tuckerlan

My ignition timing is at 10 degrees btdc it checks out good i just went out and check that. My air filter has been recently replaced and isn't clogged(if only that was the issue that would be too easy), i have never touched my idle screw so i can assume that it is fine, but is there a way to check that? But i did remove my tps when i did my rebuild but if that was mis calibrated wouldn't it have been bad the first couple weeks i drove it, how would the adjustment go bad while driving? I do notice that it runs really well if i reset the ecu and it would probably even be drivable but after about 10 minutes of idle it has the same issues as before is there anything that slowly gives the ecu signal? ect?

Edit: i did notice my negative battery cable looks a little frayed where it connects to the battery could it just be something as simple as a weak ground not giving good power to the ecu?( just ordered new battery terminals). Also the vf signal is different now at idle its 0.03-0.04v and when given throttle it jumps up to 3.75v should is it possible that its getting leaned out somehow when given throttle?

2ToyGuy

Remember, the "real" idle adjust screw is under the big cover screw. The thing you usually see when looking at the TPS.
You can check the IAS, or more likely the o-ring on it, but you have to pull it out. Remove the cover screw, then screw the IAS in until it bottoms out. counting the turns, including fractions of turns very carefully. Then unscrew the IAS all the way out. If it's factory, there's a good chance the o-ring is dry and brittle. They only last so long, after all.

You can get the o-rings everywhere. Usually in sets of o-rings.
Put a light, thin layer of Vaseline or silicon dielectric grease on the o-ring when you put it on. It will seal better, and make the rubber last a lot longer. Screw the IAS all the way down, then back it out to the count you had when you removed it. That will be CLOSE. Put a tach on the truck, don't rely on an in-truck tach, use an external tach. They're cheap, and readily available. Then set your idle with the IAS once the truck is good an warm.

Frayed battery terminal wire connections, positive OR negative, can cause all kinds of mysterious problems that can't easily be found. Well worth repairing or replacing. I recommend going to Marine Terminals on the battery, then cut the end off the cable that goes to it, slide some melt-wall heatshrink on, and crimp on a good sized ring terminal. Shrink down the heatshrink, making sure the inner liner melts down completely. Then, the terminal will slip onto the Marine Terminal easily, and remove just as easily. It also keeps the acid mist out of the battery from getting inside the insulation, and corroding the wire, with no external indication. As more and more strands break, less and less current can flow. As the wire flexes with motor and vehicle movement, it can cause problems to come and go.

Good luck!
Pat☺

tuckerlan

I pulled the IAS out of the vehicle and it was all gummed up and dirty as well as it had a broken o ring. I went in and cleaned it all out and replaced the o ring and got the idle set but unfortunately it didn't fix the issue. But i did measure my vf signal again but i tried to cause a lean condition by removing the brake booster vacuum line while the engine was running and the signal jumped right to 3.85v when i did that so that tells me that my ecu is reading correctly or i can at least assume so. that means it probably has to be something mechanical right? like a vacuum leak or something wrong with the fuel system? so what would or could cause the ecu to read that its rich and not be able to compensate? im not gonna give up on this 4runner any ideas are greatly appreciated thank you

maxvp01

Don’t forget to take vacuum line of charcoal canister, need to eliminate the evap system as the culprit. Just put a small bolt or screw in the vacuum hose you take of when performing this test. The engine actually sucks in fuel vapor from this point, if the canister is saturated it’s possible your sucking in raw gas. When you pull off vacuum line there shouldn’t be any fuel dripping out of it.

If you had a vacuum leak the engine would most likely be running lean, you also had the truck spitting raw fuel out the tailpipe at one point so I think it’s safe to say your still running rich. However if you did want to double check your vacuum lines this is the picture I use:




If installed incorrectly it would’ve been bad the entire time yes, you can drive with it mis calibrated but it will tell the computer the wrong position your gas pedal is at. You need to do this adjustment with a feeler gauge and a multimeter, easiest to do with the throttle body on a bench. This is a very precise adjustment.

tuckerlan

Okay i will try disconnecting that vacuum line, im assuming your talking about the line that goes from the charcoal canister to the TVV. I will also check my vacuum line routing, i have the egr deleted at the moment but thats been off and was running fine for months with it off prior to the rebuild. Im also noticing my engine backfires sometimes way louder then the rest its so loud it sounds like a shotgun going off in your ear its weird though cause when it does that it sounds like its coming from the engine bay not the exhaust. I will also check my tps i have a hanes manual and the ohm readings were all in spec ive measured them mulitple times. But where do i put the feeler gauge my manual doesn't state clearly where do do so.

tuckerlan

Okay i have an update on the 4runner, i noticed when i had the timing light on when the vehicle revved up it would go all crazy so that made me think to ohm out the coil. So i went and tested the coil and the readings were wayyyy off so i replaced it and it runs 60% better, it idles and purrs and can rev up now but it still backfires and sputters half the time. should i replace my ignitor as well? im certain its the original. i also measured my tps resistance and that checked out all good. if anyone knows anything else i should try on my ignition system let me know. it seems my car has multiple parts wrong at once which makes me believe my old harness shorted all my electrical out

tuckerlan

Is there supposed to be a difference in ingition timing when the diagnostic port is jumped because when i connect my timing light without the jumper wire installed and compare it to when my jumper wire is installed the ignition timing reads exactly the same? and if that is the issues could it be a bad distributor? faulty ecu? still haven't ruled out why its running rich, i dont wanna have to buy another o2 sensor, does it really make a difference having a brand new bosch o2 sensor over an new denso sensor? same goes for the coolant temp sensor should that be denso or is autozone brand sufficient? after replacing the fuel pressure regulator ive dialed in the fact that it gets progressively worse as it gets warm which leads me back to the ECT or the O2 sensor.

2ToyGuy

The sensor, both of them, should be Denso. Bosch is designed for European cars, Denso is for Japanese vehicles. Never the twain shall meet.
Yes the Bosch stuff SAYS it fits/works like OEM, but it doesn't. Some Bosch items might fit the hole perfectly, and even function within tolerance, for a while, but the truck is designed to use Denso sensors, and they send the correct information to the ECU. The Bosch sensors send information, but usually it's not exactly the same, nor is it exactly correct. For your truck. Works great on European vehicles, though

Have fun!
Pat☺

tuckerlan

oh jeez okay i will now start looking for new denso sensors i suppose. Is there any other sensors that have to do with the air/ fuel mixture being rich that i should look into before replacing those other sensors again? it seems to run alright when cold not perfect but its also a 3.0 so you cant expect much suppose, but it progressively runs richer and richer as the temp gauge gets higher and higher, its so rich that there is fuel in my oil and my plugs are extremely black. but i also shouldn't rule out my ignition ignitor or distributor because it runs way less rich after a new ignition coil which is extremely confusing to me. Is there anyway to test the ignition ignitor? ive read into it a bit and cant seem to find any real answers on how to test those.

Edit: i also tried disconnecting the vacuum line to the charcoal canister from the TVV and put a bolt in it and the line was dry and there was no fuel in the line. Also is there any way to test the ECU because my car has had several problems over the last year ive owned it and has never once thrown a check engine light. i cant get it to throw one even if i try, ive disconnected sensors that shouldve thrown a code but havent. but if i swap my ecu to a different one i have the check engine light comes right on for code 27, meaning the new ecu i have is for a california vehicle out of a different year but it still shows that my CEL ligths up and my diagnostic system works.

maxvp01

I could be wrong but these sensors effect A/F ratio and the open/closed loop status:
-O2 sensor
-ECT
-AFM
-IAT (built into your AFM)
-TPS
-RPM affects as well but that’s tied in with TPS

Not really sure there is a way to test the igniter module, just the coil. I had that go bad on my lincoln and basically I couldn’t start the car it just kept turning over. But then again that’s a ford platform, could be different with toyota.

To force a code just unplug your ECT, that SHOULD set it. My wires broke off mine one time and it set a hard code. However I have forgotten to plug in my AFM before and it set a stored code for the AFM and IAT.

Don’t unplug them with vehicle running, unplug with vehicle off, could short something out.

Best way to test the ECU is to back probe the wires under it when performing certain tests. That basically tells you if the ECU is receiving the right signals, and verifys wiring harness’s integrity. There’s a page in the FSM about it under the EFI section.

Basically there’s no way to test the ECU itself, you have to test everything to it. If all that is good then it’s most likely your ECU. However you have had two ECUs and I highly doubt that’s your issue, but it very well could be.





Luckily I have the pictures of it stored in my phone! Good luck!

maxvp01

Forgot to add this-
I have been making a list of everything that can possibly cause a rich condition while trying to solve my own rich condition. Maybe this list can help you out:

EFI Circuit:
-ECU
-Wiring Harness
-AFM
-IAT
-ECT
-TPS
-O2

Mechanical:
-Fuel Pressure Regulator
-Injectors
-Blockage in fuel return
-Tight Valves (I think this may be a cause but I am not 100%)
-Vacuum Leak
-Exhaust Leak (Before O2 only)
-Spark
-Timing (Belt and Ignition)
-EVAP

Im still brainstorming the list but this is what I have so far. There could be more

tuckerlan

Thank you for all the good information, I finally figured out the issue today. So it was running rich because it had a bad distributor housing, very weird and very rare issue. So the distributor shaft somehow was slightly bent and it was giving it a very weak and inconsistent spark causing it to run rich by not burning the fuel properly, and it would studder at higher rpm because the spark could not be produced strong enough and fast enough to let it run past a certain rpm. Also it explains why the ignition coil made a big difference because it was probably weak from age and heat and when i replaced it with a newer stronger one it allowed the spark to be stronger which is why it revved higher but still not enough to fix the issue. weak spark also explains why my runner didn't shoot black smoke and it sprayed raw fuel instead because it wasn't burning it all. Maxvp01 maybe you should check your distributor and or ignition coil that could be why your pickup is running rich even after you've done all that work to it, i wish you luck with yours and i appreciate all the ideas you gave me.

maxvp01

Glad you figured it out, thanks for posting your solution too.

I’ll have to check that on mine. Yours must’ve gotten bent somehow during the rebuild.

2ToyGuy

Thanks for letting us know!
Pat☺

tuckerlan

Turns out im still running rich at the moment i measured the vf signal today after driving it to Tahoe and back because it seemed really sluggish and smelt like fuel. i Measured it and it was at 3.76v which is sensing that its on the lean side and adding fuel so im probably gonna start with putting a new denso ect in because i believe my autozone one might be the culprit. Ill make sure to update the results from that. when at idle its a little choppy and as soon as it hits 1500 rpm it jumps directly to 2000 i cant keep the rpm within that range its either below or above. But past 2,000 rpm it runs like a dream. but i assume since the a/f ratio is only that slightly off it has to just be the fact that my sensors arent oem replacement.

maxvp01

TPS incorrectly adjusted or out of spec?

Will cause a rough idle and weird acceleration, by “past 2,000 RPM” it might sense WOT or once you get passed 3,000 RPM it goes into open loop mode and no longer reads the sensors therefore running better.

Would definitely look at TPS first. That can also cause a rich condition.

2ToyGuy

+1 on the TPS.

Note: OEM is ALWAYS the right replacement part. Toyota engineers were pretty good in their day. Not the electrical engineers, but the mechanical ones knew their stuff.
Just consider how long even the first gens last, and their resale value. They're worth it too.

Keep using OEM. Maybe more expensive, at first, but consider the cost-per-mile. You've got an OEM part that lasted 30+ years and 300,000+ miles. Do you think a cheapo aftermarket do that? I don't. Just me, though. Your choice

Pat☺