I have a "05 Toyota Corolla, purchased new. It's been a fine running vehicle, with one exception. For several years now, when the weather starts to turn colder in the fall, it develops a pinging problem when accelerating from a cold start. In the middle of winter, it never really goes away, even when the engine is up to temperature. I've tried premium gas, and the dealer has tried adjusting the timing, all to no avail. Any ideas as to what I should do, other than ignoring the problem?
It is unusual for an engine to ping when it is cold because the pinging or rattling sound is created by engine vibrations due to fuel igniting too soon. This can be caused by incorrect spark timing, the wrong spark plugs, high compression ratios or hot spots in the cylinder. Cold winter air usually reduces all these pinging conditions because it prevents the fuel from igniting too soon.
My first thought was to blame the EGR (Exhaust Gas Recirculation) valve. This valve reintroduces exhaust gases into the cylinders to reduce cylinder pressures and temperatures. This is done under cruise conditions to reduce exhaust emissions. However, the EGR valve closes during acceleration so maximum power can be produced. Therefore the EGR valve shouldn’t be causing the problem even if it was stuck open or closed.
There could possibly be a problem with the computer program that controls ignition timing during cold engine operation but I could find no information on updated programs for your vehicle. Since neither premium fuel nor different ignition timing have helped, I suspect that the noise you are hearing may not be a ping from the engine. It could be a rattle caused by a heat shield on the exhaust, a loose baffle inside the catalytic converter or muffler, or an engine component touching the body because of a soft or broken motor mount. While these suggestions may sound absurd, diagnosing noises have taken me down the wrong path many times.
Look for dented or broken heat shields first. Remove a damaged one temporarily to see if the “pinging” goes away. Banging on the outside of the exhaust with a rubber mallet may help find a loose baffle. Brake-torquing the engine in gear while someone checks engine movement can locate weak motor mounts. I have no explanation why the noise appears only in cold weather other than metal contracts with the cold. Perhaps this allows a part to move. This problem will take some time to pinpoint. Wish I could help more.
I have a 2006 Jeep Cherokee. I had a leak in the radiator and repaired it by adding Bars Leak to the coolant. However I think that it developed an air lock as after that it wouldn't drain the coolant from the reservoir tank into the engine. I removed one of the rad hoses (it doesn't have a radiator filler or cap) and poured coolant into the engine that way. It doesn't overheat and seems to be fine, however it still will not drain the coolant from the reservoir to the engine and I believe that there might still be an airlock in the system. What is the best way to resolve this problem of adding more coolant to the engine itself if I have to?
The reservoir tank is part of the pressurized cooling system. The coolant level in the tanks should increase slightly as coolant temperature rises and lower slightly as the coolant cools down. Air should normally be purged into the reservoir as the engine operates, but it can sometimes be difficult to get it all out of the heads and block. If you had an air lock (air trapped in the engine) you would probably experience two symptoms. First, the engine may overheat and blow coolant out the reservoir tank. Second, the heater would blow cool air.
Because the heater is a high part of the cooling system, air will collect there easiest. You can remove one heater hose (with a cold cooling system) and add coolant in the hose, or you can partially remove the hose with the engine running and the reservoir tank cap off. This will release air and some coolant from the heater hose. Add more coolant to the reservoir as necessary after reconnecting the hose. This should eliminate any air lock.