Need help, don't know where to start. 2002 180K miles

I'm stuck until my mechanic can look at it in a few days. Recently replaced the fuel cap seal after check engine and VSAC lights came on - fixed for two months, now lights back on. Been living with intermittent wipers temporary failures. Two weeks ago my six year old battery died, replaced. Lately, won't go into AWD, lights flashing. But now there's a serious running problem - intermittent no response to the accelerator pedal, unless I step on it about a two thirds of the way down. Will creep at idle on level ground, then with a lot of throttle, will accelerate with a clunk from the drive train. Same thing in reverse. Might go away for a bit, then happen again, but now it's parked because yesterday there was intermittent no response at all to the accelerator pedal.
I keep it clean under the hood, connectors look clean. I've cleaned the throttle plate (didn't need it) and the MAF sensor - should I try replacing the TPS? I don't have a code reader, but have decent mechanical skills and a multimeter...

 

Go to any parts store, they will read any codes for free.

 

Maybe I wasn't clear - I can't drive it. Just wondering if there's anything I could try until it's in the shop (probably towed) two days from now.

 

Code readers aren't expensive and they're a good investment. So are schematic diagrams (I bought a factory Toyota 4Runner schematic book off eBay). Look at the diagrams and see maybe if all the electrical issues trace back to the same area.

 

Guess I thought a description of these pretty dramatic symptoms might give a clue...
Related question: While it was not safely drivable, I fixed my intermittent wipers problem by removing and cleaning the switch.
Got me thinking. I've had the AWD lights flashing all through this episode, unable to use. Could some other failure like 4WD confuse the computers into causing a seemingly unrelated problem like mine? Yesterday I barely limped home, today after fixing only my wipers it runs fine with no dash lights showing, except the 4WD...
...and what about having the battery fail, like mine did a few weeks ago - can that cause other problems? Put another way, should I fix the AWD first and see if the accelerator problem stays gone?

 

Toyotas are simple vehicles, as long as the fuses are good the next thing to check are the Relays. Relays are hard to test because its only purpose is to switch small amp control to large amp circuit but you can't test amperage on a relay with simple multimeter. My suggestion is to replace All relays after 10 years or 100-150k miles and a lot of electrical issues can be resolved.

 

My problem is intermittent, so what's the correct procedure for finding whether it's a bad throttle body, or just a bad TPS - change the TPS and see what happens? Apparently they're the same codes and symptoms...?

 

You do really need a code reader. A cheap one is fine. You literally can't work on modern cars without one. Also, for Toyotas, when the CEL is on it turns on the VS/TRAC/ABS lights. Those extra lights are meaningless until you fix your CEL (Check Engine Light).

On the 2001-2002 Throttle body you have a TPS and a PPS (pedal position sensor) that can go bad. Both are what tells the ECU how much throttle you are giving it. If they both don't "agree" you are getting drive-ability issues. Usually it's the TPS but as these rigs age, I've seen more issues with the PPS pop up. The TPS and now the PPS appears to finally be available to buy. TOYOTA will only sell you the whole TB assembly. For me it was worth just getting the whole assembly. I bought her new in 2002 and the TB was the only major repair she ever has gotten. Regardless, if you don't want to go big, start with the TPS.

But the code is the key and you need to know this before throwing parts at the car. The ECU will tell you what it doesn't like.

AWD? Did you mean 4WD?

For the 4WD issues, you're probably looking at a more better code reader that can get at those codes. I don't know, I have never had an issue with mine.

 

Oh and vacuum lines. Check them. If there is a leak the ECU will throw you a lean code.