I just want to say I love this site. I have been using this site to diagnose and fix my toyotas since my first one almost 10 years ago! It wasn't untill recently that I couldn't diagnose somthing just by searching so now I am here as a new member asking...

My girlfriend recently bought this 92 4Runner 3.0 with a bad rod knock and since she had the old engine from the truck she totalled last year we decided to just swap in hers. Everything went super smooth which was an omen for trouble to come. The engine went right in (swapped leaving the trans in place, a first for me) and started right up, well, after I rebuilt the starter. (The solenoid contact must have gotten turned sideways while removing/installing the power wire, no biggie) The truck drove just fine with no hesitation problems. I also had to do the knock sensor relocation mod since I did not feel like taking off the lower intake to change the knock sensor wire. (apparently this wire is different from the '90 P/U and '92 4Runner)
After clearing the codes and making sure that the CEL stayed off I decided to check the TPS adjustment (only slightly off, the shift points were a little wacky before readjustment) and set the idle/timing. The next day my girlfriend took the truck to work and said the truck was close to undriveable.
I test drove the truck and found that after driving for 10-15 minutes it would hesitate under acceleration and the longer i drove it the worse it would get.

Things I have done to try and diagnose:

1. new fuel filter - no difference (was pretty clogged though)
2. TPS unplugged - no difference
3. 02 sensor unplugged - no difference
4. EGR system disabled - no difference
5. FPR disabled - no difference
6. Jumped b+ and Fp in DLC connector - no difference
7. tried known good VAFM - no difference
8. inspected vacuum hoses - they look good and connected properly as far as i can tell
9. New plugs and wires as of engine install

The guy we bought the truck from said he had put a new fuel pump in. He cut a hole in the floor under the passenger rear seat to get to it. I am thinking about pulling it back out to make sure the screen is installed to the pump correctly and I want to see how much rust is in the bottom of the tank after knowing how much came out of the filter. I am also thinking of hooking a small light bulb up parallel to the pump and having my girlfriend sit in the back seat to see if the bulb flickers/goes out while the problem is occuring. I will be purchasing a fuel pressure tester on my next paycheck and the accron banjo bolt adapter refered to in other threads. I hope to be able to route the hose out of the hood near the wipers to watch the gauge while driving. That won't be untill around the 28th so I hope to be able to check some other things in the meantime.

Other tests I want to run:

1. Obviously fuel pressure as I mentioned
2. MFI electrical trouble shooting tests as per FSM
3. Engine/body electrical grounds - I read somwhere that certain bad grounds can cause misfires or hiccups.

Basically the truck idles just fine at around 700 rpm. (I accidentaly set it a little too low but I already filled the screw hole with rtv to keep the screw from coming out because it was idling at 1400 before.) If I drive the truck real easy the problem won't arise. It isn't untill I try flooring it that the problem starts. The truck suddenly loses power and the RPM's drop to about 800 before revving back up, and as long as I leave my foot down it will keep doing this. In neutral the engine does not miss a beat unless I shift into N while the problem is happening and keeping my foot on the gas. As I continue to drive the problem gets worse once I make it happen up to the point where I feel unsafe to make a left through a light untill it changes. One thing that seems to work the last couple time I drove it and it was acting up was letting my foot of the gas while coasting, shifting to N, shutting the engine off, waiting about 5 seconds, and then starting it back up. I have not a clue left. Other problems i have read about seem quite different than this.

Has anyone experienced this?
Am I on the right track here?

Thanks in advance.

 

If you got a lot of rust out of the fuel filter as you said, i bet the inside of the tank is full of rust, and is probably restricting fuel flow through the pump. So you need to pull the pump and look inside the tank to see how bad it is. Let us know what you find.

 

Thats definatly a thought of mine. But would it not still affect it without a load being exerted? The other thing that scares me about looking in there is how I should clean out what I find. My buddies and I were joking about how to turn a wet/dry vac into a jet engine and I think this is the perfect time to to find out! just kidding. The other thought I had was to empty the tank out completly and let the rest evaporate before pouring a bucket of jb weld into the tank to glue all the rust in place... again just kidding, but really how would I clean it out? just take it off and rinse it?

 

There is probably enough fuel getting through the pump to run the engine at idle or lower speeds, but under hi demand like trying to get on the freeway the pump can`t supply the fuel needed because its plugged up. If the tank is really rusted on the inside you will need to replace it, cleaning it out won`t stop the rust from coming back. You can get a new gas tank from www.partstrain.com .
There should be a drain plug on the bottom of the tank.

 

Well I pulled the fuel pump out to take a look in the tank and the fuel doesn't have any floating bits in it. But, there is quite a bit of rust on all the surfaces. I supose being aggitated while driving would get alot of that crap suspended in the fuel and clog up the strainer. The strainer IS pretty caked (I am attaching a couple pics).
Also there are a couple springs inside the strainer to keep the strainer from crumpling up under suction. I am assuming they aren't bent when the strainer is new, and they are pretty mangled now as you can see in the pics. If that strainer is caked enough that the suction is crumpling it, I am guessing that is enough restriction to starve the engine of fuel.
I would like to just put a new strainer on and drive it to make sure that is the problem before replacing the tank or even cleaning it out. Really i would like to just put the fuel pump back in and leave the strainer out and test drive it really quick but i know this is a terrible idea...