Hesitation, weird shifting on my Sienna

[SoulRaven]

My 2004 Toyota Sienna with 152K miles is having acceleration issues. Any sudden acceleration and it will hesitate a good solid 2 seconds or so before actually engaging. It was barely noticeable for a while but now it happens every. single. time. Fully replicable. (I should note, I avoid this whenever possible to drive the vehicle gently, but sometimes it's unavoidable. That's usually the time you actually need the vehicle to respond, for safety.)

The other thing isn't replicable, it often "jumps" into another gear with barely the lightest tough on the pedal. Only happens at low speeds, averaging once per day.

I'm told my transmission fluid is still fine, by eyes more expert than mine.

According to my research a new transmission is generally the "fix" for this problem. However, also according to my research, it isn't uncommon to get the transmission replaced and yet the issue to continues. Apparently it's a known problem with Siennas and people tend to just give up after a lot of money is sunk into repairs that don't fix it. From what I read the engine itself is another potential cause, with the computer's connection to the gas pedal being yet another potential culprit.

I have limited funds. How do I even begin to tackle such a thing in a smart manner? Any suggestions?

(As a side note, just last week I got a nail in my tire--in the sidewall. Les Schwab is legally prevented from even trying to repair it. I patched it myself [new experience for me] with a little help but I think it's leaking. Since my van is AWD the alternative is not as simple as just getting a replacement tire. For now I'm fine with just topping off the pressure every day. But seriously...I could use a break in mechanical stuff...I was just getting on top of learning to change my oil!)

 

[sephson]

I'm nowhere near enough of a mechanic to comment on the potential transmission issue, but as for the tire, sidewall damage generally means the (forgive the pun) end of the road for the tire.

It sounds like you may be facing an issue I had to deal with twenty years ago. Do you spend your limited funds on repairs to the vehicle you have now, or do you start looking for a new van? When I faced this choice, I bought a "new" car and sold the old one for $500.00. Replacing the failing transmission on my '76 Ford Granada would have been the better choice. The "new" car was a maintenance headache almost from day one.

More recently, a friend of mine, who also has limited funds, had to decide whether to replace the engine in his Mazda or start shopping for a new car. He chose to replace the engine. All this did was buy him a little time. Now, less than a year later he's looking at having to buy a "new" car that he really can't afford because he spent what little money he had repairing the old one.

I don't know which path is the better choice for your situation, but either way, you likely have a limited window in which to make decision before circumstances force a decision on you.

 

[SoulRaven]

Thanks for the reply, sephson.

The plan was to pass this van along to my bf once he purchased the rig that was to be mine and we swap. The buying/selling process is very tricky to navigate without swapping due to SSI restrictions--if my accounts ever total over $2000 for more than a month then my income stops, but if I ever have more than one vehicle then the second vehicle is counted as a resource, and that also makes my income stop.

Does anyone else have mechanical advice for me or am I on my own for this one?

 

[steamjam1]

Does the engine rev up, and it takes 2 seconds for the vehicle to respond, or is it when you press the gas, and nothing happens for 2 seconds and the engine catches up to your foot?

Also, when you shift into reverse, does it take a second or two for the vehicle to go into reverse?

 

[SoulRaven]

Does the engine rev up, and it takes 2 seconds for the vehicle to respond, or is it when you press the gas, and nothing happens for 2 seconds and the engine catches up to your foot?

Also, when you shift into reverse, does it take a second or two for the vehicle to go into reverse?

For the first question, both, actually. With sudden acceleration, it's always the latter, and is replicable every single time. With slower acceleration occasionally (maybe 3X/week) the engine revs up without any acceleration. I've never kept at it for two full seconds to see if it changes, I tend to back off the gas immediately and try again. Sometimes it takes two tries, often just one is enough to accelerate normally again.

Reverse is fine, aside from the occasional jumpy problem I described (vehicle jumping fast when the pedal is barely touched). The 2 second delay issue has only ever occurred with sudden acceleration, and frankly I've never attempted sudden acceleration when backing up my vehicle before.

 

[steamjam1]

For the first question, both, actually. With sudden acceleration, it's always the latter, and is replicable every single time. With slower acceleration occasionally (maybe 3X/week) the engine revs up without any acceleration. I've never kept at it for two full seconds to see if it changes, I tend to back off the gas immediately and try again. Sometimes it takes two tries, often just one is enough to accelerate normally again.

Reverse is fine, aside from the occasional jumpy problem I described (vehicle jumping fast when the pedal is barely touched). The 2 second delay issue has only ever occurred with sudden acceleration, and frankly I've never attempted sudden acceleration when backing up my vehicle before.

Toyota all-trac (Not sure if they still called it that in '04) has always been famous for funky action when its wearing out. From what you describe, I would start looking at the transmission solenoids since it revs up and hesitates all the time under sudden acceleration, but only sometimes under slow acceleration. Its reverse being ok is a sign the main pump is working. I don't know if these transmissions of this era have lock up torque converters, but if it does, it could be whatever controls it thats starting to fail, which would explain it sometimes jumping on you when the throttle is barely touched.

 

[29chico]

If I were diagnosing the problem in question I would test the throttle position sensor first  (AKA: TPS). 

If the TPS tested good I would then test the manifold absolute pressure sensor (AKA: MAP).

If you know someone who is good with an electrical multi-meter you could Google up the tests for the above mentioned sensors.  Most likely the test procedures on the above mentioned sensors are not difficult.

 

[cherterr]

It sounds like you have more going on than my simple Sienna issue where it was just jumping at gear changes. I had a transmission flush done ($125) at dealership, and that fixed MOST of it. I still now drive like grandma til I'm in overdrive. I was pretty bad about just stomping the gas pedal and GOING.. lol

Hope you get it fixed.

 

[flying kurbmaster]

Does anyone else have mechanical advice for me or am I on my own for this one?

you are not alone but I have not got a clue, as to what might be wrong. I had an issue once a few years ago not shifting out of second, I went to a transmission shop and asked, it turned out to be a 100.00 speed controller, if I were you I would take a morning get a  list of several transmission shops in your area and go and ask the same question, explain the symptoms, to get a few expert opinions, might even want to try the Toyota dealers.  You may come out with a few different opinions but you may also find that a larger number of them agree on what the problem is, worth a try, you got nothing to loose by asking around other the a bit of time, and you will get a bit of an education at the same time. If if it is a common issue with these vans then a few people have ran into this problem before and they are out there it is just a matter of finding them. Good luck avoid going in on busy days Fridays, or first thing in the morning lunch time of last thing in the afternoon, they will have more time for you.

 

[29chico]

Any progress on the hesitation?

 

[SoulRaven]

Any progress on the hesitation?

Thanks for asking.

A lot of urgent things came up, pushing this to the back burner, but I'm working on it as I'm able to.

I used the Techron fuel additive to see if that helped. It made the van run significantly smoother, but no improvement on the shifting issues. I've noticed far less of the jumpiness when I barely touch the gas, though it might not be all the way gone.

My dad sprayed some stuff on the valve designed to clean it out, that might have helped some too, but regardless the problem still isn't solved.

I've spent the past several hours attempting to locate the throttle position sensor, and have been unsuccessful. I don't know if that's because Google doesn't seem to have any usable info available specific to Toyota Siennas, or because it's just located in a difficult to access place, or if it's just my inexperience/incompetence. But if I cannot check a single sensor when I have half the day to do it then it's unlikely I'm going to be able to diagnose this issue myself.

It doesn't seem to be worsening in a hurry, and only really a problem when there's a need for sudden acceleration.

Plan is next time I have a free window (hah!) I'll start taking it to mechanics and see what they say.

 

[highdesertranger]

rock auto will have the sensor. they also give you the part number to take to your auto parts store. also don't replace parts that you are guessing are bad. this type of shotgun approach to auto repair seldom comes out in your favor. if the sensor is suspected it must then be tested to verify that it is bad. sometimes it's better to pay a little more to have the actual problem found. however in this day and age finding a tech that really knows how to find the problem is like pulling hens teeth. highdesertranger

 

[SoulRaven]

if the sensor is suspected it must then be tested to verify that it is bad.  sometimes it's better to pay a little more to have the actual problem found.  however in this day and age finding a tech that really knows how to find the problem is like pulling hens teeth.  highdesertranger

That's why the plan was the test the sensor with my multimeter. Apparently there are a few different sensors that could be causing the issue, maybe or maybe not, and they can be tested this way. IF you can find them and get to them. Today's plan was to see if it would be feasible to do that, since it would potentially save a lot of money and hassle. Unfortunately, the answer is no.

 

[eDJ_]

Since it is later than a 96 model,  could you take it by an Advanced Auto, or Autozone....perhaps an O'Rielly auto parts store and ask if they can put a diagnostic read out instrument into the diagnostic plug under the dash by your right knee.   It may give you some readings that will help you locate  the problem.   I think they will do this for you for free.  

The Computer in your Car,  The OBD-ll

http://www.pencomputing.com/frames/obd2.html

 

[29chico]

That's why the plan was the test the sensor with my multimeter. Apparently there are a few different sensors that could be causing the issue, maybe or maybe not, and they can be tested this way. IF you can find them and get to them. Today's plan was to see if it would be feasible to do that, since it would potentially save a lot of money and hassle. Unfortunately, the answer is no.

I looked into the throttle position sensor situation and it looks like the TPS is built into the throttle body that is a drive by wire controlled system.  Apparently this kind of problem can be an issue even for a dealer tech. 

Link of failed attempt to repair of a 2004 Sienna van by the dealer throwing on a throttle body assembly and a accelerator pedal assembly in the hopes that it would fix the car:

http://www.justanswer.com/toyota/5uwrh-toyota-sienna-le-2004-sienna-le-5tdza23c94s030638-dtc.html


If you work down to the bottom of the link you will see that the vehicle owner stated that the problem turned out to be an interference problem with the throttle blade that controls the volume of air drawn into the engine.

 

[Van-Tramp]

My old Datsun 280z had the same problem. I troubleshooted it for years before, just be luck, I replace all the vacuum lines under the hood and blamo it was fixed. Just like that. Total cost to fix, about $3 (after spending a grand or more on it trying to fix it). A tiny vacuum leak will wreak havoc on your computer. Worth a shot. Cheap and easy too.

Other things would be any cracks in the rubber hoses (they call them "boots" between your air filter and the TPS itself. It needs to be a completely sealed system.