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R. Niznick
Dodge Dakota
11/25/2001
19:35:02
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 Subject: over-revving
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Message:
Someone help..please!! I have a 3.9 '98 Dakota and here is my most recent problem. When I am driving between 65-75 mph my engine revs up about 150 RPM. I really notice this because of the dual exhaust I have installed. I recently had a soft overhaul of the tranny for another problem. I've been told by the dealer that it is the overdrive, but, when overdrive is off it still does it just at a higher rpm. Anyone else experiencing this or have any suggestions? Could it be the throttle position sensor? This occurs mainly when I am going uphill or going over uneven highway pavement. I haven't a CLUE!!!???
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CW
GenIII
11/25/2001
19:50:06
|  RE: over-revving
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Message:
Sounds like the torque convertor clutch is locking and unlocking. This can happen with a misadjusted brake switch. When ever the brake switch is pressed the computer unlockes the torque convertor. Have someone stand behind the truck, you depress the brake and have them tell you exactly when the brake lights come on. If you just barely have to move the pedal then it is to sensetive and is probably coming on over bumps on the highway. To adjust you pull the center pin outward and you will hear a ratcheting sound as you pull it out. Hopefully this will do it otherwise you will have to take it back and have the trans looked at.
2001 4.7 5sp RC 3.92 LSD sport plus
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R. Niznick
Dodge Dakota
11/25/2001
22:04:06
| RE: over-revving
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Message:
The one thing I forgot to mention... when the engine jumps rpm it only happens for about 2 seconds, then it goes to normal. I.E., cruising at about 75 mph, the rpm is at about 2200 rpm, then for about 2 seconds it jumps to @ 2350 rpm. I will try the brake sensitivity and let you know what I identify. Thank you for your time and assistance.. have a great Mopar day!!!
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Jcr7079
Dodge Dakota
11/26/2001
01:00:29
| RE: over-revving
IP: Logged
Message:
This has happened with my dak for a while.
Ive tried everythign to get rid of it(sensors, etc.)
It seems to me that the fluctuation is a
computer glitch in some daks. My friend has
had the same prob with his dak. I think that the
suggestion made by CW is a good one but
with our problem that wouldnt necessarily
cause it to happen the way it does. Try this to
see if my theory proves correct on your daks
pcm: While driving at roughly 62 mph or 1950
rpm(This is the border of overdrive where it is
most likely to downshift) hit the gas just a tad, i
mean very very little gas, and see if the rpm
goes up the 150 then back down and then
climbs as it should due to the increased
throttle. Then hold it again at the 1950rpm
mark and step on the gas slightly and keep
even slight pressure on the brake(trying to
keep speed same with adding a little gas) and
see if it spikes again. It should spike on the
test without the brake and it shouldnt spike on
the test wiht the brake. What this proves is that
regardless of throttle position or brake
pressure( ie. CW's suggestion) the truck shifts
on cue of rpm and Mph, indicating that it is a
computer glitch. If this test proves right for you
go to your dealer and ask them for a flash and
also let me know!!
Josh
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CW
GenIII
11/26/2001
09:21:58
| RE: over-revving
IP: Logged
Message:
It will go up 150rpm when the brake is depressed slightly because that unlockes the torque convertor allowing 150rpm of slipage in the convertor.
2001 4.7 5sp RC 3.92 LSD sport plus
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nbfdexp901
GenIII
11/26/2001
13:28:19
| RE: over-revving
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Message:
my truck does the same thing, even when the cruise is on...i'd think if the brake sensor is bad, it would shut off the cruise...right? well, if anyone gets a solution, lemme know so I can fix it...unless I get my new 2001 dak 8-)
Brad Sippel
Black '98 SLT 3.9 V6
Thunderform with 500W Legacy Amp
K&N Filtercharger, Dual Exhaust with Rhino Muffler
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NiPs
Dodge Dakota
11/26/2001
16:03:13
| RE: over-revving
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Message:
CW is also ignoring the fact that the torque converter locks and unlocks to prevent too much heat from being generated by the slipping(intentional) by the converter. However ones converter may be told to lockup and unles based on judgments by the pcm or other devices.
The only simple way to test the converter is to manually run a wire to it. YOu can make a switch that will be like this, PCM controled or Locked up, do a search and you should find links to do this. If you manually have it in lock-up mode and you see this strange jump you can tell there is something wrong with your truck that needs to be fixed as it's not natural.
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Zed
Dodge Dakota
11/28/2001
13:34:14
| RE: over-revving
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Message:
Its your TPS sensor, my 99 did the EXACT same thing yours is doing. I replaced it and it never did it again. It was about 60 bucks. There are some other posts on here about this condition. Thats how i found out what to fix. The posts are from way back in July if you want to find them.
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CW
GenIII
11/28/2001
14:41:55
| RE: over-revving
IP: Logged
Message:
If it continually locking and unlocking then it will creat extra heat in the trans and cause premature TC clutch wear. You can also have the dealer test it with a hand heald scanner but all that tells you is that the clutch is holding doesn't tell why it is locking and unlocking all the continualy.
2001 4.7 5sp RC 3.92 LSD sport plus
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R. Niznick
Dodge Dakota
11/28/2001
18:41:30
| RE: over-revving
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Message:
I used the great search engine and am going with Zed on this one.. must be the TPS. Thanks to everyone for there input, this is a great website!!!!Mopar or No car:)
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