Power loss at higher RPMs

[JustinOhio]

I have a 2000 Firebird, 3.8. It's got 110k on it. It's always ran really well but recently it has a power loss at higher rpm's. It seems like over 3500 or so, the engine stops producing more power, then it has to struggle to even get up to the shift point. This is especially noticable on the highway when I need to pass. I'll floor it and it'll downshift to 2nd, and as it's approaching redline it just doesn't have any umph, once it shifts into 3rd, it picks up and goes again. Once in a great while, the check engine light will come on while this occurs, but immediately shuts off after it shifts and the rpms drop back down. I took the car to a parts store and they said it will not show any codes unless the engline light was still on.

So where should I start?

Any help would be appreciated.

[97RSSM90]

Re: Power loss at higher RPMs

assuming all the sensors are fine, i would change fuel filter and and test fuel pressure. i would also make sure check spark plug wires and change spark plugs. does it take a while to start while the car is cold?

[2.8 Bird]

Re: Power loss at higher RPMs

Yeah, look into Fuel Filter.

[Atrum Rosa]

Re: Power loss at higher RPMs

Sounds a bit symptomatic of a clogged cat and your getting intermittent back pressure misfires. I don't know why our cars eat catalytic converters so often, but I had to replace mine recently after similar problems. Gave me a good excuse to put in a new exhaust.

[JustinOhio]

Re: Power loss at higher RPMs

assuming all the sensors are fine, i would change fuel filter and and test fuel pressure. i would also make sure check spark plug wires and change spark plugs. does it take a while to start while the car is cold?

No, the car starts fine at all times.

[JustinOhio]

Re: Power loss at higher RPMs

Sounds a bit symptomatic of a clogged cat and your getting intermittent back pressure misfires. I don't know why our cars eat catalytic converters so often, but I had to replace mine recently after similar problems. Gave me a good excuse to put in a new exhaust.

This may make some sense, I've noticed sometimes at idle there will be some type of exhaust rattle underneath the car, like something is loose and only vibrates that way at a certain rpm... I didn't realize the converter could cause that much problem?

[01PewterDropTop]

Re: Power loss at higher RPMs

My car use to bogg down at 3500-4000 rpm was 1 bad O2 sensor, bad cat, and a crack in the exhaust manifold flange where it bolts to the engine

[jnxV6]

Re: Power loss at higher RPMs

I have a 2000 Firebird, 3.8. It's got 110k on it. It's always ran really well but recently it has a power loss at higher rpm's. It seems like over 3500 or so, the engine stops producing more power, then it has to struggle to even get up to the shift point. This is especially noticable on the highway when I need to pass. I'll floor it and it'll downshift to 2nd, and as it's approaching redline it just doesn't have any umph, once it shifts into 3rd, it picks up and goes again. Once in a great while, the check engine light will come on while this occurs, but immediately shuts off after it shifts and the rpms drop back down. I took the car to a parts store and they said it will not show any codes unless the engline light was still on.

So where should I start?

Any help would be appreciated.

The codes will still come up even if the light is not still on, so have them check it and see what it says.

[Bird_Of_Prey]

Re: Power loss at higher RPMs

Or go to a different place. Whoever told you that doesn't know what they're talking about. I wouldn't arbitrarily throw parts at it until you have a good diagnostic.

[thebeewantsboost]

Re: Power loss at higher RPMs

definitely start with the code there's a handful of things its could be.

[Rob Bell]

Re: Power loss at higher RPMs

You could try getting under the car and banging on the cat with your fist and listen for any rattling. If it rattles you know the cat is bad. It's probably clogged up.

[BrakeStand]

Re: Power loss at higher RPMs

I was dealing with a very similar problem. Turns out my cat was only letting through around 30%. I got a high flow put on for $250 and it is like driving a new car. If you know a good mechanic they should test it for you it only takes 5 minutes and they shouldn't charge you for the test. You will probably notice the car heats up to temp quite quickly. If you listen to the car while it is running when you rev it up it will sound like the muffler is in the front of the car instead of the rear if it is clogged badly enough. Oh, and the reason our cars usually eat catyltic convertors is typically the intake manifold gasket leak, so if you have not already had the plastic one removed and replaced with a metal one and the dexcool replaced with something different it's worth looking into.

[JustinOhio]

Re: Power loss at higher RPMs

I did have the car checked by a mechanic a few months ago when the car was in for some suspension work (now that I remember). The mechanic said that it was an issue with the MAF sensor, he said he cleaned it out and it seemed to run better. He was right, it did help a little but it's still nowhere near what it should be. He probably overlooked the issue with the cat. Maybe I should just have a friend cut it out and put a straight pipe right through it, is that something that would help performance either way?

[BrakeStand]

Re: Power loss at higher RPMs

Yeah, mine said the same thing originally. K&N yada yada. He cleaned it and I got a little bit smoother idle but still no power or ability to maintain highway speed. Now I have a new cat and my bird pulls like crazy compared to before. :o

[BrakeStand]

Re: Power loss at higher RPMs

A straight pipe would help performance but is not street legal. It will of course make the car louder as well. The higher flow cat will also help performance over stock. You can get a high flow catco cat for like $50-80.