What should I try next?

How's it going guys? Bear with me because this is going to be a hella long post. I've been going around and around with my Tacoma for the past year and a half or so in attempt for it to be back in somewhat normal running condition. She's getting up there in age and miles; 2008 Prerunner v6 with 345k miles so I am well aware that she's not as young as she once was and is bound to show it. I've had a severe performance issues from the truck such as; hesitating upon acceleration or bogging down, loss of power at speeds being unable to pass people or maintain speed, RPM fluctuation at lower speeds of 35mph or less, and overall pretty crap fuel economy at least not as good as I would expect it to be. I've replaced a lot of parts over time and I will list what I have done below and keep in mind I have had no check engine light except for a lean or rich condition in the past and a current catalytic converter code due to the ones closest to the manifold being removed.

Currently replaced parts or cleaned:
Fuel pump (replaced)
MAF sensor (replaced)
Throttle body (cleaned)
Throttle body gasket (replaced)
All 6 fuel injectors (replaced)
Fuel pressure regulator (replaced)
Intake gasket (replaced)
Spark Plugs (replaced)
Catalytic converters next to manifold were removed due to being clogged
Put Heet in fuel tank to get rid of any suspected water in it

In light of this laundry list of actions taken in order to improve the performance of the vehicle they have most definitely helped but did not fix the issue completely. The truck still has episodes of sluggish performance that is starting to become even more of a pain in daily driving and has gotten me into some pretty dangerous situations.

Understanding the age and mileage of the truck I had a lot of evidence to convince me that it was a combination of issues that lead to it and I have felt like I did most of what should have been done. The only thing I have not done is replace the o2 sensors but I figured that if it were an o2 sensor issue it would have thrown some sort of code somewhere. As I stated, in the past I had a lean running condition and I replaced the fuel pump and it later turned into a rich condition and it depended on the climate as to which it was. When it was warm and muggy, lean. Cold and dry, rich. The fueling conditions got bad enough to where it destroyed my cat and in efforts to save $600+ I simply and illegally busted them out and it had a period of running well then it started running bad again. Time goes by and I decide to really dig into the issue and replace a lot of fueling components and gaskets such as what is listed above. The situation got better but then came back and someone suggested I perhaps had water in my gas tank. I addressed that issue with some good old fashioned heet and it worked well and I noticed that the occasional sluggishness was not as often but it is still there especially this time of year when it is very warm and muggy. In the winter time the truck runs much better than it does in warmer weather almost like nothing is wrong with it with it very seldom performing poorly.

So to end this sob story of my high mileage headache I was wondering if anyone has any advice on what I should try next besides driving it off a cliff. I was also wondering despite all the repairs done could the issue have come full circle to me removing the cats and causing the downstream o2 sensors to have issues. Anything helps and I'm willing to go into detail with anything needed.

Thanks a lot.

 

C4

 

At this point try some diesel

 

Maybe try a new coolant temp sensor; they’re pretty inexpensive. It starts well when the engine is both cold and hot?

 

I will say that is one of those things I wish I had changed when I had the intake and everything off. I did not think about it until I saw it and kinda prayed it wouldn't be that simply due to me having to pull all that crap back off again. Thee only thing that doesn't convince me is my coolant temperature through a scan tool appears to be normal unless, of course, it's giving me a faulty reading.

 

You need to tell us what a scan tool says. I’d BUY a midrange scan tool to see what it really is doing. What’s things like fuel trims doing? For the money you’ve dumped into parts, but the scan tool instead.

 

Did you do a compression/leak down test?

 

The Short and long term trims read normal from an idle. When driving on the other had the short terms will stay pretty close to the 0 not reading anymore than 5 on the positive and negative side. The long term at least where I have witnessed on LTFT2, the number will shoot to -25% when you let of the throttle and then snap back into normal ratios. That's the only thing I have noticed that, to me, seems abnormal.

 

I have not. The only reason being is I haven't dug that deep into it yet and if it appears to be an issue such as that I'll probably get rid of it. I'm just seeing if there could be anything else I can do from the outside that I may have missed in the process.

 

I agree. That’s a pretty large swing on trim. I’m stumped because you’ve replaced everything fuel related. Could you have crud in the tank???

 

As I stated I did address a possible water issue in the tank and it did seem to improve it drastically, but what you proposed there wouldn't surprise me. Is there anyway that you know of on how I could check that?

 

This is what I’d do next. With that many miles, compression may be on the low side.

A can of jectron with premium fuel and a good long drive ending with flooring it hard uphill does wonders for mine when it starts to feel sluggish.

 

So an Italian tune-up

 

I would have done it when the plugs were removed seeing how many miles are on the engine.