CB1100 Idle speed instability problem

[Barkingshins_imp]

I did not get involved with this issue until ~ Dec 3 (just joined the forum a month prior), post #549.

In the beginning, without access to pages of the FSM, inquiries began with general diagnostic questions.

By post 561, thanks to several pages of FSM review, courtesy of a dedicated forum member, we got a bit more scientific.

By post 563, the IACV was looking likely, for Dave's situation, but we had a good team effort going and Max wanted to be sure all else was ruled out, before encouraging Dave to replace the IACV. IACV replacement is a time consuming pain, but it worked.

However, I want to emphasis that the IACV may not be the only idle issue. Pdedse solved (temp or permanent unknown) his issue with a TPS cleaning. One member solved the issue with fixing a damaged wire to the TPS, etc. Research the post by Max regarding TPS calibration.
Basics, per Max's recent post: Key on-rotate throttle full and return, repeat twice-key off.

So, if there is no vacuum leak, start checking battery connections, all sensor connections, then start checking voltages and resistances. Each how-to-check a sensor page in the FSM begins with checking connections.

The ECM (FSM 5-11) controls fueling (injector pulses) based upon input from
MAP (FSM 5-18 & 19)
EOT (FSM 5-21 & 22)
TPS (FSM 5-23 thru 25)
IAT (FSM 5-26 - 27)
IACV (FSM 5-74 & 75)

Post 561:

Suggestions if you experience low/high idle issues:

1. Check for active codes, per page 5-12 & 5-13 of the Factory Service Manual, checking the codes lists on pages 5-15 & 5-16

2. Check for stored codes, per pages 5-14 of the FSM

3. If no codes, then insure that there is no vacuum leak. An unlit propane torch applying propane to intake areas, engine at idle, will detect a leak by listening for a change in idle speed. Check vacuum hoses and fittings, one 4 way (17201-MCJ-003, $7) and one 5 way (17201-MCZ-003, $5.60), then snug all 8 clamps from throttle bodies to intake.

A. Disconnect Throttle Position Sensor connector (engine OFF), clean contacts (contact cleaner available at Home Depot or Lowes, etc.), check for damaged wiring and reconnect. GO FOR A RIDE. If issue persists, continue

B. Disconnect Idle Air Control Valve, clean contacts, check for damaged wiring and reconnect. GO FOR A RIDE. If issue persists, continue

C. Follow TPS diagnostics per pages 5-23 thru 5-25 of the FSM. Note comments in posts 615, 618 & 622, especially see Max's post 632 regarding TPS output test. If output is not 0.5 VDC, loosen fasteners (ignition on, engine NOT running) and rotate TPS to obtain 0.5 VDC, throttle closed. After adjusting TPS throttle closed output, do a throttle calibration with ignition on, engine NOT running, by SLOWLY opening and closing throttle, 2-3 times. GO FOR A RIDE. If issue persists, continue

D. Follow IACV diagnostics per pages 5-74 & 5-75 of the FSM. If OK, then remove IACV, clean IACV port and check for unobstructed travel. If not OK, IACV (16430-MJF-D01) is $119.13 from Honda. GO FOR A RIDE. If issue persists, continue

E. Follow EOT (Engine Oil Temperature Sensor) diagnostics per 5-21 of FSM, particularly resistance value of 2.4 to 2.9 Kohms (2,400 to 2,900 ohms) at 20C / 68 F. If not OK, EOT sensor (37750-KPH-701) is $34.56 from Honda. GO FOR A RIDE. If issue persists, re-check the FSM diagnostics. Note that a faulty ECM is a possibility, albeit rare. The only time I recall a failed ECM on a Sportster, was due to an internal 5 VDC sensor power supply failure.

The EOT (Engine Oil Temperature) sensor and IACV (idle Air Control Valve) are available from Honda. The Honda Rune Forum has posted a TPS replacement for the Keihin JT6H TPS: 16060-MBZ-A11, $114.29 from honda. This is for a 2006 CB600F. The Rune Forum posted that this sensor is a Keihin JT6H, but we have not yet verified compatibility

For non-USA owners, check that the latest ECM program is installed by your dealer.
To keep much of this in one place, here is some more general testing guides:

Code Retrieval
With ignition on or idling, sidestand down, the Malfunction Indicator light (MIL) / Check Engine Light (CEL) will blink a Diagnostic Trouble Code (DTC), if the code is active.
Long blink = 1.3 seconds is a 10 value
Short blink – 0.5 second is a 1 value
Example: 2 longs + 5 short = DTC 25 (does not distinguish between 25-1 or 25-2)
For a stored code, with engine off, under the left side cover, short brown and green wires in Data Link Connector (DLC). With ignition switch on and run/stop switch in run, read code after MIL illuminates once and goes off. If MIL stays on, there is no stored DTC.
The following test condensations are a collaboration by PopGun and SportsterDoc; exclude the use of Honda diagnostics tools, requiring only a multimeter (volts and ohms).
This is a work in progress. At this point, by not utilizing the Honda MCS (Motorcycle Communications System), resistance is available only for EOT and TP sensors. With additional research/input from fellow forum members, we intend to add data to this thread.
Meanwhile, if a code is active and the following tests provide in-spec values, it is likely that the sensor has failed/is failing.

DTC 1-1 MAP (Manifold Absolute Pressure) sensor low voltage or DTC 1-2 MAP (Manifold Absolute Pressure) sensor high voltage
With MAP connector disconnected, ignition switch on, stop/run on, probe connector outside 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.
With ignition off, check MAP output center pin light green/yellow wire for no continuity (infinity) to ground. For DTC 1-2, check for continuity to ECM connector.

DTC 2-1 MAP sensor hose connection
Check electrical connectors and manifold vacuum hose is intact/connected

DTC 7-1 EOT (Engine Oil Temperature) sensor low voltage
Measure resistance of sensor between terminals of 2.4 – 2.9 K ohms at 20 degrees C/68 degrees F.
With ignition switch off, sensor disconnected, check connector pin to red/blue wire for no continuity (infinity) to ground.

DTC 7-1 EOT sensor high voltage
With ignition switch off, sensor disconnected, check for continuity of red/blue and green/orange wires to ECM connector.

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.

DTC 9-1 IAT (Incoming Air Temperature) sensor low voltage
With ignition switch off, disconnect the connector, check pin to green/blue wire for no continuity (infinity) to ground.

DTC 9-2 IAT (Incoming Air Temperature) sensor high voltage
With ignition switch off, disconnect the connector, check continuity of gray/blue and green/orange to ECM.
The only issue I've ever had with a MAP was out of spec voltage output, resulting in pinging on my 2002 Sportster 1200S. It would be at the bottom of my list of possible culprits (unless the vacuum hose is loose, causing a vacuum loss), but here is the check sequence:

DTC 1-1 MAP (Manifold Absolute Pressure) sensor low voltage
Black/yellow wire (common to TPS) junctions to yellow/red to ECM A9
Light/green to ECM B28
Black/green junctions to green/orange to ECM A18

Step one
MCS test (dealer): With ignition one, stop/run on, check for ~0 vdc. If ~0 vdc, go to step 2. If not, diagnose intermittent failure.
Step 2

With MAP connector disconnected, ignition switch on, stop/run on, probe connector outside pins black/yellow (+) to black/green (-) for 4.75 to 5.25 vdc. If ~ 5 vdc, go to step 4. If not, go to step 3.

Step 3
Check continuity on black/yellow to ECM connector A9. If continuity (expect ohms =/< 0.1), replace ECM with known good and recheck. If no continuity, replace/repair black/yellow – yellow/red wire.

Step 4
With ignition off, check MAP output center pin light green/yellow wire for no continuity (infinity) to ground. If grounded, replace/repair light green/yellow wire. If not grounded, got to step 5.

Step 5
Replace MAP sensor with known good unit.
Clear the ECM self -diagnosis memory data.
With ignition on, stop/run on, is DTC 1-1 indicated? If yes, replace ECM. If not replace, MAP sensor.

DTC 1-2 MAP (Manifold Absolute Pressure) sensor high voltage

Step 1
MCS test (dealer): With ignition one, stop/run on, check for ~5 vdc. If ~5 vdc, go to step 2. If not, diagnose intermittent MAP failure.

Step 2
MCS test: With MAP disconnected, then ignition on, stop/run on, jumper black/green to light green/yellow (middle pin). If ~0 vdc, replace MAP. If not, go to step 3.

Step 3
With jumper removed and MAP connector still disconnected, ignition switch on, stop/run on, probe connector outside pins black/yellow (+) to black/green (-) for 4.75 to 5.25 vdc. If ~ 5 vdc, go to step 4. If not, replace/repair black/yellow – yellow/green wire or black/green – green/orange wire.

Step 4
With MAP connector still disconnected, ignition off, check for continuity from light green/yellow to B28. If continuity (expect ohms =/< 0.1), replace ECM with known good and recheck. If no continuity, replace/repair light green/yellow wire.

DTC 2-1 MAP sensor hose connection

Step 1
MCS test (dealer): With motor running, check MAP at idle. If reading changed, diagnose intermittent MAP failure. If not, go to step 2.

Step 2
Verify MAP sensor hose properly connected

Step 3
MCS test: Replace MAP sensor with known good unit. With motor running, check idle speed with MCS. If reading changed, replace MAP sensor. If not, replace ECM with known good unit and recheck.
If all else checks OK, then check the IACV:

IACV testing, per FSM 15-41 & 15.42:

Note: These tests may be done with IACV mounted, by lifting rear of fuel tank and removing right side throttle body cover.

1. After clearing stored DTC, per page 5-14, recheck for stored DTC 29-1. If none, then prior DTC was intermittent.

2. Measure resistance of each of the four wires at the ICAV connector (disconnected, harness side, not IACV side). Continuity to ground should be infinity. If not, the wiring harness has a short to ground.

3. Check continuity to ECM, from disconnected ECM 33 pin to disconnected IACV 4 pin connector
Positions are numbered with locking tab up:
ECM A6 black/yellow to IACV connector postion 1 (left)
A17 black/red, position 2
A16 black/blue, position 3
A7 black/orange, position 4 (right)

4. Measure IACV resistance, (IACV side, disconnected), facing with locking tab up at airbox side (mirror image of connector):
position 4 black/yellow (right)
position 3, black/red
postion 2, black/blue
position 1, black orange (left)
a. black/yellow to black orange (2 outside positions), 99-121 ohms at 77F/25C
b. black/red to black/blue (2 inside positions), 99-121 ohms at 77F/25C
If resistance out of spec, FSM declares IACV faulty

SportsterDoc... holy crap! This will certainly keep me busy for awhile. But seriously, thank you.

One question... have others reported their high idle issues being a clear function of engine temp? Because mine definitely is...

Rather than take the freeway, I intentionally chose a route home from work this afternoon that's usually fairly stop-and-go thinking that it would afford me many opportunities to monitor my idle rate along the way.

At cold start it did the usual 1500 RPM thing but, being 87º in Minneapolis today, by the time I got to my first stoplight, it was up to temp and idling at a respectable 1100 RPMs or so. So far so good. However...

By the 2nd stoplight it had crept up noticeably to 1200-1300. A couple more stoplights later, in the 2 minutes or so that I sat there waiting for the light to change, I was able to actually observe the tach slowly go from 1400 or so up to 1500 and beyond. After a fairly long stretch of wind in my face, sitting at another stoplight, it was back down to 1300 or 1400 RPMs but crawling back up again.

This is probably old news to all of you who have been grappling with similar issues for months now, but this is the first time that I noticed a direct, linear relationship between engine temp and idle rate. From reading other posts here, I was under the impression that it was like a switch was flipped and, BAM!, you're at a 1500 RPM idle that could be temporarily cured with a TPS reset or toggling the kill switch on/off - none of which have ever worked for me.

As near as I can tell, the hotter my engine, the higher my idle rate.

I'm going outside momentarily to begin working SportsterDoc's troubleshooting steps, but just thought I'd add this observation, for whatever it's worth.