Test Clearance between
lever and stop screw Between terminals Resistance / Resistance/
'85-'88* (ohms) '89*-'95 (ohms)
1. 0.00mm (0.000") VTA - E2 200-800 470-6100
2. 0.57mm (0.0224") IDL - E2 < 2.3K < 2.3K
3. 0.85mm (0.0335") IDL - E2 Open / Infinite Open / Infinite
4. Wide Open Throttle VTA - E2 3.3K-10K 3.1K - 12.1 K
5. n / a Vcc - E2 3.0K - 7.0K 3.9K - 9.0K
Table 1: 22RE (2.4L-4 cyl) - TPS Adjustment Specifications
In the above tests, you are actually simulating various throttle positions and rotating the TPS on its base to achieve all the above conditions.
• Test #1 simulates the closed throttle position, with the throttle valve fully closed and the throttle stop lever in contact with the throttle stop screw
• Test #2 and #3 test the transition from idle to normal operation
o Note that the exact feeler gauge values are not terribly important, use the closest gauge you have to the value, or stack two thinner gauges to make one the right thickness. Its unlikely you'll be able to adjust the TPS by hand to 0.001" anyway.
• Test #4 tests the wide open throttle (WOT) setting.
• Test #5 just measures the entire resistance of the outer-most current track seen in Figure 2
On my TPS, I measured a value of 500 ohms for #1 and 5000 ohms for #4 and the other values within spec. By setting the #1 resistance to roughly the middle of the range, the rest of the settings were dead on. One final test, not listed in the FSM, would be to run the TPS shaft from idle to WOT and watch the VTA-E2 resistance and make sure it increases monotonically, no drop outs or dead spots. If you observe abrupt resistance changes, the TPS could have a burned area on one of the current tracks. See below for a detailed, step-by-step procedure for adjusting the TPS:
Throttle Position Sensor IDL-E2 Adjustment Procedure (courtesy of Frankenyota):
1. Loosen both screws attaching TPS to throttle body.
2. Attach multimeter to TPS terminals IDL and E2 (the bottom two terminals on the TPS). You can use alligator clips to make this easier or use small ¼” lengths of vacuum hose to hold them on
3. Insert 0.85mm (22RE) or 0.77mm (3VZE) feeler gauge between throttle stop screw and throttle plate (see picture)
4. Move TPS body CW/CCW until ohms reading on multimeter is infinite (open)
5. Move the TPS body very slowly CCW until you find the end of the resistive strip, the meter will indicate <2.3Kohms of resistance
6. Move the TPS body extremely slowly in the CW direction until the meter goes to open/infinite again
7. Tighten the top TPS screw being very careful not to disturb the adjustment
8. Remove the feeler gauge and insert a 0.57mm (22RE) or 0.50mm (3VZE) feeler gauge
9. The meter should (hopefully) indicate between 0 and 2.3Kohms of resistance, if it does tighten the bottom screw and reconnect the electrical connector, if not go back to step 4 and try again
10. To check whether the adjustment was successful start the engine and insert the timing test jumper, if the idle speed decreases audibly it is working normally.
While the above tests performed at the TPS itself do verify that the sensor itself it functioing, it does not test the continuity of the wiring in the harness that ultimately connects the TPS signals to the ECU. If TPS problems are suspected and the TPS itself checks out fine, then repeat the above tests at the ECU connector pins to verify they are reaching the ECU properly
Symptoms of a bad or mis-adjusted TPS include:
• Varying idle speed
• Hesitation while accelerating
• Poor fuel economy
• Inability to correctly set base ignition timing
o I.e. you jumper the timing check connector and the idle and timing don't change
Seemingly unrelated systems can also be affected by a malfunctioning TPS, including Electronically Controlled Transmissions (ECT). Problems can include poor shifting and hunting between gears due to the engine computer seeing apparent throttle position changes coming from a flaky TPS. Since it is the TPS that tells the engine's ECU that you are idle, if that setting is off, setting timing can be difficult, since insertion of the timing check jumper won't have any affect on the engine.
So, how does a TPS fail? Most likely one of two things will cause a TPS to fail. If you look inside one, you'll see it basically consists of a printed circuit board with a combination of conductive and resistive strips in a circular pattern, over which wiper contacts slide. This serves to generate the various reistance readings at varying throttle positions. The usual failure is for what used to be a low resistance to become an open connection (i.e. infinite resistance or ohms on a meter).
Upon visual investigation, its usually the case that the contact area on the PC board is burnt or dirty, leading to the open circuit reading. Putting too high a current through the TPS circuit (possibly due to a short circuit in the engine wiring harness) could lead to contact burning, but more likely is that a foreign substance entered the TPS and initiated the problem. A common cause of this is using throttle body cleaner in the throttle body without removing the TPS. The cleaner can wick into the TPS via the actuator that rotates the TPS. The cleaner can attach the PC board and components and cause it to fail. If cleaning the throttle body, be sure to remove the TPS, and also try to avoid getting engine cleaner and water on the TPS, its not totally sealed.
When re-installing the TPS, one handy tip is to replace the stock screws with allen head screws, the you can use a ball-headed wrench to access the screws while the throttle body is in place. Another tip for removing the throttle body is that if you keep the radiator cap on and use a bolt to plug the coolant hose that connect to it, there is no need to drain the cooling system as the Factory Service Manual recommends. You may lose a few ounces of coolant, but its no big deal.
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