I always had no problem on the highways in my jeep, untill now. I just recently put a 4.5" rubicon express extreem duty lift on it. It came with the 1" transfer case lowering kit and the shims for the front and rear axle to correct the driveline. I also have a 1" body lift. The jeep will drive fine around town all day, even in the summer heat. I was leaving denver a couple weeks ago. on a highway going about 45. then the engine started to bog down like it was out of fuel or no air. when I depressed the clutch the engine reved fine. but when I engaged the drivedrain agian, the engine would bog down unless I decreased my speed. I started to climb a hill (about 6% grade) and it got so bad that it would not go over 15mph! (in a 5min period). Agian if I depressed the clutch, it would rev as high as I wanted it. If I pulled off to the side of the road and turned it off for 10 sec. It would start right away and drive fine around town. this happends every time I go on the highway. The only other time I can make this happen is at high rpm in 3rd gear going up a little street hill. any Ideas anyone? Thanks, Rich Jeepncolo

I would have to believe that your fuel pump is shot theres probably not enough fuel pressure under load. you might want to check into that I am almost sure you are still running the stock mechanical fuel pump with the inline six, so your best bet would be to check that first and if thats the case replace your fuel filter too. If I were you, I would add an additional filter before the fuel pump somewhere on your rubber hose, that runs off the frame. dirt and debris can kill a fuel pump quick.

and/or your fuel filter

you could also get an elictric pump.

I'm not sure if we got all the info correctly or did I miss something. All you did was install the 4.5" lift right? Did you add new larger tires to make the lift look good? If you increased your tire size then the problem lies with improper gearing. We will need to know the tire size from what you had to what you have now to help you with the proper gearing selection. Just trying to cover all basis before you spend money on things you don't need.

Good point,,, sorry. I had 31" goodyear MTR's all the way around before the lift and it drove fine on the highway. I still have the same set on after the lift,,, I know,,, It looks funny but after a $1000,00 lift I didn t have much left Please let me know If I need to add anything else!!!Thank you all for your help!!!

Thanks, Rich Jeepncolo

Ok guys,, please tell me if I'm wrong in my thinking.... I put a on a electric fuel pump today. I went out for a test drive. I got it up to 65mph and climed a small incline. The jeep ran fine for the 15 min I was on the highway.... I turned around and started to head home (mostly down hill). then about 10min down the road, it started to act like it was out of fuel or not enough air agian. Here is my thinking,, its not my fuel and air (since I was able to climb a hill at 65mph), its not my drivetrain (for the same reason, and I was going mostly down hill). and its not my ignition system ( for the same reason).

One thing I did notice is that The problem started after the temp gauge was up over half way. please tell me if im wrong but it looks like I might need to look at the cooling system? Thanks agian for your help!!!

Thanks, Rich Jeepncolo

Might be wierd but could your fuel lines be close to something getting hot? I have heard stories of the fuel getting hot and causing problems.

It's a possibility that your cooling system could be a problem, but more in likely not, your engine got up to operating temperatures within the 15 minutes or so a normal car would take so maybe its running a little warmer than normal but hey its summer it could happen. This might sound crazy, but have u ever gone through and replaced your rubber fuel lines with a smaller diameter recently on accident? if so it could cause a slight restriction, remember carbs only need a small amount of fuel pressure and any small amount of restriction could not permit the 6-8 psi of fuel pressure that it needs. oscar also pointed something out really good your fuel lines might be running next to your exhaust system, with the warmer weather and your engine now running a little bit warmer now your fuel is turning to vapor before it gets to the carb...but hell I still believe something is up in the fuel system.

sounds like vapor lock to me, my old ford pickup started doing this after i rplaced all the rubber hoses and it turns out the line going to the carb was a little long and resting against the intake manifold, i'm lucky it didn't blow up!!

You could also replace your fuel filter while your at it. They are very cheap and if water has gotten in you fuel it might cause something like that, it would probably cut off though. Also that year jeep didn't require Cat's but if some crazy owner installed them it might be a possibility for those to be the prob. Unless your fuel line is almost directly on the header it shouldn't vapor lock especially on the highway. Jeeps have a hugh amount of air going through the engine compartment. I have a carb V8 and never have prob with vapor lock. It's been lifted and everything.

I had the same trouble in my lifted 86 CJ7. I thought it was the fuel system. ( Mine is MPI). So I did the fuel line ,fuel filter ...
Well the trouble always came back on hot days after a cruise at speed, and once in Jawbone Canyon on the drive out. Acted like fuel starvation. 2000 RPM max and could not pull a hill without a backfire and loss of revs. Turned out to be a set of bad plug wires combined with an old Cap and Rotor. The Heat made them fail and lose the spark to the ground path of their choice, not the spark plug. Good Luck, this problem made me nearly crazy.