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Please point me in the right direction if this is not the place. I got a 93 4runner 5sp 3.0 4x4. Runs good but.... motor started "pulsing" or "lugging" at cruising speed (mild load with just a little throttle 2500ish RPM). If you give it more throttle before the lugging gets bad the the engine catches on and take off or you need to downshift too get the RPMs up in the poser band (3000+) range and all is good. I replaced the TPS based on all the stuff I had read up on. Cannot say that has made a difference. I guess when I think I have it adjusted correctly things get better - and if I over comp one way or another it seems to move the issue slightly up or down on the RPM range. If I unplug the TPS it seems I still feel a little bit of the issue but not as bad. btw: I changes our the fuel filter and have changed out 99% of the vacuum hoses. Rig has 250k and the plugs were done at 210k. Wires look good but I cannot confirm that they were changed or the condition of the rotor (just have not pulled it to look yet).
This has got to be something simple but it is eluding me what to do. I am sure one of you guys has seen this before. Please help! I need this to be AWESOME for my wife who love this rig.
I used to pull a pretty good hill coming home every day. One night it started missing under load going up the hill, but I made it home. I popped the hood and revved it a couple times and got a good light show along the spark plug wires. Replaced the usual ignition components and my issue went away. Now I do it religiously.
I think I'm have the same issue, at first it runs great then when I give the beans from a stop its gutless don't even ask about going uphill either- I've done a lot of work to it so its kinda pisses me off and makes me question my skills lol anyways. I started with my exhaust leaks so I had a muffler shop weld up all my exhaust leaks around my Y pipe and aftermarket headers when i got it back it was really quiet lol drove great but then it started losing power it took a while to get up to speed on the highway. No check engine lamp on so i got no direction on where to look except maybe my throttle body since my idle is too high 1100 rpm at start up and stays there. I think its supposed to be around 800rpm with my timing at 10 degrees BTDC.
800 RPM with the timing at 5° with the jumper in the test jack, and roughly 12-14 with the jumper removed.
A couple possibilities for the fast idle speed: The IACV isn't closing completely like it's supposed to, and/or the o-ring on the Idle Adjust Screw is brittle/disintegrating. Or a mix of the two.
Bear in mind that the Idle Adjust Screw is the smaller screw UNDER the large cap screw. Not that I mistook the two...ahem. Easy to check, just screw the IAS down all the way, counting the number of turns it takes, including partial turns. Don't crank it down super hard, just until it touches, then unscrew it all the way out. Check/replace the o-ring. It's a small, commonly available o-ring, easy to find. If it got brittle, and they do, it can drop pieces into the air channel it fits into. They all must be removed. The channel must be clean and clear of obstructions. I always coat the o-ring with a thin layer of Vaseline or Silicone Dielectric Grease. It gives a better seal, and preserves the o-ring so it lasts much longer. Then just put the IAS back in, and adjust it to where it was when you removed. It might not be the correct position, but it's a good starting point.
The IACV is pretty easy to check. The FSM actually has a very good write up on "how-to". They get old, and start to fail closing all the way when the engine warms up. If that happens, the idle will be high, as the TB is getting more air than it should be.
If you're going to take it apart and clean/adjust it, get an impact screwdriver. You WILL need it so you don't strip the screws that hold it together.
Finally, check all the vacuum lines for cracks/leaks.That includes the large tube that runs between the AFM and the TB. The flexible corner pieces get brittle with age, and can develop cracks, allowing extra air in that should be there. Again, hi idle.
i guess the the next part of this diag would be vacuum hoses unless you guys think i missed some thing? coolant passage ways look clear no build up. pretty clean from the last time i pull it
o-ring holding up fine i've replaced the tps and connector about a year ago went 2 more threads lower from last time, i'm at a point of replacing the throttle body?
[QUOTE=Wavejumper;52480260]Please point me in the right direction if this is not the place. I got a 93 4runner 5sp 3.0 4x4. Runs good but.... motor started "pulsing" or "lugging" at cruising speed (mild load with just a little throttle 2500ish RPM). If you give it more throttle before the lugging gets bad the the engine catches on and take off or you need to downshift too get the RPMs up in the poser band (3000+) range and all is good. I replaced the TPS based on all the stuff I had read up on. Cannot say that has made a difference. I guess when I think I have it adjusted correctly things get better - and if I over comp one way or another it seems to move the issue slightly up or down on the RPM range. If I unplug the TPS it seems I still feel a little bit of the issue but not as bad. btw: I changes our the fuel filter and have changed out 99% of the vacuum hoses. Rig has 250k and the plugs were done at 210k. Wires look good but I cannot confirm that they were changed or the condition of the rotor (just have not pulled it to look yet).
This has got to be something simple but it is eluding me what to do. I am sure one of you guys has seen this before. Please help! I need this to be AWESOME for my wife who love this rig.
Thanks in advance.
Jeff
Last edited by Wavejumper; 10-24-2022 at 08:55 AM.
Please point me in the right direction if this is not the place. I got a 93 4runner 5sp 3.0 4x4. Runs good but.... motor started "pulsing" or "lugging" at cruising speed (mild load with just a little throttle 2500ish RPM). If you give it more throttle before the lugging gets bad the the engine catches on and take off or you need to downshift too get the RPMs up in the poser band (3000+) range and all is good. I replaced the TPS based on all the stuff I had read up on. Cannot say that has made a difference. I guess when I think I have it adjusted correctly things get better - and if I over comp one way or another it seems to move the issue slightly up or down on the RPM range. If I unplug the TPS it seems I still feel a little bit of the issue but not as bad. btw: I changes our the fuel filter and have changed out 99% of the vacuum hoses. Rig has 250k and the plugs were done at 210k. Wires look good but I cannot confirm that they were changed or the condition of the rotor (just have not pulled it to look yet).
This has got to be something simple but it is eluding me what to do. I am sure one of you guys has seen this before. Please help! I need this to be AWESOME for my wife who love this rig.
Thanks in advance.
Jeff
Update - changed the cap and rotor - they were defiantly fouled. It ran great and the issue went away. YAY! BUT... next morning the issue was back... going to check the cap tonight and see if it fouled or not.
I've gotten brand new dist caps that have a hairline fracture in you can't see, but strongly affects the running of the truck. In a bad way. It may be, whether it LOOKS bad, the distributor cap has a crack in it. I just re-replace it, and away I go.
The cap also has an o-ring where it meets the metal. That needs to be in good shape.
A small dab of silicon dielectric grease in all the plug wire connections can help a questionable connection alot, makes them much easier to put on and take off, and keeps dirt and moisture out. I use the stuff in every electrical connection I lay my grubby paws on It really helps, especially in the environment automotive connections have to suffer through.
800 RPM with the timing at 5° with the jumper in the test jack, and roughly 12-14 with the jumper removed.
A couple possibilities for the fast idle speed: The IACV isn't closing completely like it's supposed to, and/or the o-ring on the Idle Adjust Screw is brittle/disintegrating. Or a mix of the two.
Bear in mind that the Idle Adjust Screw is the smaller screw UNDER the large cap screw. Not that I mistook the two...ahem. Easy to check, just screw the IAS down all the way, counting the number of turns it takes, including partial turns. Don't crank it down super hard, just until it touches, then unscrew it all the way out. Check/replace the o-ring. It's a small, commonly available o-ring, easy to find. If it got brittle, and they do, it can drop pieces into the air channel it fits into. They all must be removed. The channel must be clean and clear of obstructions. I always coat the o-ring with a thin layer of Vaseline or Silicone Dielectric Grease. It gives a better seal, and preserves the o-ring so it lasts much longer. Then just put the IAS back in, and adjust it to where it was when you removed. It might not be the correct position, but it's a good starting point.
The IACV is pretty easy to check. The FSM actually has a very good write up on "how-to". They get old, and start to fail closing all the way when the engine warms up. If that happens, the idle will be high, as the TB is getting more air than it should be.
If you're going to take it apart and clean/adjust it, get an impact screwdriver. You WILL need it so you don't strip the screws that hold it together.
Finally, check all the vacuum lines for cracks/leaks.That includes the large tube that runs between the AFM and the TB. The flexible corner pieces get brittle with age, and can develop cracks, allowing extra air in that should be there. Again, hi idle.
Good luck! Let us know what you find
Pat☺
(update on my ˟˟˟˟box)- After I cleaned my throttle body and adjusted the iacv collar ring further down my idle is alot better. Idles low on cold start but once it warms up it purrs at 750-800 rpm with timing set at 10 btdc (i looked at my emission tag under my hood for idle spec). Took it for a test drive I was happy for a second it was really responsive and wasn't gutless for once.....then it came back fml lol.... any ways I started looking into my egr system. Noticed my egr valve is too clean on the inside like it's not working, slapped a vacuum gauge in between my egr top port and that green vsv....I'm getting intermittent vacuum running down the road at 30-40 mph 2800-3000 rpm 3 gear.... also it's gutless.
It has been a while - still fighting this thing... ended up taking it to a shop (specializes in toyota's) - they came back with - "replace the distributor and ignition control module" - then they wanted WAY too much for the parts. I took it home - ordered the new "hard to find" parts from RockAuto and swapped them out. Runs fine at idle - but seems to have a miss or cuts out at anything above idle - does get a bit better above 3k. I have gone through the FSM and tested ALL the electrical and everything is within spec. I am now leaning towards a possible fuel issue....? as I said - it idles great if a bit high but if I give it any throttle it starts to cut out - more throttle up to about 3k and it starts to get a bit better but still has the issue. drop the throttle and it is pack to idling just fine. Here is video of it in action: https://www.wavejumper.net/94_toyota/img/IMG_7991.mp4
09-29-2022, 06:30 PM
