'99 Civic won't accelerate past 50 mph

[lumpkcha]

My Civic just yesterday stopped accelerating above 50 mph. I can have the pedal to the floor and it won't go past that point. The rpm's will go up, but not the mph. I noticed a hissing sound coming from underneath the car as I accelerate. And there is an occasional high pitched squealing type noise. Personally I think it is the catalytic converter, but I'm no expert. Does anyone have any feedback? Please and thank you.

 

[XpL0d3r]

What engine's in the car? Mods?
Automatic or manual?
Does this happen when the engine is cold, at operating temp, or both?
Is the check engine light on? If not, does the check engine light work?

You mention that the speed will not increase but the RPM's do... can you elaborate here? Are you still able to get into the higher RPM band? If you accelerate slowly, are you able to continue past 50? The reason why the RPMs would increase but the speed would not is likely related to the transmission.

If you have an automatic, it sounds like it's not shifting into gear properly.

If the catalytic converter was the issue (i.e clogged), you wouldn't be able to increase RPMs either.

 

[lumpkcha]

Not sure how to tell which engine is it. It's a cylinder, as far as I can tell. No modifications. It appears to do this whether the engine is hot or cold. Not sure if the check engine light works. It could have burnt out. It was on for about 4 months earlier in the year and went out recently when I had a new muffler and tail pipe installed. Funny story, the catalytic converter fell off and was dragging on the highway as I was driving to my auto mechanic. All in all, it was bouncing on the road for about 5 miles. This is why I am hoping it's the catalytic converter. I'm screwed if it is the transmission.

 

[XpL0d3r]

So automatic transmission?

A clogged cat would also prevent the RPM's from increasing because that exhaust gas is getting backed up.

Your RPMs are increasing, so it's likely that the car is trying to switch gears and something is preventing it from doing so. I don't know automatic transmissions very well to be able to help much further should this be the case.

Go for a test drive and count your gears. See if it makes it to 2nd, then 3rd, then 4th. If you've been reaching speeds of 50mph you're out of 1st gear.

 

[lumpkcha]

Yes, sorry, automatic transmission.