Backfire, power loss, cylinder 1 lean, engine bog.

I have a 01 tacoma with a 2.7 engine and i am having serious power loss problems. This began after a 5 hour trip back from high altitude 10000 feet to sea level. The truck ran good for the trip but started having trouble the next day after about 15 minutes of running. It will idle smoothly and with very slow pressure on the peddle i can get the engine to rev up without missing. If i put it under a load going down even a flat road it will act as though it is going to die. Bad hesitation, hardly any power and a loud vacuum sound comes from the intake. The deaper you put your foot in the peddle the worse it gets. If you maintain even half throttle it will occasionally backfire. At idle or up to about 20 percent throttle if done so gradually the truck will run fine but with more than 20 percent or even normal acceleration speed it will bog out and feel as though it has lost fuel. I only got one code from the computer and it read cylinder 1 lean. The truck has 130k. Any tips would be much appreciated im lost where to go from here. I have a feeling this could be electrical related or fuel delivery. Thanks

What i have done so far
Cleaned throttle body and upper intake.
Cleaned and tested mass air flow sensor.
Replaced spark plugs
Replaced fuel filter
Tested egr valve
Checked all vacuum lines.

 

What are the codes

 

Bad lifters or wiped cam lobe do that...but a timing chain jump would do that also. Check your codes...could be a number of things.

 

It showed a p0171 cyliner 1 lean. I considered a timing chain jump but figured if that were the case i wouldn't be able to get it to smoothly run at 3000rpm. At idle and very gradual acceleration the truck runs perfect. Its only when you give it gas at a decent rate that it acts up.

 

MAF... But you said you changed that?

 

I didn't change the MAF but did clean it really well with evaporating electrical connection cleaner. I tested it by running the truck with it unplugged and the truck loped and hardly wanted to run then plugged it in while running and it instantly went to a smooth idle and ran better. I know that's not a true way of testing its full working function but did eliminate the concern of it not working entirely. One other symptom i forgot to mention was when at rest for a while or cold start facing slighly downhill it has had a hard time starting. Usually fires the secound you turn the key and smooth idles. While downhill it takes a couple cranks and it will sputter for the first couple revolutions of the motor then run clean. Part of why i was concerned it could be fuel delivery related. What do you guys think.

 

Fuel pump failing?

 

id go with this. get a fuel pressure gauge to test with.

i had my old 240 do the exact same thing. slight throttle the car would rev up fine, but any more and it would miss and eventually stop climbing rpms.

 

i ordered a full service Manuel and borrowed a fuel pressure gauge i will try that out tomorrow and let you guys know. thanks

 

Well today we checked mass airflow, throttle position sensor, vacuum system pressure, fuel system pressure, and some other things and still no luck finding the problem. Everything is in perfect working order. At a loss as to what is causing this so it's going to the shop for a full diagnostics tomorrow. Cross my fingers they can tell me something I don't already know. Here goes my next paycheck. I will let you know what I find. Sounds like I'm not the only one who has had this problem.

 

Got it figured out today. It ended up being a pinched fuel line above the fuel tank in the rubber hose. somehow it came loos from its clips and got pushed up above the fuel tank and pinched. Suspicious how that would have happened but its fixed now. My local shop was trying to tell me it was a bad mass air flow sensor and a plugged catalytic converter but thankfully it was a simple fix. Thanks for all your suggestions.

 

ok sorry if this sounds stupid but, do you have any amps in the truck? you possibly need to check the ground of your truck going from the negative battery to the frame, it sounds stupid but I have heard that a week or bad ground can cause some awful problems