Hi all, new to the forum but not to the 80s/90s yotas. But the bulk of my experience is with the mighty 22RE.

car in question: 1988 4Runner V6 M/T 217k

Basically what I've noticed happening is when the truck is accelerating when it's humid/wet outside it will stutter kind of like a misfire. I thought I could get around this by replacing plugs/wires/etc. But it remains. This weekend I took the dist. Cap off and put some clear silicone rtv around where the cap meets the distributor (nobody seems to make the seal/o ring anymore) and also took the AFM on top of the airbox and sprayed with some MAF sensor cleaner and resealed also. Just trying to eliminate the condensation/water from that area. This helped a little but this morning that stutter was back a little bit.

So far I've replaced a bunch on this truck:

• Timing belt/water pump and tensioner
• ECT coolant sensor
• Fuel pump and lines and filter
• Spark plugs wires cap etcO2 sensor
• All new vacuum lines
• Replaced EGR valve with used part- seems to function normally

I have done a bunch of other work besides which is unrelated to the issue (new radiator, tires, etc.) but this is the stuff I would think could be even remotely related.

I am getting a code 51 from the diag box for TPS/AC switch problem, I don't think the TPS could cause this but I'd like to know your thoughts. I do wonder if maybe my catalytic converter is clogged up? I am getting "normal" mpg/acceleration but it definitely could be better. Kinda hard to tell since the 3L is so slow and inefficient as is.

Open to any and all opinions/thoughts! TYIA

 

The TPS can definitely make an intermittent stutter that feels similar to a misfire. I've had that happen and it would appear and disappear randomly until I finally got the code after a few months of pulling my hair out. I think it puts the engine at the wrong point on the computer's fuel map from time to time. There should be a troubleshooting procedure in the manual for it, and a calibration procedure as well if it is ok but just out of adjustment.

 

Oh ok, kinda figured the TPS was more idling related than acceleration, but I guess that makes sense. I went ahead and ordered a Toyota one just in case but I'll go ahead and get some alligator clips for the ol multimeter also. Thanks!

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Just wanted to update y'all: the new TPS resolved the issue! The true test will be tomorrow because it'll have rained all night so hopefully all goes well. 🤞 Still have to "set" the TPS per the FSM but it seems to work just fine without hardly any adjustment right now anyway. Maybe I got lucky and don't need to? Idk it's my first time.

 

If it were me, which it's not, I would absolutely check the TPS alignment according to the FSM. Sounds like it's right to me, but it's best to be certain. Especially the Idle Switch alignment. If it's right, wonderful. If it's not, it can cause some odd troubles.

Glad the rest is solved, though!
Have fun!
Pat☺

 

Definitely on the to do list, need to get some feeler gauges tho first. I think it is a little off because I do notice my idle is a little lower than it was (600) when warming up but not quite all the way warmed up. Once it warms up fully it's back up to 850. But overall pretty pleased. I was really banking on this being the fix because honestly I think the next thing in line was checking all of the wiring and ecu

 

Maybe check the IACV for that low idle problem? It may be opening too far, too soon. Or not closing correctly? Something like that. Is the air tube from it up to the throttle body in good shape? Are the water hoses to/from it in good shape, not clogged up or anything?
I would also pull the idle adjustment screw out completely, and make sure it's o-ring is in good shape, how old is it, after all, and that the air passages under it are clear of debris and dirt. A small shot of carb cleaner through them can do wonders. A thin layer of Vaseline on the o-ring when you go to install it will give it a much improved sealing capability, and it will make it last much longer.

I AM glad it's working overall pretty well now. Now for the little, nit-noid details

Have fun!
Pat

 

You may want to check your air intake hoses. If there are cracks in them, it does cause problems all over. Since you said it was raining and there is humidity in the air, it can cause the hoses to swell a bit and mask the problem.