probably why it backfires, a crank/cam correlation test must be done to check that cam timing is correct.
Jun 7, 2020 at 9:04 AM
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PALOSBB40
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  • 53 POSTS
Hi, thank you. i had the car three years and never replaced timing chain but did do oil changes at regular intervals.
Jun 7, 2020 at 9:11 AM
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AL514
  • ✓ASE Certified Mechanic
  • 5,587 POSTS
  • ASE Certified Mechanic
Have the timing chain checked by a professional technician, a lab scope should be used to check the crank and cam timing, just lining up the timing marks may not give you the whole picture.
Jun 7, 2020 at 4:43 PM
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