Scrussanation

also since your there replace the injectors why now

4Xtruck

Thanks for the suggestions. I'll remove the plenum and fully clean it, but it will be a while before I can get to it. Please help me understand the reason behind replacing the injectors when the plenum is off. I use Chevron gasoline and believe it does a good job of cleaning anything in the fuel system.

yadudej

Sorry I haven't responded, been busy with work and the truck, but thanks for all the help so far, I have done a full tune up, cleaned the tb, cleaned maf, replaced the ignitor and coil pack, checked my timing with a gun.....allll of that has not fixed it yet,my injectors are fine also. Also just like scrussanation mentioned, I also have my egr blocked and all vacuum lines blocked, but I did that awhilee back and it ran perfect (blocked off solely for convienece as my state of oregon doesn't require visual inspection)

yadudej

Also I have owned the truck for less than a year so I haven't done any valve work or anything with the exhaust or cat...could either of these be causing the misfire?

osv

with 300,000 miles on the engine, the plenum is most likely going to be fully gunked up inside... cleaning that out is a nightmare, it'll require a lot more than just a car wash spray... I used oven cleaner, including on the back of the throttle body, which requires removing the tps, which would then require re-adjusting the tps... see the 4crawler site for more info.

sending injectors out for cleaning because they have 300k miles on them is a good idea, but i'd first try basic troubleshooting before tearing anything apart.

check for vacuum leaks and correct vacuum hose routing.

4Xtruck

Temporarily, till I have the time to tear apart and clean the plenum, I sprayed throttle body cleaner through all the vacuum ports on the plenum, checked the lines for any vacuum leaks or blockage (none) and checked the operation of the EGR (works fine). Warmed up, the truck runs smoothly at about 750-800RPM. When I turn on the A/C, that drops to 500RPM which is workable yet not as smooth. Is there anything else I should look at when I clean the plenum? OSV, I'd appreciate a link to the tps adjusting instructions, though I'm hoping I can clean it without removing the tps (separating the throttle body from the plenum and cleaning separately. I'll thoroughly spray the plenum with throttle body cleaner to soften the gunk and then use my pressure washer to spray it away. I'll keep doing this till it is clean. If I need to use oven cleaner, I have some available.

osv

making sure that those ports were clear is a good idea.

just start with oven cleaner... what I did was put it in a shallow cardboard box, and soak it multiple times, then take it down to the engine bay of the car wash to spray it out... you don't want any of those chemicals on you.

some people have posted that lye(?) or something in certain brands of oven cleaner is hard on the aluminum, so you may want to check that out.

you can do certain tps checks at the cpu plug connectors, just run some wires from there to your voltmeter up in the engine bay, where you would be manipulating the tps:
http://forums.off-road.com/toyota-su...e-1300rpm.html

if you get any gunk in the tps, it'll be ruined, and it'll be nearly impossible to clean the tb with the tps on it... i'd test the tps first, per the above.

osv

when you turn on the ac, the idle should speed up, not slow down, here is where to troubleshoot that:
http://www.4crawler.com/4x4/CheapTri...ne_Pix/13.html

are you sure that the vacuum hoses are routed correctly?

I don't think that you'll find plenum cleaning in the fsm, because it's not a cure for anything... there is an egr port in there that could get blocked, but that's not consistent with the problems you are seeing.

4Xtruck

The vacuum hoses are routed correctly. When I remove the vacuum lines from the A/C VSV and then connect them to each other, the idle goes up. I'm not sure if the problem is a bad A/C VSV or it's just not getting the signal it is supposed to get. How do you recommend I test the A/C VSV?

osv

with the wires plugged into the vsv, maybe try reading dc voltage across those two electrical connectors on the vsv, see if anything changes when you turn the ac on/off.

I recently picked up one of those harbor freight vacuum testers, it's proving to be pretty handy... i'm wondering if you could use it to read vacuum through the vsv?

RSR

The Amsoil Power Foam does a great job on upper intakes...
https://www.yotatech.com/forums/f116...tuneup-271923/

RSR

FSM: http://personal.utulsa.edu/~nathan-b...24vacuumsw.pdf

4Xtruck

I'm having difficulty getting those connectors apart. I assume I need to squeeze and pull, but nothing happens.

4Xtruck

OK, I got it apart and tested it. Not a lot of air goes through, but it works as required. There were no shorts and the resistance was 40, but it definitely wasn't 680 degrees F.

4Xtruck

OSV, I forgot to mention the voltage to the VSV is 12vt when the A/C is running and 0vt when it is off. With the current reaching the valve, I'm sensing the valve is probably defective electrically or partially clogged. I'll put a pressure gauge on input and output, this morning, to see what the difference is. Is there a way of cleaning partially blocked VSVs?

Also, what are your thoughts on the Amsoil Power Foam. It sure looks clean.

Dauphinc

I found mine was missing a little when warm because of a bad tps connector (it was coming unplugged). Maybe that will help.

4Xtruck

Here is the information on the vacuum readings:
Intake A/C off = 18"
Intake A/C on = 14"
Exit A/C off = 0"
Exit A/C on = 5"

I guess we've got some type of blockage here, reducing the vacuum coming out of the VSV. Is there a way to clean it out, or do I just need to replace it?

Kiroshu

Hmm.. I was under the impression you found the repair path in your earlier postings...?

Still missing firing/stumbling only with engine warmed up...?

Cold start injector stuck open/leaking...?

Overheating fuel pump...?

Overheating distributor pick-up signal coil...?

Damaged wiring (signal igniter/injector) harness running from igniter/coil assembly across engine to intake manifold injector harness...?

Coolant temperature sensor faulty...?

Exhaust system restriction...?

Idle speed incorrect/Out of adjustment...?

Moses1126

New here so im sorry if im posting in the wrong area. Recently got a 91 toyota pickup dlx 155000 miles for 1000 bucks. Was driving it for about 3 months until one day it over heated and a hose blew off. So i replaced the hose and did a full system flush with the radiator. Next day i was ready to go to work and was backing down my hill when it shut off, no hesitation just shut off. Had it parked for 2 days, got a fine for parking against traffic then my father in law towed me back to my house. Went to start and it wouldnt start. It would crank but not turn over. got some codes and got starter signal issue and knock sensor. So i got a new coil and ignition coil, and new knock sensor and still wouldnt start. So i pulled the valve cover off and low and behold my distributor rod was pulled out so the gears werent contacting eachother. got a new distributor and it started right up. But now i have an issue of a surging idle... Got the codes 31 and 24. Cant seem to figure it out. Can anyone help

RSR

Seafoam Spray -- You need the straw for the amsoil, and it works okay (I think it does a better job cleaning your combustion chamber than anything in the intake...). But it is good insofar as it helps with gradual rather than shock removal of carbon... Shock isn't good.
Amsoil Power Foam -- Does a great job cleaning the intake, not sure about combustion chamber.

I do a full recommended process over in that thread I shared. But generally speaking, SeaFoam is feel good rather than effective... I think a combo of Amsoil and a good fuel injector/upper intake cleaner via fuel line is a better way to go.