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Discussion Starter #1
So...

About 3 days ago my 3.8 decided to go from a smooth machine to a hesitating, stumbling, shaking one. Again, this is seemingly out of nowhere, nothing was touched in the days prior.

Your input is much appreciated!!!

Symptoms:

- Very rich exhaust smell
- Rapidly fluctuating rpm's (at idle)
- Oil pressure gauge drops (at idle)
- Transmission feels very warm (next to center console)
- Car shakes badly when stopped, and when cruising
- At part/full throttle, it smooths out
- "Jolting" feeling when cruising
- Sometimes it will run fine for a little bit, then go back to shaking

Almost seems computer/electrical related?

Ruled out:

Vacuum lines
Fuel Pressure regulator
Spark wires & plugs
Distributor cap/rotor
O2 sensors
Ignition Control Module
MAF sensor
Clean Air Filter
IAC Valve
TPS
Fluids are topped off
 

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11,961 Posts
So...

About 3 days ago my 3.8 decided to go from a smooth machine to a hesitating, stumbling, shaking one. Again, this is seemingly out of nowhere, nothing was touched in the days prior.

Your input is much appreciated!!!

Symptoms:

- Very rich exhaust smell
- Rapidly fluctuating rpm's (at idle)
- Oil pressure gauge drops (at idle)
- Transmission feels very warm (next to center console)
- Car shakes badly when stopped, and when cruising
- At part/full throttle, it smooths out
- "Jolting" feeling when cruising
- Sometimes it will run fine for a little bit, then go back to shaking

Almost seems computer/electrical related?

Ruled out:

Vacuum lines
Fuel Pressure regulator
Spark wires & plugs
Distributor cap/rotor
O2 sensors
Ignition Control Module
MAF sensor
Clean Air Filter
IAC Valve
TPS
Fluids are topped off
Exactly how did you rule out those in boldface text?

How does the car start in the mornings after sitting over night? Is it stumbling right away?
 

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Discussion Starter #3
All of those in bold face text have been replaced recently, and in the mornings it has always been somewhat difficult to get going, I've just gotten it in the habit of letting it warm up/giving it some gas for a few minutes, now it is a continuous stumble, once I put it in drive it just about dies
 

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I'd be willing to bet your Catalytic Converters are clogged..

If you're mechanically inclined to do so..Drop your exhaust at the manifolds, and see how she runs..

One other extreme sign of clogged Catalytic Converters is they'll be shining "cherry red" when you look at them in the dark..

Like I said though..Drop your exhaust...It'll be loud, but if you do it during the day your neighbors shouldn't mind too much.. :D



Rayo..
 

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A vacuum gauge can also tell one if there is an exhaust restriction. However, with all due respect to Rayo, such restriction will usually be most apparent at high rpm ranges like full throttle.

I take it there are no codes.

If not I would go ahead and perform basic cylinder power balance, compression and leak down tests. Just to rule out mechanical possibilities. Like a valve that is sticking intermittently. A vacuum gauge can also show a sticking valve.

Other things that come to mind are injector(s), and the wires/connectors to injectors, EGR system, and intake manifold/head gaskets failures.

Here is a vacuum chart that shows some of the readings and causes.

http://www.freeasestudyguides.com/graphics/vacuum-readings.gif
 
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