asas9800

Hey all. Im new to the forum but have been lurking for months now. I have a 92 4runner with a 3vze in it and I have a problem that's driving me insane. After the truck is completely warmed up, meaning Ive been driving for atleast a half hour, if i mash the gas to wot from a dead stop, the truck bogs at 2000rpm and has no power. then after about two or three seconds, will sort of free up and go. my foot stays down the whole time. Any Ideas? Ive changed and adjusted the tps. its within spec. Ive replaced the maf and checked its spec. ive replaced the fuel filter, it has a fresh tuneup on it. the transmission is freshly rebuilt and heads look brand new. the egr works properly and all cylinders fire correctly. keep in mind its only when i mash the gas and only from a dead stop. I also experience a slight power loss when im really putting it through the paces in 4wd. especially soen here in loose sand. any help will be greatly appreciated.

skypilot

iTrader: (1)

Dude; thats not a problem. You are flooding the engine with air & no gas. This is a drag racing issue. You have to dump large quantites of fuel into the intake to make up for the loss in air velocity. Since your AFM isn't being forced open you are getting no gas. On a drag car we put in a bigger accelerator pump to cover that sudden influx of air. On an FI car its programmed to burst the FI's when the MAF is at minimum and TPS is at maximum performing the same function.

That engine will never be a race contender, its simply got too much bad DNA. It may work sortof when cold due to a higher pressure from the fuel pressure regulator for cold warmup programming. But a drag engine it will never be; ever.

asas9800

Im not trying to race in it or anyting. Im in south texas and do a lot of fishing. Usually we travel up 10 - 35 miles of beach and at times i need to plow through some really loose sand. Only when i try to power through i end up bogging. Im wondering if the problem is as simple as getting a new fuel pump? im sure the one on is original. Would that explain why I experience actual power loss and not bogging in 4wd?

James Woods

iTrader: (1)

A slow responding O2 sensor can cause your issue, the O2 sensor basically controls the amount of fuel supplied to the motor from monitoring the air fuel ratio in the exhaust, I have seen this problem and pull the O2 sensor and find it covered in black soot, you can try to clean it off and see if it helps or just replace it if you find it in that condition.

asas9800

would a gunked up o2 explain power loss when traveling normal speed in 4wd through moderately soft sand? For example, this last weekend we were coming back through some loose stuff and i put it in 4hi. i took off normally and as the sand got looser, i felt the truck gradually decrease in power. when i gave it more gas, nothing happened. what do you think could be the cause of that?

James Woods

iTrader: (1)

I couldn't tell you for sure without driving it myself but a few things that make it fall on its face when accelerating are the O2 sensor, clogged cat, TPS, VAFM, coolant temp sensor for computer, leaking injectors, could go on and on. Check your spark plugs for signs of fouling from too much fuel, check codes, exhaust, O2 sensor, fuel pressures, compression. Also it could have just been that you were loosing traction in the deeper sand.

asas9800

it shoots a code 25 at me. air/fuel ratio too lean. everything else seems to be fine. i replaced the fuel injector seals, had the injectors themselves cleaned, the cat was taken off an s10 and put on mine because i bought it without one, its good on gas, runs smooth, has compression. all the good stuff. thats the only code, and those are the only problems with it.

asas9800

oh and fuel pressure is about 46 and increases to around 53 when you give it gas. do fuel pumps stop working intermittently? Ive checked the pressure 3 seperate times and each time its reads the same.

James Woods

iTrader: (1)

Thats your problem, you are not getting enough fuel. Check for vacuum leaks, timing and also it could still be your O2 sensor.

asas9800

but youre thinking definitely not the fuel pump?

James Woods

iTrader: (1)

Can't say for sure but its a long shot that the fuel pump is bad if your fuel pressure is normal, I would start with checking all of the intake ducting for leaks and then check the O2 sensor, if that checks good, you may want to start checking the VAFM, timing, valve clearance and so on. A lean engine will cause lots of issues if not taken care of as the engine will run hotter than normal and can cause overheating, cat converter failure and general accelerated wear and tear.

93toyrunner2

What spark plugs do you have in it? What brand wires?

skypilot

iTrader: (1)

Lean is bad... Very bad.. I bet you get the code only only when you are out on the sand. Pull a plug or two and look at a spark plug chart. White is lean & black is rich; brown is ~ . Black on a drag engine is Ok, it fills up the clyinder with liquid and increases compression, on DD its not good.

O2's are a hundred bucks or so... see if you can borrow one. This is my latest thing since it saved my son's car ( & me a lot of work). CataClean; you can get it in NAPA stores costs ~25 /35 bucks and is supposed to clean FI's o2's & cats (took two bottles). But his car also had a bad fuel pump from letting the fuel tank go empty too often & it overheated and failed. Yours at 46psi is Ok. look further downstream. Was filter changed at some point ~ flow restricted (volume)?