87tonkatoy

Just got an 87 four runner, 22re 230000 miles 5sp, supposed rebuilt motor per P.O. Truck sat for 6 years or so.... compression tests at 170 to 175 all cylinders so probably was rebuild at some point. Valve seals were dried up and stuck to intake valves burning lots of oil.... computer put out code 5 and 11 (O2 sensor) (TPS IDL circuit). So....... I pulled head changed valve seals head gasket head bolts other gaskets...... injector seals were crumbled so replaced all. The little screens in injectors were clean.... cam timing is good distributor installed on correct tooth. I replaced TPS and O2, plugs, wires, cap, rotor, fuel filter, air filter. Adjusted TPS as best i could to FSM and the tech write up on 4Crawlers site... So.... with TPS PLUGGED in truck starts and idles fine but the moment you open throttle it cuts out completly..... With TPS UNPLUGGED starts idles fine and revs up. Drove it 17 miles to work and home like that (welded new exhaust there only reason drove it). It ran extremely rich and missed badly most of the trip and when under load, but made it. So im certain (but could very well be wrong) that its something in the EFI system but not sure where to go from here?????? the engine "seems" like its mechanically dialed in though I haven't adjusted valves yet...... New TPS bad? (seems to check out but it seems really hard to get it adjusted in spec) Why so drastic when TPS plugged in? I understand why running so rich with out TPS plugged in but could that cause the missing? I timed it with the jumper in but if the system is not working properly then it cant be right i assume. Not sure if cold start injector is functioning properly tomorrow I will look at that.... so any ideas?

whokrz

Welcome to yotatech.
In my sig is a link to factory service manuals.

I have read that people diagnose a bad tps by unplugging it and if it runs fine it is a bad tps.
I think that when you unplug the tps the ecu goes into fail-safe mode as described on page 210 http://ncttora.com/fsm/87-4Runner/to...4runner_88.pdf (warning 82mb file) This would give the ecu a default code for all sensors to keep the engine running. In my opinion if your tps checks out to the FSM specs consider it good and move onto the next suspect. If it checks out bad then adjust it, if still bad then replace it.

Do you still have a check engine light on with the tps plugged in?
I would set the valves, check the flapper door in the air flow meter, the ohm of the air flow meter, the ohm on the O2 sensor, pulse of O2 sensor, cold start system, temp sensor, vacuum leaks and cracks in the hose between the throttle body and the air flow meter.

87tonkatoy

update.... I ohm tested AFM at first it tested bad, was not getting correct ohms on 3 tests.... i pulled it apart, it look good but may be a little wear on slide points. Re tested and all tests were good... put lid back on re tested then tested bad again.... took lid off and it worked again... even used two meters and keep getting good then later bad...... the flap moves freely and all components inside move nicely. With the cost of one im in no hurry to replace it till i know for sure... BUT what I did figure out is that the FSM has a test wear you unplug the TPS and short the IDL and E2 terminals on the plug side (to computer not sensor) to check the "fuel cut out rpm" when I do this test it mimics the symtoms exactly as when the tps is plugged in, it revs till about 1400 and cuts out... (which is in FSM spec with terminals shorted). however when I ohm test that circuit on the TPS itself it is within spec though it is difficult to get my feeler guages in there so I may be inaccuarate but that circuit in the TPS should not be a complete short as it is very high ohms and at some points infinite..... No codes from computer but as I unplug things it puts out codes then I clear them and only o2 code here and there but its running super rich during alot of my testing so that may account for that...... no vacuum leaks apparent all lines and intake tubes in nice shape pretty damn sure no leaks..... probably try new tps and check junk yard for AFM which leads me to this question what years and models have same AFM or is it unique to year model? and could this "fuel cut off" feacture be controled by another component?

whokrz

On page 290-291 it tells you how to check the values at the ecu. Using this should allow you to make sure that the TPS and the wiring is correct and the ecu is getting the correct information.

On page 274 I think when you jump IDL - E2 it mimics the TPS reading of idle. When they are not jumped it mimics the TPS reading of throttle open.

On my truck when it raises the RPM at idle, then cuts and repeats this over and over it is always the air bypass. You can read about it on page 272. Basically it makes a air leak that bypasses the flapper in the throttle body when the engine is cold. The ecu knows the engine is warm, and the throttle is at idle. It expects this valve to be closed, if it is not the extra air causes the RPM to rise and then cut

I would definitely get another air flow meter and make sure that it passed ohm. I am not sure which ones are compatible, but I think that they changed threw out the years. You could try a search on here or maybe someone will post the answer.

87tonkatoy

another day of testing......

all tps connections check out good at plugs at computer......

although the diagram of the plug in the FSM is not what mine is.... I have an 87 made in Nov 86. There must have been some changes.... anyhow through continuity testing i was able to track down wires.

When proceeding to check AFM wires to find them in the plug I found connection to ground on both ends of plugs un plugged from both comp and afm as well as connection between four of the wires next to each other on the same plug....... not full continuity but connection at like 1k ohms which I can only assume is a problem in the harness where mulitple wires maybe melted together or mice eatin or just wore through at a bend point???????

Maybe the AFM signal is not making it properly making comp think is still idleing there by enableing idle fuel cut off system? Not enough light to dig into harness today but just to make me feel better before i jump into the harnes there should be none of this happing correct?

On another note went to local junk yard no AFM or ECU but did find rear window with good tracks still to replace my completly rusted track rear window for 9 bucks

87tonkatoy

actually have full continuity on four wires to ground on AFM plug.... the four wires all have about 1k ohms between them..........

whokrz

If you are checking the wires and think they are melted together disconnect the air flow meter and then check. The air flow meter could be causing the continuity not bad wires. You stated that your air flow meter was not reading correctly on the ohm test. Because of this I would not expect to get proper readings form the air flow meter at the ecu.
I would recommend getting a air flow meter that is functioning properly and then recheck at the ecu before tearing into your wiring harness.

87tonkatoy

I am on the hunt for a AFM cant hurt anything anyways...... the test was with AFM unpluggued and computer unplugged I was checkin for continuity to see which wire went to which spot on computer side to then be able to check the AFM readings, so the continuity to ground is with computer and AFM completely disconnected on both ends.. so in theory those wires should not touch anything, not ground not each other...... according to the electrical diagram in FSM the ony wires in this portion of the system that connect within harness is the E2 that goes to AFM as well as tps and some others.... (I think thats the one the comp sends power out on and the other and the return????) It just seems really fishy that four of the seven wires have continiuty to ground with everything unplugged. So I'll check some more junk yards for AFM but I think the fun is just begining..... I have once in the past completly pulled a harness on a 77 corvette and "rebuilt it" as it had had a major short and melted wires. Was no small job. On the bright side at least its living up to its title of "project truck" thankx for your help so far i'll keep updating

whokrz

If everything was disconnected and you know its the wires then yes the truck is going to live up to its name. You might want to check on the airflow meter side of the wires. It should have the same or very close reading that you got on the ecu side if the wiring is fried . Just trying to make sure that you have the correct wires is all, but it sounds like you have your work cut out for you.