Car will not go fast?

Hello WELOISE11,

Does the whistling sound only happen when you accelerate, or does it happen all the time such as when it is idling?

A vacuum leak or air intake leak is a possible source of the whistling noise but would be louder at idle. Such as sitting in the driveway and not in gear.

An engine makes the most vacuum at idle and as RPM increases vacuum will decrease and possibly decreasing the whistling noise.

Also, a vacuum leak will cause the engine to have what's referred to unmetered air entering the engine. This can cause acceleration problems, affect fuel efficiency and an illuminated engine light. I know you said there was no engine light, but I would take it to AutoZone or another parts store of your choice and see if there are any codes. Sometimes, not often, the engine light will fail to illuminate because the conditions are not fully met for the code to set. I mostly want to see if there are any "History Codes". The code will be stored but the light won't be on.

A lot of things can cause a whistling noise on a vehicle. They may be related they may not. Did the noise start the same time the acceleration issue started?

How long has this issue been going on?

I did find a Technical Service Bulletin (TSB) for lack of power and acceleration because of a restricted fuel line, but I would need your entire 17-digit VIN to ensure it pertains to your vehicle. If you could provide that and answer these questions, we can start ruling out some things.

Thank you,
Brendon
2CarPros

Hello WELOISE11,

Can you check the VIN I only got 16 digits.

Right now, I don't think it is the CAT and you should get a code. But I don't like to rule anything out yet until we can eliminate other things as a possibility.

To me it sounds like a big vacuum leak. But you should have a code for that. But we won't rule it out yet either.

We need to find out what the whistling noise is. I would have an assistant sit in the car and hit the gas while you listen under the hood and see if you can determine where it is coming from. We need to determine if it is related. Does it do it in the driveway if you rev it or only while moving?

Try to look for the noise while the engine is cold so for one the fans don't come on and muffle the sound and two, I want to see if it gets louder or softer as the vehicle warms up. If so, this could point more towards a gasket possibly.

Try this article as well and see if you can determine where the noise is coming from:

https://www.2carpros.com/articles/car-whistling-noise

In the meantime, double check the VIN and send it to me and I will see what I can find on my end.

Thank you,
Brendon
2CarPros

Hello WELOISE11,

Interesting. Did lack of power show up at the same time as the whistling noise?

Thank you,
Brendon
2CarPros

Hello WELOISE11,

Okay. So, they might not be related. I would try to identify which part of the engine bay the engine noise is coming from.

I would also check your belt. I am adding an image of some common belt problems.

Also, check your battery terminals and make sure they are clean.

While once the car is started the vehicle runs off the alternator, corroded battery terminals can put more strain on the alternator and cause premature failure.

I really don't think it's the Catalytic Convertor. It isn't that common for it to clog. If the cat wasn't working properly, you would have a code by now and you don't. This vehicle is pretty fuel efficient and there is nothing to indicate the catalytic converter has failed. A lot of things are possible but in diagnosis you have to look at more probable causes and work your way from there. Otherwise, you are just going to keep throwing parts at it and I am here to help make sure you don't have to do that.

The Kia Forte is not a bad car at all. I knew a sheriff that owned one with over 240,000 on it and we just serviced it for him.

Let's take it one step at a time and eliminate each possibility one by one.

Please check your belt for wear using the attached chart and check your battery connections for corrosion. If there is any make sure to remove and clean.

Thank you,
Brendon
2CarPros