2000 Grand Marquis, Transmission shudder?

[ima72]

I have been having an ongoing problem with this car. As your driving along, usually around 35mph and when you are light on the pedal and start to give it some gas, or sometimes when just starting out from a light it will suddenly hesitate and then go. it is random, doesn't always happen. It seems better with the OD off( OD light onthe dash), but even then after it happens the traction control light will now come on and the OD light on the dash goes out. After replacing the spark plugs, fuel filter, air filter, fuel pressure regulater, fuel pump, and TPS I gave up and to it to the dealership for their 'expert diagnosis. The replaced #1 coil and cleaned the egr ports & updated the PCM.($500 later!) It did fix the steady misfire, but not the problem noted above. I took it back when the MIL light came on, they retested it for NC and said there was no misfire, it felt like trans shudder? I don't want to take it back there again I think they are guessing as much as I am! Any ideas?

[cobradude360]

first off how many miles? and second i would go and have the system flushed

[ima72]

83k miles. I forgot to mention that I did have a trans flush done as well. I'm just not sure I believe it is a trans problem. Some one mentioned a lock-out solenoid?

[Rick S]

I had the same kind of thing happen to my 2000 Grand marquis. I put my computer reader on and it said to replace the speed sensor on the transmission. I did that and have had no problems sense. The switch was available at my local auto parts store and took 10 minutes to do, I can't remember the cost but it wasn't much.

[ima72]

Fixed! The problem was another bad coil. Found it the hard way but it worked. Since they are easy to change I bought 1 new coil-on-plug assy and started at #1, replacing each coil and test driving. Got lucky and hit it #4. Been running running great for a couple months now.