Rough Idle after Tune-up

[1425956]

Hi all. I have an 84 GMC Sierra Classic SWB with a 305 engine and lock-up TH350. This truck is new to me (have had for 3 weeks) and has 74,000 original miles on it. Because the truck has been sitting for the last 9 years, I decided to freshen some stuff up, tune-up and fix random leaks. Below is a list of items and parts that were replaced or repaired.

-Dropped the trans to replace the front and rear seals and replace the trans filter, fluid and gasket. (Was leaking bad and is still leaking!)

-The original owner had someone replace a leaking tank and they didn't know what they were doing. He/she got the straps too tight on the replacement tank but failed to replace the fibrous material between straps and tank. The relatively new tank developed a hole from a crease so I replaced it. The replacement tank was clean and rust free inside and out.

-I replaced the fuel sending unit because the fuel gauge bounced around and the original strainer was trashed.

-I replaced the original A/C Delco plugs, wires, cap and rotor with new Borg-Warner parts (except plugs, they are Delco). All wires were re-routed back through the original wire holders/looms and are away from the exhaust manifolds. All 8 spark plugs looked like cardboard.

-Drained the rear end oil, replaced pinion seal and rear diff cover gasket and refilled with 80W-90 gear oil.

-I changed the engine oil and filter.

-I removed the fuel filter located inside the Q-Jet and installed a new clear in-line fuel filter.

-Replaced the exhaust flange donut gaskets.

-I noticed the rubber hose connecting the trans vacuum to the intake was nearly deteriorated so I replaced it.

-Someone removed the smog pump and capped the A.I.R. on the manifolds.

In addition to a continued trans leak, my engine is now idling rough. However, I drove the truck 2 hours from the place of all of this work to my house and it ran better than ever!

My first thought was that since there was a vacuum leak, part of the improved performance was due to the vacuum advance now able to work because of a fixed vacuum leak. I know there are two different types of vacuum, above and below the carburetor.

I decided to run to town yesterday (after my truck sat all night after the 2 hour trip home) and that is when I first noticed the rough idle. I started it and let it run for a few minutes, then headed to town when my truck decided to die in the middle of the road. It cranked right back up but was surging real bad. Once I get the engine rpm past 1K rpm's or so, it takes off. However it does not have the pep it did on the trip home.

My first thought was I knocked a vacuum line loose but I could not find anything loose after an inspection this morning. I used starting fluid to spray lines with the to see if I could locate the vacuum leak. When I sprayed the passenger side of the engine, the idle did smooth out a bit but I could never really define the area. I took each line off the carb and plugged it to see if I could locate a problem there. Blocking the various vacuum ports on the carb did not change anything.

The research I did today led me to possible trans leaks on detent cable and dip stick grommet. I did not replace either of those seals/gaskets but I will do so. My bigger concern is the engine running smoothly. I am fairly proficient with SB Chevy's and have built several of them with success.

I can hear the valve in the P.C.V. rattling but I think that is normal. I have not looked at the E.G.R. valve yet. There is also a hissing noise that sounds like it is coming from the carburetor but it may be the normal air movement.

I am not really interested in removing all the emissions equipment if it is not necessary. I want to keep the truck as original as I can and keep everything operational. BUT, I want dependability and maximum mileage.

I am really at a loss...Any ideas? I double checked all wires to make sure they are plugged in and they are. What am I missing?