Rough Idle-Hear me out.

T

Terminator

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Hello,

Of course I searched for this prior to posting but no threads addressed my exact issue. I had recently replaced all coil packs, all spark plugs, new air air filter, fresh oil change. New EGR, and unrelated, a new radiator but my question is, my 2006 LS has a rough idle when fully warmed up, and the A/C off. In other words at lowest idle. When the A/C is turned on, as you know the idle automatically ticks up, smooth idle. And when the car is warming up the idle is up a bit, so its smooth. Acceleration is smooth, no codes. Only at full warm up when A/C is OFF, the car has a pretty bad idle. Before I did all the above work, the car idled smoothly at all times. I cleaned MAF, un plugged the TPS, and IAC. Cleaned the TB, to no avail. I read somewhere a bad fuel pressure sensor could cause a lean idle condition thus a bad idle, but I would think that would throw a code. I dont know. Any help would be greatly appreciate.
 
Terminator said:
... I cleaned MAF, un plugged the TPS, and IAC. ...
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So, either you really don't have a 2nd gen (2006), or you don't have an IAC to unplug.
What year do you really have, or what are you calling an IAC?

They are COPs (Coil On Plug), not coil packs. Anyway, what brand did you use? Did you verify all the spark plug gaps? OEM EGR valve? What did you clean the throttle body with? Did you check for air leaks?
 
This was all done to spec by a professional mechanic. I unplugged the TPS and the sensor on the other side of the TB. Im new to Lincoln. (we call them coil packs on the Mustang Forums, I have an 03 Cobra (Terminator). Air/Vacuum leaks would throw a code. Everything was replaced with OEM stuff.
 
Terminator said:
...Air/Vacuum leaks would throw a code. ...
Click to expand...

Who told you that? Small ones, such as would cause roughness at low RPM, certainly will not throw any code.

The part on the other side of the throttle body is the throttle actuator.

The LS is very sensitive to spark plug gap. You have to check and set each one. Out of every set of pre-gap'd plugs I have bought, at least one or two were wrong by a fair amount.
 
Im speaking from experience. My Cobra had the smallest of vacuum leak, threw a code, car idled fine. Took months to track it down. (Also the other sensor I unplugged must be the sensor on the EGR) Anyways, I did have a suspicion the plugs may not be gapped right. I may take it back and have them check....
 
Terminator said:
Im speaking from experience. My Cobra had the smallest of vacuum leak, threw a code, car idled fine. Took months to track it down. (Also the other sensor I unplugged must be the sensor on the EGR) Anyways, I did have a suspicion the plugs may not be gapped right. I may take it back and have them check....
Click to expand...
The Mustang is a whole different breed than the Lincoln LS ...my wife has a 4.0 V6 mustang and it's nothing like the 3.9 V8 LSE I own ...trust me just because Lincoln is Ford don't assume the Lincoln LS is strictly Ford ...Jaguar has extream influence in this car ...hence the Lincoln LS is more S-Type than any Type of Ford car...Joegr has forgotten more about the LS than any of us will ever know ...minus 04 Sport maybe ...the spark plugs must be gapped correctly...I thought this was BS also... but after years of owning different LSes I have become aware of this most crucial specification that needs to be performed on all Lincoln Lses if you want to have the 3.0 and 3.9 purring like a kitten ...also make sure your mechanic is using dielectric grease on the (COPs)
 
Absolutely agree. I'm not playing down anyone's knowledge of LS's. Heck thats why I'm sking here.. I've been working on cars for over 30 years, there is always something to learn. The guy was just coming at me like I'm stupid. He could have just helped rather than "who told you that?" And "that's not what that's called", etc. I appreciate all the input though.
 
And for the record, vacuum leaks do throw a code on LS's , because I had 1 and it threw the code. Tracked it down to the little hard vacuum like to the fuel pressure sensor being cracked.
 
Terminator said:
And for the record, vacuum leaks do throw a code on LS's , because I had 1 and it threw the code. Tracked it down to the little hard vacuum like to the fuel pressure sensor being cracked.
Click to expand...
If you haven't downloaded the Forscan Program onto a laptop I suggest you do it ...It's FREE...I think you can get this off of Amazon for $20 bucks ...it will help you chase down all those peskey little gremlins on the Lincoln LS...
OBDMONSTER ELM327 USB FORScan OBD2 Adapter for Ford Car and Light Truck, ELMconfig Scanner with MS CAN/HS CAN Switch, Diagnosis on Windows with V1.5 PIC18F25K80 Chip
 
Vacuum leak. Loose hose connection or bad intake gasket. Try spraying carb cleaner around the intake seal and see if you don't hear a change in the idle.
 
@Vee8Guy Ive done all of that. I actually wanted to post an update. The culprit was the fuel pressure sensor(as I suggested in my very first post). Smooth idle now. Thanks.
 
When mine went out in my 2003 V8 Sport it set an error code?
No code when you scanned the car?
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.
.
 
clubairth said:
When mine went out in my 2003 V8 Sport it set an error code?
No code when you scanned the car?
.
.
.
Click to expand...

Depends on how it fails. Some failures are detectable and will set a code, others are not.
Example: Sensor goes out of range - set a code. Sensor reads incorrectly, but still in range - no code.
 
Good info. Glad you found it. In my experience a vacuum leak at the manifold doesn't throw a code, but you will get some occasional misfire codes.
 
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