Previa Gs

[DebbieB]

I have a Previa with a "flat spot" problem which is terrible in the cold weather.

Basically, it will cut out without warning. It does it if I am trying to pull away, or accelerating or just going round a round-a-bout. I can do a 70mph run along 7 miles of dual carriage way, get to the round-a-bout at the end and it will cut out as a I drive round. It's dangerous too, as I lose my power steering. The car is an automatic and so I have to column change to neutral, re-start and maintain control of the car with very heavy steering, all the time hoping no-one hits me!

I have been to my Toyota dealer who initially told me the map sensor needed adjusting and did so for me. The problem didn't occur for a couple of weeks but then continued as before. I was then told it was a fault on my model and that the map sensor needed replacing (over £600) but they couldn't guarantee it would cure the problem. I took it to an independant auto electrician who could find no fault on his computer analyser, but agreed after driving the car for two days that it was dangerous. He tried to obtain a replacement map sensor but had no luck.

I don't know what to do now. Does anyone have any ideas?

The car is a Previa GS Automatic, 1997 YOM.

[peterc]

Watcha mate,

Not sure if this is really going to help. but i had exactly the same problem on my Vauxhall Calibra(automatic). I would approach a roundabout and as soon as i lifted my foot off the accelerator and brake, the car would stall. Like you say, very scarey trying to steer/brake and restart at the same time !!!!

Anyway, the problem with the car was the idle valve was knackard. Now i know we are talking differant cars here, but maybe it will point you in the right direction.

You might want to check that all the air intake hoses are ok(not split or loose). Maybe check your air filter is not bunged up. Sometimes if a hose is split or loose, it will pick up the warm air from the engine(when its slowing down) and this confuses the MAP sensor.

Hope this helps

Pete

[DebbieB]

Thanks for that. It would appear from reading through the other info that this is a common problem, with many possible options but no definate solutions. Very annoying! Will try speaking to dealer again.

[Biker Baz]

Hi Debbie,

Im new to both this forum and the Previa!

Just purchased a 1992 2.4 GL maunal with similar problems. When cold it stalls when hot it runs fast. Also this gives a nasty flat spot, so when you pull out of a junction you end up stuck in the middle of the road slipping the clutch to get the thing moving. (of course you don't have this option)

I called a Toyo. dealer who explained the engine idle speed is determined by two sensors found on the cyclider head near the thermostat.

These sensors change resistance depending on the temperature of the engine and vary the idle speed as required.

Seems to me that my sensors don't react and have a fixed value which gives slow idle when cold and fast idle when hot.

Your scenario seems to be the sensors never detects the cold start and presumably this has an adverse affect on the engine speeds sensor, thus a steady idle speed cannot be obtained.

Does your motor ever idle? If yes what speed and is that when hot or cold?

Try calling a Toyo. dealer that doesn't know you. Ask for tech service rep. Explain the scenario then offer some technical jargon about the temperature sensors and resistance etc (to prevent him telling you to take it to them for costly diagnostics). In return he will probably give you reasons for that information not being accurate and offer the correct (important) information to prove you cannot know as much a the "official dealer".

Ultimatley this will narrow down the number of possiblitys for the fault.

Hope this helps!

Im taking my motor back to the dealer before the three month warranty's out! This way if any sensors need replacing the can cover the costs!

Is your motor petrol? If yes flip back the passengers seat to reveal the engine cover. Lift the cover you will see the inlet manifold. A large black pipe (approx. 3inch diameter) joins directly to the silver inlet arrangement. You will see a fairly large diameter slotted screw recessed in silver alluminium part vry near the pipe slightly off to one side. The screw slot point upwards.

With the engine running and warmed up turn the screw out CCW. This will increase the idle speed. Ensure you do not increase the idle too much, as its an auto it will pull alot when you select drive!

I have a Previa with a "flat spot" problem which is terrible in the cold weather. 

Basically, it will cut out without warning.  It does it if I am trying to pull away, or accelerating or just going round a round-a-bout.  I can do a 70mph run along 7 miles of dual carriage way, get to the round-a-bout at the end and it will cut out as a I drive round.  It's dangerous too, as I lose my power steering.  The car is an automatic and so I have to column change to neutral, re-start and maintain control of the car with very heavy steering, all the time hoping no-one hits me!

I have been to my Toyota dealer who initially told me the map sensor needed adjusting and did so for me.  The problem didn't occur for a couple of weeks but then continued as before.  I was then told it was a fault on my model and that the map sensor needed replacing (over £600) but they couldn't guarantee it would cure the problem.  I took it to an independant auto electrician who could find no fault on his computer analyser, but agreed after driving the car for two days that it was dangerous.  He tried to obtain a replacement map sensor but had no luck. 

I don't know what to do now.  Does anyone have any ideas?

The car is a Previa GS Automatic, 1997 YOM.

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