A Super Stumper: The Mint 1992 Toyota Pickup... that runs like Junk

Hello, Cartalk friends! I have a stumper for you. I have a gorgeous, mint 4x4 1992 Toyota pickup…that runs terribly. Sometimes, it won’t start. When it does start, it often idles very, very low. (Idler tension cable was adjusted up but it didn’t help.) When I drive it, the idle goes up and down between very low and 4000 RPM. Sometimes, it stalls out all together, regardless of what I do to the clutch, brake, or acceleration. In an engine diagnosis, Knock Sensor came up, but there’s a new one, and the cable harness is fully gone through. It’s got a new engine with 67,000 miles on it, a new fuel pump, and just about every part has been replaced. It’s been to about 10 mechanics, all of whom can’t figure it out. Anyone from the Internet have any advice? Thanks so much in advance.

Give some specific details on the engine, most are 4 cylinder but there might a few V6’s in that truck. We need a lot more info, like is it a multi port FI or a throttle body FI. I suspect the issue is in the FI system, but more info needed.

Right…4 cylinder, 6 cylinder, carbureted or injected? Lots of things were changing in 1990-1992…

I presume this isn’t the 4 cylinder 4AFE engine, right? Which engine is it? Adjusting the idle on my 4AFE equipped Corolla of that same vintage isn’t done using the cable. It’s hard to believe that’s how is it supposed to be done on your truck. The Corolla has an air bleed bypass screw to adjust the idle rpm. If that screw is used to fix some problem that isn’t supposed to be fixed that way, the idle rpm roaming symptom can and almost always does occur.

I had one of those, a 91, started to run crappy and I traded it in. Not sure what went wrong, but got an 03 ranger brand new for $10300. Ran perfectimundo u to that point, but said to self do not want to deal with it. I am not sure what to suggest, but in my case it seemed like the brains were fried. Ran fine until, and it was very sudden. 120k as I recall.

I owned a 1990 hi-lux 2wd.model The last of the 2-bbl carb models on a 4-cyl 22R engine. 1990-1/2 models dumped the carb and came with multi-port EFI (22R-E) and 5-speed standard. Running crappy and hard to start, I’d look first to vacuum leaks, then ignition spark leaks, overall spark strength, ignition timing, valve clearances, cam timing, and compression testing.

Have it looked at by a good independent mechanic. I can see by your comment “Idler tension cable was adjusted up but it didn’t help” that you are not savvy in the workings of a vehicle engine. Do yourself a favor and let a good mechanic find your problem. Keep that mint '92 on the road for a few more years…maybe longer.

@RockyCoastlines; I believe that the computer is under the passenger seat and if so can be easily pulled out to get trouble codes. The instructions and code definitions were pasted to the tops of computers on Japanese inports of the early 90s. Check that out. It might save you some time and money. A 10mm wrench, phillip head screw driver and a very small blade screw driver plus a pencil and paper would be needed if you want to go that route.

Also, doesn’t that model have a swinging door Mass Air Flow sensor? If so it should be carefully tested with a digital volt ohm meter.

Remember . . . it IS almost 25 years old. Most vehicles that old are a labor of love and not a daily driver. My advice is is start simple and go through the various systems of the vehicle, starting with electrical, start to finish, then move to fuel, timing, etc. If it’s that much of a mystery that 10 mechanics couldn’t figure it out you have to start at ground zero. IMO, that is. Good luck! Rocketman

And also, @Rocky, I recall that the Mass Air Flow sensers of that time triggered the fuel pump to operate. The fuel pump remained off until air flow opened the senser enough to trip a switch that signaled the computer to turn on the fuel pump. Like so many problems posted here you need a good manual or on line link to wiring diagrams and diagnosis/repair data.

“It’s got a new engine with 67,000 miles on it,”

What year is the engine?
Did you bring the ECU with it?

I have a 1993 maxima that had a lot of those same symptoms, it was the mass air flow sensor.