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Question for you mechanics (98 Tacoma)

Seth_88

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Feb 22, 2000
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#1
I've got a 98 Toyota Tacoma that has 63,000 miles on it. It's a 4 cyl. 5 speed 2 wheel drive with standard cab/bed. When I'm driving at 1/4 throttle or so it seems like the truck dies. It takes off again if I give it more gas , but it is very annoying around town etc. It doesn't do this all the time, just seems like at that 1/4 throttle or less.
I've replaced the spark plugs, wires, air filter, checked vacuum hoses etc., but have had no luck.
Anyone have any suggestions?
 

Casper250

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Dec 12, 2000
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#2
Just a stab in the dark, might be fuel pressure. Does the car idle fine?
 

Seth_88

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#3
Yes, it idles and runs perfectly except for the hesitation. Could it be a fuel filter?
 

DougRoost

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#4
The idle question is a good one since it could allude to what I'm about to recommend. In the old days people knew to periodically clean or rebuild their carburetors due to varnishing and cirt buildups. Well, with EFI you still have to periodically clean the throttle valve. If you haven't, remove the hose from the air filter and such that go into the throttle valve (usually easy to spot by the throttle cables being attached to it). It should be some sort of butterfly valve, may even have multiple butterflies depending on engine. Get some Gumout or other spray carburetor/fuel cleaner and a couple a shop rag or two. Open the throttle body and clean everything you can see, especially the backside of the butterfly(s), since they get dirty from the pulses doing a bit of reversion in the intake manifold. Spray it and wipe it down, repeating as necessary until it looks new again. Use a shop rag instead of paper towels so no pieces of it go into the manifold.

Even if this doesn't solve the problem you should do it as periodic maintenance. Likewise with runnning some fuel injector cleaner through it every oil change (I like Chevron Techron, which is available at most auto parts stores).
 

DougRoost

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#5
A clogged fuel filter will result in an engine that runs worse the faster you go. But again, if it hasn't been changed in awhile do it since it's periodic maintenance and cheap insurance.
 

Seth_88

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Feb 22, 2000
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#7
I finally figured out the problem, it was the Throttle Position Sensor. Cost $50 and took about 10 minutes to install.
 

gnarlykaw

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May 20, 2001
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#9
u didn't mess with the base idle setting before you found the TPS did ya?