tuckerlan

Ive had my 1993 Toyota 4runner 3.0l v6 4x4 for about a year now and it has been nothing but constant trouble. I've done a lot of work over the past couple months to the engine itself, the engine has been fully rebuilt, new bearings, rings, gaskets, etc its a brand new engine. it has about roughly 50 miles on the rebuild and was running very strong and had decent power considering it was a 3.slow. it was all going well until i was driving it down the road roughly at 30 mph 2nd gear at 2,500 rpm and in the blink of an eye it had an extreme loss of power it was studdering all over the place when throttle was applied and was not driveable. I diagnosed and realized the engine has been running extremely rich since then as if the choke was pulled like on a carburated vehicle. i've replaced and or tested tps, vafm, etc(coolant temp sensor),02 sensor, replaced wire harness, new ecu, tested injectors, cold start injector, cold start injector switch, fuel pressure regulator,new fuel pump, vsv switches, replaced and added electrical grounds, the engine also has new spark plug wires and a new cap and rotor. ive tried everything i can think of and the vehicle is still running poorly it sometimes idles perfectly fine but it refuses to go past 2k rpm and shoots black smoke out of the tailpipe and backfires. one thing i have noticed is when the vehicle first is fired up it runs perfectly for about a second or two then the rpm drops and it will run poorly again making me suspect something wrong with a sensor possibly because it runs fine for a second or two until it gets signal from a faulty sensor somewhere? and awnsers are greatly appreciated, no im not gonna 3.4 swap unfortunately i live in California and cant pass carb.

scope103

Welcome to YotaTech.

1. Have you checked ignition timing? The spec is on the under-hood sticker.

2. Have you tried to pass SMOG? The report could tell you a lot.

3. Have you tried a "cylinder efficiency test"? While idling, pull each plug wire, one at a time. Does the idle fail to change on one of them? That cylinder may be missing, which is a very common cause of high HC ("running rich").

4. Compression test?

tuckerlan

Thank you for the quick feedback i forgot to mention that i did set my ignition timing correctly by the book 10 degrees btdc with the diagnostic port jumped as required but i will try pulling the plug wires one at a time to see if that does anything. and i could try and get it to pass smog but it wont move under its own power to even drive there and ive already had a local toyota shop try and diagnose it but they couldnt find anything

tuckerlan

I just preformed a "cylinder efficiency test" and the engine was negatively effected after each individual spark plug wire was removed meaning that all cylinders are getting spark at the right timing.

tuckerlan

Still no update on the 3.0, i feel like ive checked everything that could change the air fuel ratio does anyone know what could effect the air fuel ratio besides what i have listed above any input would be appreciated

maxvp01

subbed. i have a rich condition that i have been trying to figure out for months.

I believe my problem lies in my wiring harness. I have no CEL, but have had mice living in my truck and ate wires on it before. (sat for 9 years). However you said you replaced your wiring harness.

What does your vf signal tell you? This can help you figure out of the computer is trying to compensate or not, and what the computer is seeing.

EDIT: vf signal link
https://people.well.com/user/mosk/Vfsignal.htm

tuckerlan

thank you for the input i just tried testing the afm based off what that website had listed and i belive all the readings are in spec i just replaced that sensor roughly a week ago trying to diagnose the issue but still no forward progress. i had the vehicle sent to a local toyota specialist and they looked at the vehicle for about a week and could not figure out what was wrong with it they just suggested to test all my ground wires even though i have a replaced wire harness. i went through checked and cleaned all the electrical grounds i found but is there any grounds besides the ones on the cam bearing cap, passenger side of engine block coming from the negative baterry terminal, top of the intake manifold, and the one grounded by the ignition coil?

i went through today have a better description of the symptoms just in case it gives anyone ideas
1. idles perfect with little vibrations here and there nothing to really be concerned about
2. gets up to temp in expected time not using coolant or burning oil
3. when throttle is applied it physically wont rev past 1,700 rpm it starts shaking and bogging
4. when its running there is a constant smell of gas and there is fuel spraying out of the exhaust my entire driveway looks like it got sprayed with black paint
5. the fuel gauge drops extremely fast and you can watch the gauge moving down
6. with the intake manifold off you can look into the intake runners and see puddles of fuel where the valves seat

Any ideas are greatly appreciated thank you to the people who already threw out some ideas

maxvp01

That link does not test the AFM. The VF signal is a refined O2 signal and will help you figure out your fuel trims. This test will put you in the right direction by telling you what the computer is being told, and how the computer is reacting to that command. Once you figure out the voltage from your VF go back on that website and compare to the chart to see if the computer is trying to compensate or not. It’s possible your computer thinks the engine is running lean and consequently is dumping fuel into it.

Heres an example:
My truck is running rich like yours. I did this VF test and something is telling my computer that the engine is running lean. My computer is being told it’s lean, so it’s dumping fuel to compensate. My issue lies where the computer can’t figure out that it’s not lean due to a lack of communication somewhere, as I have replaced all sensors MULTIPLE times like you have.

Also when you said you tested your injectors, how did you test them? If they are new they could have a higher flow rate than stock too

tuckerlan

this is kind of a dumb question and I should already know this by now but im only 17 and am a slow learner. on that website it says to connect the terminals t-e1 are these terminals in the diagnostics port or are they somewhere else? am I connecting a multi-meter there or am I just bridging the gap and measuring with a multi-meter elsewhere?

Edit: i have never actually replaced my injectors, I rebuilt them with new seals and filters. and how i tested them was I pressurized them with brake clean and pulsated 12v of power and made sure they were not stuck but this wasn't a very accurate test in terms of watching the spray pattern of the injectors. after I determined they weren't stuck open or leaking i tested the harness by determining each injector has a constant 12v then I disconnected the fuel pump relay and had my buddy crank the motor and i grounded a test light to the battery and got a flickering light in the negative side of the injector plug showing that the harness is supplying a proper circuit to each injector

Mr. Z.

I doubt your issue is related to this since your running the 3vze, but I had the same issue after purchasing an '86 22R.
The rig sat for years and had a motor put into it before taking it's place in a barn. It took me forever to find why the thing was running rich. Same symptoms as you describe.
It turns out the fella that put the "new" motor in, installed a Cali. 22R in a Federal truck, so the "smog" parts were not able to "talk" to the ECU. After removing the two Cali. parts, and installing the Federal smog parts, it ran like a champ.
Cheers

maxvp01

Dont sell yourself short! I’m 20, we all start somewhere! I remember I was 17 in highschool and my AC compressor on my honda imploded and the pulley seized on it. Took me 2 weeks to change out everything, now it would take me a day haha.

So TE1 and E1 are in your diagnostic port, same with VF and OX (o2 sensor). There should be a sticker on your diag port cap that has a diagram of which pin is what. If not there is posts on here that have it.

Im assuming you have not checked for codes since you aren’t sure how to jump TE1 and E1. Your scan tool is a paperclip. Stick it in those two pins and before doing the VF test see if you have any codes.

Once codes are checked, and you still need to perform the VF test, you will keep TE1 and E1 jumped, then put one meter lead on a chassis or battery ground, and the other lead on the VF pin. I had to use some homemade jumper wires to perform the test while inside the truck for meter to sit beside me.

As for your injectors, have you put a fuel pressure gauge on the truck at all and see if the pressure bleeds to 0 pretty much instantly after truck is turned off? If it bleeds to 0 you have a leak somewhere. Internally (injectors, fuel pump) or externally (fuel line, crush washer etc.)

tuckerlan

thank you for the response, yes i have checked my codes i did bridge the diagnostic terminals and the check engine light has a constant blink meaning there is no codes. tomorrow I will go and try to preform the vf test and let you know how that turns out. thank you for the motivation to keep trying as well, I rebuilt the engine myself in my garage and it ran great for a couple weeks but im starting to doubt it because i have been trying for months to get it driveable again and so far ive had no success. as for the injectors where should i attach a fuel pressure gauge? and when i test it should the pressure hold after the vehicle is off or does it slowly drop?

maxvp01

Easiest place is to tap into is the cold start injector bolt. The pressure should hold, indicating no leaks.

tuckerlan

I just preformed the vf test and i was pretty surprised to be honest. The vf was pegged at the richest reading which i think means the ecu and all the sensors are reading correctly, cause the ecu senses that its running really rich. When i did the test i had the vehicle at operating temp at idle and when i measured the volts it was 0.04v and i would give it some throttle to about 1700rpm where it wont go any faster it would start to shake and bog the vf measurement would jump up to 2.25v. does that seem right? or is that not how its suppost to react? i suppose the next step is to test for fuel pressure and see if my pressure is too high causing too much fuel to enter or it will tell me i have a leaking injector or something along the lines of that

maxvp01

You did do this test with TE1 and E1 jumped? So you are correct when the ECU senses it’s running rich, the 0V confirms that. The 2.25 is most likely a little off from your multimeter as the website states it falls into the 2.5 category which is “normal”.

Normally an ECT sensor would cause a rich condition where it dumps fuel into the truck like this, but the computer is seeing a VF trim of “2.5” which indicates systems are normal. This leads me to believe the O2 sensor is out of whack, because the feedback isn’t telling the ECU to lean it up at all. (The VF would stay at 2.25 when revving at 1700?)

You said you replaced or tested all the sensors. Which ones did you replace and which ones did you test? What brands did you replace the sensors with?

Also go to your diagnostic port, get truck up to operating temp, and idle. Put one meter lead on OX1 and the other on ground. 900mv or 0.9V is rich, 100mv or 0.1V is lean.

It should be fluctuating from rich-lean-rich-lean etc. and average around 0.5V. Try this test at idle, then try revving at 1,700 like you did before and see what results come from that.

tuckerlan

So when it was at idle the ecu was sensing that it was running rich 0.04v but when i would try and rev it up it would jump to 2.25 for a second and the drop back to 0.025v with the rpm still at 1700. I replaced my ect with duralast, vafm with reman from napa, o2 sesor with a bosch, new oem wire harness, rebuilt oem injectors, new oem fuel pump, and i got a used working ecu from pick and pull. everything else was just tested working. as for testing the ox1 reading i did that yesterday when i did the vf signal i dont know what this means but what it measures is at idle its at 0.88v and when i rev it up it drops to anywhere between 0.25-0.50v

edit: today i went out and re measured the vf signal and today it was different then yesterday. today it was 1.06v at idle then when revved it would drop to 0.04-0.50v. im not quite sure what these readings mean or where they should lead me though.

maxvp01

So the computer knows the engine is rich, and when you rev up to your 1700 and when you hold it there your basically trying to see what would happen when your coasting down the road.. at least that’s how i interpret it..(website says to rev to about 2500 but you say you stall past 1700.)

So we know the engine is running rich no matter what. It knows it’s rich so ECU is cutting fuel by 11%-20% according to the info on that VF website.

The fact you see puddles of gas dripping out the back of the tailpipe is very odd. You have replaced all the sensors, fuel pump, reman injectors, regulator, all of that stuff. Very strange..

1) So you didn’t mention anything about emissions so try unplugging the vacuum line going to your charcoal canister and put a little bolt in the end of the vacuum line. (this will eliminate the charcoal canister being saturated)

2) Check and report back your fuel pressure readings (tap into cold start injector, make sure to replace crush washers afterwards)

3) Get a Denso O2 sensor, the bosch one doesn’t work as well with these trucks, they are very picky.

tuckerlan

yes i agree its a very strange issue and a very annoying one. im glad you agree with the fact that my ecu understands its rich. I picked up a fuel pressure tester on my way home from work tonight and should be able to squeeze in some time tomorrow and will report back then. Thank you maxvp01 you have been super helpful with my questions and I appreciate it.

tuckerlan

okay im back with an update finally. i tried a fuel pressure test and i wasn't able to find the necessary adapter i needed to attach the fuel pressure tester to the cold start injector but i was able to thread it into the port where the fuel pressure regulator goes. it obviously wouldn't give a proper reading of pressure this way because there was no pressure regulator but i at least could see that there was no leaking injectors because the pressure held solid. i then pulled a vacuum on my fuel pressure regulator and it was very finniky, it opened at different pressures each time when tested multiple times. so i went ahead and just replaced it and it ran a little better after that and no longer sprayed fuel out of the exhaust. but the issues are still relevant and it still wont move under its own power. one good thing was i can now rev the engine to about 2,000-2,200 rpm where as before it wouldn't go past 1700 which is one step forward at least. any ideas as to where i can go from here? Thank you

maxvp01

Don’t forget to see what happens when you take vacuum line off charcoal canister

How is your ignition timing looking now? any change after regulator? Check idle screw too, maybe not enough air bypassing aswell, at one point mine was choking the engine pretty bad to where engine flooded out at idle.

This is a step way back, but have you checked to see the condition of your air filter? not clogged or anything? have seen some posts where people tried just about everything and it turns out it was a clogged intake with leaves etc.

Have you messed with TPS at all during rebuild? Not taken off or loosened at all? If you loosened it and “eyeballed” where it went this could cause problems too. Very specific way to “calibrate” it.. I experimented with mine before and it can make the truck run very poorly, one time I even made it so it could drive itself in first at very low rpm. (high rpm ran like crap lol)