Overdrive problem

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Gerry Blodgett

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Sep 13, 2007
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Location
Santa Rosa, CA
I have a 2003 ST w/129,000mi. On a recent trip down Baja I noticed that when the truck is weighted down and I start up a hill in overdrive, it starts to hiccup, like the engine is missing. If I take it out of overdrive it improves. I managed to make it down to Cabo and all the way back to CA. My mechanic down in MX replaced the fuel filter and suggested I put in Fuel Inj cleaner. None of it worked. I'm about to take it in to a tranny place - any suggestions?
 
Gerry, Maybe it was too much weight. I don't use overdrive uphill under 2K revs.

Ed
 
I didn't check the rpms but I only had the bed loaded with gear for my trip, I wasn't towing or anything like that. Also, the car also hiccuped a little on steep grades even in high gear so I tend to think it's a tranny problem. Also, I would think that the truck would downshift before starting to act up like that. I was just wondering if anyone else had experienced this. Thanks for your reply.
 
A Thunderbird I used to own had identical symptoms. Ended up getting the tranny rebuilt. Just sayin'....
 
It sure sounds an awful lot like a misfire to me. Try this, start it up,set the parking brake, mash the brake pedal as hard as you can and then put it in drive, now slowly push on the gas until you have it floored and see if hiccups...or misfires on you. A secondary misfire will usually rear it's ugly head when the vehicle is under load...just like you are describing
 
sure sounds like you need new plugs, hence the misfire.. when you're under load, the cylinder pressure rises, making it harder for the plug to fire. When you shifted out of OD, you lightened the load on the engine...
 
Thanks for all the replies. I just got back from a trip and read them. After reading the last entries regarding the plugs, I remembered that just before I left for Mexico (when this problem started) my mechanic had just replaced the plugs and wires as part of servicing the truck for my trip. I will take it back into him to check if this is at the root of my problem.
 
Took the ST back to mechanic who had replaced plugs and wires before my trip. He checked the computer and there was no indication that engine had misfired. He has driven it several times and can't get the problem to replicate (naturally). So I'm joining him tomorrow morning to drive it with him and try to get it to actup. Frustrating! Has 130K miles - maybe it's time to look into newer replacement.
 
^^^^^



That's because he doesn't know what he is looking for. If he is just pulling codes then no he won't find anything. I fhe knows how to look at and decipher "mode 6" data then he will find the misfire...I am almost positive you have a misfire
 
Thanks tech, I'll suggest it to him. We drove it together the other day but couldn't replicate the problem. It seems to happen only when I'm cruising at freeway speeds with a slightly loaded-down truck and it starts up a grade. As it reaches the limit of the overdrive load, it starts to jerk and hiccup and I have to gun it to downshift or manually shut off OD. If it is a misfire, why doesn't the check engine light go on?
 
Ford's are the worst ones for not turning a check engine light on for a misfire. There are many variables that determine if the light should be illuminated or not. The pcm keeps track of the number of times any given cylinder has misfired, when that number exceeds a set limit the light turns on. A intermittent misfire might never set a check engine light and that is where mode 6 data comes into play. Mode 6 data is basically the "test results" of the monitors that are run on the vehicle and if you can decipher the data you can learn alot of valuable information before the check engien light ever comes on...such as which cylinder is misfiring. If you are having a secondary igniton misfire issue you should be able to get it to act up by doing a good power brake...this is all things your mechanic "should" know though. Also a fuel pressure and volume test would be good info to have as well
 

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