Engine power loss at startup

Greetings. About a month ago, my 2011 (V-6) Wrangler Unlimited occasionally would exhibit a rather strange loss of power after being parked overnight. The engine would start and idle normally, but would "bog down" as I pulled out onto the paved road. Simultaneously with the power loss, I would hear an unusual low-pitched hum or rubbing sound from the front of the vehicle, and the traction loss dash light would come on. After babying the Jeep along for a couple of hundred yards, the accelerator would begin to respond normally and the Jeep would run like a top the rest of the day. This problem is getting progressively more common, now occurring just about any time the Jeep sits idle 2 or 3 hours. Last week, I decided to try letting the engine warm up a bit before leaving the driveway. Engine would idle normally, but I was surprised to find that the engine would not rev above about 2000-2500 rpm. After taking to the open road, however, it would still accelerate normally after driving it 100-200 yards. Code reader showed an intermittent engine miss, but nothing that seems to describe what is occurring. Any ideas?

 

Welcome! Post up the service code for some internet diagnosis

 

AS the CEL is on have the system scanned, its free at most auto part stores, copy and post ALL codes...

Any recent work, repairs, modifications?

 

Thank you both. Looking for where I recorded the codes. Will post when I find them. No recent work, repairs or mods.

 

Could not get code numbers from mechanic, but he said that the only codes were for 1) misfire on #6 cylinder, and 2) a code associated with the "gascap" message on the instrument panel (which has been a long-term problem). I also have a perpetual "airbag" light on, due to a non-deployment collision with a deer.

Back to the problem at hand...
When I started the Jeep this morning, the engine, as usual, would not rev above about 2000 RPM. As I eased down the road, gingerly working the accelerator, the Electronic Stability Control (ESC) light came on, as did the Anti-lock brake (ABS) warning light. These lights stayed on until the next time I started the engine. A third warning light - a green one - came on for about a half-second, then promptly went off...so fast that I could not identify the symbol on the light. After driving about 100 yards, the engine began running normally, with no missing or hesitation.

Suspecting a faulty fuel pump, my mechanic checked the fuel pressure and found it to be within the normal range, even when the engine was running bad at startup.

Reading the Owner's manual info about the ESC warning light, it says that when the ESC system is activated, it will make a buzzing or clicking sound - likely the low-pitched hum that I described in my original post.

So, does anyone have an idea why a temporary power loss at start-up would be associated with a ESC warning light and an ABS warning light? Mechanic is stumped, as am I.

 

BTW, the mechanic cleared the CEL code for the #6 cylinder misfire, and the CEL is no longer on. But the problem continues, of course.

 

be sure to use a scanner capable of reading ABS codes.
Might want to look at live data at start, voltage, fuel trims, o2 voltages.

When the fuel pressure gauge is attached record PSI, then leaving KOEO observe fuel pressure drop - pressure drops Xpsi in 5min..

before clearing code - was freeze frame checked for any hints?
use owners manual to ID the green light...

 

Thank you for your suggestions. After seeing similar symptoms in another forum, I had my mechanic replace the rear wheel speed sensors this weekend, and that appears to have fixed the problem.

 

I think I got a letter in the mail a few months ago that said the wheel speed sensors are covered by a lifetime warranty and if they go bad any jeep dealer would fix them under warranty. I wonder if you could get your money back if you shelled some out??

 

That's interesting...I don't remember getting such a letter. I appreciate the info, but round trip to the nearest Jeep dealer is about 75 miles...probably not worth pursuing, as my repair cost, including labor and parts, was about $70.