New issue, zero throttle response after "cold" start

[gorilla57]

Well, kinda interesting issue arose today. Started up the truck, pulled out of the garage far enough to shut the door and took off pretty slowly. Gave it throttle and it revved up to 1500rpm and no more. Gave it more throttle and truck started jerking a bit. Let off the throttle to make a stop at a stop sign and it took off normally after that. Truck ran fine the rest of the morning even after multiple shutdowns. Ok.....so maybe just some funky glitch between the trans and the engine. Parked it for 4hrs today and pulled out of the garage to run some errands, does the exact same thing...... This time I quickly switched over to the voltage gauge and its reading 12.5v and slowly raises back up to the "normal" 12.8v when the batter is fully charged. Watched my voltage the next few stops and noticed it dipped down to 12.2v when taking off from stoplights. Figure the battery is going bad since the voltage hits 14.3 when coasting up to a stoplight ("smart" alternator is working fine). Stop by AutoZone and load test the battery and it load tested just fine. Truck ran fine again after multiple starts this afternoon, no codes either.

Anyone else experience this lack of throttle for a short period after a "cold" start?

 

[Richard320]

Check the ground connections. Plenty of people here have complained about problems. If things contract when cold, you'll get low voltage to everything.

 

[gorilla57]

Check the ground connections. Plenty of people here have complained about problems. If things contract when cold, you'll get low voltage to everything.

Problem is...."cold" start for me was 100deg for the first start and 108deg for the second. It has been damn hot, but I'll throw a wrench on all the grounds.

 

[gorilla57]

Welp, I did way too many things to fix this to nail down exactly what I did "right". No throttle problems this morning.

So, here's what I did....disconnected the IBS to have the computer reset the charging profile that it has learned for the battery, hooked up a charger and fully charged the battery overnight, pushed in all the fuses in the under hood fuse box (well known problem with Wranglers having fuses/relays that weren't seated all the way and about 1/3 of mine were not all the way seated, good QC there FCA), checked all my grounds and they were all very tight. Started up the truck, pulled out of the garage and took off down the street just like I did yesterday. Truck revved up just fine and shifted gears like it had done every other day until yesterday.

Here's something new though, might be due to "resetting" the IBS. At idle, the truck is charging at it's usual 12.8-12.9v and when I put it into gear, it now jumps up to 13.9v pretty fast. Put it back into park, back down to 12.8v.

 

[WXman]

"Dead pedal" is common on the FCA diesels. I've even read about it on newer Cummins trucks. But, it's very random so it's hard to diagnose the exact issue. GDE says it's a flaw in the powertain calibration due to how they're dealing with emissions.

 

[Rossum]

"Dead pedal" is common on the FCA diesels. I've even read about it on newer Cummins trucks.

If this is indeed common, owners should report it to the NHTSA. A dead accelerator pedal is a safety hazard.

 

[WXman]

If this is indeed common, owners should report it to the NHTSA. A dead accelerator pedal is a safety hazard.

I did several weeks ago. Hopefully others will too. But in the end, FCA will wait as long as possible to take any action.

 

[gorilla57]

Yeah, know what "dead pedal" is, I have owned a few Cummins powered Ram trucks before. But...this wasn't dead pedal as I've ever heard of someone reporting on the forums. The usual dead pedal is usually a few seconds and then it will finally take off. My issue was probably 15-20 seconds, held 1500rpm, motor shuddered and trans wouldn't shift out of 2nd gear. No codes what so ever. I'm kinda thinking this was all voltage related. When I looked at the voltage gauge after the 2nd time it occurred, it read 12.2v when taking off from the 1st stoplights. This leads me to believe that the voltage may have dipped below 12.0 when taking off immediately after I started the truck, since startup is the biggest draw a battery sees. I could be way off base here, but it's been fine since charging the battery and disconnecting the IBS. If this is a variant of dead pedal, then this is utterly ridiculous that FCA allowed programming like this to be released to the public.

 

[gorilla57]

A little update for this issue. Ever since I disconnected the IBS and charged the battery.....ZERO problems. The alternator ramps up charging as soon as I put the truck in drive instead of letting the voltage dip to 12.2v like I saw previously. When the alternator ramps back down when the battery is charged, I still never see below 12.6-12.7v, so something was wrong with the charging algorithm that the truck was stuck in.