The car is a 3.0 V6 with auto trans, has about 120k on it now, and was scrupulously maintained by the previous owner. We've had it for about
6 months, during which time it has functioned flawlessly. In the last month or so I have noticed that at low to mid throttle demand the car seems to "buck", and it feels like the transmission is disengaging then re-engaging. Increasing the throttle demand alleviates the problem. I may be imagining it, but I think it is worse when the weather is cold.
Any suggestions or opinions on what the problem may be are appreciated. Thanks in advance to all.
I've broken CV joints before; it doesn't feel like that to me. I had an old Chevy wagon a while back with a bad throttle valve cable- it kept "hunting" for which gear it should be in...or a standard transmission if you jabbed your foot onto the clutch pedal a couple of times while you were driving down the road.....that's a lot like what this car feels like it's doing, shifting in and out of gear at low throttle demand conditions. Other than that there is no vibration or "clunking", which all the bad CV joints I've experinenced did before they failed.
My plan at this point is to do the cheap, easy stuff and change the filter and fluid (the level seems fine, but I've wondered if it's experiencing a temporary drop in fluid pressure due to a clogged filter or dirty fluid). Does this model have a modulator-type valve that reads engine vacuum? Seems to me a low throttle demand might result in a vacuum variance, which a dodgy modulator might mis-interprete.
As for the transmission servicing, I haven't gone through all the maintenance records to see, but the previous owner religiously followed the manufacturers specs for regular maint., and took it to the dealership every single time (they soaked him for a couple of hundred every trip, too). I'd guess that whatever should have been done to it was.
My vote is for the TPS - Throttle Position Sensor. Classic symptom at partial throttle, ECM engaging/disengaging the TCC (40-55 Mph with a variable light load) thinking the throttle is doing a TIP In/Out.
Change the usual suspects. Plug wires, cap, rotor and plugs first. Then TPS, VSS and fuel filter. Check all the small vacuum hoses for cracks and leaks while your at it.
Try this... Hold constant speed with your right foot on the gas. Very lightly, engage the brake with your left foot. If the symptom is alleviated it may likely be a fault with the lock-up torque converter if so equipped. Have you had the computer codes read?
Ok, at the risk of sounding stupid, could you spell out the acronyms you used- ECM, ECC, TIP? I'm less convinced now that there is a transmission problem, but I still don't have a lot to go on. This is my very first Ford, and without a lot of time or money to go hunting the problem, I'd like to narrow down the list of suspects as much as possible.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.