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2003 Tacoma surging

Hey guys, I have a 2003 toyota tacoma 4x4 with the 3.4l engine. Recently I have noticed that while accelerating I am losing power. I first noticed it would surge while going slowly uphill and since it has started happening all the time. I especially notice a serious dip in power during freeway acceleration at around 3000 rpm. The truck has 100000 miles on it. I have changed the plugs, run injector cleaner (the stuff you buy at the gas station), cleaned the throttle body, changed the air filter, and cleaned the mass airflow sensor. I have played a little with the throttle position sensor and that seems to have some affect on the timing of the surge but it is hard to tell. Of course toyota doesn’t service the TPS for that year but rather try to sell you a new throttle body $1100.00!!! Could this be the catalytic converter or maybe a faulty injector? Also, I have not changed the timing belt yet.

I’m sure the timing belt is past due for a change (if it has one - are you sure its not a chain?) but this wouldn’t cause these symptoms.

The nest thing is to get a fuel pressure gauge on it (and I didn’t see fuel filter on your list) & check the fuel pressure under load, and get a vacuum gauge on it to check for exhaust blockage.

Yep, did the fuel filter too. Was going to do the fuel pump next but wanted to get a little insight first.

Most of what you’ve done so far is just good basic maintenance stuff that’s good to have done no matter what & not too complicated or expensive.

Its time to start diagnostics. So just in case its what you’re thinking, I’d certainly not replace the fuel pump unless I knew it was the problem.