1997 Toyota Previa

toyota
previa

#1

Don’t know how old your post was but I have the sMe issue. Have spent heaps of time uder the car and may (May) have found the problem. I am not a mechanic and am after advice. At the distrubutor I removed both vacuum hoses attached a longer one to check the diaphram (if it has a diaphram) and air flowed freely back and forth between th two ports. Wirh engine running at idle, this action had absolutly no effect on the idle rpm. What is the go. The manual does not detail the function of monifold and ported vacuums operations in the distributor. Engine 2TZ-FE, no EGR, australia.


#2

Hi @RobertLackner it seems your question is referring to someone’s problem that’s posted on another web site (most likely Car Complaints). Unfortunately, we can’t see that text. Could you describe your problem a bit more specifically so others might help?


#3

G’day Carolyn,

I went back to the original post (Toyota Tarago, there are only 2 post there) and put this reply in.

Quote;

“I have the same issue. Have spent a lot of time under the car and found the possible cause or contributing factor. Just after some guidance before focus in on the perceived problem. I am nota mechanic.

The distributor has manifold (source unknown) and ported vacuum ports. Both lines provide vacuum as expected. With engine running and both lines disconnected from the distributor I connect a spare hose to the ported inlet on the distributor and apply positive and negative pressure. To my surprise there is zero resistance. Air flows freely back and forth and there is no change in the engine rpm. I was expecting the typical zero flow when applying a vacuum.

Is the air supposed to flow between these ports or am I on the right track and will need to replace the distributor body?”

Unquote.

I am not well versed on how to use on line forums/sites.

Thanks for getting back to me so quickly.

Regards,

Robert.


#4

OP, edit your original post to describe what problem you are having on your 97 Toyota Previa. You should see a little icon that looks like a pencil at the bottom of that post, click it to edit.

I have a Corolla w/4afe engine from 5 years prior, and there’s no vacuum hoses connected to its distributor. Totally electronic ignition. So your post about the vacuum hoses and the distributor is a mite bit confusing. Maybe the ignition system configuration is different between the USA and Australia. Probably other stuff is different too. My Corolla has an EGR system for example.


#5

Here’s the original post from the other site, being acompter numpty, I have no idea what’s going on but looks like I can paste from there to here. Either or as long as someone can hopefully provide guidance. OP from other site, Quote; "It starts a little while ago but only use to happen around the 90km mark…Didn’t realize it was doing any other time…Now its all the time and always around the 2000revs mark. doesn’t matter what speed and only when i am trying to get a bit more speed happening, never slowing down…It starts to feel like its chocking for petrol. it does this pulling chugging thing. Sometimes its much more jarring than other times. can be quite a powerful jarring other times its just a small pulling feeling. But definitely getting worse.
Have had it had the mechanics 6 times now and he is out of options. He has changed plugs and leads, coil, distributor cap, injectors have been cleaned but nothing seems to be working. I am just about out of money and patience…lol.
Unquote.

Which promted my post, quote; "Don’t know how old your post was but I have the same issue. Have spent heaps of time under the car and may (might) have found the problem. I am not a mechanic and am after advice. At the distributor I removed both vacuum hoses, attached a longer hose one to check the diaphragm (if this design has a diaphragm) and air flowed freely back and forth between the two ports on the distributor body. With engine running at idle, this action had absolutely no effect on the idle rpm. (‘ADDITION’ Both vacuum hoses are supplying vacuum levels that seems appropriate to manifold and ported.) What is the go? The manual does not detail the function of manifold and ported vacuums operations in the distributor. Engine 2TZ-FE, no EGR, Australia.


#6

I would check the fuel filter and fuel pump. I owned a Previa for many years and know them pretty well.


#7

OK, I understand your post now OP, thanks for clarifying. When performance problems show up only at higher rpms, my first guess, be suspicious of the fuel pressure dropping, and/or the ignition system not producing a good spark at the higher rpms. Both systems are taxed more at higher rpms and engine loads that lower rpms and light engine loads. Suggest to rig up a way to display the fuel rail pressure while you are driving. If it drops precipitously coincident with the symptom, you’ve found the problem. Likewise measure the ignition system primary voltage supply. If it is dropping below 12 volts at the higher rpms, again, you’ve found the problem. If the ignition system needs any routine maintenance to bring it up the manufacturer’s suggested maintenance intervals, that should be done first.


#8

Thanks, That’ll give me something to focus on for the next couple of weekends.


#9

I think the 21 year old diaphragms have failed.
I recommend replacing the whole distributor if it has a lot (more than 200,000km) of miles.


#10

The external appearance of the distributor housing does not have the typical diaphragm housing that is attached to the side of the Distributor. There are two ports that come out the side of a small area where the housing attaches to the engine. I can’t for the life of me see where a diaphragm would be positioned. The manual does not provide and exploded view to see how the vacuum advance system works.

Is there such a thing as a vacuum advance system the does not use a diaphragm?

Never the less, whatever the system may be, I assume each port should still hold a vacuum when a vacuum is applied?

Am I right or is there more to the ported and manifold systems than my 850 Morris Mini Minor experience/knowledge limits me too.