Hello All

My '87 P/U qualifies for NV Historic plates this year and at 320k miles, thought I might finally get around to an issue that has troubled me for going on 10 years. Not that I've been totally ignoring it. Will list my efforts at the end.

The engine starts quickly from cold, goes up on high idle, and as the temp gauge climbs to about 1/2 it's nominal reading, idle speed drops and the engine begins to run roughly, with a random popping sound from the tailpipe. The idle drop happens without any input from me (no tapping of throttle) and seems to be initiated by a thermal sensor triggering. I suspect the idle may be dodgy at the higher idle rpm as well, but does not become pronounced till the idle drops.

Mileage is 15-18, power is nominal with no miss under full throttle/top gear/low rpm conditions.

Efforts to date:

Plugs, plug wires, cap, rotor, EGR circuit cleaned (totally blocked), valves adjusted, vacuum leaks searched out w/ WD40 spray, carb mixture screw uncapped and lean drop performed (as best I could with rough idle). Keep meaning to make time for a carb overhaul (no records it has ever been done...did I just answer my own question?). High miles on O2 sensor. Don't recall the compression readings from a few years back, but, as I recall, they were around 110# (?) and consistent on all cylinders.

Kinda hoping there is some adjustment screw I can turn 1/4 ccw, but doubt it's that simple. Also, hate to throw $$$ at random parts if I'm overlooking something easy.

I'm essentially a very lazy guy and have learned to live with the situation, but since the truck has all indications of going another 300k, decided to get serious and try to make it stop hurting.

Suggestions welcome.

 

Does the 22r have a Coolant Temperature Sensor? Just sounds similar to an idle issue that I had when my 22RE had a coolant temp sensor going bad. Sorry, haven't worked on a 22r in 15 years. I did also have an issue with the 02 on my 86 22R.... it did something similar.

 

You're describing my truck exactly, sam everything, except the compression.
The popping is backfiring in the exhaust. Is the cat clogged, i know mine is and it does this as well.
Black soot at the ol' tailpipe? Probably running rich, which is why it runs rough, and causes the popping.

 

Thanks for the input, guys.

With everything EFI now, finding carb techs is getting pretty hard.

Regarding the cat, I don't have to meet any emissions standards in my area, and while I do want to be a good citizen, suspect the cat may not be operational and if I gut it, the world will not be that much worse off.

My only experience with a clogged cat was when the vehicle flat out refused to run above 2k.

Regarding the 22RE advice, I believe we are in two different worlds.

Thanks

 

Not 22re advice,....... I'm asking what/how, if any type of "Automatic" 'Carb adjustments' take place according to Temperature(Ambient or Internal)......??? The 22R doesn't have any ECU related coolant temperature sensing going on?

 

Pretty sure I have a CA model (48 state did not have an O2 sensor). And yes, there are a number of solenoids in the emission control system fed by the ECU. Also two thermostatically controlled switches...one at 13C and one at 50C (117F). Also, the O2 sensor does not appear to be heated, so it may be triggering an event when it comes to operating temp.

Looks like I've got lots of detective work to do, but have the FSM.

thanks