Friday, July 24, 2009

Engine Tune

Very worn throat and valve, valve is being held up out of the groove it has worn.

Cleaned and ready for rebuild. Two stainless washers were added on top of the body on the shaft to prevent the valve from cutting into the throat again. After cleaning, the rubber gasket visible in the first photo required trimming with an Xacto on its crown to allow the washers to rest on the body.

When I picked the truck up from the previous owner, one of the first things it needed was an engine tune and the reinstallation of the emissions controls. The idle control valve had been disconnected and it soon became apparant why it had. When reconnected, the idle went to approx 2000 rpm. A quick examination of the throttle body revealed that the idle adjusment screw was as far in as it could be and a couple of sensors had been disconnected.
I've now welded in an aftermarket catalytic converter with O2 sensor, replaced a defective T2 sensor and defective thermostat, and rebuilt the very worn throttle body.
The throttle body had a pretty big groove cut in the lower portion of the throat where the butterfly valve had been rubbing for years. This had allowed the valve to settle into the groove and opened up a large gap at the top. A couple of stainless washers on the top of the TB to support the valve, some JB weld in the throat (along with wiring repair of the throttle switch) and the throttle body is back in business.
When the engine was restarted, things were back to normal with the exception of a lack of ignition advance at around 2000 rpm. A swap of ECUs from my parts vanagon fixed that.

I'd originally bought my 86 parts van for the engine, transmission and syncro drivetrain, but things like the ECU will prove invaluable. At $1400 to $2200 for a new ECU, the $1600 I spent on the 86 syncro (which I'm still able to drive!) seems like a bargain.

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