My truck is Confused!!

[jman]

Took truck in for the sticky idle that has been covered here several times. It does this quite often, but is worse when cold. Usually you tap the throttle and it will stick at 1000rpm. Of course it behaves when at the dealer as I'm tapping the idle to see if it will stick and as expected it won't. I say fine I'm sure it will do it again so if the Tech can't get it to do it no sweat.



This is was the Tech says, "I'm confusing it by tapping the throttle". Wow!! I can't seem to confuse any of the several others I have tried this in to see if I have a problem. It also wasn't "confused" for the first 78K miles. :-laf I bet it is pretty sticky tomorrow since it is supposed to be 40 degrees. We'll see I guess. I really don't think my Cummins is the one that is "confused". :-laf

 

[Slow Six]

My truck did the same the same thing plus a couple of other issues. The problem was caused by improper pin sizes on the connector blocks to the ECM. A block with the right size pins and/or holes was spliced in and fixed the problem. The down side of it is it cost me $1400 for the fix as I was over the basic warranty. The ECM is not part of the engine. DC admitted there was a problem with the wrong size pins being supplied but would not consider any good will.

 

[rbattelle]

DC admitted there was a problem with the wrong size pins being supplied but would not consider any good will.

Wrong size pins, or corrosion on the PCM plugs? I've never heard of this "wrong size pins", but there was a problem (and TSB) regarding an issue with PCM connections (automatic trucks only) corroding and causing problems.

jman - I think it's probably a faulty APPS. Depending on when your truck was built, the APPS is either under the driver side battery, or on the intake manifold just in front of the intake horn. The one on the intake manifold is a simple potentiometer (which are prone to "dead" spots), whereas the one under the battery is a hall effect sensor.

Ryan

 

[jman]

The thing that is weird is that it is terrible when it is cold. We had a cold spell last winter with single digit temps and I was stuck in traffic in 1st gear. I would accel and then let off and it would stick at 1000 rpm and I would have to push HARD on the brake pedel to get it to come down. This with it in gear. It will do it in gear idling down the road also. I'm not doubting you, but why would it be so much worse when temps are very cold. I do have an issue with the cruise that it seems to surge and hunt as you crest a hill. I have never had a dead pedal, yet anyway.



Thanks



PS.



Slow Six,



I e-mailed the service advisor the "Sticky Idle" thread with your comments and he said he shared them with the Tech, but that didn't seem to spark anything. I told him what you described as "SPOT ON" and I may have well talked to a wall I guess.

 

[rbattelle]

Your truck is a 6-speed, why would you be braking down to idle in gear?

If it's worse in cold weather, that could mean it's a lubrication problem. Maybe the pedal isn't actually returning properly?

Where is your APPS located?

The cruise issue may or may not be related. Cruise on manual trucks is entirely contained in the ECM, so it has nothing to do with the fuel pedal.

Ryan

 

[jman]

I was in 1st gear and I acceled then deceled and the idle stuck at 1000rpm so I pressed the brake w/o pushing in the clutch to see if it would come down. It did but with a fair amount of force on the brake before it gave in and idled down.



Door says built 7-03 if that helps.

 

[rbattelle]

Well, it might be an issue with the APPS, but you'll really need to do some more diagnosis first.

Best thing to do is connect an OBD-II monitor to it and wait for it to stick. Then read off the % throttle. That'll answer the question whether it's APPS or something more serious.

You'll have to drive around with the monitor until it happens.

Ryan

 

[jman]

Another thing to note. If you tap the throttle to say 1100 rpm it is VEEEEERRRRRYYYYY slow to return to 750rpm. Another thing is it is only like this at operating temperature. If you tap the throttle right after you start it is is up and down very fast. If you are at operating temp and you shut it off and restart it is up and down very fast.



I guess it isn't hurting anything, just more of an annoyance I guess.

 

[rbattelle]

Another thing to note. If you tap the throttle to say 1100 rpm it is VEEEEERRRRRYYYYY slow to return to 750rpm.

Hmmm... now you're starting to sound like an injector problem. Slightly leaky injector bleeding fuel into the cylinder.



As I recall, some other people have had this problem. Can't find a thread on it, though.



BTW, whoever told you your truck has 2 APPS's was completely full of it.



Ryan

 

[jman]

It seems like the FCA has been discussed several times with these types of things. It is just weird that it is so much worse with cold temperatures. Truck runs great, gets great mileage, great oil analysis with no fuel in the oil. It has been doing this for at least 20K miles. It is supposed to be 40 degrees in the morning and I'll bet a lot of money it will be a sticky sucker until it warms up in the afternoon.



BTW, The tech told the service advisor to tell me this. That's what I mean when I say my Cummins isn't the one that is "Confused".

 

[lubeguy]

any black smoke? common rail inj can feed the cyl if not shutting off cleanly. some times a block off tool or a infared temp gun can find the cuprit. look for a hot cyl or cyls. this problem can cause a slow decel also.

 

[jman]

It doesn't seem to smoke bad at all. A slight haze on acceleration, but it isn't a black cloud by any means. Maybe I'll call the dealer I usually go to and see if they would run some injector tests to make sure everything is alright before I turn 100K. If they test OK then I'm just going to drive it. Oil Analysis show no fuel so I'm not going to stress about it.

 

[DE Jeeper]

My truck has been doing exactly the same thing since I put on my FASS. Now in putting on my FASS I had the take my throddle assembly on and off several times because of an interfearence with the Jake brake vacuum pump. I figured I may have kinked the cable or loosened something. The thing is the truck still reads it as an idle position because the Jake will kick on if I switch it on and it will drag the idle back to 700. Also, at the same time the Jake would turn itself off for a 5 sec count for no reason (no troddle input). If I touch the throddle it will kick on with it's normal delay. I think some how the 2 problems are related. I am getting a reoccuring fan clutch code that says I should replace it, but it is operating correctly and I don't feel like spending $350 for a ghost problem. Again I am wondering if this is sending the motor into a high idle? BTW, the ADDS is only 3 months old.



The strangest thing of all is that I replaced the high pressure sensor on the AC yesterday and I had neither the high idle or the Jake cut off problem happened today. I am not yet convinced the problem is fixed, but if I get a couple trouble free days out of it I may have found the cause.



My local 5 Star Dodge diesle tech could figure it out either and just looked at the truck confused. He was also the same guy that couldn't figure out my hard start. Meanwhile all 6 injectors were firing incorrectly per Don at F1. With his rebuild and upgrade it now starts great, but it had no effect on the high idle issue.



Hopefully this helps in some way.



Aaron

 

[Semicrazy]

My truck has always done this since I have owned it.



If I tap the throttle it will hold 1000rpms or I notice it will do it on its own when the cylinder temps get to cold. The only way to get it to stop is to hit the brake pedal hard.



I found it to be when my temp gauge drops below approx 190 after already being warm and/or EGTs drop below 300F in the manifold.



That is the only sort of correlation that I could find.



Is it correct, who knows? But it sure does make me feel better and make me think that my truck and I are not that crazy.

 

[DE Jeeper]

Well day 2 with no high idle or Jake Brake cut out. It seems a little crazy, but fixing the high pressure switch on the AC might be the fix????? I guess time will tell.



Aaron

 

[cerberusiam]

Well day 2 with no high idle or Jake Brake cut out. It seems a little crazy, but fixing the high pressure switch on the AC might be the fix????? I guess time will tell.



Aaron

You might want to check the the wiring harness that runs from your AC pump back to the ECU. Below the AC compressor close to the frame rail the harness had a tendency to run on the lines and bare the wire. The intermittent contact caused all kinds of strange and anomalous behaviours. Since you were working around there you may have just moved things enough to stop the short.