Strange rattling sound from the engine when RPM goes down from 3,000.

ANSWER : Hi there. The noise that you are hearing is heat shields on the exhaust system are loose causing a rattling noise. Either the shield on the manifolds are loose or the shields on the catalytic converter are loose. If you need further assistance with locating the rattling noise, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : Hello there, a few possible items can cause a similar noise to what you describe. Most likely it is an engine misfire, fuel pump problem, worn out fuel filter, dirty idle air valve (which you may be able to clean), or an oxygen sensor. I’d start by examining these components and trying the tips outlined in the linked articles. If you still need help, a qualified technician such as one from YourMechanic will be able to diagnose this fault and perform any repairs required.

ANSWER : Hello, thank you for writing in. The first thing to do is check around the vehicle, specially under the body where heat and other protective shielding may be used, the exhaust hangers holding the exhaust pipe, and under the hood. You are looking for any type of broken bracket, broken shield, stripped screw, or other component that can rattle and move with the forces associated with accelerating. When the engine is cool, you can also tap on the exhaust system and wiggle it to see if you notice a similar sound or feeling. Most of the time an exhaust rattling would be noticeable while in park if you rev the engine. Try to replicate the noise in a way in which helps you pinpoint its location exactly. For more help with this diagnosis, contact our service department to schedule an appointment.

ANSWER : Hi there. Check the distributor or coil packs to the vehicle. The surging would most likely be caused by the electronics getting old and causing a delay in the spark ignition. I recommend replacing the spark plugs and wires and then retesting for the condition to reoccur. If you need further assistance with your engine surging, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : Hi there. A binding accessory could be causing your concern. Simply remove the drive belt and recheck. If the problem goes away, this eliminates the fear that there could be something goin on with the engine or transmission internally. It sounds like this could be the water pump. If the water pump is binding or leaking, it can cause the belt to slip and make it seem like the engine gets bogged down. Usually a visual inspection quickly uncovers the leak. However a properly executed pressure test is the best way to uncover leaks, both current and potential. I suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a car is making a noise inspection.

ANSWER : Hey there. Thanks for writing in today about the rattling / hissing sound coming from your 2004 BMW. I experienced a similar issue and it was in fact a vacuum leak. However, there are several other symptoms of a vacuum leak that you should consider before diving in and buying replacement parts.

Typically, the hissing sound will be accompanied by a lack of power on acceleration, loss of fuel economy and in some cases, an engine misfire. If your car is experiencing any of the following, then I’d say the issue is definitely vacuum-related.

A worn out clutch will also produce several driving / performance loss issues, as well as commonly produce a rotten egg smell. If you need additional help looking at the problem, contact one of our local ASE certified mechanics, to pinpoint the cause of the hissing noise and make the appropriate repair.

ANSWER : Hello – the P1346 problem code you have indicates a camshaft timing problem (variable valve timing to be specific), and is at least part of the cause of low power. The cams are out of time, relative to the crankshaft. The hissing sound from the throttle body area is likely an air leak from a hose, or some other portion of the air intake. The tapping sound could be a variety of faults, worn/leaking hydraulic valve lifter, worn cam, piston slap, etc. I recommend a timing belt service to get the cams properly timed, performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.

ANSWER : Hello. From what you describe it would appear that your vehicle may have more than one issue.

Belt chirping is usually caused by a worn belt or tensioner. If either component wears out the belt may loosen and chirp when the engine is started, or cold.

The low rpm low quality idle can be caused by a few different things. I would look at the idle air control valve, as that is the component that maintains the vehicle idle, and at any vacuum hoses that may be cracked or damaged, and possibly leaking. This is more likely for older or high mileage vehicles.

If you’re unable to pinpoint the issue yourself, consider YourMechanic, as one of our mobile technicians will be able to come to your home or office to diagnose your starting issue firsthand and make the necessary repair to your car.