Running rich

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Keepjeepin

New Member
Joined
Oct 17, 2021
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3
Location
Charlotte NC
I’ve changed out both O2 sensors, complete tune up, new fuel pump, new muffler (not the cat), ran sea foam, still running rich…the only thing I haven’t done is clean out the throttle body….any suggestions or input?? 97 TJ 160,000 miles otherwise runs great!! 🤷🏻‍♂️🤦🏻‍♂️#help
 
What are the symptoms you're experiencing to make you believe it's running rich?

Have you hooked it up to a live data OBDII scanner? That would tell you quite a bit as oppose to just throwing parts at it.
 
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I have and nothing com
Chris said:
What are the symptoms you're experiencing to make you believe it's running rich?

Have you hooked it up to a live data OBDII scanner? That would tell you quite a bit as oppose to just throwing parts at it.
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up; I planned on doing everything I did when I bought it anyway as I knew it needed most of that work done, but nothing on the scanner
 
Keepjeepin said:
I have and nothing com

up; I planned on doing everything I did when I bought it anyway as I knew it needed most of that work done, but nothing on the scanner
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I’m not talking about scanning it for codes (if that’s what you meant). I’m talking about hooking it up to a device that reads live, real time data. If you do this it will point you in the right direction almost certainly.
 
What brand of O2 sensor did you install? NTK? Bosch? Store brand? Did you replace upstream, downstream, or both O2 sensors?
 
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Hoping to revive this thread as I'm having a similar problem. New o2 sensors all around (4 total; ntk per @Jerry Bransford recommendation), new cat-back exhaust (original cats), new plugs, cleaned out iAC last summer, smooth idle, no codes (now that I've changed the o2 sensors). I don't know if acceleration is strong or weak b/c I've only ever driven this TJ - it's at least consistent in the 18 months I've owned it. Temp seems ok, just between the 1 & 0 of the 210, though I've read that it should be b/w the 2 & 1...not sure if that's a big deal? I have a replacement thermostat (per recommendations by users here: Superstat 195). Haven't checked the IAT sensor to see if that's sooty, but I might replace it b/c I don't know when it was done last.

So I just swapped hard for soft top in preparation for the warmer months to come. While driving or idling, I'm overwhelmed by a smell that I think indicates that I'm running rich? Not burning, but it's like someone took the odor knob on the exhaust smell and cranked it up to 11. Make sense?

I also decided to track my mpg for the first time and am currently tracking to about 10-12 mpg (4.0, manual, 180,000 miles), which is lower than I would have expected.

So, do I replace the IAC and the thermostat? Or could it be something else? I'd love to be able to putz around town and not worry bout carbon monoxide posoning.

TIA!
 
Check for exhaust leaks, too. A leak upstream of the cat can be particularly smelly. I had a car that leaked at the turbo outlet flange and I felt like I was gonna pass out when I drove with the windows open.
 
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PhillyJake said:
Hoping to revive this thread as I'm having a similar problem. New o2 sensors all around (4 total; ntk per @Jerry Bransford recommendation), new cat-back exhaust (original cats), new plugs, cleaned out iAC last summer, smooth idle, no codes (now that I've changed the o2 sensors). I don't know if acceleration is strong or weak b/c I've only ever driven this TJ - it's at least consistent in the 18 months I've owned it. Temp seems ok, just between the 1 & 0 of the 210, though I've read that it should be b/w the 2 & 1...not sure if that's a big deal? I have a replacement thermostat (per recommendations by users here: Superstat 195). Haven't checked the IAT sensor to see if that's sooty, but I might replace it b/c I don't know when it was done last.

So I just swapped hard for soft top in preparation for the warmer months to come. While driving or idling, I'm overwhelmed by a smell that I think indicates that I'm running rich? Not burning, but it's like someone took the odor knob on the exhaust smell and cranked it up to 11. Make sense?

I also decided to track my mpg for the first time and am currently tracking to about 10-12 mpg (4.0, manual, 180,000 miles), which is lower than I would have expected.
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What size tires are you running, what ratio is in your axles, and what model year is it? Your Profile is devoid of any information like that, it helps to answer your questions so please add that info asap. Your engine should be running at or very close to 210 degrees. Below the '2' on the temperature gauge is too cold which would indicate the correct 195 degree thermostat, non-failsafe, should be installed.
 
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Jerry Bransford said:
What size tires are you running, what ratio is in your axles, and what model year is it? Your Profile is devoid of any information like that, it helps to answer your questions so please add that info asap. Your engine should be running at or very close to 210 degrees. Below the '2' on the temperature gauge is too cold which would indicate the correct 195 degree thermostat, non-failsafe, should be installed.
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Fair point - I'll have to update my profile...done! But I'll paste it here:
  • 4" Zone Lift (installed by PO)
  • 33" Tires on 17" wheels (installed by PO)
  • Barricade Rear Tire Carrier/Bumper
  • LED Head & Fog lights - KC A-pillar lights
  • Upgraded stereo
  • Rancho Shocks
  • Stock T-cases & gearing
  • NV3550 Transmission (@pagrey you guessed it - not sure what the lower boot is so I'll have to look into it, thanks for the tip!)
Re: the thermostat, mine rests consistently between the "1" and "0" in the 210, so I should leave the stat alone, right?
freedom_in_4low said:
Check for exhaust leaks, too. A leak upstream of the cat can be particularly smelly. I had a car that leaked at the turbo outlet flange and I felt like I was gonna pass out when I drove with the windows open.
Click to expand...
This is a good call, though I'm not hoping to find anything. I only replaced the cat-back b/c I had a cracked muffler (the cold weather made the hot leak clear, which is how I diagnosed), but I didn't bother checking the cats themselves since my new o2 sensors cleared all my codes. I don't know how to find an exhaust leak, so I'll search around, but if you have any go-to methods, I'm all ears!

Thanks, all, for jumping into an old thread and sharing the wisdom! I'll look into the boot and the cats!
 
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PhillyJake said:
Fair point - I'll have to update my profile...done! But I'll paste it here:
  • 4" Zone Lift (installed by PO)
  • 33" Tires on 17" wheels (installed by PO)
  • Barricade Rear Tire Carrier/Bumper
  • LED Head & Fog lights - KC A-pillar lights
  • Upgraded stereo
  • Rancho Shocks
  • Stock T-cases & gearing
  • NV3550 Transmission (@pagrey you guessed it - not sure what the lower boot is so I'll have to look into it, thanks for the tip!)
Re: the thermostat, mine rests consistently between the "1" and "0" in the 210, so I should leave the stat alone, right?

This is a good call, though I'm not hoping to find anything. I only replaced the cat-back b/c I had a cracked muffler (the cold weather made the hot leak clear, which is how I diagnosed), but I didn't bother checking the cats themselves since my new o2 sensors cleared all my codes. I don't know how to find an exhaust leak, so I'll search around, but if you have any go-to methods, I'm all ears!

Thanks, all, for jumping into an old thread and sharing the wisdom! I'll look into the boot and the cats!
Click to expand...

I just block the tires and let it idle in neutral with the parking brake set and roll around underneath with a creeper and feel. A leak may have a small amount of soot accumulated around it, or you can feel tiny puffs of exhaust escaping. If it's big enough you'll hear a characteristic bvvvvvvvvvv from it. (think of the last time you saw a Dodge Neon or a Pontiac Sunfire and it's the sound it was probably making)

Mine was especially difficult to find because it was hidden under a heat shield covering the entire hot side of the turbo and the downpipe all the way to the cat. Fortunately the TJ isn't packed so tight as to need that much shielding.
 
PhillyJake said:
So I just swapped hard for soft top in preparation for the warmer months to come. While driving or idling, I'm overwhelmed by a smell that I think indicates that I'm running rich? Not burning, but it's like someone took the odor knob on the exhaust smell and cranked it up to 11.
Click to expand...
Of course, we're not able to smell it like you can, but your description doesn't sound like 'rich'? To me, that means unburned fuel smell.

Since you just replaced the exhaust, that is what I'd be focusing on for leaks. If you make a simple smoke machine like used for vacuum leaks, you can shoot it up the tailpipe and check that way. If your shifter boot is bad, they are NLA. There is a thread on here about how to use a different manufacturers boot and modifying the bottom plate to fit.
PhillyJake said:
I also decided to track my mpg for the first time and am currently tracking to about 10-12 mpg (4.0, manual, 180,000 miles), which is lower than I would have expected.
Click to expand...
Have you installed a new speedo gear to match your tire diameter? If not, use a GPS to calculate distance instead of the odometer for your next MPG check.
 
PhillyJake said:
Fair point - I'll have to update my profile...done! But I'll paste it here:
  • 4" Zone Lift (installed by PO)
  • 33" Tires on 17" wheels (installed by PO)
  • Barricade Rear Tire Carrier/Bumper
  • LED Head & Fog lights - KC A-pillar lights
  • Upgraded stereo
  • Rancho Shocks
  • Stock T-cases & gearing
  • NV3550 Transmission (@pagrey you guessed it - not sure what the lower boot is so I'll have to look into it, thanks for the tip!)
Re: the thermostat, mine rests consistently between the "1" and "0" in the 210, so I should leave the stat alone, right?
Click to expand...
Well, you're undergeared for the 33" tires with the stock factory 3.73 axle ratio. Being undergeared means you engine rpms are lower than how the factory designed them to be at which can cause the engine to be running a little less efficiency. Regearing the a more appropriate axle ratio like 4.56 would raise the engine rpms to where they should be and my bet is your mpg would go up probably several mpg, not to mention its around-town and highway performance would be significantly better.

For a little 'for example... I bought my present 2004 TJ with 35" tires. Its automatic transmission has an Overdrive ratio that drops the rpms WAY too low. So its previous owner undergeared it with 4.88 gearing which would have been appropriate for your 5-speed manual. But with my automatic transmission its gearing should have been 5.38 to raise the rpms up where they'd be with 4.88 gearing and your 5-speed transmission. So what happened with the 4.88 gearing the rpms were so low with my automatic transmission that it had sluggish performance and it was only getting 11 mpg, it never made it to even 12 mpg. So I regeared it several years ago to 5.38 and my mileage suddenly jumped to 14.6 and its around-town and highway performance finally became adequate/good.

That all boils down to it sounding like your engine is on the edge of lugging and regearing it to 4.56 would definitely help its performance and very likely its mpg too. And don't compare your Jeep's rpms to your other car(s), cars with their lighter weight, better aerodynamics, and significantly smaller tires that have less rolling resistance. Cars don't need nearly the rpms that a Jeep does with oversized tires. 2700-2750 or so rpms is entirely appropriate for 70 mph on the freeway/expressway in a Jeep.

So I'm betting regearing to 4.56 would substantially help performance and likely improve your mpg too.

And if your temperature gauge is saying 210 once warmed up, that's right where it should be. :)
 
Trying to find out if I can increase my fuel economy by changing tire size. I have a 1999 TJ with a 4.0 and a 32RH 3 speed automatic. It has a Dana 35 with a 3.07 rear axle ratio I am running 15 inch rims and 31x10 inch BFG all terrain tires I have 7K on a rebuilt motor that is all stock I have replaced the exhaust system including the catalytic converter.I get about 14 to 15 on the highway I have not checked in town mileage. The research on increasing gas mileage related to fuel and engine mods varies so much from what I can tell it is what is so I thought what about tire size and gear ratio.
Thanks
 
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