Acceleration is poor until 4500rpm.

[windman]

Hello friends, here is my new problem on our KJ.

Kj is 3.7 limited with bifuel setup. It can either run on LPG or Gasoline. Problem which i face is evident on both fuels. Spark plugs, air filter, TPS are new. MAP was replaced 15k miles ago. Also crank position sensors was replaced together with map. IAC iworking correctly. There is no check engine light. No erratic idling either on cold or warm engine. No vibration or harsh shifting. Only shuddering for 2 second during reversing on uphills. ATF is new, i replaced it last year, it is still clear red. Mopar branded fluid.

Problem is, when you want to accelerate hard, and when you do full throtle, it kicks down or even you can manually shift to 2nd gear, cruising at 40 mph or lower, without being effected by the speed you are travelling, (except the 4th gear at higher speeds) there is a power loss.

it feels like i am travelling with 4 overweight friends sitting in car, when i decide to accelerate faster than usual, and when it reaches to 4000-4500 rpm, they suddenly decide to evacuate the car because of lowered body weight, car starts to accelerate faster until it shifts to higher gear.(4th)

technically speaking, it feels like fuel rate to engine is lower than ideal, or catalytic converter is cracked, engine cant rev quicky, or feels like a huge diesel turbo lag before 4500rpm (imaginary turbo of course on this 3.7 engine)

even i shift it to 2nd before a kick down happens, same applies. low power before 4500 rpm. on colder climate, general performance is much better. since summer arrived few weeks ago, it feels worse.

I have been driving this car before giving it to my wife last year, there was no such thing. i realized this problem lost month.

Any comments?

 

[ftaa]

you need the transmission serviced.. my guess torque converter is shot or on the way out

 

[John3seventeen]

What size tires do you have and what gear ratio?

 

[Jbergun]

I never get to 4500rpms unless i gun it hard average driving i get to 3000 maybe

 

[windman]

you need the transmission serviced.. my guess torque converter is shot or on the way out

this is what i am afraid of. relaxed driving is my usual style but passing cars can be dangerous if it hesitates to accelerate.

there were topics related to 42RLE and electronic transmisson management. it was something called emmc? when outside temp is getting higher performance is getting lower.

tires are stock size AT tires.

i tried to rev the engine standing still, before the rev cut kicks in and when i release the gas pedal, muffler makes funny pops. also water is driping from the joint which fixes the muffler to the pipe coming from cats.
will a destroyed muffler clogs and restricts flow and will it allows exhaust gas flow over high revs as gas can push the rusted internals?

 

[ftaa]

this is what i am afraid of. relaxed driving is my usual style but passing cars can be dangerous if it hesitates to accelerate.

there were topics related to 42RLE and electronic transmisson management. it was something called emmc? when outside temp is getting higher performance is getting lower.

tires are stock size AT tires.

i tried to rev the engine standing still, before the rev cut kicks in and when i release the gas pedal, muffler makes funny pops. also water is driping from the joint which fixes the muffler to the pipe coming from cats.
will a destroyed muffler clogs and restricts flow and will it allows exhaust gas flow over high revs as gas can push the rusted internals?

no .... thats EVAP stuff you need a torque converter.

 

[CactusJacked]

i tried to rev the engine standing still, before the rev cut kicks in and when i release the gas pedal, muffler makes funny pops. also water is driping from the joint which fixes the muffler to the pipe coming from cats.
will a destroyed muffler clogs and restricts flow and will it allows exhaust gas flow over high revs as gas can push the rusted internals?

A clogged/melted/broken up cat converter (if yours has one) can choke the engine down like you're describing. I've had a cat melt down on an RX7 turbo, and one that broke apart inside and sent chunks into the muffler. I'd check your exhaust flow.

 

[windman]

i will go step by step. since replacing TC is the most expensive one, it is better to inspect the visualy worst part, which is rusty stock muffler.

Car is on 126000 kilometers which is aprox 77000 miles.

i do not think catalytic converters( we have one for each bank and labmda sensor reading are very similar to each other) are not good since i am using LPG instead of Gasoline all the times, and cats wont operate since no carbonmonoxide on exhaust . Even if they are not ok, i can either replace them or remove them and put lambda sensor foulers since LPG is a cleaner fuel and doesnt create problems on emission tests.

if diagnosis indicates that TC is broken, it is better to learn to live with it for a moment, and then invest on a such expensive part later.

 

[CactusJacked]

i do not think catalytic converters( we have one for each bank and labmda sensor reading are very similar to each other) are not good since i am using LPG instead of Gasoline all the times, and cats wont operate since no carbonmonoxide on exhaust .

Hmmmm... How does an LPG conversion affect my catalytic convertor?

 

[windman]

by leaving it useless. it won't convert anything. exhaust gas is only co2 and water, but this ofcourse wont prevent it to be overheated or cracked due to aging of metals other than the valuable ones inside little holes on cat surface. lets see what happens. i will report when i proceed.

LPG is cleaner and efficient but energy potential is lower than gasoline. Mine is the latest technology on LPG injection systems by using a seperate ECU and seperate injectors for each cylinder. Performance is degraded approx 20% but keeping environment cleaner (it is cheaper too becasue it is a byproduct of gasoline making process).

 

[CactusJacked]

by leaving it useless.

lol, that "How does..." in my previous post wasn't a question from me, it is a link to some info telling how LPG can negatively affect a catalytic converter, did you click on it? :emotions34:

 

[windman]

allright i did not realize that there was a hyperlink. details are very nice. my system is a "close loop "type. there is a seperate management unit which can be calibrated by using a laptop. Operator can adjust settings too.

 

[CactusJacked]

Yeah, would be nice if this site automatically made hyperlinks blue like most other places do.
Here, you sometimes need to hang a click here sign next to a link. lol

 

[windman]

update.

We checked the software version of TCM and ECU, after we upgrade the software, hesitation at higher RPMs are lowered, low end troque and responsiveness increased. There was a recall for 2004 and 2005 models. for your info.

we did not do TCM quick learn, may be i can go there and do this to see what could be the diffrence after quick adaptation on higher gear ratios.