The mystery that keeps on taking

Thanks all for the thoughts and insights on this! Okay, I'm going to try and see if I can respond to the questions raised since my truck is now running even worse than it was. The problem started about a month ago when I noticed that I was getting poor gas milage. That happened under typical circumstances so it wasn't due to some change in what it was being asked to do. That was the only thing that seemed off. About a week and a half ago, I needed to accelerate quickly into traffic and I got up to about 3000 RPM and then just hit a wall. Felt a little bit of a miss at those higher revs. Today, I had to haul a pretty heavy load, maybe 700 pounds and in about 65 miles, I went through a quarter of a tank. I'm not sure to what extent having a heavy load in the bed played a part. Some for sure. Also, when I had to rev the engine above 3000 RPM in third gear, I got a heavy stumble. The only recent thing I did to the truck was to install some of that heat shied that Eastman sells. Good stuff, I should say. Checked to make sure it wasn't so low off the inside of the hood that it was fouling with the accelerator linkage and it wasn't. Other than that I haven't changed anything from before it started misbehaving to where I am now. No new tires, I've refuled and it didn't change it's behavior. Also, to the question of the number of miles on the engine, the clock says 175,000, but the oil comes out as clean as I'd expect from a next to new rebuild. I don't know the history of this car's prior ownership but it looks like it was his baby and it wouldn't surprise me if it was rebuilt.

For those wondering about having service station attendants, in some throw back nod to the past, the state of Oregon (or Ory gun, if you're a resident)requires gas station attendants to fuel vehicles. Us normal mentally challenged types that can manage to pilot a 3,000 + pound vehicle hurtling down a highway at 70 miles per hour adjacent to oncoming traffic are, for some unknown and unspoken reason, assumed to be incapable of working the challenge of a gas pump. What can I say? At least some people who would have a hard time finding work can indeed get a job, so I'm not entirely against it, but when I'm sitting at one of those multi island stations and I have to wait for the few attendants working to get around to me when I could just do it myself and get back on the road is pretty annoying. As far as the question of did this era Tacoma even have the ability to identify a loose gas cap, what I got from my code reader was a code that,when I looked up what it might be, listed the loose gas cap as one of them. It may very well been a generic code and they were just listing all the things that might cause it. And since I'd had a gas cap that was loose in the past and it had just sent a code, I've got to believe they are tied somehow.

I've got my entire Saturday set up to play around with it and a place out of the rain to do it. Cup of coffee and car talk playing should help. I intend to try as many of the suggestions as I can before I head up to the dealership and cry uncle. So, first up, I'll unhook the battery and let it sit for a half an hour or so. I'm going to replace the plugs. Copy on the NGK 3967 - gap .043. Also going to replace the plug cables since it's past time for that kind of maintenance anyway. While I'm replacing the plugs, I'll check and make sure I'm getting spark everywhere. I wish I could do that under load, since that's when issues seem to show up but just making sure the coils are functioning seems like a good place to begin. In the past, I've checked for vacuum leaks with a propane bottle and looking for idle increases. Any suggestions on a way that's just as good (and as cheap)? I can clean the MAFS and the throttle body but not sure about how to test the O2 sensor. I'll look up the appropriate youtube video. And, I guess I'm going to have to find out what an IFC valve is and how to check it.

So, that's where I am. Thanks again for all the help! I'll post when I find out what's going on, even if it's only a dragging break caliper.

 

Hey man, I lived in Washington for 4 years in the 90’s. Out of the rain was always the first step.

Of everything you have on your list to do, cleaning the MAF sensor is the easiest. Unhook the negative battery terminal. Take out the MAF sensor. Clean it with only MAF sensor cleaner. Check the o ring. I put a film of silicone grease on a new one since mine was torn. You can get the o ring at the hardware store. By the time you are done the computer will reset when you hook the negative back up. Go for a nice 30 mile drive and be amazed at how she runs.

Here’s my thread from when I had a similar problem. You may have additional issues but without a clean MAF sensor you are starting with bad data to the computer. That’ll just make diagnostics more difficult. Good luck man!

https://www.tacomaworld.com/threads/0171-code-with-data-what-does-it-mean.555198/#post-18273013

 

Bad coil? Computer fault? My beemer developed an issue before I traded it, it ran fine until I got close to redline, than coil 1 would misfire, throw a code, and keep doing it until I reset the light. Changed the coils and plugs, same issue.

I found the final solution was getting rid of the car

 

You might want to also hook up a vacuum gauge to help tune it. Just to comfirm everything you've done.

 

At least two states require full service at every pump: Oregon and Jersey.

 

Sounds like a plugged catalytic converter.
Clean the MAF first. Then check the cat.
To
diagnose a plugged catalytic converter, you can check intake vacuum or exhaust backpressure. To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is 10 percent lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust.
Autozone rents vacuum gauges.