4bangercraig

'87 pickup, 22R with a Weber 32/36. Chevy ignition w/ Accel Supercoil. Timed at 12 degrees advanced. Jetted at 60/50, carb at baseline settings.

So I've been chasing a stalling issue around and around my engine bay. The vehicle stalls when I take it out of gear, any gear 2-5, any speed over 10mph.

My first inclination was brake booster- replaced it, its valve and tubing. Wonderfully responsive brakes, still stalling.
I discovered an intake manifold leak- fixed it. Nice clean idle and the carb tunes in spec, still stalling.
Tested the coil, it was out of spec, so I replaced it as well as the igniter with a GM style setup. I noticed a great uptick in performance, still stalling.

Compression test showed all my cylinders around 140ish. It's got 300,000 miles on it- this seems about right and not cause for alarm.

A little wibbling in the vacuum test, along with grabbing plug wires til I got shocked found a bum wire. Fixed that, threw on a new cap for good measure.

Vacuum test looks good- I'm getting 21 inches at idle. Open the throttle and it dips to almost zero then up to 25. To eliminate the possibility of an exhaust restriction, I treated my neighbors to a Friday evening test drive without the cat. Same behavior.

When it stalls- vacuum gauge begins fluctuating more than 5 inches at a low but moving centerpoint. Fluctuates around 10. Then around 5. Then the motor cuts out.

I tested my power valve diaphragm and it's blown, doubtless from the backfiring that occurred around the recent replacement of my timing chain and other timing issues.

Which are potentially pertinent-

She was nonopped for about a year following a catastrophic IFS blowout on the Rubicon in August 2011.
I took her off nonop about a month before this year's Con trip, also in August. Threw a solid axle under her front end and installed the Weber.


At this point, no stall.
But it was dieseling badly.
We checked the timing and it appeared to be retarded 15 degrees. Weeeird. We set it to 0 and took off. This is when stalling first appeared.
I heated up and vaporlocked outside of Georgetown. After some head-scratching, we checked TDC thru the spark plug hole and found the pulley to be totally wrong. Huh.
So we made a new timing mark and set it to actual zero. Stalling disappeared
Did great on the trail- only turned a wrench to tighten knuckle studs.
On the way home, stalling reappeared.
We got home and discovered that the timing had skipped and we were getting exhaust in the carburetor, black carbon crud everywhere, and awful backfiring.
The timing chain was stretched- so we replaced it, being very careful to line everything up and check sprockets, replace guides, etc.

Now the engine ran great, except for the stalling issue. While replacing the coil and playing with timing to try and root out the stalling issue, the timing mark jumped again. Radically. Like, 30 degrees advanced. For a few days I desperately operated under the presumption that the timing mark was accurate before realizing it had moved.
But if timing had actually jumped 30+ degrees, there would be bent valves.
Camshaft and crankshaft actually correlate perfectly. Pulled the pulley and the woodruff key setup is all intact- I think the pulley itself is failing. This should really be addressed, but for the time being I now have three timing marks. And when using the right one, the truck idles wonderfully. Throttle response is great. Works fine til you put it under load and then push the clutch.

So that's my sordid tale. If you got any ideas, I would looove to hear them.
I'm waiting for a new power valve diaphragm to show up. Maybe I'm drowning the motor when I come off load. Sounds good. Then again, so did the manifold leak and the weak coil.