My wifeÆs '87 pickup with a 22R Carbed engine started doing this about 6 months ago.
It would start up cold just fine, warm up and kick down off high idle just like it is supposed to most of the time. Every so often the high idle would be a little rough, then when it kicked down it would die.
It has been progressively getting worse to the point now it does this almost every time. If I can keep it running till it warms up it runs fine after that. One other symptom is #3 and 4 cyl not firing right, spark plugs show dry soot build up.

Done so far:
Compression test, 160 lbs. all 4 holes.
New plugs, wires, cap, Rotor.
New Coil, Fuel filter, Air filter.
Checked all vacuum lines.
No apparent manifold leaks.
Checked valve adj. Right on the money from last adjustment.
FSM EGR tests good. Tap test for sticking good also.

Got me stumped so far. HELP

Thinking about replacing carb with an extra one I have but don't know where to compare numbers for compatibility.
Thought it might be the Igniter but that is a $500.00 SWAG.

First thing to do.
Pull the vac line from the AAP on the carb.
(driver's side towards the front)

Plug both ends.

I'll bet your fixed from there. Same thing on my 85 carb'd truck.
If you are in a colder climate, you'll want to replace the AAP before it gets cold again.

The AAP (Auxillary Air Pump) is specifically designed to add more fuel (richen the mixture) to smooth out the high idle when cold. Once warm, it's supposed to close. As it wears out, it continues adding fuel when it's not needed, therefore, making it run too rich, and that's the soot on you plugs.
Mine was intermittant. Ran like crap after warming up. If I shut it down for a few minutes, it would run good after starting after it was already warmed up.

Didn't have enough (insert name) spay to do a good leak test till yesterday. Picked up two cans of (big guns) starting fluid and did the spray around test. Found a vac leak at the #3 intake runner gasket.
Up till 2100 last night taking it all apart. EXCEPT for the one stubborn bolt (everyone knows that one stubborn bolt all too well) had to be the one at the back of the head holding the water tube clamp. You know the one, wants to break off not break loose. Soaking it with PB blast over night. Getting ready for round two after breakfast.

Well the new manifold gasket didnÆt cure the problem. Replaced the AAP diaphragm while I was in there. Old one looked ok. IÆve about run out of ideas. I think I will go ahead and change the EGR Valve. It was acting a little funny while I was testing it. DonÆt know where else to look.

Define "acting a little funny"?

EGR valves pretty much work or don't work. A blown diaphram is the most common failure in my experience & that's easy to diagnose (won't hold vacuum) so I assume you've checked that. Sometimes they get a carbon buildup & sometimes the plumbing to them does, so if it holds vacuum take things apart far enough to rule that out, but replacing the EGR if it hasn't failed is a waste of time & $.
Dave

he he... AAP means Aux Accel pump... The main accell pump is on the other side with the lever on it.



on the rough idle... did you try turning up the idle? 3 and 4 look sooty? is there black buildup or a different color? are you losing any coolant? while its idling spray carb cleaner all over and listen for changes.