1996 Thunderbird jerking problem?

I have a 1996 ford thunderbird with a jerking problem that's been hard to diagnose due to no check engine lights illuminating and not being able to reproduce the problem in the presence of mechanics.

problem #1… When I'm cruising on the highway (at speeds around 60) for about 30 minutes or longer, the car starts to jerk violently in bunches. The jerking is short and aggressive, the tach needle drops close to zero but goes back to the RPM the car was at, ; the problem seems to go away if i release the gas pedal and let the car coast. When i press on the accelerator again, the tach needle will hit a certain RPM before it starts to jerk again. This problem has never completely stalled the car while driving, but it does interupt acceleration when the car jerks

problem #2… Recently i have had problems with taking off from red lights; when i press the gas pedal, the tach needle fluctuates up and down for about 2 seconds before the car responds. Last week for the first time, the car did stall at a red light and the RPMS went up and down for 2 seconds after i started the car.

does anyone have an idea what the problem is with the car? I've already replace the IAC and PCV valve and grommet, and i've cleaned the MAF. The last tech i went to mentioned something about an external transmission wire connection not being grounded properly; he sprayed the wire with carb cleaner, but this didn't fix or make the problem worse

Added (1). almost forgot to mention, the car has a 4.6 V8, if that helps

Thanks for the answers, but I have already tried running the DTC scanner multiple times, its says "no codes found", but there's something wrong with the car. I personally believe it has something to do with the TPS or maybe the fuel pump.

If your car has OBD2 port, then you can use car diagnostic tool to scan it, like code scanner or ecu tuning tool. You can find good quality obd2 tools from http://www.obd2life.com

Did you know that your car (1996 model) was the first year that utilized OBD-II (On-board diagnostics) that changed the way the check engine light illuinates forever?

Before 1996, the CEL used to illuminate for all problems detected by the PCM.

In 1996 and newer vehicles, the CEL illuminates only if the problem detedcted causes the tailpipe exhaust emissions to increase by 1.5 times the FTP levels when the vehicle was new.

What does that mean to you? You can have any number of problems relating to the tranny, lock-up converter, engine, fuel system, etc. And never see the check engine light come on, except when you first start it (light prove out). You should always gather DTCs whether or not the CEL illuminates.

One more thing, OBD-II PCMs also use a feature called 2-trip logic, this means that the PCM must see the identical problem twice during 2 different trips (with an engine cool down period in between) before it will actually turn on the CEL.

Using the check engine light without this understanding of how it now works is a serious detriment when attempting to diagnose a drivability problem like you are having. Connect a scan tool, look at the data parameters and gather all the codes. Memory codes are continuously set, without the 2-trip or any other rules. Lastly some codes will only set in continuous memory, they should be checked first as hard codes will illuminate the CEL.

HTH (hope this helps)