Losing power at highway speeds

[LJMolina]

His profile shows a Rubicon, so must be stock axles.

@LJMolina I'd check your torque converter's stall speed (should be 2200-2500 RPM). Is your ATF fluid clean and correct level? Any TCM stored codes?

I have the Stock Dana 44 axles F/R. Yes the transmission oil, is clean...doesnt smell burned and fluid level is always constant level when I check it. My RPM are abit higher than what your saying... Im about 2800 @ 65-70mph (when I get that high)...and no TCM codes.

I just got noticed from amazon that my cats just came in today.... The only thing left to replace is the transmission if this doesnt work, as I also replaced all the wheel bearings, U-joints.... this Jeep is practically brand new. When I did my frame swap...I replaced everything that was rusty.

 

[LJMolina]

I will check my stall speed when I leave work this evening... going back to Tulsa tonight. God...all i see is $$$$ in gas burning a hole.

 

[JSpike]

Believe it or not but there is a tool to check a cat. It's called a exhaust backpressure test kit ! Simple to use and in no time pinpoint a plugged cat or exhaust or muffler. It's a simple gauge ,hose and adapter to fit into O2 sensor, you start engine and read gauge. Normal cat, muff and exhaust at idle should be less than 1 psi. When it's hot at 2000 rpm should be less than 2 psi. If you can't get tool find someone with it and pinpoint or eliminate exhaust proplem

 

[LJMolina]

Well it wasnt the cats... at this point Chris might be right as he suggest it maybe the torque converter. I dont get any transmission slippage at all, just slow acceleration at 0-45mph and hardly zero/struggling acceleration above that. Taking it to a tranny shop this weekend.


Upside to all this, at least everything is new, and if I need a rebuilt tranny ..she should last me a long time.

 

[pagrey]

I did replace my frame just recently during winter

This is probably where your issue is. I'd bet wiring or grounds. The sensors depend on a good voltage reference to work and this is major work that could screw that up. I'd be tracing wires and looking for things that might have been damaged or not reconnected correctly.

 

[LJMolina]

Paul, You are on the right track.
I just came back from the transmission shop thinking this time it might be the torque converter.... They ran transmission codes and here is what it spit out (keep in mind I never got a codes myself or engine light at all).

Transmission Codes
P1684 - Battery was Disconnected (Obviously when I swapped frames)
P0714 - Transmission Temperature Sensor Intermittent (Mechanic said - This one could be the source of not getting a good ground)
P0884 - Power UP at Speed
P0218 - High Temp Operation Activated (Makes sense since I was on the highway trying to stay above 60)

Instrument Cluster -Codes Only
PCM/Single Board Engine Controller: Message Not Received


They recommended me to another place to get the PCM checked out, since all they do is transmissions. before I do, Looks like Im going to check and make sure stuff is all plugged in and re-verify no corrosion in the plug leads, PCM is getting good ground etc...

 

[LONGJP2]

Just recently I was getting some of those codes, so I swapped in a Wranglerfix PCM.
However, they weren't causing any issues with how it ran.

I had a similar power issue a couple of years ago, but it was the torque converter.
It was slipping and running hot.

 

[Brianj5600]

You can MacGyver an exhaust pressure gauge with an oil drain plug, a couple brass fittings, a short run of copper tubing and a low pressure gauge. I had everything laying around except the oil drain plug which will have to be drilled and tapped for a 1/8 npt. Another good tool is a lighted bore scope that connects to a laptop, tablet or smart phone. You can buy one for less than $20. The top O2 sensors are pretty easy to remove and with a bore scope allows you look at the inside of the cat without removing it.

 

[LJMolina]

I just ordered an new PCM from WranglerFix, Talking to Mark and giving him the P-codes, he indicated that my pcm is shot. With High praises from this forum, I'll take his word and went ahead with the purchase. I rather just buy a new PCM, instead of paying a mechanic troubleshooting to tell me I need a new PCM. I always had the shifting issue from 1st to 2nd anyway so at least it will fix that.

 

[LJMolina]

I just ordered an new PCM from WranglerFix, Talking to Mark and giving him the P-codes, he indicated that my pcm is shot. With High praises from this forum, I'll take his word and went ahead with the purchase. I rather just buy a new PCM, instead of paying a mechanic troubleshooting to tell me I need a new PCM. I always had the shifting issue from 1st to 2nd anyway so at least it will fix that.

The only thing left is to rebuild my tranny...god only knows if I ruined it by continuing driving my jeep in limp mode on the highway.

 

[LJMolina]

So, I replaced the PCM with a new PCM from wranglerfix, and Im still getting the same symptoms. Sending my jeep to the mechanic, I can figure it out. At least I have a backup PCM now.

 

[RMETeeJay]

So, I replaced the PCM with a new PCM from wranglerfix, and Im still getting the same symptoms. Sending my jeep to the mechanic, I can figure it out. At least I have a backup PCM now.

Did you test your TC's stall speed?

 

[LJMolina]

Did you test your TC's stall speed?

I wasnt sure how to do it, and looked at some yt vids... I couldnt tell as i couldnt tell the difference.

 

[LJMolina]

I've had transmission that slip before and this just doesn't seem like that. I'll be driving down the interstate, everything is good, 2000 rpms or so for 60 mph (don't know that for sure, just using that as an example), then all of the sudden to maintain the same speed, I've got to floor it, engine is revving at like 4500 and I can only go 30 mph. Pull off to the side and restart it and it's fine again.

I am having the same exact issue right now with my 06 LJ Rubicon...
Driving on the streets drives fine, but as soon as I hit the highway, its a struggle to maintain a constant speed...and its worse on very small highway road hills.
As yourself, I have to floor it, and hit 3400-3800RPMs to maintain about 60-65mph...and the rpms will stay that high until I let off the gas.

I have no CODES.
I have changed out the Primary and Secondary Cat Conv. with the Flowmaster Kit.
I have Changed out all 4 O2 sensors with the NTK's
I have Changed out all 4 wheel bearings
I have Overhauled both axles with new bearings

This jeep is has pretty much all brand spanking new parts... other than replacing the engine and transmission.

Im at a point taking the jeep to a transmission shop to overhaul the damn thing.

 

[Steel City 06]

What seems interesting to me is that in the case of running it 3,500 RPM plus and flooring it, it is likely one of three root causes:
(1), not enough air is getting to the engine
(2), not enough fuel is being added
(3), the engine is getting enough fuel and air, but is failing to effectively extract the energy.

(1) and (2) are pretty easy to chase down.

For (1), play the game of follow the air.

• Is the air intake blocked?
• Is the air filter in good condition?
• Is the air manifold in good condition?
• Are my throttle body and IAC in good condition and operating normally?
• Are there any intake leaks?
• Are the valves in good condition? (Compression test)
• Is the exhaust system restricted?
• Is there an exhaust leak? (Back-pressure or smoke test)
• Is there a vacuum leak?

For (2), play follow the fuel.

• Is my gas tank full? Of the correct fuel?
• Is my gas tank venting correctly? (and not pulling a vacuum inside the tank)
• Is my vapor recovery system working?
• Is my fuel pump and regulator working? (Fuel pressure test)
• Are my fuel lines partially kinked or clogged? (Fuel flow test at the manifold)
• Are my venting or vapor recovery lines kinked or clogged?
• Are my fuel injectors working properly?
• Are my fuel injectors seated correctly, and the OEM size? (Check the long term fuel trims regarding the latter.)

(3) is a little more nuanced, but it can generally be broken down into two categories, mainly control system and physical.

Physical:

• Are my piston rings allowing too much blow-by? (Leakdown test)
• Are my spark plugs in good order? (Also check for carbon fouling)
• Is my coil pack working? Are my wires (if present) working?
• Is my engine holding proper operating temperature? (Whole cooling system)
• Is my engine holding proper oil pressure?
• Is my fuel failing to ignite, burning too late, or just another cause?
• Is there some unusual power draw causing bogging? (Seized fan clutch, bad alternator, bad bearing, etc.)
• Is there an external power suck? (Bad transmission, underinflated tire, etc.)
• Is there something blocking my radiator from receiving adequate airflow?

Control (use a tuner or OBDII monitor):

• Is my PCM working as designed?
• Is the controller pulling timing for any reason, and if so, why?
• Is the controller operating outside of stochiometric for any reason, and if so, why? (Power enrichment is one cause)
• Are my long-term fuel trims generally within 5%, and if not, why?
• Is bank 1 operating differently than bank 2, and if so, why?
• Is my charging voltage adequate? (13.6 to 14.8V typically)
• Am I hearing spark knock, detonation, or pre-ignition, and when/why?
• Are my oxygen sensors working correctly?
• Are my air temperature sensors and coolant temperature sensors working correctly?
• Is my PCM going into catalyst protection mode?
• Is my PCM going into limp mode?
• Do I have any DTCs, whether or not there is a CEL?

Not a definitive guide but hopefully might help someone ask the right questions.

Messing with tuning, I have learned that the TJ pulls timing like crazy and adds extra fuel for many different reasons, and more often than not, excessively so. Just cutting back on a lot of that significantly increased power, torque, and especially fuel economy. Just with that and a few basic mods I have gone from 12.5 to 15.5 MPG on 35s, and will probably get even better on the next few tanks.

 

[Brianj5600]

Messing with tuning, I have learned that the TJ pulls timing like crazy and adds extra fuel for many different reasons, and more often than not, excessively so. Just cutting back on a lot of that significantly increased power, torque, and especially fuel economy. Just with that and a few basic mods I have gone from 12.5 to 15.5 MPG on 35s, and will probably get even better on the next few tanks.

Mine with stock tune was a total dog. Steel City 06 hit it on the head about pulling timing. I saw timing go as low as 16 degrees BTDC at WOT. Do you have a WBO2? If so how rich was it?

 

[LJMolina]

Mine with stock tune was a total dog. Steel City 06 hit it on the head about pulling timing. I saw timing go as low as 16 degrees BTDC at WOT. Do you have a WBO2? If so how rich was it?

Thats what it feels like...just wondering how timing would be so off (will be checking it soon).....but I also heard the OEM harmonic balancer pully tend to slip due to a rubber liner or something.

What seems interesting to me is that in the case of running it 3,500 RPM plus and flooring it, it is likely one of three root causes:
(1), not enough air is getting to the engine
(2), not enough fuel is being added
(3), the engine is getting enough fuel and air, but is failing to effectively extract the energy.

(1) and (2) are pretty easy to chase down.

For (1), play the game of follow the air.

• Is the air intake blocked?
• Is the air filter in good condition?
• Is the air manifold in good condition?
• Are my throttle body and IAC in good condition and operating normally?
• Are there any intake leaks?
• Are the valves in good condition? (Compression test)
• Is the exhaust system restricted?
• Is there an exhaust leak? (Back-pressure or smoke test)
• Is there a vacuum leak?

For (2), play follow the fuel.

• Is my gas tank full? Of the correct fuel?
• Is my gas tank venting correctly? (and not pulling a vacuum inside the tank)
• Is my vapor recovery system working?
• Is my fuel pump and regulator working? (Fuel pressure test)
• Are my fuel lines partially kinked or clogged? (Fuel flow test at the manifold)
• Are my venting or vapor recovery lines kinked or clogged?
• Are my fuel injectors working properly?
• Are my fuel injectors seated correctly, and the OEM size? (Check the long term fuel trims regarding the latter.)

(3) is a little more nuanced, but it can generally be broken down into two categories, mainly control system and physical.

Physical:

• Are my piston rings allowing too much blow-by? (Leakdown test)
• Are my spark plugs in good order? (Also check for carbon fouling)
• Is my coil pack working? Are my wires (if present) working?
• Is my engine holding proper operating temperature? (Whole cooling system)
• Is my engine holding proper oil pressure?
• Is my fuel failing to ignite, burning too late, or just another cause?
• Is there some unusual power draw causing bogging? (Seized fan clutch, bad alternator, bad bearing, etc.)
• Is there an external power suck? (Bad transmission, underinflated tire, etc.)
• Is there something blocking my radiator from receiving adequate airflow?

Control (use a tuner or OBDII monitor):

• Is my PCM working as designed?
• Is the controller pulling timing for any reason, and if so, why?
• Is the controller operating outside of stochiometric for any reason, and if so, why? (Power enrichment is one cause)
• Are my long-term fuel trims generally within 5%, and if not, why?
• Is bank 1 operating differently than bank 2, and if so, why?
• Is my charging voltage adequate? (13.6 to 14.8V typically)
• Am I hearing spark knock, detonation, or pre-ignition, and when/why?
• Are my oxygen sensors working correctly?
• Are my air temperature sensors and coolant temperature sensors working correctly?
• Is my PCM going into catalyst protection mode?
• Is my PCM going into limp mode?
• Do I have any DTCs, whether or not there is a CEL?

Not a definitive guide but hopefully might help someone ask the right questions.

Messing with tuning, I have learned that the TJ pulls timing like crazy and adds extra fuel for many different reasons, and more often than not, excessively so. Just cutting back on a lot of that significantly increased power, torque, and especially fuel economy. Just with that and a few basic mods I have gone from 12.5 to 15.5 MPG on 35s, and will probably get even better on the next few tanks.

Thank you Steel City 06 for this list...I will work on checking it off, one by one.....I'll report back on what items I found discrepant, for anyone else that might have this issue.

 

[Brianj5600]

Thats what it feels like...just wondering how timing would be so off (will be checking it soon).....but I also heard the OEM harmonic balancer pully tend to slip due to a rubber liner or something.

The timing is not really off for a stock Jeep. When we start modifying is when things go wrong. Larger tires, winch, bumpers, armor add weight and put more load on the engine. As load on the engine goes up, vacuum in the intake goes down. The ECM lowers timing to prevent spark knock, pinging or detonation, which ever term you choose.

My theory is that engines in good health don't have the the problem of pulling timing as much. Bad ring seal or valves not sealing is what I think causes the timing to aggressively retard.

 

[freedom_in_4low]

What seems interesting to me is that in the case of running it 3,500 RPM plus and flooring it, it is likely one of three root causes:
(1), not enough air is getting to the engine
(2), not enough fuel is being added
(3), the engine is getting enough fuel and air, but is failing to effectively extract the energy.

(1) and (2) are pretty easy to chase down.

For (1), play the game of follow the air.

• Is the air intake blocked?
• Is the air filter in good condition?
• Is the air manifold in good condition?
• Are my throttle body and IAC in good condition and operating normally?
• Are there any intake leaks?
• Are the valves in good condition? (Compression test)
• Is the exhaust system restricted?
• Is there an exhaust leak? (Back-pressure or smoke test)
• Is there a vacuum leak?

For (2), play follow the fuel.

• Is my gas tank full? Of the correct fuel?
• Is my gas tank venting correctly? (and not pulling a vacuum inside the tank)
• Is my vapor recovery system working?
• Is my fuel pump and regulator working? (Fuel pressure test)
• Are my fuel lines partially kinked or clogged? (Fuel flow test at the manifold)
• Are my venting or vapor recovery lines kinked or clogged?
• Are my fuel injectors working properly?
• Are my fuel injectors seated correctly, and the OEM size? (Check the long term fuel trims regarding the latter.)

(3) is a little more nuanced, but it can generally be broken down into two categories, mainly control system and physical.

Physical:

• Are my piston rings allowing too much blow-by? (Leakdown test)
• Are my spark plugs in good order? (Also check for carbon fouling)
• Is my coil pack working? Are my wires (if present) working?
• Is my engine holding proper operating temperature? (Whole cooling system)
• Is my engine holding proper oil pressure?
• Is my fuel failing to ignite, burning too late, or just another cause?
• Is there some unusual power draw causing bogging? (Seized fan clutch, bad alternator, bad bearing, etc.)
• Is there an external power suck? (Bad transmission, underinflated tire, etc.)
• Is there something blocking my radiator from receiving adequate airflow?

Control (use a tuner or OBDII monitor):

• Is my PCM working as designed?
• Is the controller pulling timing for any reason, and if so, why?
• Is the controller operating outside of stochiometric for any reason, and if so, why? (Power enrichment is one cause)
• Are my long-term fuel trims generally within 5%, and if not, why?
• Is bank 1 operating differently than bank 2, and if so, why?
• Is my charging voltage adequate? (13.6 to 14.8V typically)
• Am I hearing spark knock, detonation, or pre-ignition, and when/why?
• Are my oxygen sensors working correctly?
• Are my air temperature sensors and coolant temperature sensors working correctly?
• Is my PCM going into catalyst protection mode?
• Is my PCM going into limp mode?
• Do I have any DTCs, whether or not there is a CEL?

Not a definitive guide but hopefully might help someone ask the right questions.

Messing with tuning, I have learned that the TJ pulls timing like crazy and adds extra fuel for many different reasons, and more often than not, excessively so. Just cutting back on a lot of that significantly increased power, torque, and especially fuel economy. Just with that and a few basic mods I have gone from 12.5 to 15.5 MPG on 35s, and will probably get even better on the next few tanks.

I agree. Seems like slipping transmission would run high rpm but shouldn't require a ton of extra throttle...unless something was severely dragging in there which would create a metric butt ton of heat. Think about it from an energy flow standpoint...if you're pedal to the metal at 3500rpm you should be generating 150ish hp, but it should only take about 60 to maintain speed. The extra 90 can't just disappear, it's turning into heat somewhere, and that's almost 70,000 watts.

Therefore, my theory is there's something wrong that it's struggling to just produce the hp to achieve and maintain highway speed, rather than generating healthy power and losing it somewhere. With new O2 sensors and no codes I would be starting with a compression and leak down test.