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Sam
Dodge Dakota
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12/14/2004
15:50:16
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 Subject: Power lag 93 5.2 4x4
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Message:
Before I take it in for full diags, I'd be happy to hear any suggestions.
Symptom: Can't get up over 55mph.
From full stop, I get normal acceleration with pedal slightly depressed, but floored I get a severe loss in power. Engine *sounds* more powerful, but feels like it's sucking wind. Also, it takes a lot longer to shift than it should.
Work I've done so far: Changed spark plugs & wires, distributor cap & rotor, ignition coil (which helped a bit), O2 sensor, crankshaft position sensor, fuel filter. Tested fuel pressure w/gauge...pressure is within spec (~35psi), clamped off return and pressure doubled, disconnected vacuum and pressure jumped a few psi, so pressure regulator is good. EGR not stuck open. No vacuum leak. Tested MAP sensor w/vacuum pump & power source--reading changed w/increase in vacuum. Tested TPS w/ohmmeter, no jumps in resistance, smoothly transitions between low & high point.
From here I'm thinking maybe the fuel pump can't deliver under load but I'm about to break down and take 'er in for a complete diag.
Any help appreciated.
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Sneezer
Dodge Dakota
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12/14/2004
16:01:35
| RE: Power lag 93 5.2 4x4
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Check the cat. If your cat is still original it likely needs replaced. If it has begun to break down the result will be a plugged cat and possibly a plugged muffler as well. This will result in serious performance degradation.
Does it rev OK at idle? Excessive smoking, especially at startup? Have you checked for a blown intake plenum gasket? Have you replaced it in the past? If it has been blown for a while, you will have excessive oil buildup inside the intake and it will eventually start clogging the injectors. Are the IAT and IAC sensors in good shape? Both can get pretty gunked up if the intake gasket is blown. IAC on the back of the TB, IAT on the #2 intake runner on the manifold - front passenger side. Also, check for a clogged PCV valve and valve breather filter.
Hope this helps.
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Sam
Dodge Dakota
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12/14/2004
20:56:40
| More details
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Thanks for the reply Sneezer.
I haven't checked the cat yet. I suppose I can see if that's the problem by disconnecting the exhaust (I'd better do it before the neighbors go to bed, eh?).
After reading your questions I thought I'd post more details about my problem.
It idles fine. In park when I punch it or rev it up slowly, tach gets up to about 3.5K then cuts back to 2K, no matter how much throttle I give it. The sound it makes at that time is the same sound I hear when I punch it while driving to get an extra boost (passing, etc) but have no extra power.
In my original post when I said that when I'm driving and floor it I get a
"severe loss in power"
isn't accurate.
Rather, it's a severe *lack* of power. It will downshift, but the power output doesn't change when it should.
In response to the rest of your Q's:
No smoke at startup.
Checked the IAT & IAC sensors.
PCV & breather filter are fine.
Very grateful for all the help.
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Ken
Dodge Dakota
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12/15/2004
12:24:18
|  RE: Power lag 93 5.2 4x4
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Message:
I had a similar problem, and it turned out to be the fuel pump. It's in the gas tank.
Good Luck
Give me fuel, give me fire, give me that which i desire
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bykerdude59
Dodge Dakota
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12/16/2004
11:48:05
| RE: Power lag 93 5.2 4x4
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I had the exact same symptoms/sounds as you Sam. Took it to a muffler shop, told them to check my cat. They lifted the truck up, and hit it with the palm of their hand. It rattled a whole bunch. Put a new one on and drove it away with the problem solved. I would say you should do the same (hit the damn thing with your hand)and listen to what sound it makes.
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trent
Dodge Dakota
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12/16/2004
14:15:59
| RE: Power lag 93 5.2 4x4
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what do you think are the odds for a brand new fuel pump just put in to, mess up and cause that problem cause i have that problem too.. and i just got a new fuel pump.. but i checked my intake and theres oil build up on the bottom of it so i beleive my plennum gasket is toast
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Sneezer
Dodge Dakota
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12/16/2004
14:21:23
| RE: Power lag 93 5.2 4x4
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If your plenum gasket is blown, you will be fouling plugs, injectors, and over time clogging up the cat as well. That oil has to go somewhere. If it has been blown for a while or has a bad leak, it can gunk things up in a hurry. Your oil consumption will tell you just how bad it is.
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Ken
Dodge Dakota
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12/17/2004
10:12:54
| RE: Power lag 93 5.2 4x4
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Before i replaced my fuel pump i had 35psi, after i replaced it i have 52psi. Both of these measurements were taken at idle. It has made a world of difference. I smoked a Lexus GS 300 this morning on the way to work.
Give me fuel, give me fire, give me that which I desire
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Sam
Dodge Dakota
JOIN HERE
12/17/2004
20:41:05
| Victory!!
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It was the cat.
Thanks everyone.
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