I have a 2001 LS 3.4L with 127,430 miles. When the I first drive the car for 20-30 mins it shifts great, but when it warms up it shifts hard into gear.

Could it be the catalytic converter? The exhaust smells like rotten eggs.

Motor mounts?

Time to change the transmission fluid?

Has anyone else had this same problem?

 

change your fluid and filter, but don't do a flush. Our trannies are a very weak point in our cars. Mine started doing that and it lasted quite a while but eventually the tranny went out. You could also change the shift solenoids as they are also bad in our cars.

Here is a link to the new shift solenoids
GM ACDelco - Shift Solenoid #GM-24219819

 

X2

 

mines does the same thing i believe its the solenoids, sooner or later they will go but they last a while before they finally do

 

You need to have your Cat checked to see if it is in fact plugged. The rotten egg smell you mentioned is typically the dead give away sign your having cat problems. And this will effect how your much vacuum your engine can make, computer adjusting fuel trims etc. causing the hard shifts when your engine is up to operating temperatures. I just went through this with my Monte, new cat and a few other vacuum leaks and the car runs very good now.

 

I didn't even notice the mention of the rotten egg smell in your original post. I second Zippy's recommendation of getting your cat checked

 

Thank you, everyone! I will take it to a muffler shop that's close to my work and have the cat checked out.

The car starts kind of hard sometimes too.

I have new plugs,wires,pvc valve,fuel filter.

I am keeping this car and giving my 2012 Civic lease back in March. I want to get everything ready on the Monte before then.

 

I dislike being the 'odd man out' on this, but...


A rotten egg smell does not indicate a bad catalytic converter. What you are smelling is the sulfur content of the fuel. The more sulfur added to the fuel, the stronger and more obvious the smell. Try switching gas stations and see if the smell reduces or goes away.


If it were the solenoids the problem would be there whether the transmission is cold or hot. Since it happens after warm up I would start looking for a transmission - your friction discs are worn.

 

Well after reading the "Odd man out" 03SSLE (Mike) rebuttal I looked into the "Rotten Egg" smell a bit further. And it appears there is something to the claim it is fuel related. There are components that fail or are failing and cause to much fuel to be added and it's not all burnt, so it is dumped out the exhaust and hence the sulphur smell. I did have new O-rings put in at my injectors, replaced the MAF air sensor and something else causing an additional vacuum leak. Plus my CAT was clogged, but it could have happened from the failed components. So perhaps there is in fact another underlying issue that needs addressed. Here is a mechanics description of why we have the "Rotten egg" smell. So thanks much Master Mike, I have found your advice to often be spot on! Good job, thanks for the correction.

From Examiner.com By: Arthur Heberger

One of the most common things that cause a car to smell like rotten eggs that is the catalytic converter. Many people will tell you that you have a bad converter, but it is actually a symptom of another problem. By acting quickly, finding and repairing the problem causing the smell from your converter, you should be able to save it.

Your car’s catalytic converter is supposed to take in pollutants from the engine’s exhaust and convert them into clean air. Today’s engines are said to produce less than 2% pollutants, so unless there is a problem, the converter should have a very boring job. And, with a healthy well-tuned engine, the converter should last the life of the car.

However, defective engine controls could cause the catalytic converter to be flooded with fuel, which contains sulfur, hence the rotten egg smell. If not repaired, the heat generated by the chemical reaction from the increased amount of sulfur passing through the converter will cause the honeycomb shaped filter to melt. Once melted, it will be an obstruction in your exhaust system causing poor engine performance, sluggishness and stalling.

Just replacing the catalytic converter at this point is only a temporary solution. The cause of the fuel flooding the converter needs to be found and addressed before a new converter is installed, so it will not happen again.

Some things associated with flooding a converter with fuel are: a defective oxygen sensor, a leaking fuel injector, and a defective pressure regulator. Even bad coolant sensors have been known to trick the ECM into sending too much fuel.

So, if you get that rotten egg smell and you’re sure it’s not something as simple as a shorted battery, start by having your ECM scanned for codes

 

Sometimes fuel canister could be contaminated, EGR could be faulty, or it could be an evap sensor. That may explain the smell, but as far as shifting goes, I would venture to say that your friction discs are in rough shape. Trannies are $1,000 to $1,600 if you are willing to go that far. Otherwise, there is no way to know how long it will last. And I mean that positively...mine was shifting rough for about 30,000 miles and still working, though it was annoying to have that "kick". But, since I'm putting in a new engine, I am going ahead and putting a new transmission on it as well. It will now last for many years to come!