Today, I was moving my father’s old 1990 Toyota truck off the street, where it was for over a year, onto the driveway. After I was warmed it up, I noticed it didn’t rev down. The engine only did so when I stepped on the clutch or was given it enough gas to get the RPM up to shift into second gear, where it proceed to rev up again. Also, when I turned it off, the engine shut off roughly. It will likely stay in the driveway a while, but does anyone has any ideas what the problem maybe?
What engine is it? IIRC, in 1990 you could get that truck with either a fuel injected V6 or 4cylinder or, rarely and in the 2wd trucks only, a carbureted 4 cylinder. The engine makes a big difference because on the carb-ed truck the high idle is linked to the choke, on the fuel-injected 22RE 4-cylinder there’s a thermal-valve that controls the high idle and on the V6 I believe it’s controlled by the computer. In either of the fuel injected cases, likely culprits after the truck sat for a long time would be a low coolant level or a stuck thermal valve (4cyl) or idle control motor (V6). Either can be removed and cleaned.
A large vacuum leak from a broken hose or a damaged vacuum-operated component could be another possibility. Listen around the engine compartment for hisses with the engine running for that.
I would be very surprised if this is located in a cold climate area, as gasoline a year old could cause all kinds of problems.
I had some old gas and with prices at their peak last summer I added some to my truck, now that was just a couple gallons. I never noticed any difference until I ran the tank down under 1/8th 2 months later and I didn’t think I would make it home that night. It was bucking and the check engine light was more than on, it was blinking! I filled the truck (dodge ram 318) and the thing still ran poorly. I bought a code reader and reset it and changed out the plugs as the reader listed one faulty cylinder and that plug was fouled. The engine still ran rough until I added Sea Foam to 1/2 tank. Next day everything was OK. Don’t use old gas!
How long did you let it warm up for? I’ve had several vehicles which idled fast until they were put into gear, and didn’t idle normally in neutral until they’d been driven several miles.
Unfortunately, I won’t be by my parents’ home until next week. AFAIK, the truck has only been driven maybe 6-10 in the past year. It’s not very cold as it’s in the Southwest. So it probably gets around 40-50 degrees at night. It has around 1/2 tank of gas (how old I don’t know) and I let it warmed up (It was 75 degrees in the afternoon) for about 10 mins. The temperature gauge was past the cold bar. I’m unsure if it’s carbuerated or fuel-injected, I’ll have to check next time. However, when I did mention the truck problem in a call, he didn’t seemed concerned as long as the truck ran. So, it’s possible that it does drop out of idle after several miles. If it doesn’t, what are the possible consequences?