Typical Idle Sound? 4.0

[kis86]

Does the 4.0L (TJ) run as smooth as a car typically, or do they run a little rough? Mine sounds "even", no choking or anything like that, but isn't smooth and quiet at idle either. Maybe an exhaust leak, maybe just needs a tuneup?

The plugs and wires were changed in 2005, and the Jeep has been driven about 4k since then...until I bought it yesterday. I've never had a Jeep before, but my 98 Ranger ran very smooth. It just doesn't seem like it should sound the way it does :???: hard to explain

 

[xt master]

it does sound different,mainly because you have no insulation to soften the sound.I thought the same thing when I first got mine.Took it to 2 different garages to look for an exhaust leak and they could not find any.If you do think it is a leak,try looking around the head bolts and the manifold flanges.If it is not back firing or popping when you let off the gas most likely it just the way it sounds.Always worth checking out to be on the safe side.

 

[Crazy4diesels]

Mine has always been a little rough at idle. You can feel it stumble ever so slightly and sometimes even catch it on the tach. It never misses - it just isn't as smooth as you would think it should be. My M37's (early 50's flathead straight sixes) both idle better (once they're warmed up). They miss at idle now and then (you can hear it in the exhaust) but remain smooth. You would think that with all their high-faloot'n computer controls these 4.0's would idle smoothly. Oh, well... The 4.0 is still one of the best automotive engines out there. It is a strong, solidly built cast iron engine which has roots back to (I think) 1963. No overhead cam, no aluminum head, no "powdered metal" connecting rods, no modern over-engineering. The 4.0 was yesterdays technology still available today - it's a real shame they dropped it after 06. Best of luck... You can't go wrong with a Jeep!! - John

 

[kis86]

Thanks for the advice I was thinking it was probably fine, but I've only gotten 13 mpg in the last two tanks of gas...just bought it though, and it is winter. I think I'll get a new cap and some plugs in this weekend and see if it makes any difference. Anything else I could check as far as low mpg?

 

[TerryMason]

Manual or Auto? If it's an auto, then that's the correct MPG

Model | MPG (city) |MPG (hwy) |AnnualFuelCost* |Greenhouse Gas Emissions (tons/yr)

Jeep Wrangler 4WD 4 cyl, 2.5 L, Automatic 3-spd, Regular |14 |17 |$1661 |12.20
Jeep Wrangler 4WD 4 cyl, 2.5 L, Manual 5-spd, Regular |16| 18 |$1464 |10.80
Jeep Wrangler 4WD 6 cyl, 4 L, Automatic 3-spd, Regular |13 |17 |$1661 |12.20
Jeep Wrangler 4WD 6 cyl, 4 L, Manual 5-spd, Regular |14 |18 |$1556 |11.40

 

[kis86]

auto, but that was highway miles! not sure about city yet...

 

[Collin the Hen]

Has the speedo been trued? I've read that with 31's, you can add a mile per gallon. I don't know if this holds true, but it only makes sense since you would be traveling the same distance with the odometer reading a shorter distance. :scratch: I think that's right.
Plus, you're probably letting it warm up in the morning.

 

[xt master]

As far as millage it is a Jeep.Go any where do anything.It is not a compact car that is good on gas..lol:lol:

I have a 97tj with a 2.4 5 speed with 31" tires in the city on a good day i get around 13 mpg..Not sure what the highway is I dont drive it enough on the highway.

 

[kis86]

yea yea, I know it's not good on gas but I hope to get what others driving the same thing get, I'll change the plugs and see what happens when the weather warms up up a bit more. Thanks!

 

[JeepMonkey]

Hopefully, mine has always made the clicking sound. I didn't really start to notice it until after I did the exhaust. That leads me to believe that it's a leak, but performance has not suffered. The only problem I have now is a CE light that won't go off, but I investigated the codes and I think it's just cause of the vapor return hoses to the tank. Though, the light showed up as soon as I put the new header/muffler together.

good luck!

 

[Nick Mud]

Make sure you don't have a small exhaust leak where the manifold bolts to exhaust pipe. Jeep has had a problem with cracks. Had to replace mine, 99TJ & 99XJ. They changed the design mid year of 99. Have a freind cover the tail pipe with a towel, motor running, while you look under the hood. Use a flashlight and see where the manifold flange meets and bolts to the exhaust pipe is where they usually break.

 

[Rascal]

the 4.0L is ruff and tumble due to the firing order,or so i am told!
very strong engine,enjoy!