transmission problem

[badmaf]

Hello,

1994 towncar with about 98K miles. I've had this problem for about 6 months. It seems similar to the problem I had about 2 years ago and at that time I had the mass air flow sensor replaced. With that, it was jerky at just about any speed I was travelling but maybe not until I reached 30 mph and over. It isn't as bad now as it was then. The symptom is that at between 30 mph and up to 40 mph the car starts jerking. Usually I feel it at around 34 mph but I had my auto place look at it and he said it happens at around 30 mph. He said the transmission was slipping. He looked at the fluid and said it was full and looked O.K. So, any ideas on the problem and the fix? I think I've heard that my 94 is problematic. I plan on selling but maybe not for another year. Will I find myself stranded if I don't take care of it?

Thanks.

[LithiumCobalt]

I've had same problem. Can't figure it out either. I've went through all kinds of replacement parts. And, although better, it's not completely gone. There are two things that most everyone said could be the problem. First, change the spark plugs and wires. Just the slightest misfire will cause the tranny to go nuts. Next, when was the last time that you changed your trans fluid and filter? Some have recommended doing this even if it is very old - I, on the other hand, was a bit leary of doing this. It did not help my problem immediately - it actually seemed to get worse before it got better. Another thing I would check is the brake on/off switch under the dash, connected to the brake pedal. This has an effect on your torque converter, which could be problematic. It's only a $5 part, so it's worth checking. Some have replaced theirs and their weird trans shifting issues disappear. Lastly, check your throttle position sensor, or just replace it, it's only $20. This also controls shift points. This is a hard one to diagnose because I can't tell whether it is an engine misfire or the transmission acting up. Chip away at it little by little and you might find that a combination of all the little stuff might help. A lot of this stuff can be found in the tech section - take a browse in there and let us know how it goes.

[badmaf]

I had my spark plugs and wires replaced less than 2 years ago when the head gasket blew. I had the transmission flushed about 4 years ago right before the car acted up like it is now. And it wasn't the mass air flow sensor but I can't remember what the repair was. Cost me 200$. I have it in my records but don't have them with me now. I'll look in the tech section for the other 2 items you said to check. Thanks.

[Fordace]

it is usually water intrusion into the MLP/Transmission range sensor on that model year

PM me your email address, I have 3 TSBs on that model and year for that problem

[pkucan]

Speaking of TSB's are they posted anywhere? Or is that not allowed because of copyright?

[badmaf]

In my earlier post I mentioned that I had my mass air flow sensor replaced when I had this problem before. I did have it replaced but not for this problem. Then you mentioned the MLPS and...bingo...that was the part I had replaced. It has been about 3 years ago maybe 4. Could it be out again? My husband drove the car the other day and thought it was the same problem as before too. How had it is to replace?

I will send my email to the previous poster as suggested.

Thanks.

["C"]

Ever though about your OSS sensor? I replaced mine, and the weird shift patterns were eliminated. It's a $20 part and not that hard to replace on your own. It could help with your tranny problem.

[badmaf]

OK. So I couldn't take it anymore and decided to take the car to the tranny shop. The mechanic said that he couldn't tell if there was a tranny problem or not because the car was missing so bad. He said it was the engine that was making the car jerk and not the transmission. Advised me to start with a tune-up. I told him that my car was using about a quart of oil a month too. He suggested an oil change and a quart of Lucas stabilizer. So, he did that plus plugs, wires, air filter, fuel filter and a pcv valve. He did a compression test and engine is AOK. Transmission is good too. So, back to response #1 above...it was the plugs and wires mostly to blame. Gheesh! I told the mechanic that I am disappointed that my regular mechanic didn't diagnose right and he said it happens all the time. Also, he said that when a plug/wire goes bad you will usually notice it when you go about 35 mph which is what I said happened in my original post. He had an explanation for that which made sense at the time but I can't recall now. Thought I would post this so someone else might benefit.

Thanks for all your help.

[dickwells]

I also have a high miles 94 Signature and my advice is to be very leery of the coils if this problem recurrs. Good Luck

[badmaf]

Only 101K on this baby ;)

[bryanhbre]

also check the DPFE sensor. sits on the back of the motor by the air intake, I changed everything on my car last summer trying to fix the exact same symptom (slight hesitation right around 30-35mph) AFTER I had already changed that stupid DPFE sensor. Turned out the new one had gone bad. Replaced it and fixed everything.

[Chevyguy]

Coils fail more from Age/Heat vs miles

My old 93 ran SMOOTHER than my 2001 after getting two new coils and new wires. I had BOTH Trans shudder and engine misfire problems with my old 93 so I can help out here.

Best way to determine engine vs trans for herky jerky shudder...

Transmission shudder 100% regular frequency. Feels like rumble strips, with a P-71 aluminum driveshaft it rings sometimes. You are feeling the PCM cycling the torque converter to allow partial slip. Fresh Mercon V and Lubeguard can solve this, the problem was pretty severe on my old P-71 (Police) which had a least 100K of Police use. Took more than 500 miles to clear the shudder, and it did come back after the car sat for a while. The 94 Town car cured shudder IMMEDIATELY after changing the trans with fresh Castrol mercon V

Engine shudder is partial misfiring, usually only under load. Tricky thing is this is the same conditions that cause trans shudder, low speeds in 3rd or 4th gear with the PCM cycling the torque converter. Engine misfire feels more like when you are lugging overdrive in a manual trans car. Herky jerky, not as regular pattern as the trans shudder. I had LOTS of this with my 2001 as I had rusty coils (the 98 up style coil on plug COP). Getting 8 new coils for $110 solved the problem!!.