Warmed Engine - Idle start high

[DonMaximo]

I'm trying to understand WHY my idle runs so fast for so long when the engine is hot (190+ F).

According to the log, I spend very little time in Crank mode (engine=3) and then in ASE mode (engine=5). Yet, the idle runs high (2000+) for at least 5 seconds, which seems like an eternity.

Crank-to-run-taper was and still is at 2 seconds.

Just now, I reduced the ASE taper from 20 down to 5 for (CLT > 180F), which is the lowest allowable value. I will test this tomorrow.

Any additional thoughts or considerations ??

TIA,
-D

[Matt Cramer]

Try adjusting the MAT correction at 180 degrees.

[DonMaximo]

Unfortunately, this has not helped.

I approached this incrementally, reducing the air correction by 10 points. As you know, I must adjust/rebuild the VE table with every change on the air correction. So, as I reduce the air density value, I must increase VE values.

I went through this iteration 4 times until the values in my VE table were exceeding 225 (MAX=255), basically reducing all air correction by 40 points (~50%). I cannot change this setting anymore without compromising VE table and operation.

Despite these attempts, the engine still revs up high and long following hot starts.

This seems to have had little effect on the warm start behavior, so I'm almost inclined to return air correction to less the 20 points from the Base Tune you provided for this 1992 Mustang 5.0 PNP configuration and rebuild the VE table.

Until I get this issue fixed, I'm really constrained from getting to the next level of tuning (ie. AE).

Any help would be appreciated.

-D

[DonMaximo]

Additional DL & observations

I went out to lunch where engine was off ~30 minutes. When I started engine, the RPMs were not as high and it settled into idle more quickly than earlier.

After driving for several minutes, I stopped at a convenience store where engine was off for ~5 minutes. Upon restart, she revved higher and longer again.

[elutionsdesign]

Tune your idle valve. Excessive rpm at idle isn't due to fuel, it is due to air, get the idle valve to respond correctly and you'll be fine.

[DonMaximo]

Tune the idle valve ???

When engine is warmed and running, I have no issues with the idle valve or idle for that matter.

The problem only exists for several seconds at startup. Anyone around the car at hot startup, soils their pants, including the occupant.

Which specific area or setting(s) are you referring to ??

[elutionsdesign]

Look at your tune dude, you've got your idle valve set to inverted, 100% = off, that means 0% = fully open. Look at your duty cycle vs. temp graph, when its hot it is set to 2 which is fully open. Look at your datalog, when you started the car hot the valve was 0 then moved to 2 like it should. What I don't know is why the idle came down as the duty cycle stayed at 2, you obviously have something more going on physically with the idle valve/throttle body/intake plenum. Again, high idle is all about too much air flow, excessive timing at idle doesn't help either but its primarily air flow.

[DonMaximo]

First off, I sincerely appreciate you weighing in on this issue and helping me out.

I'm using the MSPNP for the Mustang 5.0.

This is not the first time someone, in the interest of helping me, has noted that the PWM valve setting is inverted. The gents at DIYAUTOTUNE have repeatedly said that it needs to be this way for the Ford and/or MSPNP unit. So unless they report otherwise, I really should leave this setting 'AS-IS' and as they recommend. Sometime back, I did try changing this setup, but it only created more problems than resolutions.

In the datalog, I see that the PWM Idle Duty is constant at 2.

The DutyCycle % however, is quite elevated at startup. During Hot Startup, this value reached 8.7 before eventually falling down to 3.2 where the engine idles nicely. If I could better understand what factors effect this measure, I may have something to pursue. I'll try changing PWM Idle Crank-to-run-taper time to 0 (from 2), but I'm not optimistic as the high idle event lasts 3-5 seconds in the datalogs.

I've also received the following advice that I will try first:
Try reducing your timing at 2000 and 2500 RPM at 45 kPa and less by 5 degrees

After reviewing the datalog, I can rationalize and understand this recommendation. I'll follow-up later.

Thoughts ??

[Matt Cramer]

Duty cycle is the injector duty cycle - it increases with pulse width and RPM.

[DonMaximo]

I've adjusted the timing, but the gremlin still exists

Reminder:
Warmed idle is fine and general Non-AE functions seem very good. Car is a joy to drive, even without AE at this time.
Warm startups for the first several seconds run high and too long and this is what I'm trying to adress.

For this latest tune, I made the following adjustments:
1) Crank-to-Run taper was reduced to 0 seconds (from 2 seconds)
2) Timing for a few VE cells at 45Map or less, between 2000-2500 RPM, was reduced by 4 degrees.

Thoughts, ideas, suggestions ???

[billr]

Your MAT correction table is seriously "non real", you might need to bring that back to reality and retune.

[elior77]

try to run the pwm valve test and see what % gives you what rpm.

your crank duty is 25 while your warmup duty is 50, you should have crank duty higher then warmup duty.

Check the valve test and report back.

[DonMaximo]

billr: I put the air correction back to the Base tune settings provided with this Mustang 5.0 PNP device. I then returned to the road to autotune the VE table again. As expected, big changes were needed and I still need to adjust values above 5K RPM.

Elior:
I performed the PWM valve test, but I could not find documentation that helped me understand the value of this testing.
When Not enabled, my PWM Idle Duty is fixed at 2. I would repeatedly enable test mode and I set idle duty % to, 5, 10, 15, 20, 25, 30, 35, and 40.

Using the datalog, I made an effort to compute Average RPM for each of these Test Settings, but this information seems meaningless to me at this time:

Idle Duty AVG
Pct RPM
---------- -------
2 1036
5 1035
10 1065
15 1038
20 1071
24 1064
30 1081
35 1050
40 1033

I hope someone can help me understand what to do with the information gleaned from the Idle Valve testing.

Regarding Crank duty v.s. Warm Up, if you look again, you'll see that I changed Crank Duty down to 0 above 175F. The Prior tune has been setup this way as well. Again, the intent of this change was to reduce enrichment at/with Hot Starts.

Thank you

[elior77]

Your valve does not move.

- Are you sure your valve is pwm 2 or 3 wires ?

The valve test show you have no control of the valve or the valve is not operational.

Address it first.

[elutionsdesign]

elior77 is correct, your idle valve is flapping in the wind which explains many things. Bottom line, if you change idle duty cycle and the idle rpm does not you have a mechanical/electrical issue.

[DonMaximo]

Really great information guys ! I've called and ordered a Borg-Warner replacement which I can pickup by tomorrow morning.

For giggles, is there a way to bench test this valve and/or the new one to ensure proper function ??

[elior77]

same way

be sure you choose the right valve pwm or stepper

[Matt Cramer]

For giggles, is there a way to bench test this valve and/or the new one to ensure proper function ??

Most Ford valves only open when vacuum is applied, making bench testing a bit of a pain.

[DonMaximo]

I replaced the IAC valve and the Hot Start issue is gone !!

Under Idle Warmup duty/steps however, I had to set the Idle PW to 40 in order to keep a decent idle going.

I wanted to check with you guys if this seems appropriate for a naturally aspirated motor. This number seemed disproportionately higher than the 302" Base tune (My engine is 363")
If you find this number is fine, then I'll adjust the remaining Colder values accordingly.

In addition, my startup seems almost too soft now (I'm not complaining <wink>). Instead of jumping to something like 1200 RPMs for a second, the engine seems to start at 600RPMs and gently climbs.
I casually messed with Cranking, ASE, etc settings, but I've not studied the subject very close yet. If you see something conspicuous in the DL, please let me know. I'll attempt to put more time into the review tonight.

This is a significant milestone and I'm very pleased with the results. Great thanks to those of you who weighed in. It's much appreciated.