1994 wrangler problems

[magna]

i have a 94 wrangler 4 cyl that after driving about 20 minutes starts missing and backfiring and will hardly pull out of it's tracks, coil and pick-up coil have been replaced. when i bought the pick up coil i found out the 94 wouldn't work it took a 97 pick up coil, so motor may have been changed. it has FI.

 

[TerryMason]

Do you get any computer codes from it?

If I had to guess I'd say it's running lean. Does it backfire when you let off the gas or when you get on it?

 

[magna]

check engine light isn't on, the backfire comes while on the gas "seems like a cyl. isn't firing and filling with fuel then it fires with a loud bang". when it's doing this you can hear the missing thru the exhaust like it's only running on 2 cylinders. i'm wondering if the computer might be breaking down?

 

[Wrangl3r93]

Sounds like an o2 sensor.

 

[97teejay]

when a engine warms up it needs less fuel, so either its a lean or rich pop, i agree with 96, it sounds like a 02 sensor.

i had a similar problem with my 97, it would only do it on the freeway, it wouldn't pop but it was shutter and loose power almost instantly during accelleraion. I hooked up a OB2 scanner and it had a low voltage code at the Throttle posistion sensor, replaced it and it cleared up the problem.

FYI I don't know if you have a schucks auto parts near you but they read fault codes for you for free...

 

[magna]

after about 20 minutes of running this jeep loses so much power it will barely pull itself, does a 02 sensor have that much control over the engine? i've had a bad 02 sensor in a honda car and the only real effect was fuel mileage. we have autozone, advance and o'reilly's where i live "tennessee". thanks

 

[TerryMason]

Autozone will read them for free.

 

[Wrangl3r93]

Yeah an o2 sensor has that much power. My friend had one go out and it was just like what you described, when you first turned it on it ran decent then after it warmed it had no power.

P.S.- What part of Tn? Murfreesboro/Knoxville(school) here

 

[magna]

i'll try a new 02 sensor and let everyone know. thanks

i'm in n. east tn. "greeneville "

 

[jfrabat]

I once had a similar (no backfire in mine, but loss of power sounds similar) that turned out to be the fuel system. I replaced the fuel pump and fuel rail complete with fuel pressure regulator and the problem went away. In my case, the hotter the day, the worse it would get... But I would go for the O2 sensor first (much cheaper and easier to change!).

 

[magna]

well i replaced the 02 sensor and it created another problem, now the jeep just quits anytime "idling or running" it will start right back up but may quit running in 30 seconds or 2 minutes. also noticed if you press the gas pedal down it will rev up until about a half throttle then bog down the rest of the way and backfire like it's running out of fuel, also when it dies it's like the fuel shut off. it didn't do this before the 02 sensor "the dying" any idea's? thanks

 

[rollmeoverplease]

have you checked the plugs? to see if fouled out

 

[magna]

when it runs it's firing on all 4

 

[jfrabat]

Even so, checking the plugs can tell you if there are other issues... I would take them out and "read" them to see what comes up...

 

[guysmiley]

Check your TPS and MAP sensor. My TPS was doing that when I swapped throttle bodies and had to modify the position.

 

[Poobah]

I would have said 02 sensor first - then check for a cracked exhaust manifold...but I think that problem is usually associated with the 4.0L / I-6 and you have a 4 cyl...though I guess it could still be the cause. Check the welds closely on the header - sometimes hard to see... The backfiring, loss of power, etc all sound like symptoms that I had and it turned out to be the cracked header.