I have a 91 3.3 4 speed buick century it started idle high then goes away with check engine but when it started to idle high it started shifting hard and now wont shift out of second gear even when shifting manually what can be done ive checked the vaccum on the modulator and thats good but it wont shift and the check engine light stays on longer and longer
My 1st suggestion would be to get a scan done for the check engine light. I'm not talking about a simple 'code reader' but an actual scan tool so all of the different sensors and perimeters can be read. You will need to get one or find someone with a scan tool which can do OBD I vehicles.
If the engine isn't running correctly this could cause the transmission not wanting to shift. 2 vehicles that come to mind where I've seen this happen.
One was a Pontiac and it wouldn't shift into overdrive. Problem was the thermostat which was stuck open and it wouldn't allow the engine to get up to proper temperature which kept the transmission from shifting.
The other was a Ford Explorer that the lady thought for sure the transmission was bad. After a test drive and investigation it was found the catalytic converter was mostly plugged which wouldn't allow the engine to achieve the proper torque and RPMs to get the transmission to shift.
Now granted neither of these examples are an exact duplicate of the problems you are having. They are simply to illustrate that engine performance (or the lack of) CAN affect the way the transmission shifts.
Hope this helps.
SOURCE: 1995 buick century transmission trouble
Most likely causes is the OD shift solenoid or less likely the VSS
SOURCE: how to replace a coolant level sensor, 2000 buick century
The coolant level sensor is located on the radiator. If you are looking at the engine from the front of the car it will be on the left side. There will some kind of clip holding it in the radiator. Removed the clip and pull the sensor out. You will lose coolant so try to swap it out quick or drain some of the coolant out. Once new sensor is installed, install clip to keep the sensor in place and reconnect the wires to the sensor. Crank the engine and make sure the coolant level is full. This should correct your problem.
SOURCE: transmission sometimes shifts hard into next gear.
Typiclly this is caused by a failing Pressure Control Solenoid. Now in some cases, since you are in the 1996 model year you may have a vacuum modulator that controls the shift firmness that can be replaced as it is externally mounted. I dont know how best to describe what it looks like, but look down on your transmission, on the front side facing the radiator and if you see a canister like device that has a vacuum line running to it, that is the vacuum modulator and you could start by replacing that and see if it helps.
If you do not have the vacuum modulator and have instead the electronically controlled version of your transmission then you will have a Pressure Control Solenoid and it, unfortunately, is located on the inside of the transmission and cannot be easily replaced without dropping the whole transmission.
The pressure control solenoid is a common issue with your transmission (4T65) and Im leaning more towards you have the electronically controlled version (4T65E).
SOURCE: my 2000 buick century is over heating fans are
Hi, these are two separate issue here.
The abnormal shift is isolated within three ares. i would suggest checking the transmission fluid level first to make sure of the proper level. if its low, you will experience Miss shifts of this nature. if the fluid level is sufficient, i recommend moving your inspection to the TCM(transmission control module). this is the control module that initiates the correct shifting intervals and it relays the actual shift signal to the shift solenoids located inside the transmission pan. if the module is malfunctioning, it will affect the shift patterns dramatically. If the module is in good condition, i would then move on to the actual shift solenoids themselves.
These devices preform the engaging of the gears within the transmission as stated above. if this device is not working or is malfunctioning, it will affect the way the transmission shifts. If you have not preformed a proper transmission flush and have not changed the filter for a while, it would help if this maintenance was initiated soon if possible.
Now, concerning the overheating issue. if the fans are running in a correct manner, this will most likely point to a faulty water pump or an faulty thermostat that may be froze(stuck in position not allowing proper water flow). the most common fix will be to preform a radiator flush. during this flush, if you notice a rusty water flow and tiny metal fragments running out the radiator, this will confirm extreme radiator damage to the inner coils and it will have to be replaced or rebuilt. I would recommend flushing the radiator and testing both the water pump and thermostat for there operational value.
Please rate and god bless:)
SOURCE: 2001 Buick Century shift solenoid
It is in the side cover on the valve body. The transmission needs to be removed to access the solenoids.
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