YJ Power Fading Away

[Sparky-Watts]

Ok, this has been going on for a couple of months now, but my '94 2.5 is getting weaker in the pony department. It's been less than a year (12,000 miles or so) since I changed plugs. Changed fuel filter last weekend. Have a K&N drop in filter, and have tried with that and back with a stock paper filter with no difference, so it's not the filter. I've opened the airbox a bit more. There was nothing I did as far as mods go when this started. It's been getting slowly worse. 4 months ago, I could maintain 75 mph against a 10 mph headwind with little trouble in 5th gear. Now it's a struggle to maintain 55 mph with no wind in 5th gear. If I keep the RPM's above 3000 or higher, it's ok, just not as good as it used to be, but anything below that and it just feels really doggy. Funny thing is, my mileage really hasn't been affected by it. I still get around 20 mpg when I drive 55, so long as I keep it in 4th gear with the RPM's around 25-2700. If I try to drive in 5th, I can make 55 or 60 mph, but I have to use so much skinny pedal, my mileage drops to around 17 or 18 mpg.

Any ideas? I haven't changed out the cap and rotor and wires yet, plan on doing that this weekend. Could it be a plugged cat? How do you diagnose a plugged cat?

Also, for about 6 months, I've been getting a gas odor while driving, or at least with the top off. While I was taking my rear track bar off a couple weeks ago, I found one fuel line that runs up on top of the tank and disappears that was leaking a bit. I tightened up the clamp and it quit, but I can still smell gas, just don't see any leakage. Could it be that there's a leak up on top of the tank or somewhere else that I can't see that is affecting fuel pressure enough to cause loss of power? Wouldn't that cause the Check Engine light to come on? (It never has come on yet).

Open for ideas and suggestions,

Slowly Fading Away Sparky
:?

 

[dropseys]

Well your are replacing cap, rotor, and wires, so see if that helps any. Is it possible you could have a fouled plug? As for repairing a catalytic converter its as easy as an extra long screw driver and a rubber mallet. You may also want to drop the gas tank to make sure you don't have a leak still. We don't want a Kansas fried Sparky.

 

[mud4feet]

Don't really know, Sparky, but have you changed you O2 sensor/s since you've had it? I know my '03 TJ showed similar symptoms (tho' the gas mileage REALLY sucked, too) and after replacing both sensors, everything was back to normal. Just a thought. Could be the cat, too. I know that'll cause some real issues..........but don't know how to diagnose other than whackin' it and listening for noises.

Best of luck, of course.......

mechanically challenged,
mud

 

[Bounty__Hunter]

If it's the catalytic converter, it'll gradually worsen as time goes on, each time it'll run but will choke the motor down to killing it as the exhaust heats up.

Check for leaky fuel injectors as well.

Heat will lower the power output as well, does it run any stronger on a cool night?

 

[Sparky-Watts]

Heat will lower the power output as well, does it run any stronger on a cool night?

No, temperature doesn't seem to make much difference. It's generally around 70 in the mornings when I leave for work, and anywhere from 90 to 110 when I come home. Yesterday morning, it seemed to be doing better about halfway along in my commute, but I think that may have been because of drafting with other cars in traffic.

So, would a leaky fuel injector be something obvious that I could see easily?

 

[Sparky-Watts]

Well your are replacing cap, rotor, and wires, so see if that helps any. Is it possible you could have a fouled plug? As for repairing a catalytic converter its as easy as an extra long screw driver and a rubber mallet. You may also want to drop the gas tank to make sure you don't have a leak still. We don't want a Kansas fried Sparky.

If I had a leak bad enough to affect power, wouldn't that make the CEL come on?

As for cleaning the cat, wow....I don't know if I can even get the thing off to do it. It's still OEM exhaust at 100,000 miles. I have no torch to heat things up, and with the gas fumes, not sure I'd use it if I did. Can't I just get me a big drill bit and drill a couple hundred holes in it?

 

[Sparky-Watts]

Don't really know, Sparky, but have you changed you O2 sensor/s since you've had it? I know my '03 TJ showed similar symptoms (tho' the gas mileage REALLY sucked, too) and after replacing both sensors, everything was back to normal. Just a thought. Could be the cat, too. I know that'll cause some real issues..........but don't know how to diagnose other than whackin' it and listening for noises.

Best of luck, of course.......

mechanically challenged,
mud

To the best of my knowledge, nothing has been changed on this Jeep except the starter, battery, and fuel filter for it's entire life. It only had 54,000 on it when I bought it, and it's just over 100,000 now. Again, would the O2 sensors trip the CEL?

What kind of noises would you listen for when whacking the cat? (other than hissing and meowing?:lol: )

Equally mechanically challenged,
Sparky

 

[Bounty__Hunter]

Don't whack the cat unless you want a rattle. I'd leave it along for now, or find somebody with an IR thermometer to check it's temp after running to see if it's excessive.

Consider sucking some SeaFoam into the intake via the brake booster vacuum line per the SeaFoam instructions. It'll clean the intake, combustion chamber, and catalytic converter. And the smoke is cool.

 

[Hazrider]

I just changed the cat on my 88 yj and the power went way up. The change is pretty easy, I got a universal fit cat. for $90.00. For my jeep I had to take off the transfer case skid plate and jack up the transfer case.

 

[TwistedCU]

take that cat off, beat the tar out of it while dumping out everything that breaks up. Reinstall

That's how you hollow out a cat.

If you have emmissions testing where you are then you need a new one.

 

[Wrangl3r93]

A few months ago when i changed my oil i spontaneously bought a bottle of the fuel injector/fuel system cleaner stuff. Didn't notice a big gain in mileage but i gained back a lot of ponies i didn't know had left the pasture.

 

[Sparky-Watts]

take that cat off, beat the tar out of it while dumping out everything that breaks up. Reinstall

That's how you hollow out a cat.

If you have emmissions testing where you are then you need a new one.

Emissions testing.....what's that?:? :lol: urple:

 

[Sparky-Watts]

Don't whack the cat unless you want a rattle. I'd leave it along for now, or find somebody with an IR thermometer to check it's temp after running to see if it's excessive.

Consider sucking some SeaFoam into the intake via the brake booster vacuum line per the SeaFoam instructions. It'll clean the intake, combustion chamber, and catalytic converter. And the smoke is cool.

I live too far from the ocean to get any sea foam, would farm pond scum work?:lol:

Thanks, Bounty, I'll give that a try, too. I stopped at the parts store yesterday on the way home from work and got a set of wires, cap, rotor, plugs, and K&N filter prep kit (not that it needs it yet, just for when it does). I'm gonna try to get out this morning before it hits 105 degrees and get those put on, so I'll let ya know what happens. Prolly start hitting the exhaust bolts with PB Blaster too.

 

[Sparky-Watts]

Well, changed out the cap, rotor, wires, and plugs this morning, and no change. It had been about 10 months since I changed the plugs, or roughly 15,000 miles. They still looked pretty good, hardly any buildup or anything on them, so that's a good thing. Guess I'll be looking at cleaning the cat next weekend. Not looking forward to that, but guess I'll have to.

Also noticed my gas leak by the tank is back, and worse than before, so I'll most likely be dropping the tank next weekend, too. Really, really not looking forward to that, never done it before, but it doesn't look like it'll be any fun. Any suggestions, tips, or advice on that?

Seriously dejected,

Sparky

 

[mud4feet]

I was wondering if you'd solved your problem yet. I know it was very frustrating for me with my O2 sensor problem.............power (what power there is with the 4banger) was WAY down and my mileage was around 14-15.............I was gettin' ****ed, to say the least. Didn't really trip the CEL until it was pretty obvious that there was a problem. Just something else to check, even though I own a TJ and you have a YJ. But that cat would definitely be a strong suspect............either replace it or remove it, IMHO.

Still mechanically challenged,
mud

 

[Sparky-Watts]

I was wondering if you'd solved your problem yet. I know it was very frustrating for me with my O2 sensor problem.............power (what power there is with the 4banger) was WAY down and my mileage was around 14-15.............I was gettin' ****ed, to say the least. Didn't really trip the CEL until it was pretty obvious that there was a problem. Just something else to check, even though I own a TJ and you have a YJ. But that cat would definitely be a strong suspect............either replace it or remove it, IMHO.

Still mechanically challenged,
mud

Still having the same problem. Did yours run rough when the sensor went out? That's the deal, mine is still running smooth, starts ok, all that. The guy at the parts store used to do emissions testing for California for 20 years, and sounded like he pretty well knew his stuff. I told him the symptoms, and he said it sounded like the cat, too. He said when it's a plugged cat, they'll still run smooth, and mileage usually won't suffer too bad, just that the power will go away. That describes my problem to a tee. Mileage has only dropped a tad, but I think it's because I have to use so much skinny pedal at the higher speeds.

I'm guessing it probably wouldn't hurt to change out the sensor anyway. Don't know how the TJ and YJ differ, but where is the sensor you changed?

 

[Wrangl3r93]

Crawled under mine when i was seeing how hard it would be to change my gf's sensor. It's located to the right of your transmission(driver's side) in the exhuast right before it bends to go back towards the rear. That's where it was on my '93yj and sarah's '97tj. Just screws out then unplug the wires and reverse for the new one. Might wanna hit it with some pb blaster too.

 

[SenorCole86]

Also noticed my gas leak by the tank is back, and worse than before, so I'll most likely be dropping the tank next weekend, too. Really, really not looking forward to that, never done it before, but it doesn't look like it'll be any fun. Any suggestions, tips, or advice on that?

Just run the thing as dry as you can get it before dropping the tank, they can be heavy. Not too sure how yours is set up, but here's how I did mine. Take off filler hoses, put a few jacks under it, unbolt the skidplate, lower it a tiny bit, undo wires and fuel lines, and then lower it to the ground. Good luck bud!

 

[pdparker]

Change the cap, rotor and wires first. Change the plugs and look for fouling of the old plugs. Use the platinum Autolites that have either two or four anodes for max power. As far as the gas, see if you smell gas as you are reving the engine. Your are probably running too rich on your fuel mixture. A catalytic converter going bad will choke the exhaust to the point that the engine will die. It creates too much back pressure and you can actually burn your exhaust valves if this goes unresolved. You may also see if your blower is functioning properly to ventilate the catalytic converter. Let the engine idle for a period of time and allow the exhaust system to heat up. If the catalytic converter is getting really bad, it will get so hot that it may actually smoke or get red hot. Either way, this is a bad sign and needs to get fixed soon.

 

[Sparky-Watts]

Change the cap, rotor and wires first. Change the plugs and look for fouling of the old plugs. Use the platinum Autolites that have either two or four anodes for max power. As far as the gas, see if you smell gas as you are reving the engine. Your are probably running too rich on your fuel mixture. A catalytic converter going bad will choke the exhaust to the point that the engine will die. It creates too much back pressure and you can actually burn your exhaust valves if this goes unresolved. You may also see if your blower is functioning properly to ventilate the catalytic converter. Let the engine idle for a period of time and allow the exhaust system to heat up. If the catalytic converter is getting really bad, it will get so hot that it may actually smoke or get red hot. Either way, this is a bad sign and needs to get fixed soon.

Well, as I mentioned in a previous post, I already changed the cap, rotor, wires, and plugs, and that the plugs looked in very good shape for only 15,000 miles on them, and they were Bosch Platinum Plus 4's. The gas odor isn't from the exhaust. I had also mentioned the leak by the tank. It does get worse when I rev the engine, but only because it causes more gas to drip out of the line. But, on a plus side, it only leaks when the engine is running, so I'm not losing too much of that liquid gold.:lol: