Odd lack of acceleration '01 4x4

wow that's scary...

Op, how are you making out on the repairs/problem?

 

Ugh, problem is back. KNN is gone, time to start going down the list again.

 

Pull the throttle body off and clean it thoroughly. Also check you PCV valve to make sure it's not clogged up and replace it (they are cheap and should be done anyways).

I would check all the vacuum lines to ensure there's no cracking or broke lines.

Then get a multi-meeter and start testing sensors.

 

I have been through all that. Still dont know what the problem was but.....one day changed my oil and drove to tampa from north florida. 5 hrs straight thru keeping around the rpm sweet spot when trans shifts into OD at 54 mph. Kept it under 60 mph the whole way. After making the round trip trans has shifted just fine. Still get crappy fuel economy tho. If im nice to it I can squeeze 14 in the city w/out the ac on. If I stay under or around 2k rpms I can get 20 mpg on highway. I think maybe its the ethanol in the fuel starting to clog the cat and steady long distance makes it burn itself clean. not really sure. Truck just started being sluggish yesterday again after 3 months of acting normal.

 

So far I have:

-replaced the MAF
-Replaced the coolant sensor
-Replaced the TPS
-Replaced both O2 sensors
-Ran Mopar CCC through it
-Piston soak
-Cleaned the EGR

Right now its not bothering me too much in the summer cause it stays pretty hot, but I know the winter its gonna be a pain.

 

I think there is a thread on here about a owner having the same/similar problems.

Something about them replacing the ECU and the problem went away. Several back and fourth swap outs of the ECU's proving the original was bad,,or going bad.

Did a mega search for that thread and came up empty.

 

Well at long last, problem fixed. MAF had to be replaced, bought a dealership part on happy hour Wednesday. Three weeks to date with no issues!

 

NEVER SHOULD HAVE POSTED, THE DAY AFTER REPORTING PROBLEM CAME BACK LIKE NOBODIES BUSINESS!

 

Did you disconnect your battery cables for atleast 30 mins and let the comp remap everything?

 

^^Give this a shot!

 

Battery disconnected for almost a full hour this last time, no effect. Gotta while before I can afford the mechanic again...

 

OP, long shot here as it has been a while since you first posted but have you checked if your CEL bulb is burned out? Possible the PO drove it for so long with the CEL on because he didn't want to solve the problem that it burned out. See if you are pulling a code?

 

My '04 2.7 auto is the exact same. I never could resolve the problem.

I have the same no power then all sorts of power problem, almost identical mpg (13ish city, high teens on the hwy) and I have also cleaned and replaced everything I can think of. No CEL and I know it works because when I had an exhaust leak beside the o2 sensor it threw a code.

 

CEL works ok, no codes.

The only thing I can say conclusively is that the problem is definitely related to temperature. The issues dissapears once the engine is hot.

My latest theory is that the throttle plate cannot open properly for some reason when the engine is cold, and the all of a sudden pops open resulting in the sudden increase in power.

 

Jacket, definitely along my train of thoughts, but clearing the computers memory with battery disconnect helps temporarily then the problem reoccurs, so I'm pretty certain its electrical as well. We will find a solution eventually although this is becoming an itch I can't scratch...

 

*Update*

Found something interesting today. Had the usual low power issue while driving up hill, and then the sudden boost at 2700rpm. However I happened to be looking at my scan gauge for an unrelated purpose and I noticed that at the exact moment I got the boost effect, the o2 sensor switched from closed loop to open loop.


Im not too familiar with how that system works, perhaps someone can shed more light on it. From what I can tell, it almost seems like the o2 sensor is going into closed loop too quickly after turning the truck on, and it needs to stay in open loop long enough for the engine to warm up longer.

Is it normal for the system to switch from closed to open like that in the middle of acceleration?

 

Started doing some research on that, there were some articles that talked about the coolant temp sensor controlling the closed/open loop and that if its faulty may not be calculating the correct fuel/air ratio. Mine definitely could have been damaged in the removal, shipping, or installation of my motor last year. Oddly enough the truck threw some codes today. P0125 and p1135 (coolant temp and air fuel sensor) I've already scheduled to talk with a shop this week so I'm not gonna fix anything and will update after the shop dips into my wallet.

 

My trucks switch from closed to open on a hard acceleration. I asked about it here a couple weeks ago, on TW, thread name, open loop-closed loop(don't know how to link).. Can't quite rember the reason but its normal.

Edit* I read my thread and my situation was switching to open loop on a deceleration. I can't rember if mine do it on acceleration or not.

 

Im curious to hear what they tell you. For what its worth, I replaced my coolant temp sensor last year and it did not affect the issue either way.

 

Good info. From what ive been reading, it seems open/closed loop is determined by a variety of factors; RPM, load, speed etc.

I read somewhere that loop issues can be caused by a improperly adjusted transmission kickdown cable. I adjusted mine to spec and my shifts are much smoother now, but it hasn't been cold enough to check the issue at hand.