Bad idle/low throttle. fine at higher throttle?

When was the last time the PSD fluid was changed?

 

Is the sound is like a 'vibration' but variable frequency?

You hear the sound when the car is not moving or only when moving?

Do you hear the sound when the car is in "P" and just the engine is running?

If you hold down the brake with your left foot, hard, and then accelerate the engine, do you hear the sound and does it change pitch with the engine speed?

If you are in EV mode (aka., the ICE is off but you are moving) do you hear the sound?

Does the pitch of the sound change proportional to the vehicle speed?

Can you make an MP3 recording and post it somewhere we can listen to it?

I don't want to hazard a guess until we know more about how the sound is generated. There are multiple, potential causes and most of them are not good news. If you are lucky, something under the car in in the engine compartment is touching the engine mount and this is just flexing / rubbing.

We want to eliminate wheel bearings; transaxle issues; and ICE issues. Knowing more about the sound helps eliminate the improbable. Your mechanic is an independent (aka., not a Toyota shop?)

GOOD LUCK!
Bob Wilson

 

Hi Robisaks,

First thing to do whenever there is a problem with low idle is to look for a vacuum leak. Especially on cars that have an older calender age. Rubber hoses tend to go bad with time.

Or at least that is the rule for Otto cycle engines. Not sure how it applies to cars with Atkinson cycle. But still, its only a few minutes to do.

On the Prius of that vintage, the next thing to do is to check and clean if neccassary - the throttle body. Over time they become gunked up, and wont close all the way. Again, that impacts engine vacuum at low idle.

A rough low idle can make all sorts of noise as the engine moves around beyond its design limits. An older car will have well worn engine mounts, letting the engine move around even more if it idles roughly.

 

it might not even be the engine, it could be the snow, and or loss of traction. Back in the winter of 06 in NJ i drove it in a pretty bad snow storm, most of newark was covered in a layer of ice and snow, when i brake i would get that reaction ( ABS kicking in ) or when i give it throttle motor TRAC would kick in

 

I was so excited to see this post as my 02 Prius with 62K miles that has the exact same problem but then was diappointed with no answers posted. Mine started about 3 weeks ago when we got a boat load of snow. (Minnesota too!) The next day I started it up and the first two seconds was perfect and then as the idle or choke (what ever it does when you first start) it starts to vibrate and make the same noise like you were driving over those ribs in the road. If I push the throttle just a bit the idle goes up and the vibration and sound stops. It will do it at all speeds (or stopped)when the ICE is running and pedal is at idle. I noticed that if I push the brake really hard it somewhat stops. (strange) The problem does go away for a day or two only to return. I thought maybe the cold was it but alas even after driving it an hour and fairly warm (30's F) it still does it! I've changed plugs, put Moble 1 0W-30 in it. got under it and chipped away a lot of ice under the engine and by the mounts but it still comes and goes. Never on electric, just gas. The vibration is very much like some would call dieseling.

Please HELP!

What is PSD? (power steering ???) and how would I clean the throttle body?

 

Get enough snow/ice around the motor, the drive belt - yes, there is one on a Prius - will contact that. I've had the serpentine belt fail on a company truck a client had, after it had been ditched by another driver during a blizzard

The snow/ice under the hood of the truck, was not removed. When I went to drive it the next day, got maybe a mile before all kinds of wonderful noises came from under the hood. Then the power steering quit, and I knew it was done. When I came to a stop, the belt was laying on the pavement under the truck.

Best way to take care of snow/ice under the hood is to leave it in a heated garage for 24 hours. If that was the problem, the noise should be gone when you drive it again

PSD: Power Split Device, the "transmission" on a Prius. It's a school of thought here on PriusChat that servicing the fluid is a *good* idea.

Cleaning the TB: there are specialized automotive care fluids to allow you to safely clean the TB. The Mass Air Flow meter hot wires can also become coated with deposits after awhile. There is a special fluid to clean that too. Never, ever use carb cleaner or brake cleaner, you could ruin the sensor

CRC Industries Automotive

CRC Industries Automotive Product Detail

 

Are there instructions posted some where on how to clean th TB?

I did not have any snow or ice in the belt area but did on the under carriage. around the motor mount etc. I thought wow after getting all that out I'll bet it runs like a charm but alas it still did it on the way to work today.

I'll see if I can clean the TB if I find Instructions some where. do you use both products? seems like the sensor would be in the TB area so to use one and not the other seems difficult. (maybe not - no insturctions yet)

Can a normal guy change the PSD fluid?

I got to get this figured out, I'm an engineer trouble shooter and it bothers me when I cant get at a diag & fix!

Thanks,

Sheldon

 

Not sure, perhaps a search will uncover it

I only have experience with a 2004 Prius. I've attached shop manual photos of the TB and MAF. I also took a photo of my Prius TB and MAF with blade open by hand, perhaps a year ago. You can see the MAF down there

You'll notice the TB has an electric drive. The free end of the shaft has a return spring. With the car completely powered down, air cleaner cover off, you can use your hand to turn the free end of the shaft.

This opens the throttle blade. Never ever use a screwdriver or other object down the throttle body to force it open. YOu can use a flashlight to inspect the underside of the blade for deposits. Use the appropriate TB cleaner to spritz off the deposits, don't use too much cleaner

It's fairly easy to remove the MAF on my Prius, and extremely easy to remove the MAF on my FJ. They appear to be the same sensor. With the sensor off, you can use the MAF cleaner to clean off the hot wire sensor inside. The bulb like thing is the intake air temp sensor

I've attached a photo of my FJ MAF before/after cleaning. My camera wasn't capable of taking a photo of the MAF guts, but the two hot wires did have appreciable deposits

Apparently, the <2004 Prius has a fluid pan for the PSD. I think forum members Patrick Wong and Bob Wilson could help you out here

Note: I've attached a pdf I made with Adobe Acrobat Pro 9. You will need Reader 9 to properly open the document

 

Jay's photos are for 2G; Classic is different because the air filter is over the throttle body. You must first remove the air filter to see what's going on. Other than that, Jay's instructions are applicable.

Regarding the transaxle (which is called PSD in this string) fluid, you can easily change that yourself if you have a 24 mm (or 15/16") socket and a plastic funnel w/ 3 foot long tail to facilitate refilling. You will need 5 qt of Toyota ATF T-IV for Classic.

For a complete job you should also remove the drain pan and clean it as well as the magnet. You will need to replace the drain pan gasket if you decide to remove the pan.

The drain plug is on the bottom of the black steel drain pan. The fill plug is on the side of the transaxle facing the radiator. Pls make sure you can remove the fill plug prior to draining the fluid.

Place the funnel between the radiator and inverter and snake the tail down to the fill plug when you are ready to add the new ATF T-IV fluid. Tightening torque on the fill plug is 29 ft.-lb, drain plug is ~35 ft.-lb (since it bolts into the steel pan), the drain pan bolt torque is around 6 ft.-lb and also needs blue Loctite.

Although the transaxle fluid should be periodically changed, I do not believe you will find this to be the cause of the noise and vibration noted.

I am wondering whether the iridium spark plugs were replaced at 60K miles per the scheduled maintenance guide.

 

As a correction, I noticed I had stated I took a photo of my 2G Prius TB with blade *open.* Actually, I tried to, but the coordination required to hold the return spring open *and* take a photo proved too much for me, so I took a photo of the blade in the normal closed position

As Patrick stated, there are some pretty important differences between the 1G Prius and the 2G Prius. Eg: access to TB, the PSD fluid change, etc

 

Thank you much for all your help. I've done all the suggestions except the trany fluid (PSD) change. I was going to research more the TI-V vs the fluid used in the new Prius. (WS I belive.) Plus I need to locate some diagrams for the fill spot. It runs really nice and so far no knoks! Even the last few days at -36 below zero runs great! I did the throttle body cleaning (next time I need to figure out a way to get the extra fluid out. Even after waiting a while it still started and then things went whacky with the mixture and it killed and erros popped up on my screen!) I cleaned the MAF, new plugs, now OW-30 Mobile 1 but I believe the thing that fixed it was bringin it inside for a day and melting it! I could not see it but I believe ice built up and as the engine vibrated it hit the firewall and really makes allot of sound. I noticed the sound way louder inside than out and that is what tipped me off.
Thanks again,
Sheldon

PS I might need a new battery. the small 12V in the trunk. Will most any thing do?

 

Hi Sheldon,

T-IV has higher viscosity than WS. Toyota recommends T-IV for Classic. However a few group members have used WS but do not report improved mpg; so its not clear to me what is the point of using WS - especially knowing that the Classic transaxle is a weak point of the car.

The fill plug is located on the side of the transaxle that faces the radiator. You'll have to get up under the car to look for this.

Regarding the battery, "most any thing" will not do, at least not easily or safely. If you don't obtain the correct battery then you will have to figure out how to connect the new battery terminals to the vehicle wiring. If the physical size is not the same then you will have to figure out how to properly mount the battery.

You will have the issue of an improperly vented battery releasing hydrogen gas into the trunk, which you may or may not care about. If you purchase a regular liquid acid battery, then in the event of an accident where your rear fender is hit, you will have acid everywhere.

Regarding the throttle body cleaning, I don't like the idea of introducing all this fluid into the intake manifold. My procedure is to remove the air cleaner housing, then use Q-tips and rubbing alcohol to scrub the black residue off the throttle body and throttle plate. However this takes more time.

 

Patrick

It actually takes *very* little TB cleaner to properly clean the TB blade and bypass air passages. Let's put it this way: if you were to clean the TB twice a year, the can should last at least 5 years

The formulation is very effective and it readily dissolves the gunk. I'm going to clean the TB in my FJ this weekend, and doubt it will take more than 2-3 quick spritz's

The puddle in the intake plenum returns within two weeks of trying to clean it out. I used to think it was the result of oil overfill. Since the dealer did the first two oil changes, and I've done all the rest, keeping the oil level between the dots, I know the oil level is not the case

I have no doubt some of it is oil vapor from the PCV system. Judging by the smell I think the rest is fuel vapor due to the Atkinson cycle

jay