I have been readying and trying to find a definitve answer to this issue and not having any luck.. I am having a studdering or misfire when going uphill or down shift with just a little gas, with no CEL code. I have noticed that when I am cruising and I give it a little gas the RPMs drop about 500 then it studders and it does the same thing going up a slight incline. I have replaced the plugs with brisk, a new PCV valve and cleaned the MAF and it ran great for a little while. Something else to note, is that it only happens after the engine warms up, in the morning she runs great as long as its cool. I am going to run some seafoam thru her and replace the fuel filter. Hoping that helps. Has anyone run into this issue? Also, would getting a diagnostic computer hooked and making her do it help determine the issue, I have a friend that can do this for me?

 

It sounds like a torque converter/trans fluid issue to me?? When was the last time you had your trans serviced?

By your description, it sounds like when your TC locks up is when you get this 'shudder' in the drive train. This can be caused by the lockup of the converter and how it's pumping the fluid thru the system. If the fluid is "old and tired", it has lost it's ability to control this effect.... When it's hot, it just magnifies this effect.

Get the fluid changed and see if things improve. If not, then your TC might be dying??

Good luck!

Mitch

 

I have heard that if you, step on the brake in drive and try to acclerate a bit you can test the TC. Is this true..If so I have done this and nothing happens.

 

I guess so.... The trans shop I took my rig to last time did this in forward and reverse before they took it on it's inital 'test drive'.... I thought the guy was going to do a 'power lock' burnout at first! They said it was to check the TC to make sure it was working correctly??

Anyway, all that would prove is that it's unlocked, right?? Your problem is when it locks, so probably not a 100% test to run in your case.

If it's been awhile since your last service (over a year), then getting one is not a bad idea anyway.

Mitch

 

What you may be experiencing is the computer going into safe mode. If the catalytic converter exceeds a certain temp (different on every series of vehicles), the computer will shut down one or even as many as two injectors to cool the exhaust. Most of the engines that are suffering from a miss at temp and over 1600 rpms will be safe mode related. I would suggest NEVER putting anything even close to Seafoam in your engine. Imagine what it is doing to your catalytic converter. Seafoam is nothing more than a 20 viscosity non-detergent oil and alcohol. Would you put a qt of 5w-20Motorcraft oil down your manifold? About the same difference. And they claim it doesn't hurt anything. If you have a Ford Manual on the engine- look under miss firing. If you don't have one, go to the Motorcraft site and search for computer codes. The entire manual is on the site. It is something like 140+ pages in pdf. Look for miss firing there. I think it is at the front of the book like page 8 or something. Hope this helps.
http://www.motorcraft.com/default.jsp

 

But the inevitable question still remains how do I get it properly diagnosed and fixed to resolve the issue?

 

Quadkeys, here is what I would do. Go to any Auto Zone and have them put their code reader on the unit. It is a free service. My feelings are that you may have an O2 sensor about to die but it may not necessarily be out of range yet. If you have no codes and it reads clean, buy the large bottle of Techron and put it into the tank when you have half tank left. Run this thru the engine and make sure to have several heat cycles so the chemicals can soak. When the tank gets close to empty, fill with 10 gallons of gas only. Go to any home center and buy a 1 gallon can of denatured alcohol. Put the entire can in the tank. Drive it. Is the miss gone. If so, you have eliminated the injectors as the problem and have identified the computer going into safe mode. The alcohol lowers combustion temps and therefore the heat in the converter. The cure may not be so simple. Lets assume that the converter is getting too hot and it is in the safe mode. Have you been running any type of additives thru engine- seafoam, fuel conditioner, etc. If yes, the additives have probably destroyed the converter by coating the catalyst and the converter is basically plugging up causing it to get hot. If you haven't used any additives, does the engine consume any oil? The question is basic: what has gone thru the engine that might possibly have coated the catalytic converter and is plugging it up? Something is restricting the exhaust flow. You need to find the answer because the fix is going to be a new catalytic converter and I think your engine has four of them. It's not a cheap fix. If you do not have any emmissions testing in your state, you can buy a performance by-pass that plugs into the O2 sensor harness and cut the converters off. The engine will run just fine without them and is a much cheaper fix. If that doesn't fix it- get back to me. There are a lot of cheap options.

 

I had the same problem year and ahalf ago. I had bought the truck with 100,000 miles and put 20,000 miles on it when it started doing the samething. I put new filter in the tranny and did a complete flush of the tranny and have not had the problem since.