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alex1567
Dodge Dakota
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5/08/2007
10:31:02

Subject: 4.7 losing power
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Any suggestions or advice would be most appreciated, here is the problem:

My truck loses power (boggs) under harder acceleration (stomping the gas to pass someone or leaving a light). At first it felt like a slipping clutch and the contact point was almost at the end anyway, so I got a new clutch - no change. The mechanic then did an engine diagnostic and found a cylinder mis-fire. He changed the plugs, and the mis-fire went away, but the loss of power is still there. A second diagnostic found no other problems with the engine (no more mis-fire, good compression, etc.) At lower acceleration (normal driving), there is little or no loss of power. The amount of bogging varies greatly, some days everything is fine, other days, it is almost impossible to drive.

Any suggestions on what could cause this? The only suggestion I have heard that makes sense is a bad catalytic converter causing too much backpressure, but the cat is not rattling, and there is no "rotten egg" smell. Could a bad cat vary in how much it is affecting the engine from day to day?

Here are the specs:
2000 Dodge dakota SLT extended cab
4.7L V8, 5 speed manual, 2wd w/ LS
K&N air filter w/ pipe (no air box or silencer)
Purchased in CA (could this have multiple cats?)

If anyone has any suggestions, please, please let me know. I am incredibly frustrated by having spent money on this truck without fixing the problem, and having no idea how to fix it. Even the mechanic is stumped. I want to get as much information as I can before I spend any more money replacing parts.

Thanks in advance,
Alex



Kowalski
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5/08/2007
15:32:10

RE: 4.7 losing power
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Your truck should have two precats with O2 sensors before the y-pipe, and a third cat without sensors after it. Same year, motor, and pollution package as mine. I thought of a clogged gas filter as well as a clogged cat; but I've never heard of either being an intermittent problem...

Before just replacing parts, it should be possible to measure fuel flow, and a plugged cat can be determined by vacuum change with rpm. Let us know what you find.

Lead, follow, or get out of the way

TexasTodd
Dodge Dakota
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5/11/2007
00:12:01

RE: 4.7 losing power
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Could be the third cat, with no sensors before or after it, ouerwise it would throw a code.

But, as Kowalski said, it shouldn't be intermittent though.

Good luck, Alex, nice choice of trucks, I have a 2001, Quad Cab, SLT, 4.7, manual, etc.



alex1567
Dodge Dakota
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5/12/2007
11:07:59

RE: 4.7 losing power
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thanks for the info!

The mechanic at the dealer said there were no codes coming from the cat, so maybe it could be the third cat...

Is the fuel filter separate from the pump, or is it all one unit? If it is separate, can anyone give me some instructions on how to inspect/replace the filter??

Alex



TexasTodd
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5/12/2007
22:18:03

RE: 4.7 losing power
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My third cat, some call it a resonator, was cut out years ago. Shop in San Antoinio, for $30.

Still passes inspections, no prob.

Try checking the fuel rail pressure first.

I"ve heard the filter and pump are in the gas tank, not readily servicable.



Kota Kid
Dodge Dakota
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5/13/2007
20:51:27

RE: 4.7 losing power
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Easiest way to check to see if the cat is clogged without a backpressure gauge is to remove the rear most O2 sensors in front of the cat in question and drive the truck see if the power is better. When your truck was missfiring it was dumping fuel into the cat which is very bad for them.

I worked on a S-10 that had symptoms exactly like yours, test drove it one day drove fine had no codes sent the customer home unable to duplicate customers concern at this time. They brought it back a week later when the problem was happening test drove it and couldn't get it over 35mph, when i got back to the shop the cat was glowing a bright shade of orange. Come to find out they had a distributor replaced to fix a missfire only a month before this trouble at another dealer.



Kowalski
GenIII
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5/14/2007
15:36:27

RE: 4.7 losing power
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Can also check with a simple vacuum gauge. Most motors should have about 17-22" vacuum at idle; and it should increase about 3-5" more at 2500-3000 rpm.

Lead, follow, or get out of the way

bfow
Dodge Dakota
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10/10/2012
22:30:12

RE: 4.7 losing power
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i had the same problem but with a the 5.9 magnum.geta new o2 sensor and she'll run good.




J1M
Dodge Dakota
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6/30/2016
14:19:26

RE: 4.7 losing power
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I KNow these are old posts; I replaced IAC, TPS, AND MAP to no success. and I just just replaced both cats and resonator. the "falling on your face" is gone under acceleration however, there is still a power loss. I am going to change the O2's next and will report back, hope this helps!



tonya crandal
Dodge Dakota
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5/31/2020
23:01:42

RE: 4.7 losing power
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Look at your coils for cracks i
had a crack big enough for
moisture ti get into the spark
plug area n cause an intermittent
loss of power just sayen




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