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1998 Wrangler 4.0 sputtering

Burch98

Member
Joined
Oct 11, 2019
Messages
31
Location
Oklahoma
Hey everyone. I’ve been trying to figure out what could be causing it but I’m least. My 1998 Jeep Wrangler has lost a lot of power recently over the past month and seems to have gotten worse. I can putt around town just fine no issues (feels gutless still) but when I get on the highway it’s bad and accelerates super slow, and then after about 10-15 miles of driving at 65+ it starts losing power and sputtering like it’s running out of gas, so I pull over and stop and it idles perfectly fine. No trouble codes being thrown, I’ve change the MAP and TPS with new duralast(probably a mistake), new CPS (standard) distributor cap and rotor, even the pick up coil. I’ve ran seafoam through it to see if it would help to no avail. I also had a exhaust leak (never noticed it but there was a nut missing on bottom between manifold and catylic converter) got new nuts and fixed that. It hesitates to start sometimes. It all just started happening recently. And I looked at my catylic converters and can see through them somewhat and don’t appear to be clogged at all. Any help appreciated. Also new fuel pump (acdelco is pretty sure) and it stays at a constant 49-50 psi
 
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Burch98

Member
Joined
Oct 11, 2019
Messages
31
Location
Oklahoma
Also have changed spark plugs, plug wires, twice. My evap system seems to be operating normally...
 
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Burch98

Member
Joined
Oct 11, 2019
Messages
31
Location
Oklahoma
Anybody got any ideas..? I’m stumped...I ran a scanner when it started acting up and initially my LTFT was running lean but when it started sputtering it jumped to +32% so super rich.
 

Bofa-Deez

TJ Enthusiast
Joined
Jul 19, 2019
Messages
329
Location
Deauville, LA
Possible O2 sensors? How many miles?

Mine started doing a similar thing, although not as bad. 4 new O2 sensors and new pre cats fixed it.
 
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Burch98

Member
Joined
Oct 11, 2019
Messages
31
Location
Oklahoma
Possible O2 sensors? How many miles?

Mine started doing a similar thing, although not as bad. 4 new O2 sensors and new pre cats fixed it.
I may have found the issue...not 100% but the duralast MAP sensor I put in might’ve been bad. I put the old one back in and it seems to run better so far still not great. Possible I messed up my 02 sensor as well since my exhaust was only partially connected to the manifold.
 
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Burch98

Member
Joined
Oct 11, 2019
Messages
31
Location
Oklahoma
Does it run normally when the engine is cold and only start stumbling once it starts to warm up?
Normally after running awhile. Thinking my MAP sensor was bad from the get go. It runs around town just fine feels like the fuel/air mixture is off but I put my old map sensor in and it’s definitely changed, feels better so far but I’m not buying duralast again even if it’s the last resort.
 
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Burch98

Member
Joined
Oct 11, 2019
Messages
31
Location
Oklahoma
It’s running lean and then the computer seems to overcompensate for that and it basically makes it run really rich all of a sudden. The new map sensor (replacement duralast, bad idea) made it basically die earlier but same symptoms, but it was way worse than before. I think I’m on the right path. Put the old one back in (original I believe, not duralast) and I’ll see where it takes me.