That is another good clue, but this type of measurement is subjective and depends on correct calculations.

If you wish to fix this X you have to get serious and either beg, borrow or S... a live data scanner, fuel pressure gauge and IR gun. Do not throw any more parts at is until you diagnose the problem.

WE need

• NO exhaust leaks prior the CAT
• fuel pressure readings,
• engine temp (real not gauge)
• O2 switching rates, B1S1 and B2S1
• LTFT
• STFT, B1 and B2
• Intake air temp.

and verify plug wires are not crossed (on wrong plug)

You might consider acquiring a computer (LT) based OBDII/CAN software and interface, cheaper than dealer scan.

 

By chance could the cam positioning sensor cause any of this?

I had pretty similar problems with my 92 t-bird SC when my cam sensor went bad.

 

Ok small update if this makes any matters better, or make more sense.

When the truck is cold, it runs perfect. When the engine temp gauge starts to move and gets just under the "C" is when it starts to flutter and idle like crap.

Also, my bro told me that one day the car was completely out of gas, and he needed enough just to get it up to the gas station, and he grabbed a gas can from out back and put in like 1 or 2 gallons, then realized after he did that he put in E-85, which he uses in his mustang....

Could that make any of this seem logical?

 

That amount of fuel will make no difference.

Have you checked your IAC for proper operation??

 

I'm not sure by what you mean by "proper operation". I did take it off and clean it with MAF cleaner, and put a new gasket on it.

 

Could the EGR valve possibly be making the idle this way? To my understandings, if it is stuck open, it will not throw a MIL, and if it is stuck open, wouldn't it make it idle rough after it's stuck open?

 

If indeed your EGR valve is stuck open it will exhibit these symptoms as it will be feeding exhaust gasses into the intake manifold..... A MIL should set as EGR flow would be calculated as "too high".

Remove it and clean, it should snap shut smartly.... no sticking or hanging.

 

So it could very well be possibly a dirty or bad EGR can cause this rough idle problem? I'm scared to take it off without replacing it, because it's the same FoMoCo one on there, and it has 210,000 miles of use on it, it is VERY rusty.

 

As Aquanaut20 mentioned, an EGR valve that is not closing is essentially a vacuum leak. By design, the EGR valve should close at idle, if not, it is a vacuum leak at idle and will cause a rough idle.

Keep in mind other things can also cause a rough idle (such as other vacuum leaks, worn spark plugs, bad plug wires, etc).

-Rod

 

The plugs and wires are brand new. maybe 2 weeks old at the latest. I've checked all the other vacuum lines for leaks and cracks and they are all good. I'm going to take off the EGR today and clean it and see if that fixes the problem, or even replace it if need be....But if the EGR is supposed to close at idle, why does the truck run fine when it's cold, but as soon as the temp gauge starts to barely move, is when the idle problems kicks in?

 

The temperature relationship is what makes me suspect an intake manifold (or similar) gasket as the source. Now that I've re-read your original post, it sounds like the plugs and wires were changed because of this problem rather than this problem starting after the plugs and wires were changed.

-Rod

 

Correct. The first thing I did was plugs and wires. Then started cleaning all the stuff like I posted, and checked for vacuum leaks, but there are none.

On another note...CEL came on today, i knew it was for the P0455, so I grabbed my scan tool to scan it, and to reset it from the computer, and on my scan tool, There is this thing called "freeze frame'' and under it, it listed things like LTFT, STFT, B1S1 B2S1 and i think a couple others....I had no idea what any of that meant, so i reset the code. Then came back to my thread here, and it was Aquanaut who said to check what those measures were?

Now, I have no idea what LTFT and etc etc etc means. Can someone explain that to me? Next time the MIL comes on, when I scan it, I'm going to write down what all those were, because there were numbers next to them....

 

To really determine there is not vacuum leak you'll either need to perform a smoke test or you could go the less expensive route and install a vacuum gauge and monitor the gauge. The vacuum level and smoothness of the needle should help you determine what the issue likely is.

STFT = Short Term Fuel Trim. This is essentially the direction that the ECM alters the fuel injector pulse width to compensate for a lean or rich condition near real-time. A positive number indicates a longer pulse width = more fuel = compensate for a lean condition. The manufacturer has a recommended range for the fuel trim numbers, outside that range suggests an issue.

LTFT = Long Term Fuel Trim. This is, as the name would imply, more of a historical, averaged explanation of how the ECM has adjusted pulse width.

Just having the STFT and LTFT numbers by themselves may give an indication of what's happening, but to really make these numbers useful requires comparisons between the readings. I remember finding an online MOTOR article at one time that did a pretty good job of explaining how to use these values. I don't recall exactly which article (I saved the PDF off) but this article seems to do a pretty decent job.

BxSy = Typically used to refer to a particular oxygen sensor. The B designator is the "Bank". Bank 1 will be the bank with cylinder number 1. The S designator is the "Sensor" position. Sensor 1 will be prior to the catalytic converter, sensor 2 will be after the catalytic converter in the exhaust path from manifold to tail pipe.

O2 sensor switching rates used to be referred to as "Cross Counts" and is the number of times the oxygen sensor voltage crosses the mid-point voltage of 0.45 volts. The Sensor 1 sensors should switch quite rapidly between something close to 0.1 V and 0.9 V when the engine and sensors are up to operating temperature. If the voltage tends to "rest" above or below 0.45 that would indicate either a lazy sensor or a rich or lean condition.

-Rod

 

I have done a smoke test and used a vacuum gauge. The smoke test was done through the intake elbow with a halloween type fog machine. There was plenty of smoke going through the system because when I unplugged the PCV elbow, smoke was coming out of there at a decent amount. Blocked off the dip stick and valve cover, and still did not find any leaks, used a high powered light to try and find anything. Even did starter fluid around all of the vacuum lines, and all over the intake, and i really mean ALL OVER...nothing at all.

The vacuum gauge read 17 inHg at idle, even with it roughly idling. I did not monitor it while driving, because I didn't have a secure place to mount the gauge while driving to check it out.

 

tap the mass air flow sensor, with the back of a screw driver handle and see it any changes, that how I figured out mine was bad.