Uncommon hesitation/vibration on start

Ok, I get it - shot in the dark, not much info, but I'm hoping that one of you guys has seen, read or otherwise fixed yourselves something similar. I will add more info as I get it, but here is the skinny:

Every once in a while when starting, the acceleration just cuts out, and then comes back 100%. Takes about 1 second, but it is like you let off the gas and then punched it again. It doesn't take 100% acceleration for it to happen, 50% or even 25% will do it. Not reproducible upon demand...very random.

I think this is related, but it also feels like acceleration is "muffled". Like it's not at 100% of the requested pedal position. And there seems to be a little bit of a tremor on acceleration. I can't tell where it's coming from but it always happens in first. This may be due to dirty tranny fluid. It is pretty brown and has been sitting for a long time. Only 115k on this motor.

What do you think???

Fuel pressure may be low -check with gauge. Also check TPS. And have the cats assessed for functionality.

Is there a way to find out if the cats are bad without paying someone to do it? I don't have a lot of tools though...
It just passed emissions fine if that makes a difference.

You can use a electronic temp guage, available automotive and tool stores/trucks. When you take reading at front and rear of each cat, should be same or a little higher at rear. Clogged cats usually have dropped temps at rear, and cat can glow red if real clogged. You can also buy a gauge that screws in o2 sensor hole. If clogged you'll get a low reading. These cats are famous for clogging. Ford dropped the ball on these during manufacture.


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Another way to check for a clogged cat, is the rent a scan tool from advanced auto, or one of the parts stores that rents them out for free. Theirs a great video I just watched, showing voltages of upstream and downstream o2 sensors. A high voltage is usually symptom of bad car. Watch video, or crawl under car with other two methods. Let us know what you find.


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In the old days, if you had a clogged cat, you could check at night, it would actually glow red. That is an extremely clogged one though.


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Oh yeah, one more easy way to check for a clogged Exaust or cat, is to hook up a vacuum gauge to an intake port. If you have a clogged Exaust, vacuum will slowly drop towards 0.


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So here is what I've come up with so far on this. Pulling a load up hill I had to manually shift out of second gear because I had the pedel pegged and it was doing about 10mph. In reverse backup up a steep incline the engine shutters(or tranny). As I mentioned in first gear there is also a smaller shutter every time...might be a bit more exaggerated when engine is hot.

My conclusion is that it's coil packs. Torque converter doesn't engage in reverse...so it shouldn't have anything to do with the converter. Other thoughts?

Wow! You have no reverse? That's probably a bad reverse pump, or worn out clutch/ band. Before you start changing coils, do a fuel pressure test at Schrader valve at injector rail. Also check out cats like I mentioned earlier. Did you ever run a dtc codes test with a scanner? You need to do this. Don't start throwing parts at your SUV. I've seen too many people start changing parts, without testing first. Don't be one of those members.


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After reading your post again, I am convinced that yours is a tranny problem. Try having the trans fluid and filter changed. If this doesn't cure your dilemma, then have the trans checked by an expert.