12-14-2017, 09:51 AM
It may be significant that there are codes for MAP, EOT, TPS, IAT, rear wheel speed sensor, each of the 4 injectors and O2...but not IACV, other than poor connection (DTC 29-1) for symptoms of "engine stalls, hard to start, rough idling".
The IACV is stepper motor operated.
A stepper receives pulses to drive to a programmed position, but provides no feedback to the ECM, for the ECM to know if the position was achieved or not...unlike a servo with an encoder.
I would expect carbon build-up may be a problem with the IACV...more on vehicles used mainly for short trips.
Popgun has a plausible theory about warping in the plastic intake manifold affecting IACV travel.
So, if visual inspection for vacuumn leaks and propane test are negative, no TPS codes 8-1 or 8-2, I would first suspect the IACV and clean it...replace if motor not operating. If no joy, then clean or replace TPS, if available.
I expect that Max was hoping Riko in Belgium had a likely defective TPS to compare with a known good unit or measure resistance per step 3 of FSM page 5-25 at 0.5 to 1.5 Kohms.
Also, since Riko's problem seems to be solved by a new throttle body assembly, which would likely have included a new IACV and a new TPS, we cannot know which one was the issue (or if a vacuum leak contributed), however, cycling the run/stop (kill) switch does cycle the IACV (FSM 5-74) and got it running after the video-documented stall and difficult restart. This may point to the IACV, as well as keeping the TPS as a suspect.
This also does not rule out an EOT issue for some forum members, but that sensor is easy to check (2.4-2.9 K ohms at 20C/68F).
These are basic TPS checks condensed from FSM 5-23 and 5-24 (no Honda MCS diagnostic instrument needed):
DTC 8-1 TP (Throttle Position) sensor low voltage
With ignition switch on and stop/run on, probe sensor contacts to verify steady voltage increase from throttle fully closed to throttle fully open.
With ignition switch off, disconnect the connector, then with ignition switch on and stop/run on, measure voltage between connector pins black/yellow (+) to black/green (-) for 4.75 to 5.25 vdc.
If no voltage, with ignition off, check continuity on black/yellow to ECM connector, for continuity of center pin sensor output black/red wire to ECM connector and for no continuity (infinity) of black/red wire to ground.
DTC 8-2 TP (Throttle Position) sensor high voltage
With ignition switch off, disconnect the connector, measure sensor resistance between black/red and black green of 0.5 to 1.5 K ohms. Then with ignition switch on and stop/run on, measure voltage between connector pins black/yellow (+) to black/green (-) for 4.75 to 5.25 vdc.
The IACV is stepper motor operated.
A stepper receives pulses to drive to a programmed position, but provides no feedback to the ECM, for the ECM to know if the position was achieved or not...unlike a servo with an encoder.
I would expect carbon build-up may be a problem with the IACV...more on vehicles used mainly for short trips.
Popgun has a plausible theory about warping in the plastic intake manifold affecting IACV travel.
So, if visual inspection for vacuumn leaks and propane test are negative, no TPS codes 8-1 or 8-2, I would first suspect the IACV and clean it...replace if motor not operating. If no joy, then clean or replace TPS, if available.
I expect that Max was hoping Riko in Belgium had a likely defective TPS to compare with a known good unit or measure resistance per step 3 of FSM page 5-25 at 0.5 to 1.5 Kohms.
Also, since Riko's problem seems to be solved by a new throttle body assembly, which would likely have included a new IACV and a new TPS, we cannot know which one was the issue (or if a vacuum leak contributed), however, cycling the run/stop (kill) switch does cycle the IACV (FSM 5-74) and got it running after the video-documented stall and difficult restart. This may point to the IACV, as well as keeping the TPS as a suspect.
This also does not rule out an EOT issue for some forum members, but that sensor is easy to check (2.4-2.9 K ohms at 20C/68F).
These are basic TPS checks condensed from FSM 5-23 and 5-24 (no Honda MCS diagnostic instrument needed):
DTC 8-1 TP (Throttle Position) sensor low voltage
With ignition switch on and stop/run on, probe sensor contacts to verify steady voltage increase from throttle fully closed to throttle fully open.
With ignition switch off, disconnect the connector, then with ignition switch on and stop/run on, measure voltage between connector pins black/yellow (+) to black/green (-) for 4.75 to 5.25 vdc.
If no voltage, with ignition off, check continuity on black/yellow to ECM connector, for continuity of center pin sensor output black/red wire to ECM connector and for no continuity (infinity) of black/red wire to ground.
DTC 8-2 TP (Throttle Position) sensor high voltage
With ignition switch off, disconnect the connector, measure sensor resistance between black/red and black green of 0.5 to 1.5 K ohms. Then with ignition switch on and stop/run on, measure voltage between connector pins black/yellow (+) to black/green (-) for 4.75 to 5.25 vdc.