Yup. Been running the Denso 234-4056 (from Rock Auto) for 3 years in mine and no issues...
A Super-Ultimate 3FE Diagnostics Thread - Let the Battle of Wits Begin
- Thread starter lelandEOD
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Yup. Been running the Denso 234-4056 (from Rock Auto) for 3 years in mine and no issues...
lelandEOD
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- #102
I'm going to dig into Oxygen sensor operation tomorrow and will report back here.
Good thought but I'm pulling outside air through the snorkel so I don't think heated engine compartment air can be the issue in my case. I think it's still an interesting idea to check the voltages at the ECU with a warm engine so I'll add it to my 'to-do' list. Thanks for the idea!
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Don't be skeptical. A good solid idle will be around 13.5.
14.7 is too lean for good idle quality, and 15.9 way too lean, though it is still enough to keep an engine running.
lelandEOD
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- #104
Kinda frustrated now. I was unable to get a voltage reading between VF1/VF2 and E2 on the check connector or the ECU terminals. I did this test a couple weeks ago and was getting the fluctuating needle on the voltmeter, as specified in the FSM. Not sure what to make of this. The O2s are clearly sending a signal to the ECU because if I unplug them the AFR goes from ~16:1 to ~9:1 pretty quick. When I plugged them back in the ARF gradually went back to ~16:1.
I have yet to play with the wideband on a carbed vehicle - would like to though (to really observe the cause and effect, can’t do much tweaking on the 3FE other than make it run like it’s supposed to). Can you get away with a leaner mixture at light load than at idle? I would think the less load on the engine the leaner you could get away with without having problems? I’ve read a few places 4 stroke gas engines won’t run over about 18:1, and know guys who tune for well north of 14.7 for low throttle cruising speed (LS engines FWIW). I guess that’s where the skepticism came from - but I really should throw a bung for the wideband on my old carbureted pickup some day and turn some screws to learn some more.. (I know it runs rich, but damn it idles nice and starts great when it’s cold!)
My 3FE idled right at 14.7 when hot, I want to say running down the road in OD light throttle was in the low 13’s and floored it was mid 12’s.
Just a double check, jumper from TE1 to E1, meter from VF1,2 to E1, no fluctuations? Unshort TE1 to E1, VF1,2 to E1 no voltage?
You’re doing good work. Keep it up.
Something I didn’t know till recently..all 3 injectors of each bank fire at once. Makes sense why swapping O2 sensor inputs would be dramatic results.
Thinking about the lean condition..the ECU thinks the motor/air is warmer than it is, the throttle signal is open less than AFM indicates it should be, altitude compensation is wrong, O2 sensor data wrong...am I missing anything? What else would cause the ECU to create a lean condition...suppose that’s the root question.
Something I didn’t know till recently..all 3 injectors of each bank fire at once. Makes sense why swapping O2 sensor inputs would be dramatic results.
Thinking about the lean condition..the ECU thinks the motor/air is warmer than it is, the throttle signal is open less than AFM indicates it should be, altitude compensation is wrong, O2 sensor data wrong...am I missing anything? What else would cause the ECU to create a lean condition...suppose that’s the root question.
Please keep in mind that I'm still learning about the EFI system and don't have much experience, but:
Since the fuel and air is still on fire when leaving the cylinder, the farther down the exhaust pipe the longer the fire has to burn, the less fuel remains unburned. Could the early placement of the O2 sensors be tricking the ECU to reduce fuel input because it is seeing too much unburnt fuel? Fuel that would normally be consumed if it had only another 24" to travel before being measured.
Since the fuel and air is still on fire when leaving the cylinder, the farther down the exhaust pipe the longer the fire has to burn, the less fuel remains unburned. Could the early placement of the O2 sensors be tricking the ECU to reduce fuel input because it is seeing too much unburnt fuel? Fuel that would normally be consumed if it had only another 24" to travel before being measured.
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LAMBCRUSHER
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Move those sniffers... they think your too rich, making you too lean. The recalibrate tps, and reset timing. You jump the test terminals but do not adjust idle speed while setting time. The ecu takes care of all of that. The o2 sensors are too close.
Some really great running F series engines don't sound perfect at idle. Idle quality is an aesthetic. A little sputtering from the tailpipe isn't significant. That video shown of the tailpipe sound - sounded the same or better than 96% of the 2Fs I've ever heard - and they've been idling like that for 30 years and 300,000 miles.
The slightly imperfect idle sound from the tail pipe video can't be used as a diagnostic tool to determine whether or not the engine is running well.
Granted, other issues are going on, but I wouldn't give much weight to a slightly imperfect idle.
The slightly imperfect idle sound from the tail pipe video can't be used as a diagnostic tool to determine whether or not the engine is running well.
Granted, other issues are going on, but I wouldn't give much weight to a slightly imperfect idle.
LAMBCRUSHER
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lelandEOD
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- #113
These seem like the most likely culprits!
I corrected my boo-boo from last night and inspected the O2 feedback voltage at VF1 and VF2 on the check connector. Here is a video clip of the voltmeter needle fluctuation I was seeing. Does this look right to you guys?
I've ordered new bungs so I can relocate the O2s further downstream too. Since that will take a while to get done, I'm going to keep plugging away at the FSM diagnostic tests.
Speaking of diagnostic tests... can anyone help me understand the intended procedure for the ECU resistance test (FI-79)? The procedure doesn't make sense to me...
INSTRUCTIONS:
1. Do not touch ECU terminals.
2. The tester probe should be inserted into the wiring connector from the wiring side.
3. Check the resistance between each terminal of the wiring connectors.
4. Disconnect the connectors from the ECU.
5. Measure the resistance at each terminal.
It sounds like I conduct these tests with the connectors connected (checking resistance from the back of the connectors) but then it goes on to say that I should disconnect the connectors from the ECU and repeat the test? This doesn't make sense - if the connectors are disconnected, how can I measure resistance with the throttle valve and measuring plate open or closed. I'm obviously missing something.
lelandEOD
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- #114
Makes sense to me. I didn't know how much farther upstream I had the O2s than the FJ62. I think it will be very interesting to see what effect moving them has on the AFR.
So my confusion is that the timing instructions say to warm up the engine (@650rpm) then jumper the pins TE1-E2. When i do this, my idle drops noticeably. The timing procedure says to adjust to 7° BTDC at 650rpm. If I follow this procedure, I need to bump the idle with the jumpers on TE1-E2 to get it back to 650rpm.
I filmed the exhaust idle just so folks could hear the pop/sputter. (Luckily for you guys) I can't communicate the smell from the tailpipe, but it's almost bad enough to send me running for fresh air (even with the garage door open). The smell also lingers in my nose and sticks to my clothes for a good while after I leave it in the garage too. Yuk.
I think it’s just odd formatting that reads funny. 1&2 you listed are just the notices, I think using the probe from the wire side is just so we dummies don’t mess up the terminals by jamming test probes in there. #3 you listed is the start of the procedure then you remove the connectors and do the checks.
• (Do not touch the ECU terminals)—Translated: WARNING! When the wiring connector is unplugged from the ECU, do not touch the terminals on the ECU with anything!
• (The test probe should be inserted into the wiring connector from the wiring side)—Translated: WARNING! As with all multi pin connectors anywhere, only insert the test lead probes into the wire side of the connector (plug) never insert the test lead to the actual pins in the front of the plug. This prevents bending pins or inadvertently touching wrong pins.
• (Disconnect the connectors from the ECU)—Translated: Step 1. Pull the wiring plugs from the ECU before doing measurements. Do not measure circuits while cable is plugged into ECU.
• (Measure the resistance at each terminal)—Translated: Step 2. After following the instructions above, now you can measure the resistance of the two terminals detailed in the chart below.
• (The test probe should be inserted into the wiring connector from the wiring side)—Translated: WARNING! As with all multi pin connectors anywhere, only insert the test lead probes into the wire side of the connector (plug) never insert the test lead to the actual pins in the front of the plug. This prevents bending pins or inadvertently touching wrong pins.
• (Disconnect the connectors from the ECU)—Translated: Step 1. Pull the wiring plugs from the ECU before doing measurements. Do not measure circuits while cable is plugged into ECU.
• (Measure the resistance at each terminal)—Translated: Step 2. After following the instructions above, now you can measure the resistance of the two terminals detailed in the chart below.
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You got it. The values should be very close to the measurements at each component. So for example if you are reading 2500 ohms at THA-E2 on the AFM, your reading at the ECU connector THA-E2 should be the same with just a little added for the wiring resistance (as long as the temp is the same when you made both measurements).
Are u sure you calibrated your afr gauge correctly? Some afr gauges are a pain to calibrate and some can be calibrated for various different types of fuels so make sure you have the correct fuel type selected. To get accurate o2 sensor readings you will need a digital graph of the voltage wave.
