Ok i have had my 1994 z28 basically bone stock for about a week now and it will not go over 4000 rpms at about 3800 it seams to lose all power if i keep it under 3500 it has all the power in the world but once it gets up there nothing can hold the gas on the floor and stays between 3800-4000, my guess is the Catalytic Converter but i figured i would ask here before i change or get rid of it because i do not get emissions where i live please any ideas

 

What happens when you rev the engine? Does it still have issues?

 

It runs great till it his 3800 or so, once it get there its like it just stops no power kinda bogging but not really

 

I just came to search for my problem on my 94Z. Today my 6spd car would not got above 2,000rpm. It would just fall on its face in any gear. Idle was fine and as along as I dogged under 2,000rpm it seemed fine No hesitation. But the tach was just dropping to zero and going erratic when I tried to give it gas. I'm thinking it's the fuel pump at 152,000 miles and I havnt changed it in the last 10years I owned the car. I got no check engine lights, but I'm curious to see what fuel pressure is. Fuel filter was replaced recently. I don't think it's my opti cause I been through 3 failures and this was nothing like the opti going. But I have not tried to rev motor in neutral to see if it would go above 2k rpm.

 

I thought I had a plugged cat and took it to a mechanic and they drilled a small hole and could test it. The guy didn't even charge me. You might just change the fuel filter if you don't know when it was done last. Did the car run good when you test drove it?

 

They shouldn't need to drill a hole. They can attach a pressure gauge in place of the O2 sensor or the AIR connection (if you still have AIR connections).

 

It was the same when i test drove it it was the right price though but im 95% sure its the cat its acting just like my s10 did when i clogged up the cat on there.

 

i had the same problem exactly as you explained all i did is tune up sparks, wires, o2 sensor, and changed the opti spark and then the car ran back as good as new but first check the wires if they are good and the sparks or do the opti spark first cuz it always been a problem with these cars

 

My guess is it could be a number of things. There is a chance the cats clogged, but it ends up being something else. I always get stuck on one idea and when I am the surest, I am always wrong

 

What kind of Gas do u use, because i was putting unleaded in mine and then it started bogging down at 4000 rpms, so i switched to super unleaded and now it runs like a champ.

 

i have been putting premium in since i bought it and the man i bought it from sad he changed plug wires opti. with in the last 6 months

 

Low octane fuel will cause the PCM to pull timing and reduce performance, but it's not going to prevent the engine from going over 4,000rpm.

 

My battery was shot and the alternator not charging and it caused my rpm's to stop in the higher rpm's at least when going wot. Is the charging system in perfect working order? It is a free test and does not take long. Probably not it, but eliminate the easy free or cheap stuff first. Plus you are dealing with a car not maintained or kept up recently in all likely hood.

 

Does anyone know how to test an opti its not the cat replaced it (mrmint69 you are so right) the guy i bought it from said he replaced the plugs and wires.

 

Im just getting lost reading everything i can im tiring not to just throw parts at it