2003 Toyota Tacoma V6 hesitation

I need some help. My '03 Toyota Tacoma 3.4L 5spd has been hesitating only during the summer months for the past 4 years. It now has 110,000 miles on it and it seems to happen on hot days after its rained. I'll go to take off from a stop and it seems like its starving for fuel/air/spark...whatever. I'll have the pedal floored and it will finally take off after like 5-10 seconds of lag. I won't let anybody else drive it because it's dangerous. Then when I shift to 2nd, it does it again. Of course it won't reproduce the hesitation in the presence of a mechanic. I've replaced the MAF sensor, fuel filter, air filter, spark plugs, wires, coils, cleaned throttle body and used Fuel Injector Cleaner. During the winter, no hesitation at all. It's more severe with the A/C, but still happens without. Toyota couldn't reproduce it either and it will not throw an engine code.
Has anybody experienced this? Any suggestions?

 

have you changed the fuel pump? Try different gas. I personally don't put "cheaper" gas in my vehicles. (kangaroo, cowboys) those types of gas stations. I always use BP and put lucas fuel treatment every oil change. There might be water in the tank as well. I would start with changing where you fill up and if that doesn't work, try changing the fuel pump.

 

I changed to Shell gas consistently for the last month and it still happens. Haven't changed the fuel pump, but I'd think a bad fuel pump would give me problems starting, no? It runs fine other than the ridiculous hesitation

 

true didnt think about that... have you done a seafoam treatment? half in the tank and half through intake manifold. youtube on how to do it..
EDIT: also, with that kinda mileage, have you changed the timing belt? i definitely know that wont fix it, but its preventative maintenance on a vehicle with high mileage. Ask this guy, he knows more about engines than anyone I know of....
http://www.tacomaworld.com/forum/south-east/227374-marion-bumper2bumper-automotive-alabama.html

 

I've never done a seafoam treatment, but I'm gonna have to YouTube it because I have never even heard of it, haha! I changed the timing belt at 90,000. Oil is changed every 3,000 religiously. Temperature always seems consistent, so I don't think it has anything to do with the thermostat or radiator.
What gets me is the fact that it only happens in the spring and summer heat. Once it cools down in the fall to winter, it won't hesitate. Seems to happen more after its been driven in the rain. Not when it's raining, but for several days after.

 

I have almost the exact same problem but im in the 3.4l automatic. I haven't replaced as much as you, but started with spark plugs and a fuel filter. The fuel filter seemed to help a bit (with a more severe fuel supply problem i was having), but long story short my next best guess is the fuel pump.

Like you mentioned though, I generally have more problems on startup in comparison to problems while stopping (this has occured though)

 

I've never had problems on startup, but it will start to lag while I have steady pressure on the gas and cruising.

 

Sorry...I mean I don't have problems stopping. Starting is the reason I posted in the first place...haha!

 

ahh finally someone with the same problem as me. Problem started last summer, engine would hesitate for a few seconds from the go then once I was cruising at low RPM's it would also dip down about 100 rpms for a good second then go back up. I replaced my fuel filter, put some fuel injector cleaner in the gas tank and the problem slowly disappeared.. but then again so did the heat. Sure enough this summer the hesitation is back so I blame it on the damn AZ heat but sounds like I may need to look into a new fuel pump. Let me know if you pull the trigger and see results.

 

I'll keep you posted. Do the same for me. It hasn't been doing it since its been kinda dry around here. Once I drive it in the rain for a while or during heavy rain, it will do it again, I'm sure. I'd imagine in Arizona, it's gonna be really intermittent.

 

It's monsoon season right now and next week we are expecting some moisture so I'll see if I notice it more

 

Either of you replace the fuel pump yet? Mine is having a mid throttle hesitation and lacking acceleration. Feels like I am dragging a boat anchor. Took it to a local Toyota guy this morning and that was all he could think of. No CEL and nothing else he could find. Wanted to hear someone say they have replaced it and fixed the problem before I drop that kind of money.

 

Interesting--I want to know TOO!!
Do not have the problem--subcribed to this thread-With all the things that were replaced--what could it be?
I recently put in a different brand of gas--noticed a huge difference in performance-SHITTY--Normally use EXXON--had to pick up some diesel fuel and figured I would just fill up the gas too--Mistake--BACK to EXXON for me.
BP and Shell make my truck run bad--do they have MORE ETHANOL??
REAL GAS is worth the extra $$$ you spend--Have you tried REAL GAS?
Most Farmers Co-Op--carry real gas--Just a thought--could not hurt on your next fill up.

 

I said screw and ordered the Walbro 190lph pump off of the URD website after I spoke with Gadget. He said he has been running one since 97' with no issues. At $100 it is also a third of the price that Toyota quoted me ($347) for a new pump from them. In their defense the Toyota one is the complete fuel pump and mount assembly; which I do not need. Also, since I am running the 7th injector, the higher flow of the Walbro may fix my problem plus give a bit more power than I originally had. It should be here Monday and I will give an update as soon as I get it in and give it a test drive. Crossing my fingers!

 

Just to give a heads up; new pump did not fix the problem for me!

 

Well I guess I can scratch the fuel pump idea. It's gotta be electrical...

 

Yours might be different than mine. The fuel pump changed nothing but i went ahead and bought the walboro fuel pump as un upgrade if add injectors and other mods later. So nit a complete waste of money.

I did find a open vacuum port on the supercharger intake. Replugged it and reset the ECM and it ran great. It eventually starting running crappy again but not as bad as before. I would say it is 80% right now. I can drive around normally just fine but don't have the WOT pull it used to have. Whatever my problem is the ECM starts detecting it after the reset and adjusts to save the engine. I am going to continue to keep looking at possible lean out issues.

 

hey guys im having the same problem in my 04 doub cab 3.4l. I also change spark plugs and oil on reg basis. I run gas from all gas stations that are decent brand and flow through gas regularly because my truck is my work vehicle as well. 164,000 miles and don't know what to do, in my mind i figured it was the fuel pump or filter but good thing i read this thread. What now? somebody has to know what's going on too many people having same issues.

 

I have the same hesitation problem on my 2003 Doubletaco TRD V6. Started cropping up a little last summer only. Dealer could find nothing and said just use injector cleaner. I did then it maybe improved or the weather just got cooler?
This year (at 203300 miles) it's back and 10 times worse. Again though only on hot days (over 80 degrees) and it is unpredictable. I read up on the web and decided to put in a new Mass Air Flow Sensor.
Problem totally went away and codes dissapeared too! BUT FOR ONLY A WEEK!
By second week same stuff crept back in slowly. Third week became worse than ever!
I blamed it on the aftermarket quality of the replacement part and bought another new MAS from the dealer at x3 cost....problem went away again...BUT this time only for a day!!!
I figure if it only occurs on hot days it can't be the fuel filter or pump or air cleaner ect. Got to be a chip or electrical component of some sort?
What do you guys think?

 

Today, my Neighbor complained of the same problem; we changed out the O2 sensor and now it runs like a scalded Pig.