My 2013 G5 Arrow PCM Idle

[F2V]

I had the Arrow PCM installed at 5100 miles. Since the PCM install, the car idles at what looks like (on tach) 750rpm's on start up ( prior to PCM, idle was 1000 rpms's on start up), and stays at 750 throughout long and/or short haul driving. Presently, the car runs fine without any problem, however I imagine this could be problematic on very cold start ups in winter....although my Viper will never see a winter :-) As an aside, I recall reading on a thread here, where it was said that the car idles at 1000 rpm constant with the PCM...

Anyway, what does your G5 with the Arrow PCM idle at, during start up and at normal driving...and is the PCM idle adjustable? Tks.

[Steve M]

The idle is adjustable, but only if you have the software to do it. Target startup idle RPM generally varies by engine coolant temps (ECT), with higher values at lower ECTs.

That said, startup target idle RPM is generally dictated by one thing: emissions. For a vehicle that has to pass emissions, you want the cats to light off as soon as possible. Generally, you up the idle RPM and pull timing to speed things along. This keeps the EPA happy, and baby seals all breathe a sigh of relief when you decide to wake the dead by starting the 8.4L monstrosity that sits between the front tires of your Viper.

Your Arrow PCM, however, is for off-road use only, so none of that applies. Why waste the extra gas to have a higher idle RPM on a cold start if you don't care about catalytic converter longevity/efficiency?

[Crotalidae]

I spoke w/ Mark about this after my install...it idled at 1k during the relearn process & has now dropped to around 750 all the time...

[ViperGeorge]

On a new Gen 5 the idle stays at 1000rpm for around 500 miles then it drops back to 750rpm. Since the Arrow PCM is new does it assume the car is new and therefore does it set the idle to 1000rpm for the first 500 miles or so??

[Dman]

For me Stock PCM starts at 1000 and works its way down. Arrow idles at 750 all the time.

[JonB ~ PartsRack]

The idle is an 'adaptive' element of the PCM/RCM. Did you have a dealer do the install ? Not required, but a dealer-install procedure includes an update of the adaptives like the throttle-pedal and idle. 750-790 is the OE target for warm-idle and an OE car should reflect that too.

NOTE: The TACH sampling occurs much more frequently on the PCM/RCM, so you will also notice a more responsive tach. So you might just see the normal drop faster?

Great Mod !

[RAY W]

Your stock pcm would have idled at 1000 rpm for the first 500-1000 miles. With 5100 miles your idle rpm should have been down to 750. Maybe you didn't notice it had dropped down. Most people who have installed the Arrow pcm report that the idle goes back up to 1000 rpm for an additional 500 to 1000 miles after the change. Then back down to 750. If the 1000 rpm is necessary for cold weather warm up I would think the computer would read the IAT , water or oil temp and lower it back to 750 when the engine is at operating temp.

[Stealth]

Your stock pcm would have idled at 1000 rpm for the first 500-1000 miles. With 5100 miles your idle rpm should have been down to 750. Maybe you didn't notice it had dropped down. Most people who have installed the Arrow pcm report that the idle goes back up to 1000 rpm for an additional 500 to 1000 miles after the change. Then back down to 750. If the 1000 rpm is necessary for cold weather warm up I would think the computer would read the IAT , water or oil temp and lower it back to 750 when the engine is at operating temp.

The way I look at it, the Arrow PCM is the tune that SRT intended and preferred; OEM is what was required to meet emissions. The car seems happier with the Arrow PCM.

[Steve M]

The way I look at it, the Arrow PCM is the tune that SRT intended and preferred; OEM is what was required to meet emissions. The car seems happier with the Arrow PCM.

Bingo...a lot of the neutering of the OEM calibration was done to satisfy emissions requirements, including federally mandated catalytic converter longevity requirements (8 yrs/80,000 miles). What's even better is that the Arrow PCM still uses a somewhat conservative calibration, so you don't sacrifice engine longevity in the process.

[mjorgensen]

During the initial learning sequence the rotational drag is learned by the PCM, during the A/C on and A/C off run times. If the engine is new or has high drag the PCM keeps the rpms higher until the engine breaks in, this is the same thing as a very cold start when the engine is harder to turn over until it is warmed up.

[Steve M]

During the initial learning sequence the rotational drag is learned by the PCM, during the A/C on and A/C off run times. If the engine is new or has high drag the PCM keeps the rpms higher until the engine breaks in, this is the same thing as a very cold start when the engine is harder to turn over until it is warmed up.

Interesting...since these PCMs use torque-based calculations, this makes a lot of sense. Thanks for the insight.

[F2V]

Thanks for all the input.

However, It has been said a few times above, that the G5 no longer idles at 1000 rpm on start up, after about 500 milles and/or after break in. My 2013 G5 has idled at 1000 rpm's on start up (as originally stated) right up to 5100 miles everytime I cold start. After the PCM install, car no longer idled at 1000 on cold start up. This abrupt and very noticable change is what prompted my post. So what's up...is (or was) my specific car an anomoly?

[DZnutz]

^once the car warmed up did it drop to ~750?

[F2V]

of course, and this process continued from 0 to 5100 miles...well pass any break in period, until pcm install. please read my post today, again

[DZnutz]

well my car currently has ~500 miles on it and it idles at 1000 regardless of temp... so the fact that yours would drop to 750 right from the beginning is strange as well

[Dman]

My '13 has 2350 mis on it.

Stock PCM when hopping in and starting, starts up idle at 1,000 RPM, it then settles down within a pretty short time, like by the time I get out of the garage/driveway. With the Arrow PCM, it starts right to 750RPM whether it's ice cold or 180 degrees on the temp. I believe this is the same as what you're writing. I've felt this was normal. When I've read the stock RPM drops after 500 mis I took it to mean that it hangs at 1000 for the first 500 mis and then after it'll settle after start up cycle, but not necessarily right at start up. Again, mine will start at 1k then drop stock, or start right at 750 with the Arrow. Right or wrong, that's what mine does.

[ViperTony]

Whoever did the Arrow PCM install should be able to help you. If not, why not contact Arrow directly? If anyone can explain the idle, it would be Arrow.

[F2V]

Whoever did the Arrow PCM install should be able to help you. If not, why not contact Arrow directly? If anyone can explain the idle, it would be Arrow.

No problem Tony, just thought the coincidence was strange, and 750 start up in freezing cold weather would be problematic. Also Dman (above) confirms my claim that the 1000 rpm start up lasts much longer than 500 miles or break in.

Now, with that being said here is another pcm 'coincidence'. Prior to pcm install, my day light running lights operated properly. After the install, they would operate intermittently (more ofter off than on), and when they turned on, the dash instruments and screen would go dark...very difficult to see them. I wound up turning them off in settings, to avoid this problem and finding a dealer to deal with.

Don't get me wrong, I'm satisfied with the pcm's improved throttle response, skip shift delete, decel rumbling...as for more HP, gotta wait till back in Florida, as roads in my region preclude power driving, even with the MCS at lowest setting.