A Super-Ultimate 3FE Diagnostics Thread - Let the Battle of Wits Begin (1 Viewer)

lelandEOD

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Fellow 3FE compatriots,

I’m running into a stubborn problem with a freshly rebuilt 3FE I’ve installed in a '73 FJ40 and want this thread to serve as a case study on the diagnostic tests illustrated in the Toyota 3FE Engine Supplement.

Brief backstory-
The engine I’m working on is the second 3FE I’ve had for this truck. The first was just a runner I picked up at a swapmeet. Since it made good compression, I made the decision to clean up and run it while I sourced a second 3FE that would go under the knife for a proper rebuild. I ran that first engine for almost two years and had constant problems with occasional pinging, suspected lean-running, smelly exhaust, etc. In September 2016, it blew a head gasket as I literally coasted into my driveway. I had pulled my hair out up to that point, trying in vain to figure out what was going on. The exhaust smell always made me think it was running fat, but a spark plug inspection always yielded white looking plugs. I went through several sets of O2 sensors too as I thought it was a sensor-related problem for the longest time. I also changed my fuel delivery system to better supply fuel under load, but nothing solved the smelly exhaust and the dead spot in the mid-rpm band.

After the head gasket popped, I convinced myself the problem was due to excessive oil consumption - it did burn a quart or so between changes and the engine had over 260k on it. My thought was that if the valve guides and/or seals were toast the motor was sucking too much oil into the combustion chamber. I theorized this excess oil was flooding the exhaust with excess hydrocarbons and confusing and/or damaging the O2 sensors. I further theorized that this explained the white spark plugs as the ECU might be trying to compensate by leaning out the mixture – exacerbating the problem and killing the head gasket. (Spoiler Alert: I don’t think this was the case)

Why you ask? Because I now have a completely rebuilt and reconditioned 3FE sitting in the truck and things are not well. I used all new Toyota parts (ever try sourcing NOS "T" marked bearings for a 3FE? - loads of fun). Literally, a full-retard rebuild: all rotating parts magnafluxed, polished, and balanced. Toyota bearings, Toyota rings, Toyota oil pump, Toyota cam gears… The head received new Toyota valves, new seats, guides, and springs by a very reputable ‘cruiser shop. Also, since I had gone through so much frustration troubleshooting the old engine issues, I also installed a fuel pressure sender on the fuel rail and a wideband O2 sensor/controller (downstream from the factory sensors) to make future troubleshooting efforts easier.

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Last week, I topped off the oil, double-checked my connections, solved a ground-fault in the AFM circuit and fired it up - only to discover that it is running EXACTLY like the old engine <Heartbreaking>. It has the same very slight sputter in the exhaust at idle; the exhaust fumes are pungent and very noxious hot or cold and I can hear a slight miss when warm (at idle as well as when it revs). Following the instructions in the FSM, I’ve re-adjusted the valves on a warm engine and set the timing according to the specified procedure.



The engine starts easily. I think I can hear it go from closed loop to reading off the O2s as it warms up and the idle drops. That’s when I can really start to hear the miss in the exhaust pipe. I’ve only driven it up and down the highway a couple times. As I accelerate, I can feel what I would describe as a slight dead spot in the 1,800-2,500 rpm range. Fuel pressure at idle is steady at 34 psi at idle and increases to about 40 psi while accelerating. Also, the Innovative wideband O2 sensor is averaging 15.5:1 air/fuel at warm idle so it is running slightly lean. DANG! The A/F ratio fluctuates while under acceleration but I can say it appears to be rich (~10:1 under acceleration) and goes full lean when I let off (~22:1) before returning to about 15.5-16:1. Double DANG.


This brings us up to now. I’ve decided I need to go back to basics, start from scratch, and begin troubleshooting all over.

Let the Battle of Wits Begin.
 

lelandEOD

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Questions that need to be answered:


-When should the VSV receive a voltage signal?


-This engine is a mix of 1988 – 1992 parts as I have collected and kept ancillary stuff from four engines over the years. Are there issues with mixing AFMs, throttle bodies, and other sensors that may be mixing values that the ECU cannot interpret?

Can the high altitude compensation feature built into the unit be checked for operation? I see no way to check this function provided in the FSM and it doesn't appear to have a corresponding engine code to indicate a malfunction.
 
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lelandEOD

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Knowns:

  • The battery is making good voltage: Ok (12.9v)
  • Ground connections checked from battery post to frame; frame to block; block to tub - ECU to chassis and harness ground points: Ok
  • Spark plugs gapped to: .031” per FSM (NGK BPR5EYs)
  • Plug wire resistance test: Ok; all tested <25k ohms
  • Engine manifold vacuum: Getting 14-15 in/Hg @ idle when warm (@ ~4,500ft/ele)
  • Searched, poked, prodded, plugged, and cursed after any sources of vacuum leaks: none found – will have engine smoke-tested in the near term to completely rule it out
  • ECU is not throwing any codes
  • ECU has been swapped with a spare to eliminate the possibility that it was internally defective
  • TPS has been adjusted, readjusted, tweaked, re-readjusted. I feel at this point it is spot on and can be eliminated from the suspect list
  • New (aftermarket) FPR was found to be faulty - did not hold pressure after shut down - replaced with spare unit and FPR tests within spec now
 
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lelandEOD

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Here's a list of the 3FE Engine Supplement Diagnostic Tests that I believe are pertinent to this problem: Some of them are already yielding results while others have yet to be accomplished. I've highlights the problems I've found in red.




FSM Diagnostics:


  • FI-29 ECU voltage checks. No errors except as follows: THW -E2 (water temp sensor @ 176°) 1.59v (supposed to get .1-1v) (need to conduct water temp sensor resistance test found on FI-73)
  • FI-33 TPS voltage test: Voltage tests Ok, except VTA-E2. VTA-E2 w/valve fully open gets 3.7v instead of 4-6v.
  • FI-35 AFM voltage test: VS - E22 (plate closed): 3.96v (supposed to be 4-6v); (measuring plate fully open): .48v (supposed to get .02-.08v)???
  • FI-36 AFM voltage test: OK (got 1.4v)
  • FI-37 Water Temp Sensor voltage test: Over Volt (got 1.59v @ 176°)???
  • FI-38 Fuel injector voltage test: Ok
  • FI-40 ISC voltage test: Ok
  • FI-43 Check connector O2 sensor ECU voltage test: not yet conducted
  • FI-45 Fuel pressure tests (42.6psi ON w/+B and FP connected; 46.0psi w/FPR vacuum hose disconnected; 40 psi w/FPR connected at idle. ***Update: replaced FPR with a spare and now it holds pressure after shutdown.
  • FI-50 Cold start injector resistance test: Ok - (3.9 ohms)
  • FI-55 Fuel injector resistance test: Can’t perform this until the manifold is removed
  • FI-62/63 AFM resistance tests: Ok
  • FI-64 Throttle body vacuum tests: Ok - no vacuum on R or EGR at idle; vacuum present at other than idle
  • FI-65 TPS resistance tests: Ok; within spec
  • FI-66 TPS adjustment: Ok; within spec
  • FI-67 ISC Operation test: Ok
  • FI-68 ISC valve resistance test: Ok
  • FI-72 Cold start injector time switch test: Don’t think this is a problem as the truck starts easily when cold; must remove air filter housing to access.
  • FI-73 Water temperature sensor resistance test: Checks ok (resistance = 1.85k @ 68°F); will double check at stone-cold and at operating temp.
  • FI-74 Water temperature switch resistance test: (Controls FPR VSV operation): must remove and boil in oil bath to check
  • FI-75 O2 sensor ohmmeter test: not yet accomplished
  • FI-77 O2 sensor heater resistance test: Ok
  • FI-77/78 ECU voltage test: not yet accomplished
  • FI-79 ECU resistance tests: not yet accomplished
  • FI-80 Fuel cut RPM test: not yet accomplished
  • IG-5 Perform spark test: Ok
  • IG-7 Bench test ignition coil: Ok
  • IG-7 Inspect distributor air gap and pickup coil resistance: Ok
  • Verify vacuum tube routing: FPR vacuum routing correct; distributor cap to air cleaner correct; BVSV to Charcoal canister VSV correct.
  • Adjust valves: Ok, adjusted per FSM
  • Adjust ignition timing: Ok, adjusted per FSM
  • Verify function of evap control BVSV and VSV - no vacuum at idle but can feel vacuum when rev’ed. Need to check for no vacuum on cold engine
  • Verify function of charcoal canister: Ok
  • Verify function of fuel pressure VSV: Unknown- no voltage at VSV at warm idle
 
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lelandEOD

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Exhaust temps:


A friend told me to check the individual exhaust runners for temperature variation that might isolate the miss. I used a Fluke IR Thermometer, testing each cylinder, and repeated the test over and over to get a reasonable average of each cylinder (I got some pretty wild fluctuations in temp that I can only ascribe to gas concentration and casting thicknesses on the manifold). The technique I used was to track the peak temp as I waved the IR laser around the exhaust runner between the head flange and point where the manifolds merged. I recorded the peak reading which are presented in this table:


Screen Shot 2018-02-19 at 3.11.03 PM.png




I was hoping to see one cylinder significantly hotter or colder than the others. Rather, what I found seems to be a relatively even progression of exhaust temps moving from front to back, which seems to make sense given that Cylinder #1 is closest to the cooling fan and radiator. It looks like #6 is getting the short end of the waterjacket-stick. Thoughts?
 

60Works

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I have two 3FE's behaving similarly, only worse. The flat spot between 1800-2500 will barely accelerate at all. Once past 2500 it takes off as if nothing was wrong but then overheats. It acts like the mixture is off and by carefully increasing the throttle you can feel it pick up and want to run. Slightly too much throttle and it falls flat on its face. The 1800-2500 is very consistent on both vehicles regardless of gear. In neutral without a load, it revs freely with no dead spot.

On one of the engines I have swapped various known good parts to try and find the culprit. Not only did I swap in parts from a good runner but I installed the removed parts into the good runner to double test. Neither the good or bad engine threw any codes. None of the following parts fixed the bad engine nor hurt the good one:

O2 sensors
MAF sensor
TP sensor
EGR valve

I hope you can solve the mystery.
 
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Definitely need to take a closer look at your AFM, inspect the ohm's as per FSM spec (FI-63) I think that's where I would start. THose can be adjusted by the way, very carefully...this can help with your air fuel ratios....i wouldn't suggest that unless you have a wideband by the way...

Also, TPS will do some weird stuff if you got that out of whack also....definitely need to check that soon
 
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Condition of fuel injectors? Guessing good... have you inspected the harness splices at the injectors? Looked for melting under the plenum? What have you done to calibrate the tps? How about the afm? That tps calibration can be picky...
 

lelandEOD

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Condition of fuel injectors? Guessing good... have you inspected the harness splices at the injectors? Looked for melting under the plenum? What have you done to calibrate the tps? How about the afm? That tps calibration can be picky...


The TPS is an excellent place to start as it’s one of the diagnostics/adjustments that I’m not entirely certain I am doing correctly. I will scan and attach the pages from the factory service manual, but I know I get confused because of the language used. The FSM says to turn the sensor clockwise until the needle deflects (which is one of the reasons why I bought a analog voltmeter - so I can actually watch the needle move).

I don’t get squat on the voltmeter unless I start fully clockwise and move the sensor counterclockwise. Then I see a deflection. I’m just not sure on adjusting it correctly. Whoever designed the throttle body and throttle position sensor on these trucks was a flipping sadist.
 

lelandEOD

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Since I couldn’t buy new factory fuel injectors, I had the set on this truck benched, flow tested, and rebuilt. It’s always possible that one of them is acting up though. I was hoping to see evidence of a spark or injector problem on the manifold temperature readings.
 

lelandEOD

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Definitely need to take a closer look at your AFM, inspect the ohm's as per FSM spec (FI-63) I think that's where I would start. THose can be adjusted by the way, very carefully...this can help with your air fuel ratios....i wouldn't suggest that unless you have a wideband by the way...

Also, TPS will do some weird stuff if you got that out of whack also....definitely need to check that soon


I liiterally have four different air flow meters sitting here. One of them has been opened before but the connections are still good. At some point -if I get desperate enough - I don’t mind tweaking it to adjust the mixture. But for right now, I feel like that would just be masking the underlying problem. I feel like I should be able to figure out why it’s running lean without altering the AFM.
 

60Works

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Is there an emissions component that sends a signal or responds to rpm? I've got to think the 1800-2500 rpm consistency is important.
 

lelandEOD

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Is there an emissions component that sends a signal or responds to rpm? I've got to think the 1800-2500 rpm consistency is important.
I don’t know but I think it’s very interesting that you and I are having the same flat spot. It almost feels like a fuel starvation issue but I’m literally watching the fuel pressure stay right around 40 pounds under acceleration so I doubt it’s a supply volume or regulator issue.
 

red66toy

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Is there an emissions component that sends a signal or responds to rpm? I've got to think the 1800-2500 rpm consistency is important.
Pretty sure the EGR function is linked to RPM in some way. I have read before of a "turbo feeling" kicking in above 2500 rpm when the EGR is malfunctioning is some way. Nevermind
 
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Speedometer kicks out a speed signal, so, yes, speed is a factor. Is your speedo hooked to the cable? Also, you did not mention if you’d inspected the harness...
 
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And I gotta say I think doing the ecu test is worth it. That and did I mention tps being of fairly pretty much up there might be number one culprit type of thing. Might wanna dual that in first...
 

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