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Unread 09-15-2013, 04:35 PM   #1
b_a_mech
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1994 YJ Wrangler 
 
Join Date: Dec 2011
Location: Navarre, Florida
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Running rich

So is there a "quick" adjustment that can be made somewhere to lean my 4.0 out a bit? I have searched (here and google) and it seems mostly Cherokees have had issues but appears they haven't found a fix. My issue is not major, I'm not having any codes, rough idle or general running issues....just looking to see if I can lean her out just a little bit because I've noticed the exhaust is a little richer smelling than normal. Not burning any oil and MPG is steady at about 15....thanks for the help in advance

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Unread 09-15-2013, 06:41 PM   #2
jsawduste
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Ahh no. The AFR is controlled by the inputs into the ECM except when in open loop. Unless you have a bad sensor (which would throw a code) or simply worn out plugs, cap etc not much you can do.

I`d like to se a Cherokee with the issue. Someone doesn't know what they are talking about.
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Unread 09-15-2013, 07:28 PM   #3
coolin4u
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Quote:
Originally Posted by b_a_mech View Post
So is there a "quick" adjustment that can be made somewhere to lean my 4.0 out a bit? I have searched (here and google) and it seems mostly Cherokees have had issues but appears they haven't found a fix. My issue is not major, I'm not having any codes, rough idle or general running issues....just looking to see if I can lean her out just a little bit because I've noticed the exhaust is a little richer smelling than normal. Not burning any oil and MPG is steady at about 15....thanks for the help in advance
I have the exact same issue,runs fine,doesnt miss,check engine light not on but strong odor like it is running rich.Mine did throw a code for the o2 sensor once when i checked it but i would have thought it would have turned on the check engine light.I may end up changing it just to see if it helps.
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Unread 09-15-2013, 07:40 PM   #4
b_a_mech
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Quote:
Originally Posted by coolin4u
I have the exact same issue,runs fine,doesnt miss,check engine light not on but strong odor like it is running rich.Mine did throw a code for the o2 sensor once when i checked it but i would have thought it would have turned on the check engine light.I may end up changing it just to see if it helps.
I do know that when your cat goes bad you start having stink issues but mine is only 2 years old and from what I've read it is not a excessive fuel smell
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Unread 09-15-2013, 09:17 PM   #5
b_a_mech
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Quote:
Originally Posted by jsawduste
Ahh no. The AFR is controlled by the inputs into the ECM except when in open loop. Unless you have a bad sensor (which would throw a code) or simply worn out plugs, cap etc not much you can do.

I`d like to se a Cherokee with the issue. Someone doesn't know what they are talking about.
Plugs and wires and cap are 1,000-1,500 miles old (regular champions for plugs)

And I certainly hope you sir are not referring to me......unlike some on here.....if I have a question it's because searches have failed to answer it
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Unread 09-16-2013, 05:40 AM   #6
jsawduste
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Quote:
Originally Posted by b_a_mech View Post
Plugs and wires and cap are 1,000-1,500 miles old (regular champions for plugs)

And I certainly hope you sir are not referring to me......unlike some on here.....if I have a question it's because searches have failed to answer it
No not at all. The Cherokees are a bit more advanced then our YJ`s.

One thing you might check is the Fuel Pressure. If the pressure is on the high side you may be dumping more fuel but still be within the parameters of the O2 sensor. On my stroker I can play with fuel pressure and make the AFR rich to the point of the exhaust burning your eyes at idle and not throw a code.

In fact I`ve played with fuel pressure and adding an air bleed to the throttle body plate to get the AFR`s at idle along with ratios at larger throttle openings. Currently run 43 lbs of FP with 24 lb injectors.

Another distinct possibility is actually the fuel you are burning. Florida RFS (Renewable Fuel standard, March 2008) required MANDATORY 100% blending of ethanol for public supply of gas by 12/31/2010. The ethanol laced fuel can give you just the issues you are experiencing.
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Unread 09-16-2013, 07:05 AM   #7
vadslram
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As said above. Pressure regulator, injector leaking, one of many sensors on the way out are your most likely suspects. You may not be throwing a code because it isn't going into closed loop and so it won't look for error.
If your temp sensor is reading cold for whatever reason then it will run rich, not go into closed loop and not throw an error because it is still reading some temp just not warm enough to go into regular running mode.
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Unread 09-16-2013, 07:45 AM   #8
b_a_mech
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I did just switch to the Ford 19lbs injectors....guess I better look at that rail pressure.
And on the ethanol mix crap....I only have 2 gas stations around here that don't serve it and they are far enough away that I don't get to fill up with it often enough.
And the only temp sender I gave to worry about is the one on the thermostat right??
I can change that and see if it changes anything.
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Unread 09-16-2013, 08:27 AM   #9
jsawduste
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Quote:
Originally Posted by b_a_mech View Post
I did just switch to the Ford 19lbs injectors....guess I better look at that rail pressure.
And on the ethanol mix crap....I only have 2 gas stations around here that don't serve it and they are far enough away that I don't get to fill up with it often enough.
And the only temp sender I gave to worry about is the one on the thermostat right??
I can change that and see if it changes anything.
The stroker likes 100% fuel but like you the closet station is to far away to make it convenient.

The ethanol may have eaten the FPR. Possible and worth checking.

vadslram is right on the money with the temp sensor (you are correct, the water neck) not allowing the engine to go into closed loop thus no codes.
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Unread 09-16-2013, 08:37 AM   #10
Que89YJ
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You say it is smelling rich, what kind of reading are you getting on the temp sensor when it is warm? You should see.3-.4Vdc on the output. To add to the closed loop x100. Just curious....you did put back in the tstat. Too many people are running around without them not knowing that it will not go into closed loop without the tstat and will run rich.
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Unread 09-16-2013, 11:37 AM   #11
b_a_mech
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Quote:
Originally Posted by Que89YJ
You say it is smelling rich, what kind of reading are you getting on the temp sensor when it is warm? You should see.3-.4Vdc on the output. To add to the closed loop x100. Just curious....you did put back in the tstat. Too many people are running around without them not knowing that it will not go into closed loop without the tstat and will run rich.
I'll have to check....yes I run a tstat but I think they didn't have 195 and I stuck a 185 in. But I know I'm good on temp because I was having temp issues and my gauge isn't the best indicator so I check things regular with a digital IR gun. Numbers off the block range from 195-215
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Unread 09-16-2013, 12:01 PM   #12
Que89YJ
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185 is good. It goes into closed loop at 180. You can still check the O2 sensor voltage and see if it is reading high.
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