Is the flapper in the AFM moving freely?
A Super-Ultimate 3FE Diagnostics Thread - Let the Battle of Wits Begin
- Thread starter lelandEOD
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Haven't opened it, but I can hear it tap shut when you turn off the truck.
Well yeah if it didn't open it wouldn't run. I've been through TPS issues and had crappy idle.. but not a laggy throttle? The FSM and 1988 New Features publication should be top of the list for understanding and solving issues with the 3FE.
I want to adjust the throttle with the FSM but I know that if I open it up and play with it, I'll get the truck stuck in one spot while I wait for parts.
I'd rather have this on hand. If the FPR was any indication of how much one thing can make a truck start and run a ton better, I don't mind throwing $90 at one sensor.
I'd rather have this on hand. If the FPR was any indication of how much one thing can make a truck start and run a ton better, I don't mind throwing $90 at one sensor.
There's a feeler gauge procedure in the manual. I have always just set it so that when you just barely open the throttle, it opens. Just put a meter on it.
red66toy
Supporting Vendor
Nothing to open up and get you stuck adjusting the TPS. Should be an easy procedure with a multimeter. Best to do it on the bench but you can do it on the rig. Just a bit more fiddly making sure the shims are in correctly.
Hey guys. May I suggest two possible causes for the hesitation on acceleration. I ran into the same hesitation when I bought my FJ80. I used to own an auto shop and worked on European and Japanese cars. I had a BMW 740i come into the shop with an off idle hesitation.
The BMW repair solution was to adjust the Throttle Position Sensor. The procedure is to turn the Idle Stop Screw on the Throttle Body about a quarter turn until you can feel or hear the sensor click as the contacts separate. Then loosen the fastening screws for the sensor and rotate it slowly till you hear the contacts reconnect. This will raise the idle speed slightly as the throttle butterfly opens up a hair. You will need to adjust the idle speed back to specifications using the bypass screw on the Air Flow Meter.
The reason for the off idle hesitation is: the air flow in cubic feet per minute at idle is set low at the Throttle Body, and the Fuel Map in the Electronic Control unit is not synchronized to the lower air flow. The adjustment brings the two into synchronization.
The second issue I have seen in some cars with the Bosch K-Jetronic system, used in the 3FE engine, is the Air Flow Meter tends to get out of adjustment in some cars. I used the following procedure to adjust the Air Flow Meter on a Jaguar XJ6.
The Air Flow Meter regulates fuel delivery in the Part Throttle range, approximately 1,200 to 1,800 rpm in most engines.
Attach a High Input Impedance, digital, Voltmeter to the Oxygen Sensor lead off the Exhaust Manifold. The sensor will have to be disconnected from the Electronic Control Unit for this adjustment.
Make sure you have high octane Premium fuel in your fuel tank and your ignition timing is set to factory specifications before making this adjustment. Run a bottle of Chevron Techron Fuel Cleaner before the adjustment to make sure your injectors are clean, no carbon buildup on the injector tips or intake valves which will affect fuel atomization and mixture ratios.
If you are running Premium fuel, not Regular octane, you can advance the ignition timing 2° degrees to improve acceleration and fuel economy.
Always adjust in the following order. Air, Spark then Fuel, because using the wrong order throws the other out of adjustment.
Open the black cover on the Air Flow Meter on a warm engine to gain access to the return spring and toothed wheel connected to the Wiper Arm of the resistance board.
Bring the idle speed up to around 1,500 rpm, and check the Oxygen Sensor Voltage. It should be fluctuating up and down between 0.3 volts and 0.7 volts rapidly, on what is known as the Z-curve of the Oxygen Sensor, indicating perfect fuel delivery. If not, adjust the toothed wheel one tooth in the direction that gets the Oxygen Sensor Voltage in the correct range. Replace the cover.
This will put the fuel delivery at Part Throttle in the perfect spot. Reconnect the Oxygen Sensor and road test. I have used this procedure to get near perfect readings of Carbon Monoxide and Hydrocarbons during California State Emission Tests.
I am assuming no mechanical defects in the engine and correct fuel in the tank.
I have read other posts on this thread and other posters have mentioned the Throttle Position Sensor and Air Flow Meter, however they have not explained how to adjust them for optimum performance. You can have brand new perfect parts, but if they are out of adjustment, the engine will run poorly.
Note: Fuel delivery at Idle and Part Throttle are the smallest amounts over the rpm range of the engine. Therefore the smallest adjustments must be done in very small increments.
I have loved my FJ80 for over 30 years, got 200,000 respectful miles driven with no complaints. I do not drive off road or deliberately maltreat my truck in any way. I have no need for unneccesary driving on rough tracks of any kind to prove a point that is of no use except to shorten the life of the truck's components.
Toyota built an awesome well balanced machine, which needs no modifications or improvements whatsoever. Any attempts to modify the truck will backfire severely, wrecking its reliability and causing breakdowns.
Enjoy your Landcruiser, Toyota built an awesome irreplaceable machine. Happy driving.
ToyotaWeapon
The BMW repair solution was to adjust the Throttle Position Sensor. The procedure is to turn the Idle Stop Screw on the Throttle Body about a quarter turn until you can feel or hear the sensor click as the contacts separate. Then loosen the fastening screws for the sensor and rotate it slowly till you hear the contacts reconnect. This will raise the idle speed slightly as the throttle butterfly opens up a hair. You will need to adjust the idle speed back to specifications using the bypass screw on the Air Flow Meter.
The reason for the off idle hesitation is: the air flow in cubic feet per minute at idle is set low at the Throttle Body, and the Fuel Map in the Electronic Control unit is not synchronized to the lower air flow. The adjustment brings the two into synchronization.
The second issue I have seen in some cars with the Bosch K-Jetronic system, used in the 3FE engine, is the Air Flow Meter tends to get out of adjustment in some cars. I used the following procedure to adjust the Air Flow Meter on a Jaguar XJ6.
The Air Flow Meter regulates fuel delivery in the Part Throttle range, approximately 1,200 to 1,800 rpm in most engines.
Attach a High Input Impedance, digital, Voltmeter to the Oxygen Sensor lead off the Exhaust Manifold. The sensor will have to be disconnected from the Electronic Control Unit for this adjustment.
Make sure you have high octane Premium fuel in your fuel tank and your ignition timing is set to factory specifications before making this adjustment. Run a bottle of Chevron Techron Fuel Cleaner before the adjustment to make sure your injectors are clean, no carbon buildup on the injector tips or intake valves which will affect fuel atomization and mixture ratios.
If you are running Premium fuel, not Regular octane, you can advance the ignition timing 2° degrees to improve acceleration and fuel economy.
Always adjust in the following order. Air, Spark then Fuel, because using the wrong order throws the other out of adjustment.
Open the black cover on the Air Flow Meter on a warm engine to gain access to the return spring and toothed wheel connected to the Wiper Arm of the resistance board.
Bring the idle speed up to around 1,500 rpm, and check the Oxygen Sensor Voltage. It should be fluctuating up and down between 0.3 volts and 0.7 volts rapidly, on what is known as the Z-curve of the Oxygen Sensor, indicating perfect fuel delivery. If not, adjust the toothed wheel one tooth in the direction that gets the Oxygen Sensor Voltage in the correct range. Replace the cover.
This will put the fuel delivery at Part Throttle in the perfect spot. Reconnect the Oxygen Sensor and road test. I have used this procedure to get near perfect readings of Carbon Monoxide and Hydrocarbons during California State Emission Tests.
I am assuming no mechanical defects in the engine and correct fuel in the tank.
I have read other posts on this thread and other posters have mentioned the Throttle Position Sensor and Air Flow Meter, however they have not explained how to adjust them for optimum performance. You can have brand new perfect parts, but if they are out of adjustment, the engine will run poorly.
Note: Fuel delivery at Idle and Part Throttle are the smallest amounts over the rpm range of the engine. Therefore the smallest adjustments must be done in very small increments.
I have loved my FJ80 for over 30 years, got 200,000 respectful miles driven with no complaints. I do not drive off road or deliberately maltreat my truck in any way. I have no need for unneccesary driving on rough tracks of any kind to prove a point that is of no use except to shorten the life of the truck's components.
Toyota built an awesome well balanced machine, which needs no modifications or improvements whatsoever. Any attempts to modify the truck will backfire severely, wrecking its reliability and causing breakdowns.
Enjoy your Landcruiser, Toyota built an awesome irreplaceable machine. Happy driving.
ToyotaWeapon
Interesting process you use to dial in the AFM, given the 3FE's AFM wasn't designed to be end-user adjusted, as opposed to the TPS (to a degree). When adjusting the TPS I've always followed the procedure outlined in the FSM and then verified it's adjusted correctly with the procedure outlined just prior to the adjustment procedure. I assume this is what you mean when you reference something being adjusted for "optimum performance"; ie adjusted to the parameters that they were engineered to operate within.
I've always been leery of just haphazardly adjusting the AFM like many have done on the 3FE and the 22RE after installing an enlarged throttle body, so I didn't bother even touching my AFM when I put one on a few weeks ago. I'm curious now to put a meter on the O2 sensor connectors (maybe just one? maybe both?) to see if I get that 0.3V - 0.7V fluctuation at 1500 RPM when warm.
Ideally, I'd like to put a wideband O2 sensor just downstream of the exhaust Y-pipe to better monitor my air/fuel ratio, but it seems that if you're at least starting out close, a narrowband sensor could also tell you if you're dialed in or not, just without the ability to se the full range of changes under differing throttle and load conditions. Would this be an accurate presumption?
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