Our oldsmoible silhoute has had many issues , we have spent $1800 trying to fix it
A backfire is usually an indicator of either timing or vacuum. Though you didn't include the year or engine size of your vehicle, the timing is not adjustable, and more than likely NOT your issue. This brings us to what it most likely is: Emissions System/ Vacuum/ Air Induction. The slower your vehicle goes (the less open your throttle is) the MORE vacuum there is present in the intake manifold. The faster your vehicle goes ( the wider open your throttle is) the LESS vacuum there is in the manifold. When you open your throttle, it lets more Air into the engine, which, in turn, displaces the vacuum. A vacuum leak allows air into the engine, which replaces the much needed vacuum for the car to run properly at idle and lower speeds. But when the vehicle is driving faster, the symptoms of the vacuum leak may not be noticeable, due to the fact that the engine is utilizing the extra air intake. The symptoms, however, return when the vehicle returns to idle. Using a 3/4" hose, you can put one end of the hose to your ear and probe the engine with the other end. Using the hose a stethoscope, listen for any "hissing" sounds coming from the intake or hoses, to detect a vacuum leak. Spraying Brake Cleaner / around the manifold, while the car is parked and idling, and listening for the engine to surge as the Brake Cleaner is being sucked into the engine, is one method that can be employed, though, I must say, with extreme caution. An open spark plug wire can cause the spray the ignite! There is also the option of having a smoke test done by a qualified technician, to locate a leak.
An Engine backfire is merely a condition where the cylinder in question has a poor air /fuel and spark ratio or timing. A leaking Fuel Injector can cause a backfire as well, such as the backfire that is present when too much starter fluid is used. First: get the codes pulled for your Check Engine Light for free at Autozone or Orielly's. Look for O2 sensors to be reading a Lean condition , which indicates a vacuum leak, or not enough fuel ( as in clogged injectors) if it a clogged injector, the code should say "misfire" and indicate which cylinder(s) has the issue. If the code has O2 sensor "Rich" condition, you are looking at too much gas being dumped into one or more cylinders, or not enough air. Though, by your description, it is more than likely a mere vacuum/ air issue.
MR. VINCENT, ASE MASTER TECH, MOBILE MAN CAN ,LLC
Oct 18, 2016 |
Cars & Trucks