Cleaning of Throttle Body & intake manifold

Hello everyone,

I am new to car maintenance. I own Aveo Hatchback 1.2L petrol model year 2008. It has rough idle & Hesitation problems, has MIL on.

I checked that P0404 is shown in pending DTCs using my scan tool, that relates to EGR circuit range issues, which means EGR valve is stuck.

I went ahead & removed the EGR valve for inspection, its pintle is not moving freely, and it has black deposits inside. I will give it a try cleaning with some carb cleaner & see if this clears this issue. If this issue is with EGR position sensor, I might have to buy a new EGR valve.

I also removed EGR pipe that connects to Intake manifold & EGR port.

Next i removed the Air box & Throttle body for cleaning, After removal of throttle body, the upper intake manifold is seen with black brown fluid inside everywhere with a 2-3 mm level at the bottom. there are some hoses that connect intake manifold to cylinder head & those also have this fluid.

I really do not know, if this is normal or i should just clean the intake manifold completely.

I just removed the negative battery terminal before removing these parts. And left the terminal unconnected since yesterday, as i am yet to clean all these parts. I am doubtful, if this erases some critical data on ECU.

Advise on this (Cleaning of Throttle body, EGR valve, EGR Pipe, Intake manifold & ECU with disconnected battey) would be of great help.

With Best Regards,

I'd clean it up as best you can and reassemble it. As long as that EGR valve is moving smoothly you should be okay.

That all sounds like all too typical build up from the pcv systems that all cars have now a days.. The egr is going to be clogged with exhaust residue though, (dry flakey, looks like lava rock).

If you take the time to clean it up and worry about it, lose sleep at night and such, then I would install a catch can on the pcv system. The egr stuff, you can't really get rid of.

I have "serviced" an EGR system (different car, though) the same way you describe: removed, soaked & cleaned the valve body, the accessible EGR passages, and the position sensor with carb cleaner and WD-40. It made a noticeable improvement in driveability (it was very dirty to begin with - engine hesitation at times before cleaning).

Removing your battery cable should have no negative effects.

Thanks everybody for your valuable suggestions.

I am still awaiting for parts (EGR valve Gasket, EGR pipe gasket, PCV valve, Breather hose, PCV hose, Engine Air Filter & Throttle Body Gasket) from the parts dealer.

I have never a serviced a car before, so i am still going through the Service bulletins to make proper repair plan. This weekend, I plan to buy a Torque Wrench, can somebody advise on type (Ratcheting, click type, Snap on,etc, toqrue range, manual/ digital)? i m a newbie..

Do i need to take off the intake manifold for cleaning? as i see deposits of oil inside the upper part of intake manifold.
Reading from the Service bulletin, I need to get rid of Fuel system pressure first to be able remove fuel rail first. This will help to get better access to intake manifold bolts.

i am not yet clear whether I need to drain the engine coolant before removing intake manifold. Surprising, there are no instructions in service bulletin related to this. I just dont want to get into any trouble ahead...

There is an adaptor to which the EGR valve is bolted, it has heavy carbon deposits inside the ports for EGR valve & EGR pipe. I need to to remove this adaptor as well. Its not clear to me, if coolant will bleed after removing this adaptor.

Advise on all these points will be of great help to me.. I am eager to receive your responses. thanks..