Idle has gone nuts

#1 · March 11, 2019, 6:17 pm

Quote from scottyb on March 11, 2019, 6:17 pm
Hey folks,

Issue: Idle changed to erratic, with a lot of variance in rpm, and generally a rough idle.   This occurred at the end of a 30 minute cruise, when I was fine-tuning accels for open throttle lean popping. I got the popping pretty much settled for sudden acceleration, and it idled just fine at several stop lights, very smooth, proud FiTech customer. Upon hitting the home driveway again, idle suddenly went bad – surging and dropping. RPM falls and rises from 400s to the 1300s while its struggling to be smooth.

Set-up: FiTech 30001 / Command Center 2.   432ci Mopar (on 383 block). Cam is Lunati w 224/230 @050, setting is on number 2 with 11in at 760 rpm. Cruise runs 16-18psi on the controller. O2 sensor in header collector, just 2 inches past long tube header, angle is good. Not running ignition control - ignition is stock Mopar two-wire distributor with FBO HR688 12V ECU and Flamethower coil running 12V. Blue wire to coil is steel sleeve shielded up to the FiTech bundle (most of this wire lays about an inch from any bundle). White wire on 12V ignition/12V start. Temp sensor is the one that came in the box, motor runs generally on the cool side. Timing is running 18 deg at low rpm and 37 total (alum heads). CC2 fuel pressure gauge holds steady at 58.

Tuning: The unit has been working pretty well. I had gotten up to fine tuning AFRs, and raised them to 14.1 idle , 14.2 cruise, and left 6000 alone (13-ish). Plugs tan to brown, but looked good and showed timing as a bit conservative. Idle has been well behaved, and IACs can be pretty low, often showing 3 to 4. Starting issues were mostly solved by dropping prime shot to 150, up cranking by 10, and lowering after-starts by 10. This system made the motor smoother and with more torque all around – barks the tires pretty hard in 2-3 shift at 74mph. Cruises quieter, too. Previous, the RPM readings looked like most videos out there, showing variances 100+ rpm while idling smoothly. Did I mention I have been very pleased with the product? After 150-200 miles, and lots of reading the forums, I was making progress.

Debugging this idle issue: Tried smoothing the idle with loop increases, it helped a little, but barely. Lower the low AFR back to 13.9 - deeper tone, a little smoother, but again, a minor effect. Fuel smell is fine, and no obvious richness. Changed idle screw setting (and reset TPS zero), but no luck either. Unplugged in-dash tach from coil, no effect. Snugged the O2 sensor mount, still using the clamps but they seemed good. Snugged unit intake mount bolts for grounding assurance. Clipped on a ground cable from battery to the TB, no effect. Pulled and plugged all the vacuum tubes and PCV one by one to search for vacuum leak, no change effect. Vacuum gauge, no detectable drop from before install. Timing is holding fine. CC2 is venting and runs cool. Measured zero vacuum coming from small rear port on the TB – is that only ported from the back barrels?   Reset software to factory default 198 load, then only changed the prime shot to 150. Reset learn. No effect on the issue, maybe the defaults even amplified the issue.

Suspects?: Bad O2 sensor? Already? The consistency and responses of the data log readings seem to say O2 is OK (but new to me). IAC motor? Bad electrical connection somewhere? Bad MAP sensor?  Unit was purchased in October, and installed in December. All ideas appreciated. Data log Dashboard16 dropboxed. The weirdness is really pronounced at around row 175+ in this file.    Bear in mind it is coming off a reset with only about 15 min idling and revving, but the issue shows in the data.

Thanks again, ScottyB Austin Tx

https://www.dropbox.com/s/9kutlesnk9ixs9n/DashBoard16.csv?dl=0

Hey folks,

Issue: Idle changed to erratic, with a lot of variance in rpm, and generally a rough idle. This occurred at the end of a 30 minute cruise, when I was fine-tuning accels for open throttle lean popping. I got the popping pretty much settled for sudden acceleration, and it idled just fine at several stop lights, very smooth, proud FiTech customer. Upon hitting the home driveway again, idle suddenly went bad – surging and dropping. RPM falls and rises from 400s to the 1300s while its struggling to be smooth.

Set-up: FiTech 30001 / Command Center 2. 432ci Mopar (on 383 block). Cam is Lunati w 224/230 @050, setting is on number 2 with 11in at 760 rpm. Cruise runs 16-18psi on the controller. O2 sensor in header collector, just 2 inches past long tube header, angle is good. Not running ignition control - ignition is stock Mopar two-wire distributor with FBO HR688 12V ECU and Flamethower coil running 12V. Blue wire to coil is steel sleeve shielded up to the FiTech bundle (most of this wire lays about an inch from any bundle). White wire on 12V ignition/12V start. Temp sensor is the one that came in the box, motor runs generally on the cool side. Timing is running 18 deg at low rpm and 37 total (alum heads). CC2 fuel pressure gauge holds steady at 58.

Tuning: The unit has been working pretty well. I had gotten up to fine tuning AFRs, and raised them to 14.1 idle , 14.2 cruise, and left 6000 alone (13-ish). Plugs tan to brown, but looked good and showed timing as a bit conservative. Idle has been well behaved, and IACs can be pretty low, often showing 3 to 4. Starting issues were mostly solved by dropping prime shot to 150, up cranking by 10, and lowering after-starts by 10. This system made the motor smoother and with more torque all around – barks the tires pretty hard in 2-3 shift at 74mph. Cruises quieter, too. Previous, the RPM readings looked like most videos out there, showing variances 100+ rpm while idling smoothly. Did I mention I have been very pleased with the product? After 150-200 miles, and lots of reading the forums, I was making progress.

Debugging this idle issue: Tried smoothing the idle with loop increases, it helped a little, but barely. Lower the low AFR back to 13.9 - deeper tone, a little smoother, but again, a minor effect. Fuel smell is fine, and no obvious richness. Changed idle screw setting (and reset TPS zero), but no luck either. Unplugged in-dash tach from coil, no effect. Snugged the O2 sensor mount, still using the clamps but they seemed good. Snugged unit intake mount bolts for grounding assurance. Clipped on a ground cable from battery to the TB, no effect. Pulled and plugged all the vacuum tubes and PCV one by one to search for vacuum leak, no change effect. Vacuum gauge, no detectable drop from before install. Timing is holding fine. CC2 is venting and runs cool. Measured zero vacuum coming from small rear port on the TB – is that only ported from the back barrels? Reset software to factory default 198 load, then only changed the prime shot to 150. Reset learn. No effect on the issue, maybe the defaults even amplified the issue.

Suspects?: Bad O2 sensor? Already? The consistency and responses of the data log readings seem to say O2 is OK (but new to me). IAC motor? Bad electrical connection somewhere? Bad MAP sensor? Unit was purchased in October, and installed in December. All ideas appreciated. Data log Dashboard16 dropboxed. The weirdness is really pronounced at around row 175+ in this file. Bear in mind it is coming off a reset with only about 15 min idling and revving, but the issue shows in the data.

Thanks again, ScottyB Austin Tx

https://www.dropbox.com/s/9kutlesnk9ixs9n/DashBoard16.csv?dl=0

#2 · March 12, 2019, 7:43 am

It sounds like something has changed when you drove it into the driveway. I've had to change O2, TPS, IAC stepper, but now seems good. Here's what I would do:

1) Look at plugs again

2) If they look different than what your they should look for the AFR reading, bad O2.

3) Make sure your settings haven't changed

4) Look for any wire movement that may have introduced interference

Good luck

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Idle has gone nuts