Is this normal?
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Senior User
Joined: Feb 2004
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From: Marietta, GA
Is this normal?
I just got back from a long road trip. On the interstate, I noticed that my '99 4.0 OHV/5 Spd was having trouble maintaining speed when going uphill. I had 3 adults, 3 dogs, & a weekend's worth of stuff, so it was loaded down more than usual, but on a good hill I would drop from 80 to 70 & a couple of times had to drop it to 4th to keep it at 70. The engine didn't seem to want to go much over 3500 RPM, maxing out at around 3750. I don't know what the rev limiter is set at from the factory.
I was just wondering if it was normal and, if not, what I should look at first.
Thanks!
I was just wondering if it was normal and, if not, what I should look at first.
Thanks!
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Joined: May 2004
Posts: 130
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From: Rock Hill, SC
Were you running with the cruise control on? Where are the hills you are driving up? are they good size hills or straight up mountains on the interstate? My truck goes uphill with the cruise on unless it's got a load on it. As for the RPM's, have you tried running up the revs somewhere around town? Most vehicles have a terminal speed going uphill, especially when you are in overdrive. The O/D gear is not designed for pulling hard, just to let the vehicle run higher speeds at a lower RPM. I used to live in the mountains, and on some of the hills no matter how hard you kept your foot to the floor, the vehicle will not go any faster even in a lower gear, this is because you have probably reached the limit of the horsepower of your vehicle. How fast did your truck go in 4th when you got to 3750? It may just be that it wasn't designed to go any faster up that hill.
I also think that the limiter is set at or near 5200RPM.
I also think that the limiter is set at or near 5200RPM.
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Joined: Aug 2000
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Sounds like it was loaded down pretty good; that may be normal. One thing that will affect upper rpm power is the IAC, if it gets dirty. You might try cleaning it, and install fresh plugs and wires, maybe clean the injectors.
I agree with NRK though, you probably reached the limit on those long hills.....
I agree with NRK though, you probably reached the limit on those long hills.....
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Senior User
Joined: Feb 2004
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From: Marietta, GA
It was in Connecticut that I noticed the problem. Not real steep hills, but long ones. I couldn't get over 75 in 4th, and dropped from 80 to 70 in OD/5th (it's a manual trans).
I know it will rev over 3750, now that I think about it. I've hit close to 5K on a hard take off.
The IAC is on my to-do list. Maybe I'll get to it this weekend.
I know it will rev over 3750, now that I think about it. I've hit close to 5K on a hard take off.
The IAC is on my to-do list. Maybe I'll get to it this weekend.
Posting Guru
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One thing that will affect upper rpm power is the IAC, if it gets dirty.
Oops, I misspoke. I didn't mean to say the IAC (idle air control), I meant the MAF (mass airflow sensor). Must have been sober when I wrote that..... 
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Joined: May 2004
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From: Caracas, Venezuela, South
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From: Marietta, GA
Originally Posted by waro
Hey you guys, how do you clean de MAF sensor..???
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