Air flow sensor issues

Submitted: Saturday, May 04, 2013 at 13:00
ThreadID: 102010 Views:1358 Replies:3 FollowUps:4
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I have a 3.4Lpetrol 95 series prado (2000). I am travelling around Oz for the year and had an air flow sensor problem in Adelaide.
The car intermittently lost significant power and acceleration. The problem worsened to the point that the car wouldn't go faster than 50km/hr with foot flat on the accelerator.
It got changed and the problem was immediately fixed. Interestingly, the diagnostic tool never came up with an error code.
Since Adelaide, we have done about 5000km and are now in Geraldton. Done some off roading but nothing too extreme.
The same problem has reared its head but is very intermittent. I have cleaned the air flow sensor and it hasn't helped. The air filter was changed recently and isn't very dirty.
Just wondering, is this likely to have happened again? The air flow meter was a genuine Denso part and expensive so I don't want to get another one unless I really need to.
I know this model is known to get contaminated air flow sensors (looking at forums) but this seems ridiculous. The mechanic in WA said it is a very rare problem and an air flow sensor hasn't been sold in WA for nearly 2 years!
Nothing at all comes up on the diagnostic tool again and the car is otherwise running fine.
A mechanic in Geraldton suggested it could be the fuel pump but the 95 series has a fuel pump for each tank and the problem occurs independently of which tank I am using. Surely it is unlikely that both pumps are failing.
We are heading to Darwin and will be doing some pretty remote driving so want to sort this out before heading into the wilderness. If we were staying around a big city, I wouldn't even care.
Any thoughts would be much appreciated.
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Reply By: Member - J&R - Saturday, May 04, 2013 at 14:21

Saturday, May 04, 2013 at 14:21
Did you scan for Toyota codes or just OBD?
AnswerID: 510303

Reply By: olcoolone - Saturday, May 04, 2013 at 16:16

Saturday, May 04, 2013 at 16:16
James it could be a number of things, even with a scan tool it will not always tell you what it is at fault..... it will only point you in the direction and you have to go back to good old diagnostic skills.

Chances of two of the same things failing is pretty isolated and unlikely, what it could be is something as simple as the plug at the air flow meter or wiring in the loom...... the other mechanic may of thought it was the air flow meter and once changed has disturbed the plug or wiring making the new one work, there may of not been a fault with the old one.

Get someone with a REAL scan tool that can read Toyota as said above and get them to have a look at the data from and to different components (not a scan DTC).

AnswerID: 510308

Follow Up By: James C10 - Saturday, May 04, 2013 at 18:58

Saturday, May 04, 2013 at 18:58
Great help. A standard DTC was used. Would only toyota dealers have an appropriate tool? Is it worth biting the bullet and taking it to a Toyota dealer or an auto electrician?
FollowupID: 788408

Follow Up By: olcoolone - Saturday, May 04, 2013 at 22:10

Saturday, May 04, 2013 at 22:10
A DCT is like a street directory, it will tell you where the street is but it will not tell you the house number..... in other words a DTC can be generated by the component itself or by something that has a relationship with that component.

The ideal way would be to read the pin voltage and resistance and the live data from the scan tool and compare it to a known source, we have access (for a fee) like many auto elec/mechanical places for know voltage, resistance and wave forms for most vehicles to help determine the problem.

A scan tool is only as good as the guy or girl using it and not all scan tools will tell you the same information.

The other thing is being intermittent it will be the luck of the draw to finding the fault.

Some Toyota dealers are very good and some no so..... no different to an auto elec/mechanic.

I would try whatever and whoever you can.

And please don't go replacing things your self.... it makes our job much harder, we are seeing more DIYers replacing this and that because on the net they said "blah blah blah". We have had customers who have spent $$$ on replacement parts only for us to find out it was something as stupid as a poor earth under load.
FollowupID: 788418

Follow Up By: olcoolone - Saturday, May 04, 2013 at 22:14

Saturday, May 04, 2013 at 22:14
BTW new Denso parts like most reputable manufactures have a very very small failure rate....... maybe 1 in 100,000 or more when new.

In a new vehicle it can be different when they introduce a newly designed component the failure rate can be as high as 1 in 5 but most are repaired under warranty with an upgraded component.
FollowupID: 788419

Follow Up By: James C10 - Sunday, May 05, 2013 at 09:51

Sunday, May 05, 2013 at 09:51
Thanks so much.
Sounds like if it isn't doing it at that time, might be hard to figure out. Just don't want to get stranded if it worsens!
Olcoolone, you don't work in Geralton do you?!
FollowupID: 788448

Reply By: KevinE - Saturday, May 04, 2013 at 19:15

Saturday, May 04, 2013 at 19:15
G'day James,

I'm not a mechanic mate, but I'm thinking the replacement sensor may have been a dud?

I had a something fail on a Ute a few years back, after many K's of happy motoring. I took it to a mechanic & he replaced the said part. Everything was good for a reasonable time, then it failed again. Took it back, he replaced it again, this time for free. After another reasonable time, it failed again. Repeat of the above for free again & ditto! I can't remember whether it was 3 or 4 that failed, but you get the idea.

Then while changing it the last time, the mechanic nonchalantly said, I wonder if its the after market part we're putting in? After market? I thought. How about we try a genuine part! We did & it never failed again while I had it.

Just a thought! :)
AnswerID: 510317

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