I put some seafoam gas treatment in my cadillac STS v8 th...


I put some seafoam gas treatment in my cadillac STS v8 then afterwards my car has been driving different it act like it doesn't want to go past 3,000 rpm when I'm driving and it feel real sluggish Mechanic's Assistant: Hav...

I put some seafoam gas treatment in my cadillac STS v8 then afterwards my car has been driving different it act like it doesn't want to go past 3,000 rpm when I'm driving and it feel real sluggish Mechanic's Assistant: Have you noticed an increase in fuel consumption? And how does the STS start—same as usual? Yes i have noticed an difference and yes it start good Mechanic's Assistant: What year is your STS? 2008 Mechanic's Assistant: Are you fixing your STS yourself? What have you tried so far? Just got an tuneup ,[air filter](/topics-air-filter-cadillac/) replacement,and [fuel filter](/topics-fuel-filter-cadillac/) replacement Mechanic's Assistant: Anything else you want the Mechanic to know before I connect you? Sometimes it says shift to park when i already have it in park when i cut the car off

Automotive Expert
Thanks for using JustAnswer.com! My name is \*\*\*\*\* \*\*\*\*\* I'll try to answer your car questions. I'll start off with some basic checks to do, then we can get into more advanced diagnostics if needed. Let me know if any questions come up, or if there is anything I can do to help! You can update this message at anytime. - I'm sorry to hear about any troubles with the vehicle, but would be glad to try and help!

OkI can only text at this moment
Automotive Expert
- You may notice a bit of rough running as the cleaner breaks up any deposits that might be in the fuel system or on the injectors. You may see the [engine](/topics-engine-cadillac/) light come on as well at times. - Recommend having it scanned for trouble codes and see what's setting. List any codes youre seeing to the message and I'll look up diag/repair information and post to the message. - Would try driving for an hour or so at highway speeds to let the cleaner work on the fuel system and see if it runs any better afterwards. - Lemme know what youre seeing, or if any questions come up while checking things out!

I never had a check engine light come onthis been happening for about two weeks now I would of thought after two weeks it'll be running better again
Automotive Expert
I bet there's a fuel system issue going on then, would look for worn out oxygen sensors too. Check the long term fuel trims on a scan tool at idle and 2000 rpms. Most of the time you'll get a bit of a vacuum leak with higher mileage engines, or could have some clogged/faulty injectors, even though the seafoam was used. Have shop check out the engine sensor inputs to engine computer, smoke test vacuum system and [exhaust](/topics-exhaust-cadillac/) system for leaks, and monitor input from the oxygen sensors. Lemme know what youre seeing, or if any questions come up while checking things out!

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