My wife's grandparents gave us their 94 Grand Marquis as a gift but the transmission slips and the engine flares. There doesn't seem to be any rhyme or reason to when it happens, it just does. We have taken it to 3 mechanics who have run various diagnostics tests. The first one found that the fuel trim was running at 11 so he replaced the fuel pump. The second and third mechanics both agreed that a new transmission was needed, so we had a rebuilt transmission and torque converter installed.
The problem is still there. Basically what happens is that we'll be driving and feel the car slip into neutral for 5-10 seconds before re-engaging in a gear. The car also sounds exactly like you would if you revved the engine while in neutral during this time. Most of the time we stop pushing the accelerator. Sometimes we experience this when it seems to be changing gears, but many times it will happen when we are simply in cruise control, or maintaining a speed. Replacing the fuel pump and transmission has made HUGE differences in improving the problem, it is nowhere near as violent or scary now. However, it is still slipping regardless and we either want to fix it or sell the car while it is at maximum value.
Apparently her grandparents have had this problem ever since they bought the vehicle in 1998. They also had the transmission rebuilt in
2000, we just found out, and nobody they took the car to in the last 6 years has ever solved the problem. Does anybody have any idea what the problem might be? Any idea what to check? I don't know much about cars but am willing to learn. I also own a Hayne's book, so I could theoretically look for some of this stuff on my own if I knew what direction to go in. Thanks in advance!- sterling