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Jeep Grand Cherokee 4.0 ZJ Acceleration Issues: Low RPM and No 4th Gear?

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TN-95' ZJ

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Discussion starter · #1 ·
Alright, hoping this isnt a major problem but here it is. Just recently, my 4.0 ZJ has lost a lot of acceleration. When I floor the thing from a dead stop, i can only get a little over 2,000 RPM........once I start rollin though, the rpms go higher. If the hill is steep enough, i can barely get up(sometimes I have to back down and gain momentum to get up the thing. If im drivin on the interstate, its not shiftin into 4th gear.....so at 70mph im doin about 3200 RPM. When I turn on the jeep, the "O/D OFF" light is on, however, if i turn just the accessory switch on and wait for the "O/D OFF" light to turn off, the light stays off but the Jeep drives the same. I'm hoping this is nothin major, maybe a sensor, but i have no clue. PLEASE HELP!!

Thanks
 
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#3 ·
that fact that it's not shifting right and the fact that your O/D light is coming on, I'd have the tranny checked right away....before it leaves along the road to be towed home. The O/D kicking on by itself is a safety feature to keep the tranny from overheating so easily. You could have some partially blocked lines.
 
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#4 ·
Trans?

Yep! if the O/D light is involved, it could be a heat thing! get to your Trans PCM, scan for trouble code or operation variance in the scan, Iam not sure what trans you got, I would give every thing a once over, might be something simple like needs fluid? That would be too easy. and of course all of the above. The lack of or uneven fuel pressure will sure do that too! Good Luck and let the forum know if you get a fix!!! Tphoto
96 Limited
5.2Liter
Strong Stock!
 
Discussion starter · #6 ·
So right now.....this weekend, what order should i do things to eliminate this problem: torque converter, fluids, fuel pump. What do yall think. Money is an issue as always.

Thanks guys
 
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#7 ·
Direction!

Greetings! If I had a problem like yours I would check all wiring and connections in and around the trans plus the shift linkage for obstruction from correct movement. Any Codes? Then check the fluid! Level cold, Level Hot Hows it smell? Burnt? Alittle brown but mostly red? If you got a strong burnt smell that a good indicator that its a heat problem. If the fluid is not in question and the levels are fine at normal operating temp! that rules out a few catastrophic failures. Iwould probably drop the trans pan and check the condition of the fluid and filter and its contents if any. also look for any flat gaskets or loose wires or fittings on your valve body when you got your pan off. This inspection will cost you the price of oil, filter and gasket. and will help you see any Obvious Metal particles in your systems Oil. It is possible that your shift solenoid or Governor or What ever they call it is bad or the gaskets around it are brittle from heat and is not getting the correct operating pressure. Any how I would also disconnect the Trans cooler lines at both ends and flush them with clean fluid! but be cautious one of the lines may have a one way check valve in it so you would have to flush the other direction. While the lines are off flush the cooler tank, Verify it is not plug-ed. I did this service to my 96 5.2L and smoothed out my shift points.

I could go on and on with things to look for but follow the obvious and you will find the solution for the right repair. OR if you are stumped have someone you trust to physically (Mechanic) diagnose your problem and you do the repairs! I had to do this on a fuel injector issue it cost me 55 bucks labor to have a operating scan performed. The problem was pinpointed I did the Repair and all is well. I hope this gives ya a place to start. Tphoto
96Limited
5.2Liter
Strong Stock!
 
#8 ·
If transmission fluid is dark/burnt, you can flush entire system by unhooking the return line from radiator and running it into a bucket. Use a piece of hose to extend it to bucket. First drop transmission pan and check it out,.. Change filter, adjust bands and clutches. After it's back together and filled with fluid, have a friend watch the line in the bucket and start engine. After a quart of fluid runs into bucket, stop engine and add fluid to transmission. Keep doing this until fluid going into bucket looks new. Shift it through the gears as you do this to flush new fluid into valve body and through clutch packs and bands. Now you have flushed your entire transmission system... new fluid has been pumped through converter, cooler and lines.

Good Luck
 
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Discussion starter · #9 ·
Alright, I'll see if I can do that this weekend so that I stop loosing my drag races. :mrgreen: Thanks guys. If there any more ideas throw em at me.
 
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Discussion starter · #10 ·
Update: Flushed the transmission this weekend and looked at the fluid, it was a dark red/purple. Not too bad, but it didnt fix my problem. I guess I'm gonna have to do some transmission work(pay for transmission work) pretty soon here. :angry:
 
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Discussion starter · #11 ·
New Update: so yesterday and the day before that, the jeep worked perfectly and I was so pumped........but then today it started sucking again. Can anyone maybe narrow down my problem, it seems to be intermittent.

Thanks
 
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#12 ·
I have had the same problem... as I posted a thread probably a year or so ago on this issue. Some 10,000 miles later I still have it. If the motor is cold, a full smashing of the petal it's fine, however 20min into a drive it'll quit around 2500rpm..... same if u run it at 75mph for much more than an hr. If it was my fuel pump I figure it should ahve quit by now.... right? I've had it hooked up to sensors at shops and they found nuthin, probably cause they ignored my reference to the motor needing to be working hard for awhile. They replaced an O2 sensor, but it really did nothing. I just drive it under 70mph now and have no problem. The weird thing is it has NEVER given me trouble on the trail..... and everything seems to run great as long as I keep the throttle monkey in his cage... :lol:
 
Discussion starter · #14 ·
CentralGrand, I'm going to take it to a tranny shop pretty soon here and get the governor pressure selenoid and sensor replaced. I found a write-up on JU and it described my exact problem. The shop is only gonna charge $225-275, depending on the part cost. Here's the link.....

http://www.jeepsunlimited.com/forums/showthread.php?t=714496
 
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#15 ·
Loosen the exhaust pipe from the manifold enough to allow it to leak exhaust. I mean leak alot, like it doesn't have an exhaust system. Drive it down the road and see if it accelerates any better. It may be a stopped up exhaust, and the reason it won't go into overdrive is because you're itno the throttle to far to keep your speed. The overdrive operates in relation to the throttle position.

You could possibly have a stopped up convertor, or a collasped pipe. It's easy to check, before you take it to the transmission shop.
 
#16 ·
I agree with Bayman while reading the solutions and problems I was thinking converter. The exact problem happened to my pathfinder. Its much more noticeable in the smaller engines because of the pressure required to function correctly. I never thought it would have been my exhaust at all, but when I took it to the tranny shop he said it was my converter, so I took it to an exhaust shop, and the problem was gone. I took it to a normal do everything shop first and they told me I had fried my tranny. I had to replace my converter on my 5.2 all ready too. The problem wasn't the same but the do wear out. Might as well try to save some money.
 
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#17 ·
Hey TN 95 ZJ.....

Did ya fix your problem?..... I was just curious. My Jeep is still giving me problems, very few however if I take her easy. HOWEVER Jeep gurus... I have another symptom which I started getting last week... If I take a tight corner, such as an intersection and get on the gas reasonably hard in mid stride it will die, until I let off the gas..... ?????????????????? I'm not an expert but I think I need to face the music and get a new fuel pump... :-x ( I only have 93,000... Is this unusual?)
 
#20 ·
I have 180,000 miles with the same fuel pump and its a 95. when turning it strains the engine more which will can cause it to die if its not exhausting properly.
 
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kevinc
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