Intermittent strange high idle.

[Marcus2000monster]

I have noticed recently that sometimes upon cold start my truck will idle at 900rpms instead of the usual 825 rpms. Iv also noticed that when accelerating I can seemingly feel dead spots in the pedal at times. Could my apps be going out? I can rev the truck and it will still idle high but when put in gear and driven and stopped it’s back to 825. Thoughts? Also I had a P0336 come up and replaced the crankshaft sensor with a Napa part and code went away along with the symptoms so that’s out of question. 

[Marcus2000monster]

^{Any input?}

[Dieselfuture]

Gremlins 

[Marcus2000monster]

8 minutes ago, Dieselfuture said:

Gremlins 

Never thought of that! 

[Dieselfuture]

Could be a gasket between the seat and a steering wheel

If ECM is in control at idle, then who knows a loose wire connection, Gremlins inside the ECM, them little bastards are hard to catch sometimes

Edited November 27, 2018 by Dieselfuture

[Marcus2000monster]

6 minutes ago, Dieselfuture said:

Could be a gasket between the seat and a steering wheel

If ECM is in control at idle, then who knows a loose wire connection, Gremlins inside the ECM, them little bastards are hard to catch sometimes

Hahaha! 

[Mopar1973Man]

High idle is typically because someone has been playing with the APPS voltage and attempting to adjust to match the tag on the stock APPS sensor. 

 

 

Another thing that affects idle is ECT coolant temperature. The COLDER the coolant the higher the idle. You can verify this by a live data tool and check the ECT values.

Edited November 27, 2018 by Mopar1973Man

[dripley]

Mine is acting the same way. On a warm engine when coasting to a stop it will idle at 900 rpm, right when I cross about 6 mph slowing down it will drop to abot 825. I had a dose of this about 10 years ago and it just stopped doing it. I dont have clue as to what it is but mine has been doing for about year this time. 

 Damn Gremlins!!

[Mopar1973Man]

5 minutes ago, dripley said:

Mine is acting the same way. On a warm engine when coasting to a stop it will idle at 900 rpm, right when I cross about 6 mph slowing down it will drop to abot 825.

 

The high step just before stopping is normal even my truck does the same thing. 

 

Now like the 820 RPM part is most likely the pop pressure of the injectors getting too low. This advances the timing of the injection event and tends to slightly increase idle speed. Like even my truck is starting to creep up in the idle speed because the injector pop pressure is starting to fall off. The next step I'm watching for is the misfire at idle warm and the injectors are now below 250 bar. That's what happened to my RV275 I had long ago I got from @cajflynn used. 

[Guest 04Mach1]

I thought my 01 was going to blow up this morning. Thermometer on the porch said 3*F. I started my truck which was normal then went to high idle for a few seconds and then bam... 3 cylinder high idle which sounded scary at first. It's the first time I've heard 3 cylinder high idle since using the Smarty. This will be the second winter with the Smarty.

[Marcus2000monster]

Iv never touched the APPS. 

[notlimah]

2 minutes ago, 04Mach1 said:

I thought my 01 was going to blow up this morning. Thermometer on the porch said 3*F. I started my truck which was normal then went to high idle for a few seconds and then bam... 3 cylinder high idle which sounded scary at first. It's the first time I've heard 3 cylinder high idle since using the Smarty. This will be the second winter with the Smarty.

 

Lmao! It definitely throws you off the first time you hear it! 

[cajflynn]

57 minutes ago, Mopar1973Man said:

 

The high step just before stopping is normal even my truck does the same thing. 

 

Now like the 820 RPM part is most likely the pop pressure of the injectors getting too low. This advances the timing of the injection event and tends to slightly increase idle speed. Like even my truck is starting to creep up in the idle speed because the injector pop pressure is starting to fall off. The next step I'm watching for is the misfire at idle warm and the injectors are now below 250 bar. That's what happened to my RV275 I had long ago I got from @cajflynn used. 

 

Don't try to blame me for wrecking the injectors I gave you.  You need to put some miles on your truck if you want it to last!

 

PSA.  Don't ignore injector problems.  Bad injectors ruin motors (at least three different times for me.)  

[dripley]

1 hour ago, Mopar1973Man said:

 

The high step just before stopping is normal even my truck does the same thing. 

 

Now like the 820 RPM part is most likely the pop pressure of the injectors getting too low. This advances the timing of the injection event and tends to slightly increase idle speed. Like even my truck is starting to creep up in the idle speed because the injector pop pressure is starting to fall off. The next step I'm watching for is the misfire at idle warm and the injectors are now below 250 bar. That's what happened to my RV275 I had long ago I got from @cajflynn used. 

That might explain it. The firstit happened to me was on the oe injectors with about 200k on them. Never had any mileage drop on them, at least on the highway. In town was hard to tell with idling and short tripping. This time the 50's in here now have about 100k on them and I have seen a slight mpg loss.

1 hour ago, 04Mach1 said:

I thought my 01 was going to blow up this morning. Thermometer on the porch said 3*F. I started my truck which was normal then went to high idle for a few seconds and then bam... 3 cylinder high idle which sounded scary at first. It's the first time I've heard 3 cylinder high idle since using the Smarty. This will be the second winter with the Smarty.

I have only heard the 3 cylinder high idle on a video and it is quite alarming.

[Marcus2000monster]

Yup first time i ran 3 cyl i flipped a breaker.

[Dieselfuture]

3 hours ago, cajflynn said:

You need to put some miles on your truck if you want it to last!

Bit off subject, but since you're here. On your 2nd gen that you put 1.3 million miles on, how many times did you have the head off and for what reasons, what was fixed, valves, guides, just hg, did you ever touch bottom end? 

[cajflynn]

51 minutes ago, Dieselfuture said:

Bit off subject, but since you're here. On your 2nd gen that you put 1.3 million miles on, how many times did you have the head off and for what reasons, what was fixed, valves, guides, just hg, did you ever touch bottom end? 

 

I adjusted the valves a lot. One head gasket.  Lots of leaky valves, broken exhaust manifold gaskets, injectors, and stuff like that.  Nothing on the bottom end other than the tappet cover leaking.  We did put the big cam in it.  That was for fun and had nothing to do with the old one being bad.

[Mopar1973Man]

@cajflynn

 

No blame on you... You were clear about the injectors being in the 400k realm I knew it was barrowed time. I got one year of service from those after having them pop tested and cleaned up. 

 

True a bad injector will cause all kinds of issues. 

Edited November 27, 2018 by Mopar1973Man

[Marcus2000monster]

Also as i cruise down the hwy i will feel the pedal sort of go dead its not at all a major deal its very soft and hard to feel. its more of a hesitation than anything. Im thinking its got to be the injectors because i have no codes. 

@cajflynn Do you think that the more you daily drive and tow with our trucks the longer they last? 

[Mopar1973Man]

I can tell you that @cajflynn was a driving fool. (In a good way) I heard from him 800-mile day if possible. I tend to believe the more you use it the longer it will last. I'm nowhere near the level of driving that Cajflynn is but I'm much high than the average person here in M73M. The only one close to me I think is good ol Dripley (David Ripley) he's about 100k miles ahead of me but we seem to average about the same amount of miles month to month for the most part. Even looking at his truck it's holding up rather well a bit more abused but doing good!