2002 Buick Century [bogging down]

So I’m experiencing a strange issue with my 2002 Buick Century 3.1

If I start the car and immediately start to drive the car will bog down for about a mile. when turning corners or going from a stop light. I hit the gas and it doesn’t want to move. The idle becomes rough and erratic almost to the point of stalling. After a short time it straightens up and acts right.

however, if I start the car and wait 5mins before driving there are no issues whatsoever.

I guess my question is, is there some sort of “cold circuit” or sensor that has gone bad causing this weird issue?

I have already replaced - MAF, MAP, PCV, Air intake temp sensor. And have EGR and IAC in house ready to install.

You don’t say… Check engine light ON ?

This vehicle should be equipped with OBD2, an onboard diagnostic system designed to offer some possible clues about problem behavior.

If that light illuminates then trouble codes could be in there waiting to be read.

The “replace parts until the problem goes away” approach could be quite costly. Time and money spent on a proper diagnosis could behoove you.
CSA :palm_tree::sunglasses::palm_tree:

There’s a coolant temp sensor for the computer so the computer can properly adjust the fuel/air/ignition for the temperature.

Since this sensor is one of the primary inputs into the computer, the Check Engine doesn’t always come on if the sensor goes out of range.


oh sorry for lack of info.
yes the engine light is on. I have a scanner. only codes are for 02 sensors. which have been there since I bought the car 2years ago and it has ran fine since then til now. The downstream 02 sensor was cut off when someone cut the cat off the car haha. I know it sounds like that could be contributing to the problem but I don’t think so as that has been a constant from day 1 and the car just recently started having problems.

I feel like the coolant temp sensor is a reasonable thought considering it only acts up in the minutes between cold/warm.

The O2 sensor wouldn’t cause this.

When the engine is cold, the computer takes its signals from the crankshaft position sensor, throttle position sensor, MAP/MAF sensor, and coolant temp sensor.

This is called the open loop mode.

It’s not until the engine reaches operating temperature where the computer makes adjustments to the engine based on the signals it receives from the O2 sensor.

This is called the closed loop mode.


interesting. I happen to have a replacement sensor here so I will probably replace it today or tomorrow and update with results.

just an update.

replaced coolant temp sensor and it didn’t fix the problem. swapped em out, started the car and immediately started driving. after making a few stops and turns the car began to bogg down once again. after a short period of time it straightened up.

drove the car home and replaced the map sensor and egr valve too. test drove the car again and it drove fine. (but I’m thinking the car was still warmed up from the initial test drive.) gonna let the car sit a day or so and then test drive again. will update soon.

If this problem occurs 60 to 90 seconds after start up the upstream oxygen sensor is reacting slow/malfunctioning. Beginning around 2002 some vehicles go into closed loop very quickly, if the O2 sensor is sending a rich signal the PCM will lean the mixture and this can cause the engine to sag or bog.

CSA :palm_tree::sunglasses::palm_tree: