Yesterday was disassemble-your-engine-and-see-if-you-can-put-it-back-together-again day. So that was exactly what we did. Initially we wanted to do remove the cylinder head and change the valve seals but we were missing the tool to open up the head. So we only managed to remove the valve cover and throttle bodies for cleaning.
With the valve cover removed and throttle body removed. There is a large number of vacuum and fuel hoses to disconnect so it’s wise to label them properly during removal. You can clearly see the camshafts and the cam pulleys from this angle. Those were not disturbed because we lack tools to open up the head.
Here’s the throttle body removed from the engine block. You can see the throttle cable quadrant near the 2nd throttle intake.
Because there are 4 throttle bodies each feeding their own cylinder, all must be tuned properly ensure that airflow to each cylinder is balanced. The flat head screw that you see beside the throttle body intake are the bypass screws that are used for tuning. A carburetor balancer is needed to perform the tuning.
This is the other end of the throttle body assembly. This surface mates with the engine block’s intake side. The grooves running below and to all the openings is the tapping for the manifold absolute pressure (MAP) sensor. The MAP sensor sends manifold pressure to the ECU to calculate how much fuel to inject through the fuel injectors. Not shown here are the fuel injector nozzles and various vacuum tappings.
The back view of the throttle body assembly. There’s a throttle opener (doughnut shaped object with an actuating rod) and a vacuum switching valve (square shaped object with blue connector) for emission control.
And this is the idle speed control valve (ISCV) to control the idling speed of the engine. This is attached to the engine block and has a flapper valve inside that regulates flow in the vacuum line.
The reason I opened up the engine was to find the cause of engine oil consumption. During hard acceleration, white smoke can be seen coming from the exhaust and that is an indication of engine oil burning in the cylinders. A normal engine burns oil too, but at a very slow rate hence smoke will not visible from the exhaust. With the throttle body out, I can see the valves:
Now it is very obvious from this picture that a substantial amount of oil has seeped through the valve seals and are now coating the top of the valve. Once the valve opens, the oil will go into the cylinder together with the mixture of fuel and air, thus creating the white smoke at the exhaust. A top overhaul should solve this problem. But since oil consumption is still not very high, I might just put it off till next time.
The oil on the valve comes from here. The oil that is used to lubricate the cam lobes and valves have seeped through defective valve seals and entered the combustion chamber.
Soon it was getting late and dark so we decided to put everything back together again. The throttle body assembly was cleaned with diesel. Surprisingly the throttle body was quite clean. Just grime on the outside. Also readjusted the throttle cable to reduce the slack.
With everything reinstalled and triple checked, the ignition key was turned. The engine cranked for a while but didn’t start. It took a lot more cranking before it finally started. Must be due to the lack of fuel in the fuel manifold since we drained it when we removed the throttle body. Engine idled properly, no unusual smoke or sounds. Went for a drive and everything was fine.
Next up, probably going to remove the head once I get the proper tool for it and get the valve seals changed and to examine the pistons and valve seats.