Hello all...new to the forum but long time Wag fan owning a few over the years. Having an odd problem with my latest one. This is a bit long but trying to give all the info.
1987, almost totally stock. Has an aluminum radiator w/ electric fan and an electric fuel pump. 111,000 miles. Until recently, she ran like a top. Smooth idle at about 650, smooth acceleration & cruise. Timing at 12. 21 inches steady on a vacuum gauge. 12 mpg. Drive it about 50 miles a day.
A few weeks ago, the water pump bearings started howling. That is a project I would normally do myself, but I had a lot of balls in the air at the time so I sent it to a shop so it would get done. Not long after that job, it started stumbling at idle, the kind of stumble that feels like the igntion was turned off for a split second. It was not rhythmic it was random. Eventually this deteriorated to the point that it would die at every stop, had to shift into neutral & give gas at a stop to get home.
Started nosing around looking for vacuum leaks or other problems. Rechecked the timing( it was fine), thats when I discovered that with the vac advance line disconnected & plugged, it ran smooth again. Vac advance on the dizzy holds vacuum and pulls advance like it should, so I dont think it’s a leak there.
Did some research and seemed like replacing the ignition module was a good idea based on my symptoms, so I did that (Rock Auto). This made the issue better...it wouldn’t die at a stop anymore, but still idled rough with vac adv attached, smooth without it. It drives “fine” with no advance, just with less throttle response & worse mileage as you would expect.
Still reading a steady 21nches on vac gauge with advance plugged, it will bounce around 20-21 when the advance is attached. I have checked all the vacuum hose routing, everything is attached to match the diagram under the hood.
Anyone have any suggestions or solutions from their own experience? Possible CTO issue? I have seen a diagram for “simplified” vacuum routing that eliminates the high temp CTO, considering trying that to see if it helps, anyone tried that?
Thanks!