maxvp01

Have not given up yet, here’s a quick update..

I welded an exhaust system on the truck yesterday to eliminate back pressure being a possible cause, or the o2 sensor getting a false reading from exhaust leak. I put a stock chevelle muffler on it, with some exhaust pipes i cut off my friends dodge dakota (2.25” is what I read is best diameter for these trucks). Hoping it increases MPG at least a little.

I also received a snap on MT2500 brick scanner in the mail from my uncle to attempt to read the ECU. No luck there, couldn’t even pull codes with it. The scanner just lets me enter a code, or shows me diagnostic procedures.

I recently got done rebuilding a camper shell and put this on the truck, surpisingly gained 1 MPG from it. Truck currently averages about 11.9 MPG. (have not filled up since welding an exhaust on it, could possibly be better).

Really starting to think the problem lays within the wiring harness.. Have had issues with the harness before. I have been scouring the internet in search of a replacement, however if it warms up before I find one I might voltage drop each and every wire on the harness with a power probe.

87-4runner

Dang bro... I thought I was persistent!

maxvp01

Did the Vf test today according to the snap on brick scanner (MT2500) and according to information this website:
https://people.well.com/user/mosk/Vfsignal.htm

My scanner’s directions are:
“Run engine at 2500 RPM for about two minutes or until voltage fluctuates. Look for 8-10 cycles of between 0V and 5V within 10 seconds at 2500 RPM: Cycling of Vf Voltage indicates system is in closed loop operation.”

My results:
With TE1 and E1 jumpered, and my meter hooked up to read the Vf signal and revving at 2500 RPM:

My voltage does not fluctuate very fast if any, it will stay at 5V then bog a bit and drop voltage then come back up to 5V. Unsure if that is the fluctuation I am looking for, but if it is, it’s definitely not 8-10 times within 10 seconds.

When idling my voltage sits at a steady 5V. According to that website I posted this means my computer things I am running full on lean, so the ECU is dumping 11%-20% more fuel in it.

When I accelerate slowly the truck stays at 5V

However when I accelerate and let off the throttle I am at 0.136V for a few seconds then move back to 5V. (assuming this is because of decel ?)

This leads me to believe I am in open loop.

My problem lies within a few places I believe. The ECU receives 6 signals to determine the mixture.
AFM (tried a brand new AFM and a used one)
TPS (tried a Beck Arnly and OEM)
ECT (Brand new WVE or Standard)
IAT (within AFM)
RPM (engine speed)
O2 (used a bosch at first, now running denso)

I have swapped all of this out, including an ECU. All with no change

Something MUST not be communicating with ECU, there must be a nicked wire or something that’s telling the ECU false data but not enough of a problem to set a code. Thoughts?


Probably should’ve done the 3.4 swap, but i’m already in this far, i gotta see it through now!

dbittle

I'm with you brother. You've swapped the ECU without changing the way the motor runs, so the ECU is ok. You've fixed all of the sensors and are now confident they are all good. That leaves the harness, and I will testify from personal experience that one broken wire somewhere in there is all it needs to make it run like crap and drive you insane chasing it. Here's hoping it turns out to be just one and that you find it early in the search!

maxvp01

Update:
A member on the forum reached out and actually found a 1989 3vze 5spd harness (exact match) to mine. It was received in the mail a few days ago. There is continuity across all the wires in it, however not going to install it until I voltage drop the entire harness because I want to make damn sure I don’t have to pull it out again lol. Not only that but a frayed wire (3 of 15 strands left) will still show continuity.

On a side note I was browsing yota tech, and stumbled upon a Fan Clutch thread. A member stated a “locked up” fan clutch will drop fuel efficiency possibly by 2 MPG, and can possibly cause the engine to “overcool” therefore keeping the computer in open loop.

So I went outside this morning (40 degrees) and spun the fan clutch with truck cold. The fan was very resistant and stopped spinning as soon as my hand went off. Next I started truck and put a piece of paper infront of the grill, got sucked in from air being pulled (air also whooshing all around the engine bay). I guess the fan “roared” every morning but the exhaust is so loud I guess I never noticed. Oddly enough at operating temp the fan clutch spun a little more loosely than before.

So my fan clutch is bad, ordered one of those today. Will probably put that in before wiring harness to see if that changes anything.

Current MPG is hovering between 11.9 MPG and 12.0 MPG

old87yota

It is actually normal for the fan clutch to be "engaged" during startup, and stay engaged for a few minutes after startup.

Since I cannot see your fan clutch myself, I cannot say if your fan clutch is good or bad.

maxvp01

You are correct.
Just went outside started it, came out 3 minutes later, was able to stop fan with my ice scraper. (temp was cold still on engine).

Turned engine off after I found out fan was disengaged, and it spins half a turn before it stops.

Well thats crossed off the list now. Thanks old87yota!

maxvp01

This is the moment we have all waited for.. did it work..? NOPE! No codes either!

The new wiring harness was installed, soldered new ECT pigtail, new injector pigtails on the harness, voltage dropped the ENTIRE HARNESS. (very minimal drops ex. 0.03V).

I replaced plenum and TB gasket once reinstalled, made sure lower intake bolts were still tight (they were).

Next Steps:
-Homemade smoke machine to look for vacuum leaks. Maybe smoke will reveal more than pinching vacuum lines or carb cleaner..

-I have read a few posts where scope103 recommends a A/F gauge (10 LED lights) for the O2 sensor to see when exactly the truck is rich or lean. Each LED is 0.1V and the O2 has a maximum of 1V. So will see if that reveals anything.

Would any of this have an affect on running rich:
-VERY black O2 sensor and Spark plugs
-NON OEM ECT sensor
-Could the distributor have any effect on rich condition?
-Aftermarket injectors? (although wouldn’t it send a rich code because the computer can no longer compensate?)

Going to attach a couple pictures:

-Idle screw position (you can see how far it’s
screwed in and maybe compare to yours..?)

-amount of carbon in plenum

-cold start injector connector (had to share my frustration. went to pull connector off and the internals came with it, quite a remarkable sight of you ask me, luckily it’s starting to warm up..)

any suggestions at all?? i am starting to run out of ideas to look up on the forum, and ideas to try out!

87-4runner

https://www.yotatech.com/forums/f116...stment-203287/

maxvp01

On my spare AFM I have clicked it to about 10 clicks lean before and it would actually still drive (like absolute crap but it drove, drive it like that less than 5 minutes)

I then had it set at 3 clicks lean and ran it like that up until I switched the wiring harness a few days ago. I currently have my brand new NAPA reman installed. Even at 10 clicks lean beforehand It made no effect to the O2 sensor. :I

dbittle

Wow. I was sure the wiring harness would fix you up. Smoke test is a good idea though.

old87yota

I disagree with adjusting the AFM off of factory specs.

If your engine is stock, and you feel that the AFM needs to be adjusted to "fix" a problem, then the setting of the AFM isn't the root of the problem.

maxvp01

A random thought-
I had a very well known machinist in my town do the machine work and also do the valve clearances.

If the valves were too tight what would the symptoms be? Or is there any easy way to check this?

EDIT: Or did my compression test rule this out?
Cylinder 1- 174.0 psi
Cylinder 2- 164.5 psi
Cylinder 3- 168.5 psi
Cylinder 4- 151.5 psi
Cylinder 5- 169.0 psi
Cylinder 6- 168.5 psi

maxvp01

I made my homemade smoke tester, and found 3 leaks. (a silicone vacuum cap with a pinhole, brake booster line, and the emissions piece that shares the hose with AFM)






I have repaired all 3 leaks, and has not changed the rich condition. I still have a slight rough idle too. But the slight rough idle could be from it running rich.

I tested my FPR yet again, it holds vacuum, and has vacuum going to it. Also bypassed the FPR VSV to see if any difference, no difference seen.

Also changed my timing to 12 degrees BTDC, and replaced spark plugs. Here is a picture of how they looked. Some have odd spots where they burned cleanly, but around those spots is all fouled with carbon.




So instead of an air fuel ratio guage, I was thinking next step is to confirm the aftermarket “CS Performance” injectors they sent me are correct.. I originally wanted to buy some reman ones since my old ones could no longer be used (5 of them damaged where connector plugs in).

I went to buy the original style reman and they offered me a free upgrade to the “newer style denso” injectors used on newer toyota’s. They claimed it had same flow rate and better spray pattern. I got to thinking maybe they sent me the wrong injectors (that look the same) or they never got the flow rate down. I have contacted them by email and they have not yet reached out..

Anyways, I have an idea of how to test this. I am going to make a bench tester to test the flow rates and spray patterns of injectors. I will get a junkyard fuel rail with a regulator on it, buy a cheap rockauto fuel pump to get the desired fuel pressure. I will also use a pulser to make the comparisons extremely accurate. I will do a detailed write up on a new post if it works well.

I have one reman beck arnly injector of the old style (think it’s just a new filter and cleaned), and I will see if I can salvage any of my old original injectors to compare flow rate with that too.

This project may take a week or two to fab up and gather parts for, but I have a strange feeling that injector company isn’t going to reach back out.. This will 100% verify my injectors ARE or ARE NOT my problem.

I have a feeling any part of the EFI circuit is not the problem, hence the no codes and everything being replaced (sometimes more than once). I also know the computer is changing pulse width of injectors (attempting to compensate) from when I scoped the injectors a while back)

Until I fab up my injector bench tester, feel free to shoot some suggestions my way.

​​​​​​​

87-4runner

dbittle

I like the plan. If the junkyard has the injectors that came with the fuel rail and regulator, you might grab them up while you're there if they're reasonably priced. Can't have too many at this point....

maxvp01

Yesterday I mentioned I changed my timing to 12 degrees BTDC. My timing was originally at 20 degrees BTDC from what i’d been running. (TE1 and E1) were jumped out when performing this.

This morning when driving to work (at 12 degrees BTDC) I noticed it hesitated going up a small hill today (first gear) , then I went up a second small hill (second gear) and that hesitated with a lack of power too.

When it did this, it just felt like the engine was lugging, then suddenly around 2000 rpms it cleared up.

Thinking about advancing back to 20 degrees. I feel like it can be advanced more without pinging. I am running 87 octane gas. With ethonol.

(Have checked timing belt two times and it is 100% in tact)

2ToyGuy

From what I have read and understand, that ethanol is lousy for these Toyota engines. They don't get along with it at all. If you can, get off that stuff.

I think the timing is supposed to be set 10° BTDC with the jumper in. It should go to 12° with the jumper removed at idle. Idle being 800 RPM. It should climb fairly rapidly above idle, no jumper. Might be something to look at.

Good luck!
Pat☺

maxvp01

I ended up advancing the timing back to 20 degrees, and the engine has much more power than before. Mine seems to really like the advance, when I retarded the timing, it just felt very sluggish and a noticeable lack of power.

Idle is set at ~850 +\- 50 due to rough idle

I was using non-ethanol for a whole but for how rich it’s running and the rising price of gas, I just can’t justify putting it in the tank, just seems like a waste :/. However when I did use non-ethanol I did notice a slight power increase before. Surprisingly my 93’ lincoln didn’t feel that way when using it.

maxvp01

I am 99% sure I have found the issue.

I was contacted by the injector company by email today saying they were willing to take my old injectors back in and swap them out for the old style.

Today I pulled the injectors and I guess you could say they were running a little rich and leaking. This would also explain my lack of fuel pressure when shut off.

(4 of 6 injectors were cracked and broken at the base).

I guess their “upgraded” design isn’t really the best for this engine.. lol.