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Author Topic: 2.5L running rich  (Read 4255 times)

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Red93YJ

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2.5L running rich
« on: August 10, 2006, 08:15:17 PM »
Hello everyone,

I've been doing a lot of reading on the forum, trying to track down what the problem is with my jeep, but i'm not having a whole lot of luck. I couldn't find a thread using the search that helped much either, so here goes.

My jeep has no power from 3000-3500 rpms. It is fine up to 3000 then bogs big time, and struggles until about 3500 rpms where it will pick up it's normal power again and run. This is particularly noticeable in 2nd and 4th gears. When it finally "blows through" the bogging range you can see fuel smoke if you look back in the mirrors.

I pulled the codes, and got the code indication that the O2 sensor is getting a rich reading, which is verifiable by the weekly fouling out of a set of plugs (factory type champions gapped to .035).

So far I've changed the plugs (many times now), cap, rotor, plug wires, 02 sensor, and removed the catalytic converter, and the problem still exists.

What should be the next thing that I check to try to solve the problem?

Thanks for the time and input
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SMC4WD

  • Guest
2.5L running rich
« Reply #1 on: August 10, 2006, 08:23:52 PM »
My guess would have been the O2 sensor, but you said that you replaced that  :roll:.

I've been having a similar problem with my Jeep at idle.  I've diagnosed it to be my catalytic convertor...  You're problem seems different than mine...
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wrangler387

  • Guest
2.5L running rich
« Reply #2 on: August 11, 2006, 02:43:27 PM »
Their is a rich spot in that part of the stock tune I believe. I havn't really went above 3grand a whole lot, but my friend that was in my car said that my wideband dipped down into the 11.x:1 after 3 grand then went back to low-mid 14:1 AF as I stayed going for alittle bit longer. This wasn't full throttle though, half to three-quarter throttle.
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Red93YJ

  • Guest
2.5L running rich
« Reply #3 on: August 11, 2006, 04:42:46 PM »
But your jeep is running fine through that point isn't it?

This on acts like it is pushing against a brick wall from 3000-3500. And it is fouling out a set of plugs per week.

I'm wanting to think that it has to be TPS or air intake sensor related, but I was hoping I'd run across someone else who was had the same problem first.

Thanks for the replies
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wrangler387

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2.5L running rich
« Reply #4 on: August 11, 2006, 05:03:14 PM »
Yea, mine definately doesn't foul out the plugs. I do have a little drop off in power right there, but around there is where the torque curve starts to drop I'm assuming. What brand O2 sensor did you get? you did reset the ECM correct?
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Red93YJ

  • Guest
2.5L running rich
« Reply #5 on: August 11, 2006, 08:57:20 PM »
the 02 sensor came from napa.

to reset the ECM I just unhooked the battery for an hour or so.

thanks

SC
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jwrape

  • Guest
2.5L running rich
« Reply #6 on: August 31, 2006, 02:08:26 PM »
my 92 has always run rich. But I don't have a loss of power. I have the 40 TB that helps alot with power. My motor actually wakes up around 3k rpms. I am changing my o2 sensor again to try to get it to run normal.
I just replaced a rusted muffler that was making my eyes water with fumes under the tub.
Hopefully my OEM O2 will fix my issue.

I have read that aftermarket O2 sensors don't always work correctly
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SMC4WD

  • Guest
2.5L running rich
« Reply #7 on: August 31, 2006, 02:38:27 PM »
Quote from: "SMC4WD"
My guess would have been the O2 sensor, but you said that you replaced that  :roll:.

I've been having a similar problem with my Jeep at idle.  I've diagnosed it to be my catalytic convertor...  You're problem seems different than mine...


Holy Moly!!  I was right???   :D
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87comanche

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2.5L running rich
« Reply #8 on: August 31, 2006, 08:25:15 PM »
On a related topic, can you "re-jet" a throttle body?  I just put a header on, and I'm wondering if I'm going to run lean.  On my old Camaros, I used to jet up the carb after installing headers.

T
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jwrape

  • Guest
2.5L running rich
« Reply #9 on: September 01, 2006, 05:35:02 AM »
Quote from: "87comanche"
On a related topic, can you "re-jet" a throttle body?  I just put a header on, and I'm wondering if I'm going to run lean.  On my old Camaros, I used to jet up the carb after installing headers.

T

I don't think you will need to, usually most Jeeps run to rich from the factory. A header just opens up the air flow out anyways. Your not changing the air flow into the TB.
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wrangler387

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2.5L running rich
« Reply #10 on: September 01, 2006, 10:14:30 PM »
^ kind've. When you allow the exaust to flow better you end up with more new air. Not everything from the combustion makes it out each stroke, therefore when the new air comes in, you still have leftover "combusted" air.  Allowing more of that combusted air to escape each stroke means you will have more good air, so more power etc.

And you can't "rejet" a fuel injected vehicle like a carb... I honestly have almost no experience with carbs, so have no clue what you mean by that. But for fuel injection under WOT conditions there is a set fuel amount per RPM and KPA, and then things like coolant temp and air temp get calculated in also. So the only way to alter the amount of fuel is to play with the fuel pressure, run a bigger injector (both not great ways, no fine tuning). Or run some form of engine management.
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dan684

  • Guest
Same Problem Here
« Reply #11 on: September 08, 2006, 07:26:18 PM »
i'm having the same problem with my 95 YJ 2.5 TBI
i just bought the jeep and replaced plugs, wires, etc to tune it up so i havent noticed if the plugs are fouling.
any help on this would be greatly appreciated.
Thanks,
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Offline chardrc

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  • Posts: 3535
Re: Same Problem Here
« Reply #12 on: September 08, 2006, 08:17:48 PM »
Quote from: "dan684"
i'm having the same problem with my 95 YJ 2.5 TBI
,


hmm thats odd since 91 they had mpi for the 2.5...
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1990 YJ 4cly, ax5, 2.5 inch BDS lift, 31 MTr\'s,  Powertrax-lockers all around, track-bars removed, boomerang shackles, warn m8000 winch, electric fan. [sold but not forgotten]

2007 jk Rubicon 2dr

Red93YJ

  • Guest
2.5L running rich
« Reply #13 on: September 10, 2006, 06:43:20 PM »
ended up tracing my problem back to a thermostat being stuck open. Engine was running in "choke circuit" so to speak all the time because it never would get up to temperature. Put a new thermostat in it, and it's good to go.

Have since installed a blaster 2 MSD ignition coil, and a new set of MSD Plug wires, along with gapping the plugs out to .060 and the jeep is running better than ever.
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Tall Boy

  • Guest
2.5L running rich
« Reply #14 on: September 11, 2006, 08:01:55 PM »
dude, I put a header on, and a k&n filter with a rock it intake and a tbs. do I need to regap my plugs?  i have not touched anything else. i can not feel a difference after adding the header, but my old one was cracked. I got a 2001 tj 2.5l
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