03 Century max speed problems

[Nick03Century]

Hello, my name is Nick and I have a 2003 Buick century I recently bought with around 190k miles. When I purchased it, the only key they had was the (I assume) valet key, considering it only works to start the car, not on any locks. However, the car can reach speeds of 50mph and as far as I know, valet keys usually limit speed to 25mph. My car will top out at 50mph on the dot and bang some sort of rev limiter. Is this due to the key or some other malfunction?

I have so far been able to find nothing confirming nor denying my theory and any help/suggestions would be greatly appreciated.

 

[century61]

Hello, my name is Nick and I have a 2003 Buick century I recently bought with around 190k miles. When I purchased it, the only key they had was the (I assume) valet key, considering it only works to start the car, not on any locks. However, the car can reach speeds of 50mph and as far as I know, valet keys usually limit speed to 25mph. My car will top out at 50mph on the dot and bang some sort of rev limiter. Is this due to the key or some other malfunction?

I have so far been able to find nothing confirming nor denying my theory and any help/suggestions would be greatly appreciated.

I owned a 2003 Century and I am not aware of anything about the second set of keys limiting your speed. I now have a 2008 Lucerne and same thing. Of course, I could be wrong because I always had a second set of keys that looked exactly the same including the Key Fobs.

Any warning lights on?

If it were me, I would start with some basic checks - Air filter, Throttle body need cleaning? Spark plug condition and wires? Exhaust restriction?

 

[Nick03Century]

I owned a 2003 Century and I am not aware of anything about the second set of keys limiting your speed. I now have a 2008 Lucerne and same thing. Of course, I could be wrong because I always had a second set of keys that looked exactly the same including the Key Fobs.

Any warning lights on?

If it were me, I would start with some basic checks - Air filter, Throttle body need cleaning? Spark plug condition and wires? Exhaust restriction?

Yeah I’m not super sure about the key, but it is a naked key, just bare metal no chip no fob no nothing. The car has 1 code for the EGR valve but no check engine light on, the spark plugs and wires were just replaced 2 days ago. My next assumption would be the mass airflow sensor, I was informed to unplug the MAF sensor while the car is running, and if it runs any different, it’s not the maf sensor, but if it does not run different after uplugging it, then it is the maf sensor. Do you have any experience with this way of testing? It doesn’t sound very good for the car to me, but I’m not really too knowledgeable.

Oh and also since you mentioned it could be exhaust issues, half the exhaust is missing. It’s cut about 2 feet back from the muffler. You did say restriction which this is the opposite, but maybe it helps.

Can the air filter itself cause issues like that? That would be quite the cheap fix as I can pick one up online for about $12.

 

[02LTD]

If it can't go faster than 50 I would suspect that the Catalytic Converter is clogged.

 

[century61]

A car with that many miles on it is going to need some love'in to get it back into shape. I would not think the MAF is going to cause this speed issue. The car would run lean or rich when the MAF is bad. The MAF tells the computer how much air is coming into the engine. So, If it was bad the car would probably run rough. You can certainly clean the MAF sensor. Better yet hook a scanner up to the car and check what the reading of the MAF is at idle. It should be somewhere around the size of the engine. The 3800, I think it should read in the area of 3.8 . If not then just clean it and recheck it.

I think a restriction in the exhaust is probably your issue. Even though the exhaust was cut off you still have the CAT which is up towards the exhaust manifold. These tend to plug up or get restricted with age or if the car has been running poorly with things like burnt oil or coolant going thru it and clogging it.

Since the exhaust has been cut off just beyond the converter see if you can remove it from the exhaust manifold and pull it out and inspect it. The inside of a converter (CAT) is honey combed and you should be able to shine a light thru it. Most likely you will see it plugged up. Its a bit of work to take the exhaust off the manifold but if its bad you will have to do it anyways. Perhaps have a shop look at it.

Concerning the key, They make kits where you can change the tumblers in the key cylinders to match another set of keys or I think you can take your VIN number and have a set made with FOB's included. Not sure how much that would cost though.