1998 Buick Century Has My Mechanic Baffled Beyond Belief

[Brian H.]

Car: 1998 Buick Century with 88,000 miles

I need one of two things... divine intervention or the most knowledgable mechanic in the world... or so it seems. 🙂

First Problem: speedometer needed begins to fluctate... then fluctates even more.... then 10 to 14 days later, the transmission starts to shift improperly. I check symptoms on Google and many people say it's the VSS.

Fix Problem: Had VSS replaced (I don't do any labor myself as I'm pretty car ignorant). Problems fixed totally...... for about 10 days.

Second Problem: Then I notice a slight fluctuating in the needle 10 days later. The transmission begins to mess up two days later. Someone says something seems to be shorting out the VSS. So I get another one and replace it.

Worse Problem: Have the VSS replaced a second time. Before the VSS is replaced the a second time, the mechanic checks codes and the car is not showing any current codes and no codes in the history either.He replaces the VSS. I now have no speedometer movement at all when I had it before he replaced the sensor. I also have no gear other than first gear. The car won't go over 10 mph or so. It can, but the RPMs would be too high.

Tried to Fix Problem: Mechanic with 30 years experience tried to diagnose the problem today couldn't find codes today either. He checked wires for hours, PCM, wires leading from the VSS, etc. He says he has no idea what could be wrong with the car.


I was having no problems with the car starting, no gauges are messed up other than the speedometer. no other problems at all. The first time replacing the VSS worked wonders and now this.

Thanks in advance for any help you can provide.

Brian

 

[ryenie]

Well, there's only so many things it can be. The sensor, the gear the sensor uses to create its pulse, the connector, the wires, the pcm or the speedometer. Given it doesn't want to shift from first it sounds like the pcm isn't recieving the signal from the sensor, won't shift because it doesn't know which gear to be in. First thing i would try is running a new set of wires from the sensor to the pcm and see if things change, doing a resistance test is not always going to find a bad wire, if a stranded wire has 1 of 10 strands still in tact it will still show that you have continuity and pass inspection. If the gear were bad i doubt replacing the sensor would fix the issue, so i don't think it's the gear, but it should've been inspected while your mechanic was trying to trace the problem down. Also if it where just the speedometer i would think it would still shift gears because the pcm would still knows how fast the cars moving, it just wouldn't be able to display it on the speedometer.

 

[Brian H.]

Thank you so much for your help. What you said makes total sense.

Final question before I take the step you suggest is this, "Is the wire from the sensor to the PCM such a wire, i.e. stranded?"

Also, is there a technical name for the set of wires from the PCM to the sensor? I'd like to know exactly what to ask for at the auto parts store or dealer.

Thanks,
Brian

UPDATE: When I called to ask about the wires, I've been told the only thing available is a connector which connects to the VSS and has two wires that are about 5 inches long. Where would I get the other wires that go from the PCM?

 

[ryenie]

Sorry for the delayed response. The wires you can get from any auto parts store, it's stranded wire, not sure on the gauge but it's between 14-18 gauge, it doesn't have to match the wires coloring that you're replacing. It would be better to get the connector and run it from there to the pcm. You'll probably have to cut the wire at the pcm a few inches from the connector (to give yourself some extra repair room if necessary), it's pretty difficult to find the proper ends to swap in the pcm connector so you will most likely have to cut and solder and shrink wrap the wire. Butt connectors are not a permanent solution from my own experiences. Also, pretty sure the wires for the VSS are twisted around each other from the pcm connector to the vss so you want to make sure you twist them the same way, it's done that way to help eliminate any interference from outside sources. The wires at the pcm connector are purple and yellow and in the first connector to the pcm, the pin #'s are 64 & 65. Numbers can be found on the end of the connector inside corners. But you should be able to see the wires next to each other going into the connector.

 

[Brian H.]

Thanks for the reply. I don't mind the delay, that's no big deal.

As for the wires, the store I called, had no idea about the wires other than the connector and the short wires which come from it. They told me to go to a junkyard and that was my only option.


I called a dealer, the best Buick dealer in Dallas and they told me the wire wasn't stranded, or they didn't think it was.


I know you're in Tennessee, but where in Dallas could I find a mechanic that seems to know even one half as much as you know about this?


I am so frustrated with this car that I'm about to junk it and I can't afford to do that, after this car, our only other option is a 1992 Ford F 150 with 250,000 miles on it, 12mpg, one window working and no AC here in Texas.


I am not a mechanic and I can't find one locally that has any idea what to do to my car except rebuild the transmission. And even then, per your diagnosis it wouldn't work because of the wiring.


Please excuse my exasperation. But if you know anyone who knows anyone who knows anyone in Dallas who could work on this car and is trustworthy, I'd love to get in contact with them.


Thanks so much for your time,
Brian

 

[ryenie]

I've been working on cars for 20 years and have never seen anything but stranded wires used, makes me think they don't know what you mean when you say stranded. I would say at the dealership they don't have to perform wire repair they just replace the whole thing with a new wiring harness. I've had to repair at least 4 or 5 vss wires from where they were pinched in an accident or chewed by rodents, they have all been stranded wire, and the two wires for the sensor were twisted around each other. As far as knowing a mechanic in Texas, i don't even know of one where i live that i trust, except for the guy at the machine shop. Hopefully someone else on here might know someone who is trust worthy closer to you.