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Discussion Starter #1
1999 automatic ...intermittently over 50..give it gas to accelerate..starts to and then won't do it..sort of feels like fuel starvation..rpms don't seem to increase, though I will have to try it somemore.. only does it at higher speeds. Tranny fluid needs changing..any thoughts?
 

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Well ... these 3SFEs are undersized. Fine for in-town, grocery-getting, but there's almost _nothing_ there for highway passing, etc.

But, start with the basics: check the fluids (including the transfer case; dipstick is behind the right front tire), air filter, spark plugs and wires, gas cap, fuel filter, catalytic converter, etc.

If you floor it, the trans should downshift and rev high ("kickdown"). If not, then yes there's something wrong with the trans. A fluid and filter change has a slight chance of helping. If AWD, it takes a special, dealer-only fluid.
 

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thx..will have to test it some more when roads are dryer..feels like it kicks down and then balks..doesn't rev...if it happened at all speeds I'd think fuel filter or something like that..but only above 50 or so. Getting fluid and filter changed tomorrow. Discovered I had the Overdrive button set to NO Overdrive..Do you think that would have an effect?
 

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2008 RAV4 Limited V6
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thx..will have to test it some more when roads are dryer..feels like it kicks down and then balks..doesn't rev...if it happened at all speeds I'd think fuel filter or something like that..but only above 50 or so. Getting fluid and filter changed tomorrow. Discovered I had the Overdrive button set to NO Overdrive..Do you think that would have an effect?
Overdrive has nothing to do with it. If the engine balks as you say, it's either not getting enough fuel or it's not getting enough air.
 

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1999 Toyota RAV4 with 3MZ-FE 6 cylinder engine, camo wrap, OME lift, heavily modded
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You can borrow a fuel pressure test kit at many parts stores, easy to use and lets you properly diagnose the fuel system. At most parts stores it's free to borrow, they charge you for it when you pick it up, if you bring it back they refund your money.

The pressure should be 44 to 50 psi (304 to 345 kPa).
 

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Discussion Starter #7
thx..have been noticing it at different speeds..feels like a fuel issue, need to check plugs for fouling, replace wires..
 

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Start with plugs and wires. Fuel filter is very unlikely, unless you have been unlucky. It could be a build up of carbon, but that usually makes the engine run rougher at low speeds, and gives jerkiness as lumps of carbon break off and go through the engine. The intermittent nature suggests an electrical item. The Throttle Position Sensor tells the ECU that you have opened the throttle to accelerate and to richen the mixture temporarily. If it is failing it might work sometimes and not others. Valve clearances could be borderline, where they are very closed up, and sealing is becoming variable if it's done over 100,000 miles one or two valve clearances might need adjusting. A failing injector could do the same thing.


The fuel pressure regulator also can fail on high mileage cars. If you've got low pressure, then it won't atomise the fuel very well and can give poor combustion, which gives poor driveability. There is a vacuum line to the fuel pressure regulator, so the fuel pressure should increase as the load increases/higher throttle.

You also don't have to look too far for people who have had to change their injectors.

If you've got a stuck/sticking EGR valve that starts to cause problems, such as yours as well. I've actually disconnected mine because it's the cause of the carbon build-up in these engines.

Then you might need to get onto the crank sensor, which can get very dirty and give a very noisy signal, which the ECU finds it hard to read.

And then you could get on to the coils themselves, because they can fail as well. Ignition component failure starts to show up more at high power/opening throttle for acceleration, because the energy to jump the plug gap is higher for greater throttle openings and higher engine speeds, so misfires start to show up. Might not give a code, but could be the P0300 random misfire code, or cylinder specific. It always helps to read the codes, to see if there are any.
 
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Discussion Starter #9
..thx..changed the plugs and wires..two plugs were pretty loose..one of their wires didn't look good at the plug end...plugs looked ok..will take it out and drive when i get a chance...thinking about the throttle maybe sticking and will likely change fuel filter..
 
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