1985 Scottsdale V6 - Choke Light coming on at idle

[Randall]

So, recently my truck has developed what I'm guessing is a vacuum problem, but I'm not sure. When the truck is just started up, it runs fine. After the engine reaches operating temperature, the choke light comes on and the truck starts to cough and sputter when I'm in neutral (at a stop light). The engine smooths out if I put my foot on the gas a little and increase the idle speed. Has anyone else had this problem?

 

[1987 GMC Jimmy]

Possibly but it should show a little more consistency than that. Or so I would think. My biggest concern is the choke light. That makes me think the oil pressure is getting low to the point where the choke circuit is getting confused. I’d verify good warm, idle oil pressure right away so you don’t burn up your engine over a bad oil pump or a clogged pickup. Might come up with nothing there, but since the choke heater circuit is supposed to close only with sufficient oil pressure, I’d say it’d be worth borrowing a test kit from Autozone and seeing if that checks out.

 

[CorvairGeek]

Low oil pressure, fix the idle issue and verify the oil pressure. The oil pressure switches go bad with age too, not to be confused with the oil pressure sending unit, if you have gauges.

 

[Randall]

Possibly but it should show a little more consistency than that. Or so I would think. My biggest concern is the choke light. That makes me think the oil pressure is getting low to the point where the choke circuit is getting confused. I’d verify good warm, idle oil pressure right away so you don’t burn up your engine over a bad oil pump or a clogged pickup. Might come up with nothing there, but since the choke heater circuit is supposed to close only with sufficient oil pressure, I’d say it’d be worth borrowing a test kit from Autozone and seeing if that checks out.

I think you're on to something here. I'm not the best with maintenance on this truck. It is mainly used to haul trash to the dump and little things like that, so I often let it sit for long periods of time. I think there is a good possibility that the pickup screen is indeed clogged with sludge. The oil pressure was extremely low when it was idling. I think I'm going to just go ahead and drop the oil pan and replace the oil pump and pickup screen just to be safe. There's probably all kinds of junk in that pan that needs to be cleaned out anyway. Fingers crossed that that solves the problem!

 

[1987 GMC Jimmy]

Better safe than sorry. Pump failed on my truck’s original motor, and the gauge was inop so I did burn the motor up.

 

[waynew]

CorvairGeek and 1987 GMC Jimmy are right. The choke light doubles as a low oil pressure indicator light. I think it comes on if the oil pressure drops below 4psi.

 

[HotRodPC]

Thread moved to Engine & Performance >Carbed Fuel Systems