Wait, What's This?

Last night, Matt and I spent some time in the garage playing with the truck some more to see what we could come up with on the idling problems. We disconnected everything that could possibly be controlled by the computer on Saturday afternoon and still the truck would die out on its own when coming back down to idle. With no outside influence, the only conclusion we came to was that the carburetor wasn't rebuilt properly and something in the idle "loop" wasn't functioning correctly.

Matt had been questioning the rebuild originally because of the high pain in the ass levels involved in rebuilding a carburetor and the potential for something small and stupid to be out of place, ruining the whole operation. The rebuild by others prior fell under greater scrutiny when I figured out that the EGR valve certainly wasn't getting any vacuum to open it because there was a ball bearing shoved into the vacuum tube coming from the EGR on/off solenoid . . . that of course brings up more questions, but . . .

After a bit more poking and conjecturing, we were pretty much resigned to the fact that the next best step (other than selling the truck to the next unsuspecting clowns) would be to get a professionally rebuilt and bench tested carb which would include a number of the sensors we'd already replaced, bonus. We pulled off all of the sensors and connections to the carb and removed it from the manifold, making sure not to drop anything in the hole. Once out of the truck, further examination was very easy. We looked at where the idle "loop" is and that told us nothing. We checked the stamp on it and it is likely the original Carter YFA from the factory.

Removing the carburetor gave us a view of somethings we didn't have before. One of them was the vacuum tree on the intake manifold. There is a big vacuum line going to the PCV valve, a medium one going to the brake booster, some small ones going here and there and wait, what's that . . . a barb with a piece of broken hose or cap or something . . . We couldn't find any vacuum leaks in the lines, but this certainly counted as a leak. We put a tube on it, capped it and put everything back in place, learning in the process that it would be about a 30 minute job to replace the carburetor with a new one. Fired the engine back up with a little work since the carb was completely empty of fuel at this point and let it come up to operating temperature. Surprise, surprise . . . the engine held idle at 750 RPM, even coming down from higher speed!

One problem seems to be solved, there is still the matter of passing an emissions test so we can get the thing registered. We also took a stab at some of the other smaller tasks like installing the tach and freeing up the parking brake cable. I am going to look into a temporary tag so we can drive around on the up and up. Driving around for a bit to make sure this wasn't a carbon monoxide induced dream seems like a good idea, no need to rush back to fail, er test emissions.