I just got off of the phone with a local mechanic. He said right off that it could very well be the throttle position sensor. I'll post a followup on this soon.

 

Last year, I replaced my TPS on the 3.4 L with a remanufactured one with no change to the idling issue. Your mileage may vary.

 

I had the same problem for two years: truck vibrated a lot in drive when it warmed up and stoped at traffic light; vibration went away when in N or P or when a/c was on.

Cleaned MAF, TB, IAC, and changed spark plugs, fuel filter, air filter, etc. in the past two years, the vibration was still there.

Yesterday I decided to check the exhaust system (as I felt most of the vibration originated from the rear passenger side). when I pushed the exhaust pipe, the vibration went away.

Check those rubber hangers. Try to adjust them or replace them if they worn out or broken.

 

Well, I don't think it is a mechanical problem (broken mounts, etc.) I heard one person say something about the fuel pump, but it is only used on start-up.
Straight from my study notes. IF you have a MAP and a MAF together then you have a speed density system. ONLY if you have a MAP/MAF together you can unplug the MAF. If the vibration smooths out it shows the MAF is bad. If you don't have the 2 together then don't try this.
Try this to diagnose:
1. Check battery first. Make sure all connections are good
2. Remove any unneeded covers.
3. Check wires for pinching or loose. Do a wiggle test. Make the problem occur and have someone hold the brake while you wiggle all connecters.
4. Check sensors and wires to them.
5. Check vacuum lines.
I don't know if you said, but did this occur after a tune-up? If so, check the items that were disconnected while being worked on and test new items. I know for a fact that some spark plug wires that are new are crap. Check resistance in all wire lines. 0-0.3 good, high resistance is bad (of course).
For some reason I have cam sensor, ECT sensor,IAT (has something to do with air-fuel mix), and fuel pressure regulator in my thought. Also check your A/C sensor. Don't hold me to those though.
They would most likely throw codes though
Here is a website everyone should like for inexpensive scanners for your laptop. You may have to contact to see if they have any Toyota scanner stuff though.

http://tunerpro.net/

I don't want you to buy this stuff (too expensive of a way to fix problem.) When you have time though google how to test these.
I will ask my instructors about this. (One teacher is a walking glossary.)

 

txt4r: Thanks for the addition about the exhaust system. You mentioned all the same symptom we all have. I did check mine but I feel it wasn't very extensive. Could you be more specific on how to check the exhaust system. This is something I have little experience in.

bassbro1: I've actually checked or replaced all of 1 through 5. I was thinking of all the sensors you listed as well but you said they would likely throw codes and that was the same conclusion I came to last night while studying my maintenance manual. I looked over all the OBDII code possibilities and all of the sensors are there on the list (TPS, IACV, etc.) Though I'm not sure if the A/C sensor was on that list.

Someone chime in if they know of a possible culprit to cause these rough idle issues but that is not on the possible check engine codes. This may be our needle in a haystack.

Again, thanks to all for contributions to this thread. I feel if we find this solution and it helps everyone there should be some kind of celebration.

Keep the ideas coming.

 

Well I'll give you an update on mine. Replaced the fuel injectors, and 2 of the 4 electrical clip, and no change.

As far as the TPS goes, I had to adjust mine to 77 and its suppose to be at 81ohms, to get it to run better. Which makes me think that the fuel to air ratio is off some place, but I'm not positive.

I've cleaned everything that I could get my hands on, and that did nothing. I know that mine is due to a stutter in the engine.

Up&Down, when you're idling, do you ever notice a random engine shake? Thats what mine does, and I'm positive thats whats causing the vibrations.

 

Everything you're saying suggests the idle is too low. Any way to bump the idle up manually(other than turning on ac)? And, it could be related to the temp coolant sensor....inspect it visually and verify the single wire is not rotted off.

 

GiantJoeBoat: I don't get the random engine shake. Mine is pretty consistent vibration that doesn't seem to change frequency.

Zuk: I think with 1995.5 there is no way to change idle speed. It is controlled specifically with the IACV. I could be mistaken but think this right. Where is the coolant temp sensor located on a 1995.5 2.4L?

Does everyone else's bad idle kick in after the thermostat opens up? If not, go back to tranny mounts and exhaust hangers. The fact that the bad idle kicks in at operating temperature makes me think it's something sensor related.

Anyone else?

 

Yes there is a way to change the idle speed, its something you have to do when you time the engine. There is an idle control screw on the throttle body. You might want to check your TPS. http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml.

If you make any adjustments to your TPS, you have to adjust the timing. Even if the TPS is okay I would still check the timing, and idle. this is from the 93 fsm, so I'm not sure if its the same for you. http://personal.utulsa.edu/~nathan-b.../5distribu.pdf

As for me, it would seem that while we are having some of the symptoms, my problem is different. So I will stop hijacking your thread, and start one of my own. I will report back if I figure mine out.

 

This recently happened to me ('98 4Runner 3.4L Auto). The other night I stopped at a light and my girlfriend told me she felt a vibration under her feet (passenger side), I turned down the music and definitely heard a humming sound and a little vibration coming from the middle/passenger side. Seems like it does it in P-R-N-D, but quiets down as I shift down into 2 and L. Threw it in 4wd and it still did it. Got out of my truck when it was running and tried to listen from underneath outside, but I couldn't really hear anything which kind of puzzled me. Only happens when I'm stopped, but goes away as I start to move. This only happened a few nights ago, so I haven't really experienced with it as much as you guys have, I'll let you know what happens with mine though, and try to see if it happens when I'm up to temperature vs. being cold.

 

Hmm, passenger middle sounds like Tranny. Get a stethoscope or a medal rod or old fuel line and climb under your truck and start listening. I know as much as you do. I wouldn't want to tell you what it could be and really not know where the sound is coming from and what it sounds like.

 

I don't mean to bump this topic but it doesn't seem like anyone resolved the issue.

This question is for the people who are going to follow this or people who can actually search YotaTech for solutions in the future.

Does it sound like metal on metal? Where does it sound like its coming from? If your entire car is shaking and theres not too much noise, then it could be your spark plugs. Now it sounds crazy but Toyotas come factory with DUAL ELECTRODE spark plugs and my God they hate single electrode spark plugs. Your car will Idle funny and car even shut off on you.

Keep in mind that when a problem is apparent with a cold engine and not visible when the engine is warm, its because it takes a lot for an engine to startup, once its warm, it doesn't use as much energy. Notice people out there who have exhaust systems, your car idles louder when its first started up, and then gets quiet(quieter) as the engine heats up. Therefore, this renders any issue to be mechanical and related to the engine.

Hope I helped.

 

Yeah I agree with you va4runner757. But in this case the rough idle/vibration doesn't start until the engine reaches operating temperature. I can watch the temp needle and as soon as the thermostat opens fully the vibration kicks in. Any idea on that one?

 

I took off the throttle body, iac, tps, cleaned and tested everything, re-installed and still the same. Frustrating!

 

Hey All,

I purchased a new tranny mount for the truck. I'm still trying to spend money in $50 and $100 increments before taking it to the stealership. I figure it can't hurt to change mounts on a truck from 1995 anyway. It's still cold here in Bangor so as soon as it gets a little warm I'm going to change it out. A year ago a mechanic said the mount looked fine. I'll update when it happens. Later.

 

All,

Tranny mount was not the fix. The old one was in decent shape.

I was under the truck with it on stands in the back adjusting the parking brake this afternoon and noticed movement in the drive shaft and U-joints. Could this be the source of vibration? I'm doubting it because the vibration is when the car is stopped.

Anyone tried anything new for their ride on this topic recently.

Later.

 

On my Landcruiser 80 series diesel, I was told by my mechanic that it's the torque converter that causes this problem.

 

ample,

If you'll notice this was the first reply to my posting this around two years ago. It kind of makes sense. So many of the other potential culprits would be covered by sensors on the OBDII system. Even vacuum leaks will throw a code with OBDII.

So does this mean it will get worse and I'll eventually need a new torque converter?

Is this bad and expensive?

And thanks for the new direction for the thread. I encourage any others that may know about torque converters to chime in.

 

I replaced the U-joints on the 2.7 L in my sig, no joy. Still vibrating, and now I'm starting to hear a weird intermittent rattle, like a loose heat shield vibrating or something. Both trucks have been doing the vibration thing for 3-4 years or so, doesn't seem to get worse or hurt anything, but I'd love to figure it out!

 

pendrag,

That's good to know it will do it for a long time with no ill effects. I'm tempted to take it in to a dealership but God knows what it would cost for all the testing they would have to do.

I'm just going to deal with it. If I lived in a city with traffic I'd probably give a month's pay to fix it as sitting in traffic would drive me crazy. As is, I live in a rural area of Maine that sees little sitting in traffic.

Does anybody know a way to test if this is the torque converter?