Hesitation with cruise control

[David Smith]

I recently purchased an 01 ST with 49kK miles and I love the vechile but have encountered a problem that has not been resolved. I installed a K & N FIPK on the vehicle in late Feb to help with the gas milage of the 4.0. Then in early March it developed what can best be described as a stumble when you have the cruise control engaged and are going down a grade. The rpm and speed stay constant but the truck feels like it has a miss that even my wife notices as a passenger. The check engine light did not come on at this time. Took it back to the dealer and it had a pending code of 0101 so they replaced the mass air flow sensor and replaced a vaccum hose assembly. This took care of about 50% of the problem and I drove it for about 4 weeks until I got a check engine light to come on. Took it back to the dealer and it had a 0402 code so they replaced the DPFE sensor this time. I drove about 150 miles with no problems and now the hesitiation or stumble is back as bad as it was the first time I took it in So I am out about 450 bucks and still have a drivability problem with the truck



Any suggestions on where to look, I am about ready to purchase a scan tool that will capture live data and see if that will help diagnosis this issue.



Thanks for any help

 

[Mark Grumpy]

01 ST with 49kK miles

There's your problem, 49,000,000 miles.



You say it does it when going down a grade. The CC will do it's best to keep the vehicle at your designated speed, if the grade causes the truck to pick up speed, the CC will stumble, for lack of a better word. It will momentarily disengage until the lower speed is achieved. I'm guessing it does not do it on a flat road???



At 41K, the other two issues could just have been unlucky coincidence/regular maintenance.



grump

 

[David Smith]

thanks for the input I would consider this normal if it had not done this at all for the first few weeks that I owned the vehicle and it does it all the way down the grade. If it does not do the hesitation, you see the rpm decrease going down the grade then pick back up to the previous level as the grade flattens out



to bad I can't type any better sorry about the 49,000,000 miles

 

[Snooze]

I have the same problem. I had a Diagnostic run at the ford shop and we found out that it was the torque converter not engaging 100%. Instead it was only engaging 75% or so. This would cause the truck to slip back and forth on a slight down grade due to the computers confusion with the torque converter. Mention this possibility the next time you go in.



One thing they said I could do was have my trans fluid switched. They were hoping that because it was such a slight malfunction that the new fluid might resolve the problem. I did that and it did not solve the problem. The slight misses while driving down hill were still there. Oh well.



Now that I know what the problem is. I chose to just wait it out. If it gets significantly worse then I will have some work done on my trans to fix the torque converter and have some work done on gearing and costom work etc. I figured that if I was going to have my trans opened up I might as well make some good changes.

 

[Jim Burch]

My ST started do the same when in cruise control at about 70,000 miles. Took it in to a Ford dealer and there was no code so he said there was nothing wrong??? Been doing it ever since.If you hold your foot lightly on the gas pedal it does not do it.



What do you do about possible torque converter slip as mentioned by Snooze.??



This is annoying but no one seems to know how to fix it.

 

[Snooze]

I think the best option is to have it replaced. Like I said, when the time comes to have my transmission worked on, Ill have the torque converter replaced along with other things.



The good thing about this little problem is that it does not seem to get worse. I only have 50,000 miles on my truck (bought it at 40,000) and noticed it about 4,000 miles ago. So I guess we can just deal with it until its time to have our transmissions opened up.



Snoop:

The reason why your ford guys might not have found the problem is that they didn’t have enough patience. I made sure that the head mechanic of my shop absolutely knew what I was talking about. After I got the truck back he told me the complete story of how he finally found the code that supported the problem. They put about 200 miles on my truck, going back and forth, back and forth on one hill.



I think it would be around the $600 range to have the trans drained, pulled down, opened up and then refilled. I have not checked a transmission shop though; they might be tuned into doing a job like this more efficiently.