I was hoping someone or multiple kind folks could help me out with a few issues I am currently having with a 2005 LT 3800. A month back I was having issues with the car hesitating when in D and at a stop light when I let off the brake. Figured out that it was a Coolant Temp Sensor/Themostat issue. Problem resolved.

Currently though I am noticing that there is a dip in power. Not when the vehicle is driving, but when I come to a stop light I notice that the power dips a tick mark or two and pops back up. I hear a click in the dash like something turned on and then the power comes back up or it comes back up as soon as I give it gas and start moving. Yesterday though I noticed the power finally dropped a few times below the half mark when the vehicle was stationary and the wheels were turned and/or when the windows were rolled up. It's never gotten that low.

As a note I did just have the battery replaced in October 2013 so I was leaning towards an alternator issue at this point.

This then leads me to my next issue. The car starts like a champ in cold weather and heats up properly, but with the weather starting to break I noticed something I don't really appreciate. Rough idle when it's started when the engine is warm which leads me to think there is an electrical issue. Somewhere. The rough idle stops once I give the engine gas and from that point forward it drive flawlessly with the exception of the issue stated above. I have also notice that the RPMs fluctuate from 50-100 when the vehicle is starts and intermittently does that until the engine is warm.

Any help would be great. This thing is driving me insane. I am kind of tired of continually dumping money into the thing and if this is 'normal' in some fashion then I suppose it is time for me to part with it since I just sent in the final payment on it yesterday.

Thanks ahead of time.

 

Check Engine light on?

 

Nope. The check engine light is not on.

 

Had a bad thermostat and a out of range temp code. We have replaced cat pump coils wires and O2 sensors. Still drops power after about half throttle. Haven't any codes now just no power, anyone have any ideas.

 

It could just have a cpl dirty injectors....

Try running a cpl tanks of gas with injector cleaner added....

whens the last time you changed the fuel filter?.. I would also check the fuel pressure at the fuel rail... It maybe showing signs of a fuel pump starting to fail...

Maybe its also time to clean the throttle body? What condition is the screen in the throttle body? I would also try cleaning the MAF...You can get MAF cleaner at your local auto parts... Whens the last time you did a tune up on it? (Plugs and wires)... Have you done an oil change recently? hen the last time you did a fluid filter change on the transmission? Have you changed the air filter recently?

These are just a few suggestions..
Maybe someone else will chime in with other ideas...
Please be sure to keep us posted once you get it straightened out to share with other members that may run into that same issue!
Thanks for joining the MCF!

 

When was the last time you changed the MAP and PVC valve.
Have you cleaned your TB and IAC? These are the electrical and mechanical parts that can cause your idle issues. The MAP and PVC valve are inexpensive.
I don't think you have a vacuum leak as that would cause issues throughout the RPM range.
David (Stumpmi) is right, there are many issue that can come up due to a faulty MAS. I've had issues with Idle, warm starts, staying on. Even remote start would not work due a poorly operating MAS.
Just because you have no codes does not mean your mas is OK. With all the issues I've had with my mas, there were no codes. It took a diagnosis with the engine running to discover the problem.
ALSO check your connectors to ensure there is no corrosion or oxidation.
As for the clicking in the dash, I don't know. Hopefully another member can help with that!
Good luck!

 

All the above are great suggestions - I'd check for vacuum leaks as well. Just pop off that top engine cover, and follow the emission hoses. Listen for leaks (hissing sounds). Another simple suggestion take a looksee at you air filter, make sure it's breathing properly.

 

We have a shop and have maintained this car since new. We just changed trans fluid and filter along with air filter. The car has been doing this for a year or more. It is my wifes old car and we kept it for running around as it has been a wonderful car. It has 337K miles on it, 1 transmission is the only major repairs it has had. The GM cars of this vintage will drop power when it has a out of range temp code, also give you a code on the cat. The fuel filter has been changed also and fuel pressure checked. Only thing I can figure is dropping by GM and let them do a deep code clear with a TechII