when i try to start my truck it almost goes then stumbles and dies. I have replaced the fuel pump and fuel filter and the truck sounds like it wants to go but still wont. Im also gettin code 12 and 51.. i dont think 12 is a code but that is what the truck is blinking. Someone please help me out here.
Thanks,
Andy

Does the truck start up then die right away? Make sure you AFM is connected and working correctly. Check for disconnected hoses on the plenum, and intake boot. It sounds like your truck is not detecting any air coming into the motor, thus not giving it any gas.

Code 12 is no rpm signal to the ECU

Problems could be:
Distributor circuit
Distributor
Starter Signal Circuit
ECU

This is from a Haynes manual so take it with a grain of salt but that ought to get you headed in the right direction.

Good Luck

it starts and runs for less than 5 seconds then stumbles and dies. And as far as i can see all of the hoses are connected.

How can i go about checking the different circuits?

Is the flap on your afm gummed up and stuck?

From '88 FSM:
CODE...SYSTEM...........DIAGNOSIS
12.......RPM signal........No "Ne" signal to ECU within 2 secs after engine has been cranked
51.......Switch signal....No "IDL", "NSW", or "A/C" signal to ECU with E1 and T shorted.

"Ne" signal is from distributor. AgRunner's Haynes info looks good. Is the wire running from the distributor damaged?

Code 51 could be the TPS. Is the TPS disconnected? Maybe the TPS needs adjustment?

how would i adjust the tps?

4Crawler has a wealth of info on his website. Here is the process to adjust the tps.
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

You will likely need a new throttle body gasket and you need a multimeter and feeler gages. It is not difficult to adjust once the throttle body is off the engine.

89-4runner: that's a great link for TPS adjustments. What does an infinity reading look like on your ohmmeter?

troy,
My digital multimeter shows a 1 for infinity (open). If your's is digital, make sure it's set to the right resistance range. I think mine goes 0-20, 0-200, 0-2000 Ohm, etc. I'm not an electrical guy so can't explain exactly why, but I thought the ranges mainly changed display digits. I noticed the other day when I was checking my TPS that I needed to change from 0-200 to 0-2000 Ohm range because one of the measurements was say 400 ohms. Watch out for that, because it could show a false infinite.

I don't think an improperly adjusted TPS will cause an engine not to start. Even if it is disconnected it will still run, just very poorly. Is that wire that goes to your distributor connected? That will also cause the truck to briefly start up. Have you taken your distributor out recently?

I havent had the distributor apart since last summer. and yes that wire is connected. Im realy starting to run out of ideas of what the problem is. Its been 2 weeks now with no truck and im starting to think about throwing in the towl with toyotas...

Don't throw in the towel yet. I have owned my Toyota for 15 years and have had issues with all sorts of things and nothing is ever easy to fix. (That's why mechanics make the big bucks. )

Do you not have any sort of repair manual for the truck? If not, there are plenty of links to different ones through this forum. You could do a search and then print the pages you need. Worst case go to the library or bookstore and buy a Haynes or Chiltons (the real Toyota factory manual is better though). In my experience, it's always easiest to fix something if you have the manual in front of you. We can help with little tips to the trouble shooting, but it's much more difficult if you haven't read the repair manual.

Here is a link to a '93 manual that might help you.
http://www.personal.utulsa.edu/~nathan-buchanan/93fsm/

You will likely need to pull the plugs at the engine computer and start trouble shooting there.

I have a haynes manuel but it is very unhelpful when it comes to diagonosing problems. Its realy only good for replacing things and, not figuring out what is wrong.

I have the toyota manual and either a haynes or chiltons. The toyota manual is much much better. Take a look at the '93 manual link I posted. It takes some mouse clicking, but there will be good info under the MFI diagnostics and troubleshooting sections. I can go home tonight and compare it with my '88 toy manual and see if it has any additional information.

I'm not too good at this sort of electrical diagostics. Read the info from the online manual and it will probably tell you to start checking voltages and resistances at the ECU harness. You may have a break in the line running from the distributor. I have the 3.0 V6, but I will see if my engine starts with the tps unplugged. With the age our trucks are getting, it's likely that wires get corroded or broken.

I agree. To test, I unplugged my TPS today and the truck started fine. When I unplugged the 4-wire connector from the distributor, the truck wouldn't start at all.

IT RUNS... Im not sure what did it but it finally started. I just wiggled every connection i could find and knocked some junk out the airfilter and it started. And its not blowing fuses any more. Thanks for all the info guys .

First chance you get, you should go back and re-check the connections you wiggled (AFM, TPS, distributor, etc.). It would really suck to leave you stranded somewhere away from home.