twowheeled

Hi Guys, my dads 91 4unner (4wd) is completely stock. We've owned it since new. It's lived a pretty sheltered life and has most of the maintenence up to date...well oil changes at least.

It's got a bad bogging problem when you are accelerating at full throttle. At roughly 3000rpm, the engine will bog down and rpm's will actually drop down about 200 for a split second before climbing again. Doesn't seem to matter if ECT or O/D is on/off. Any idea what this could be? Airfilter is relatively clean, plugs and wires were changed about 4 years ago. I've tried a few bottles of seafoam/injector cleaner and it didnt help.

The other week I was out in the mountains climbing some gravel fire roads. Nothing really steep, I had it in 2wd with OD off. We were hauling about 600lbs of gear in the back. Power really started dropping off hard, not because of altitude either. Finally my buddy who was driving said "somethings wrong", he was WOT and the truck wasn't climbing anymore. He kept his foot on the gas and it was slowing down to a crawl.

We jumped out and I told him to put it in park, turned the heater on and blew the fan at full, thinking the engine was overheating. When I went to look at the temp gauge though it was a little higher than normal, but nowhere near high. Plus I had just put in a new rad last year with fresh coolant/bleed. We shut the truck off for about 15 minutes and let it cool, and when we started off again it was fine. Any idea what this could be?

MudHippy

Someone's bound to argue with me on this, but I'd start by checking the EGR valve's functioning correctly. Could be sticking open. That and/or some kind of vacuum leak may be occuring. Check all those hoses for cracks, and the air intake hose to the throttle body for the same.

If you don't find nothing wrong with those. My next step would be to check the compression.

No strange sounds or smells coming from it?

twowheeled

no strange sounds, tons of strange smells. This truck gets babied unless I'm driving it, I try to give it the old italian tune up (WOT, redline to burn off all the carbon desposits). I'll have a poke around with carb cleaner but last time I sprayed around I could not find any leaks. It has about 100k miles on it. Does the EFI have a set of secondary injectors or anything like that? That come on at a specific rpm?

The only issue this truck ever had was a rough idle a few years ago and a bottle of fuel injector cleaner fixed that up. I suppose it's time to clean the intake/throttle body.

MudHippy

Yeah, that's not a half-bad idea for starts.

Ever try the new SeaFoam Motor Treatment? I've found SeaFoam works real good for that, if the crud build-up isn't too heavy. They recently changed the way you use the stuff. No more just pouring it into an open intake/vac hose(i.e. the PCV hose in front of the TB or the brake booster hose)while trying to keep the engine from dying by applying throttle to it at the same time you're pouring and holding the hose steady, as to minimize spillage(which could be tricky for one guy with only 2 hands). Now it comes in a pressurized spray can with a nifty crooked red hose(similar to the ones that come on cans of WD-40)that you can feed under the end of the air intake hose where it connects to the TB after loosening the clamp a little, but still leaving the hose attatched to it. Which means no more pulling hoses to give it a route for entry into the intake. This keeps atleast one hand free for the throttle application during use, and that lessons the likelyhood of the engine dying midway through the process due to the massive vacuum loss associated with unplugging a vac hose.

I've yet to try it since the change, but I've used many cans of 'er in the old manner. NAPA sells it, if you're interested.

No secondary injectors on it. Unless the cold start injector counts. Which, for the purposes of this conversation, it doesn't. It's only active during start-up, and even then only when coolant temps are low. And it shuts itself off via a timer switch once activated.

I asked about smells because I'm trying to rule out the transmission, which I can only assume is an automatic. And would therefor be more prone to overheating, which you can usually smell real easily. And which could also be causing the issue by not downshifting properly.

twowheeled

I'll try a bottle of the seafoam, never squirted any into the intake before. I am pretty sure the tranny was not the issue because we threw it into L to lock it in first and it wasn't helping. Almost like the engine knock sensor or something was retarding the ignition. But that's impossible on a points ignition right? Dammit I'm not used to working on such ancient technology!!

MudHippy

OH, 22R then? Then yeah, no CSI, knock sensor, or TB(carb'd right?). And my expertise is evaporating quickly. Not too dang much I can tell ya about them old things. I better go hit the books!

clydehatchet

ANCIENT??? these things are state of the art... you have a lot to learn.
good luck, Welcome to YT

MudHippy

Yeah, the 3VZE is but what the heck engine are we talking about here? EFI = no breaker points. And then let's forget about post #6 there. And resume where we left off....

clydehatchet

not too sure, the points thing threw me off.

MudHippy

It's gotta be the 3vze, I mean there's no real way to mistake it for anything else right?

Maybe the points ignition comment was just a brain-fart...or purposely designed to elicit confusion. I dunno, definetely threw me off!

clydehatchet

or maybe by points, he means, in the game of overcoming the 3vze horrors and woes, the 3vze has scored all the points. by ignition, he means the 3vze is going light him on fire with all the points it made.

MudHippy

Just did a quick check, and Toyota stopped using point type ignition in 1977.

So, I wasn't even close by thinking it could be on the 22R(20R's did 'till 77 and not after). Shows what I know about those engines.

clydehatchet

another point to the superior toyota mecca.

myyota

Your engine does not have points, its got electronic ignition. Try replacing the fuel filter and cleaning the throttle body and run some sea foam through it and see if that helps.

twowheeled

bwahaha, OK now I'm totally confused as well. I've only had the hood open a few times on this thing, it is definitely the V6, but I swear its got a distributor cap in the engine bay there and I immediately assumed points ignition. No? Is it sad that I've rebuilt engines and have no clue what I'm doing under the hood of this thing?

I am completely out of my element here. My cars got fancy coil on plug thingys and a little black box.

myyota

This engine is a lot simpler than the coil on plug set up on newer cars,maybe you should get a factory service manual and start reading before you try and work on it and possible make things worse ?.

sb5walker

I would check for codes, which is easy to do. The check engine light doesn't illuminate with all codes so you have to check. If there's an issue with the engine control system that might point to it.

http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

For a jumper in the check connector just use a metal paperclip.

clydehatchet

yeah, basically with these setups, your options for repairing a bog, a miss or some sort of lag, will start with all of your basic tune up components. if that doesn't help, repairing vacuum issues and leaks. after that, you begin a thorough internal cleaning from outside the engine. if that fails, you can look forward to tearing into the engine and lookin for other issues. adjustin your timing, replacing or adjusting your points, etc are not something you should even consider. check this out. http://www.ncttora.com/fsm/

twowheeled

Does the truck have OBD1 ports anywhere to just plug in a code reader to?

MudHippy

No, it doesn't. But fear not, as it isn't needed to read the codes on this engine.

Look under the hood on the right side of the engine, behind where the battery sits.

Located directly behind the maroon colored relay pictured above, on the outside of the fuse box(your fuse box may be slightly different in design, but that won't matter), is a smaller box. The cover of which will have the word "Diag." on it. Open said box and use a wire of some sort, paperclip works good, to "jump" or form a connection between the terminals labeled TE1 & E1 on the under side of the cover you've just removed. This will put the ECU into diagnosis mode, causing the "check engine" light on the dash panel to blink. Those blinks will tell you what, if any, codes are stored in the ECU's memory.

You'll be able to understand the process of deciphering the codes by carefully reading all the info provided in the link mentioned previously(and again below). Pay attention to the description in regards to the other diagnosis mode that requires jumping the terminals TE2 & E1. This mode, a.k.a. "Test" or "2 trip detection logic" mode, is useful for better diagnosing certain codes(21,25,26,71) and requires a different procedure.
http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

The link to the full FSM can be found below for reference to the systems for which diagnosis indicates the trouble existing, most of which are listed under the heading "Engine"(click it, then look below 3VZ-E for "Emissions Control System", "MFI System", or for some codes under the heading "Ignition" back on the first page and just below "Engine", depending on which system the code(s) applies to).
http://personal.utulsa.edu/~nathan-buchanan/93fsm/