Cadillac Owners Forum banner

1 - 7 of 7 Posts

·
Registered
2005 sts4
Joined
·
13 Posts
Discussion Starter #1
Hi there, I'm Teale and I drive a 2005 sts4 and I have had nothing but problems with it since I've gotten it.

Lets start with a brief history of the vehicle. I bought the car from a private owner about 9 months ago and the guy was kind of stir crazy. When I bought it, the check engine light was on and it was reporting codes (not sure the numbers) that signaled it was running lean in the left and right banks. He had some crazy aftermarket air filter installed. I figured ok I can have the dealership fix it and put the OEM back on. I bought the car and after I payed for it, I could never get in touch with the guy who sold it. He ended up getting a sexy subaru that he said he was going to put a mean air filter on it. I rolled my eyes. Car drove ok, but you could tell it was either getting too much air or not enough air from the sounds that it made. I took it to the dealership and after taking my left kidney, they put the OEM air filter system on it and apparently the guy removed some vacuum hose that was essential to the air intake system as well. I didn't once think he was trying to fix an underlying problem with the car. After this, the car ran fine and I went on a 2500+ mile road trip and about a week later the engine light came on. I took it to the cadillac dealership and this time they took my first unborn child and told me the catalytic converter was shot and there were loose bolts. The converter was under warranty. So now I'm down one unborn child and my car is still driving a little funny. The check engine light was off. Then a few weeks later, I took it in and had it checked and they came up with an intake gasket was damaged and needed to be replace. This whole process took my second unborn child from me. The vehicle still acted funny but it drove and I was able to drive it like a sports car. (I always drive my cars like this... Ask the CTS with the performance and handling package that I flipped.) The check engine light went on again and I was on a trip from TN to PA so there was nothing I could do. On the trip, I filled up with 91 instead of 93 octane and the light went off immediately for about 2 tanks. Then I dropped down to 87 and the light went off for about another 2 tanks. Light hasn't gone off since. I ended up taking the vehicle to the Cadillac in brentwood to have them do an oil change and an inspection. They told me they couldn't get any codes off of my car but they found a missing bolt. I had to leave town and go home that day so I couldn't wait for the part. I'm still unsure of the part but I have a call in scheduled for tomorrow so I can find out. I drove it home and it has just gotten worse and worse. Then I looked around town and sought reviews on mechanics outside of the dealership and found one that many people recommended. He tried 2 different code scanners and couldn't get anything code wise except for a C0249. I had him do a tune up because I felt the vehicle was running sluggishly for a cadillac and I took the mechanic for a ride and showed him the symptoms. I got him to replace the spark plugs, the air filter, and the fuel filter along with brakes and rotors.

Now my STS is misfiring while it idles, I can somewhat feel it misfiring when I drive it. But even worse, when I drive in D, the engine tries to over rev and the check engine light blinks and then my car loses power and I have to shut it off and turn it back on. If I drive in sport mode where I manually shift gears, it drives fine. Despite that I say it drives fine, it seems to have some trouble going up slight hills in 4th so I have to take it down to third and run it >3kRPM and then switch back to 4th on the top of the hill. I've gone to advanced auto and a few other places just to check the codes but nothing. Even after the Check Engine light was blinking. The check engine light only blinks until I let go of the gas in D and switch to manual and switch go up a gear.


A few things about my driving style and quirks of the car that should help in diagnostics.
I have a heavy foot. Before I had the tuneup, 110 felt like 70 but passing the other cars tells you that the speedometer is correct. I do most of my driving on highways and main roads.
When I'm in idle (P or N) if I rev up to 4K rpm and hold it, it sounds like it is choking for hair making a dun dun dun dun sound. (i'll put a couple of videos up if it will help.)
If I continue to hold it (pedal to the metal) it will start to go down in RPM's chunks at a time. (if i made a graph it would look like stairs) Each time it bumps down to the lower level it makes a choking sound.
it will go down to just below 1kRPM and I let go of the gas and hit it again it wont go above the last down step and it makes the choking noise (at each step)
once it makes it down to 1k rpm it seems like it wants to die and it gets very shaky. I'll put it in reverse, go a couple of feet (or drive depending on where I am) and it seems to reset where it was and I could rev it all the way back to 4kRPM. I don't know if this is a feature to keep you from messing up the engine or if my car is really messed up.

So today, it was nice out so I decided I'll put some of my own labor into the vehicle. I sat for a few hours and read the threads that are in the sticky and decided to tighten the bolts on the intake (the 10 that come loose). 3 were loose. In order for me to get to the bolts to tighten them, i undid the bolts on the fuel rail and lifted it up and popped the injectors out. I didn't pull it all the way off but I did notice that one of the injectors was shiny (possibly new) while the others were dark. I tightened the bolts and reinserted the fuel injectors and mounted the fuel rail back up. Now it seems to be running even worse.

I have my service guy at the dealership taking care of contacting the other caddi dealership I went to to find out the missing bolt and he has me scheduled in for monday.

I'm here hoping someone knows what is going on before they ask me for my spleen and a good chunk of my liver.

I'll get some video and post the links if that helps.

I want to know :
is something wrong with the ignition system (even though it starts right up)
maybe a bad computer?
bad transmission?

what do you think?

Thanks in advanced - Teale.
 

·
Registered
08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
Joined
·
3,215 Posts
First rule I follow... I don't buy modified cars. Period!

I'll look very closely over the vehicle and if there is even a hint that someone has added/changed/modified something I'll walk away. It's hard to know just how far some of these "improvements" go.

I sounds like at least some of your problems are directly (and indirectly) related to the prior owner "upgrading" the vehicle. Unfortunately, there are too many hacks out there that think they know much more than they really do. There are VERY FEW people I trust to get within a country mile of my car with a wrench.

Hopefully you'll be able to get this sorted out. Some of the problems you've described aren't new. For example, a lean code on both banks.
 

·
Registered
2005 sts4
Joined
·
13 Posts
Discussion Starter #3
ddalder,

thanks for your quick reply. I know I totally shouldn't have bought it but it was a steal and it reminded me of my last car and plus I was high in love. that is water under the bridge now because unfortunately now I own it. I had all kinds of red flags go up on this car but I got it anyways.

Hopefully someone will be able to identify the problem.

----------

Also, there is a metal pipe going from the back of the intake header (the jet as i call it) that goes to the right bank where the spark plugs are. Does anyone know what that is? I'm running out of light and I accidently broke the vinyl coupler on it and I'm trying to figure out if air fuel or oil runs through it.
 

·
Registered
08 STS4 V8 1SG & 04 SRX4 V8 & 01 Monte SS
Joined
·
5,012 Posts
The revving issue you talk about is what the car does to protect itself from damage.
The rev limiter is 4k in P or N. I've never tried to force it to bounce off the rev limiter long enough to have it continue to throttle down to 1k but it wouldn't surprise me that it sounds like it is about to die as that's true as the car is countering your input.
 

·
Registered
2005 sts4
Joined
·
13 Posts
Discussion Starter #6
OK thanks ludacrisvp. That sounds about right based on what I've seen looking around these forums.

I played around with the vacuum system a little bit and i found that it gets worse when i unplug a vacuum line. I'm guessing that my problems with the transmission and the misfiring is coming from a vacuum leak somewhere. does anyone have a map of the vacuum paths or even if the vacuum system controls the transmission and it's ability to shift gears on time and disengage on time as well?
 

·
Registered
2005 sts4
Joined
·
13 Posts
Discussion Starter #7
HEY guys,
ended up being either a bad coil or an over gapped (0.065) spark plug. Never let an ASE certified person work on your car - in the same way you'd never let a cisco certified person work on your network. I changed all of the plugs and the 2 coil packs and she runs like a beauty. I have the plugs gapped at 0.048
 
1 - 7 of 7 Posts
Top