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-   -   2004 Rubicon, loss of engine power (http://www.wranglerforum.com/f210/2004-rubicon-loss-of-engine-power-237877.html)

KirbyF 04-26-2013 06:49 AM

2004 Rubicon, loss of engine power
 
Hi All,

I'm new to this site and am in need of some help. My 2004 Rubicon has no power above 3000 Rpm. It starts fine, idles fine and if I drive it slowly no problems. If I try and accelerate, say winding it out in 3rd gear it just bogs down with no acceleration increase. I can floor it and it just kind of roars and has no power. I had had a DTC stating misfire on cylinder two, so I put in new plugs and a new coil rail. From what I have been researching it may be the Cat? Or O2 sensor. Im kind of at a loss on how to proceed. I have a AEM Air Induction and Banks Cat back exhaust system. Only has 50k miles on it.

Thanks in advance for any help!

Kirby

C.L. 04-26-2013 07:15 AM

Sounds like a clogged cat or low fuel pressure. You could test the cat theory by unbolting the exhaust manifold and repeating the accel/rev test. It'd be loud as hell, but if you got power back you'd know something was clogged in there.

Alternatively you could measure fuel pressure at the injector rail while someone revs the engine. I haven't done it on a TJ, but i think there's still a schrader valve on the rail that a gauge can be attached to. Last i heard, ~40psi was normal.

Rubicondon53 04-26-2013 07:22 AM

I had a CAI on my 04 Rubi for about 6 months. Biggest waste of money I ever spent. The jeep never ran quite right with it. I removed it and went back to stock intake.. I'd start there, put the stock intake back on it.. Then again, my jeep very rarely sees 3,000 RPM.. ;). Seriously though, give it a try.

jgorm 04-26-2013 09:59 AM

Quote:

Originally Posted by Rubicondon53 (Post 3685032)
I had a CAI on my 04 Rubi for about 6 months. Biggest waste of money I ever spent. The jeep never ran quite right with it. I removed it and went back to stock intake.. I'd start there, put the stock intake back on it.. Then again, my jeep very rarely sees 3,000 RPM.. ;). Seriously though, give it a try.

Any CAI will not affect how the jeep runs in any way unless the air filter is clogged, or the pipe is much smaller than stock. If you rarely see 3000rpms, then you should give it a couple 4500+ blasts to clean out the engine from extra carbon deposits. This is known as "granny syndrome" and is fixed with a "ghetto tune up" (rev the crap out of it and drive it hard).

jeepndon 04-26-2013 11:47 AM

Quote:

Originally Posted by C.L. (Post 3685016)
Sounds like a clogged cat or low fuel pressure. You could test the cat theory by unbolting the exhaust manifold and repeating the accel/rev test. It'd be loud as hell, but if you got power back you'd know something was clogged in there.

Alternatively you could measure fuel pressure at the injector rail while someone revs the engine. I haven't done it on a TJ, but i think there's still a schrader valve on the rail that a gauge can be attached to. Last i heard, ~40psi was normal.

I agree sounds like a clogged Cat but Fuel pressure is a good place to start the Factory service manual says.


Start engine and bring to normal operating
temperature.
(6) Observe test gauge. Normal operating pressure
should be 339 kPa +/–34 kPa (49.2 psi +/–5 psi).
(7) Shut engine off.


(8) Pressure should not fall below
30 psi for five
minutes.
(9) If pressure falls below 30 psi, it must be determined
if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking.
(10) Again, start engine and bring to normal operating
temperature.
(11) Shut engine off.
(12)


Testing for fuel injector or fuel rail leakage:
Clamp off the rubber hose portion of Adaptor
Tool between the fuel rail and the test port “T” on
Adapter Tool. If pressure now holds at or above 30

psi, a fuel injector or the fuel rail is leaking.


Rubicondon53 04-26-2013 12:06 PM

Quote:

Originally Posted by jgorm (Post 3685538)

Any CAI will not affect how the jeep runs in any way unless the air filter is clogged, or the pipe is much smaller than stock. If you rarely see 3000rpms, then you should give it a couple 4500+ blasts to clean out the engine from extra carbon deposits. This is known as "granny syndrome" and is fixed with a "ghetto tune up" (rev the crap out of it and drive it hard).

You're preaching to the choir my friend , driving the engine clean is as much a part of preventive maintenance as is keeping a clean air filter .. These facts remain, hard interstate driving, loaded down with gear and trailer, it ran very rough any time while pulling a hill, ( wrapped up @ 2700 to 3200 RPMs ). Not only that, when we'd pull over to take a break, or to fuel up, it idled extremely rough, and would diesel after shut down... Since I put the stock air box back on, those issues have disappeared ... So once again for the OP, put the stock airbox back on, it takes a half hour, doing so will give you a good baseline to accurately diagnose your problem.. ;) just my well researched opinion and my experience...

jgorm 04-26-2013 01:21 PM

Quote:

Originally Posted by Rubicondon53 (Post 3686017)
You're preaching to the choir my friend , driving the engine clean is as much a part of preventive maintenance as is keeping a clean air filter .. These facts remain, hard interstate driving, loaded down with gear and trailer, it ran very rough any time while pulling a hill, ( wrapped up @ 2700 to 3200 RPMs ). Not only that, when we'd pull over to take a break, or to fuel up, it idled extremely rough, and would diesel after shut down... Since I put the stock air box back on, those issues have disappeared ... So once again for the OP, put the stock airbox back on, it takes a half hour, doing so will give you a good baseline to accurately diagnose your problem.. ;) just my well researched opinion and my experience...

It must be coincidence. There is absolutely nothing upstream of the throttle body that would cause your issues, especially dieseling. If you get dieseling on a fuel injected engine, then you have a leaky injector and the wrong spark plugs, or bad carbon build up. Are you sure you didn't change the spark plugs when you put the stock intake back on? These jeeps are map based. The only thing in the intake is the IAT sensor. The jeep will run fine with any intake, or even no intake. I've done dyno pulls without any intake and it ran just fine.

mrk130 04-26-2013 01:54 PM

Quote:

Originally Posted by jgorm (Post 3685538)
This is known as "granny syndrome" and is fixed with a "ghetto tune up" (rev the crap out of it and drive it hard).

I've always know this as the "Italian tune up".

tkfx 04-26-2013 02:35 PM

Quote:

Originally Posted by KirbyF (Post 3684961)
Hi All,

I'm new to this site and am in need of some help. My 2004 Rubicon has no power above 3000 Rpm. It starts fine, idles fine and if I drive it slowly no problems. If I try and accelerate, say winding it out in 3rd gear it just bogs down with no acceleration increase. I can floor it and it just kind of roars and has no power. I had had a DTC stating misfire on cylinder two, so I put in new plugs and a new coil rail. From what I have been researching it may be the Cat? Or O2 sensor. Im kind of at a loss on how to proceed. I have a AEM Air Induction and Banks Cat back exhaust system. Only has 50k miles on it.

Thanks in advance for any help!

Kirby

This sounds like what happened to me last week. If you have, the mini pre cats that come right after the exhaust manifold, then its probably a bad cat.

Does your engine run/sound normal at idle?

Best way to find out if its the cats is to unbolt the exhaust from the manifold and peek inside at the cats honeycombs. People say to bang on the cats and see if they can hear the sound of loose metal, but that didn't work for me when my cat went bad.

What happend to me was that the cat broke up and fell into the exhaust hole effectivly allowing little to no gasses from leaving. This reduced my engine power to the way you described. It also threw missfire codes on the cylinders where the cat was connected to. I would unbolt the exhaust and check the mini cat that's located in the front of the jeep.

Heres a link to my post about the cats, I have some pictures that you can see how a cats suppose to look and how a cat is not suppose to look:

http://www.wranglerforum.com/f5/how-...ad-236678.html

Rubicondon53 04-26-2013 09:29 PM

Quote:

Originally Posted by jgorm (Post 3686287)

It must be coincidence. There is absolutely nothing upstream of the throttle body that would cause your issues, especially dieseling. If you get dieseling on a fuel injected engine, then you have a leaky injector and the wrong spark plugs, or bad carbon build up. Are you sure you didn't change the spark plugs when you put the stock intake back on? These jeeps are map based. The only thing in the intake is the IAT sensor. The jeep will run fine with any intake, or even no intake. I've done dyno pulls without any intake and it ran just fine.

I've explained all this to many folks, all I did was put the stock air box back on and everything was fine after that, and with my meticulous maintenance intervals has been fine ever since.. A private mechanic , and a Chrysler tech guy could only suggest that the Chrysler computer just was not playing nicely with the additional volume of air. More air = more fuel .= too rich ? I put a question mark because neither of them were sure . All I know is, no problems since, and still have a perfectly running motor at 95k miles.. Nonetheless, it is a puzzle ..

KirbyF 04-27-2013 06:33 AM

Ok, so my Jeep does have the MiniCats just below the manifold. 4 O2 sensors. I removed the sensors immediately below the mini's. The sensor on the back cat near the firewall had a dent in the cage. I put my little finger inside and could feel something sticking down. I was able to put a small screwdriver in there and move it up and down. So it seems that the honeycomb material has come loose inside them. I'm going to pull the exhaust off today and look inside. Now I'm wondering if the MiniCats are shot can I remove the material inside and just have the main cat before the muffler operational. I priced the exhaust system with the MiniCats and main cat and their $600 to $700 bucks! Thanks all the advice so far.

chevymad 04-27-2013 10:57 AM

The O2 sensors monitor the functioning of the mini cats, not the main cat. So without the mini's you'll have a check engine light for sure.

tkfx 04-27-2013 01:04 PM

When I solved this problem I didn't want to drop 800 on a whole new exhaust system so. I opened up the problematic mini cat and cleaned out the inside then welded it shut. Now I'm running 2 cats with one of the minis empty. Also I do not have a CEL on.

jgorm 04-29-2013 10:23 AM

Quote:

Originally Posted by Rubicondon53 (Post 3687799)
Chrysler computer just was not playing nicely with the additional volume of air. More air = more fuel .= too rich ? I put a question mark because neither of them were sure .

Well, I'm sure:wavey: It's map based, not maf based. Intake changes do nothing to the AFR and don't add extra air because the stock flows pretty good. Here is a dyno graph with AFR with no intake. You can't get any more than that. And more air + more fuel = just right.

http://www.tricktuners.com/Uploads/2...e_11_13_14.jpg



Quote:

Originally Posted by KirbyF (Post 3688710)
I priced the exhaust system with the MiniCats and main cat and their $600 to $700 bucks! Thanks all the advice so far.

I think smog stuff has a 8yr 80K warranty by the dealer. They replaced my cats for free.


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