Lee3333

Great video-but that only works if you clean the TB while it is on the car-and you can not get the inside that way. Besides, do you want to spray the cleaner into the manifold with all that gunk and carbon deposits? Surely there must be some other way of doing it with the TB off the car. And the butterfly has to be open to properly clean it.

Besides, why would opening the butterfly with the TB off the car affect the idle speed? The computer does not know you are opening it, and the TB has no memory built in. A mechanic I spoke to today explained it well. As the carbon builds up, it fills in the gap of the butterfly which would decrease the amount of air into the engine. The comuter senses this and increase the idle speed to compensate. When you clean the TB, now it is getting more air than the computer is accustomed to, and the car idles too fast. The computer has to now reprogram itself to reduce the idle speed. It has nothing to do with manipulating the butterfly. All that can do is damage the nylon gears inside and possibl strip them.

donbrew

The "position sensor" remember that was the code? Not gears.
The GM book says to clean it on the engine.
Did the guy explain where the carbon comes from?
I have had some really rough carbs in my day, but none had enough gunk to impinge on the butterfly.

Lee3333

I was told the carbon comes from the EGR and I was thinking the PVC also. Cleaning it on the car sure would have been easier, but I don't see how you could clean it well that way.

donbrew

EGR & PCV are the same thing. That's strange, should be only oil fumes. Maybe you need a good SeaFoam top clean.

db/sb

How so?

donbrew

The hose from the top of the valve cover to the air horn. Positive Crankcase Ventilation was included in the Exhaust Gas Recirculation system. But since it's no longer the 1980's there really isn't an EGR system.

Have you got an EGR pump on yours?

Maybe a Turbo qualifies as recirculating exhaust gasses? I don't know.

Lee3333

I didn't think so, but somebody told me the carbon was from the EGR and I did not even think about it. It was not thick or anything-just a thin black film on the inside of the TB and around the butterfly. I would not think it would impair air flow since it was so thin, but the car is def running better than before.

And I am very happy and relieved that I no longer have the T/C issue. The only parts I changed which cured the problem were the 2 solenoids and the MAP sensor.

Just got back and I passed inspection!!!!! (I took a long drive this AM and racked on 80 miles without shutting off the engine).

donbrew

I am recent convert to SeaFoam top cleaning. I wish they would pay me. Give it a shot, Advance has it on sale now.

Don06

Exhaust Gas Recirculation is a system that recycles some exhaust gases back to the intake stream. The valve operates off exhaust pressure and intake manifold vacuum and usually connects the exhaust manifold to the intake downstream from the carburetor or throttle body. No pump is involved. They are still in use on some engines.

You might be thinking of the AIR [Air Injection Reactor] pumps on the 70s and 80s cars. That was a system that was used to pump fresh air into the exhaust to make the exhaust seem cleaner. Like adding clean water to a half full glass of dirty water to make the water look cleaner.

Neither of these systems has anything to do with the Positive Crankcase Ventilation system other than that the PCV is connected to intake manifold vacuum downstream of the throttle body. In theory, neither the EGR or the PCV should leave deposits on the throttle body since they enter downstream but they do.

donbrew

I can't find the EGR valve on my HHR. I can't find any exhaust gas recirc conduits either.

I can find EVAP recirculation and Crankcase fume recirculation systems, which used to be grouped together with the Exhaust gas recirc systems in an EPA kind of way. And they are inter related, since they all rely somewhat on manifold vacuum.

Kind of semantics, but this is the internets.