Yeah how many miles? Maybe its a clogged cat or something too...if you have enough miles and still actually have one, if not the fuel filter sounds like a good idea since there are no codes...i dunno tho

 

1. Fuel filter.

2. Check your spark plugs and make sure they are gapped correctly. Also make sure your wires are conducting correctly using a voltmeter.

3. Run some B 12 Chemtool injector cleaner through IMMEDIATELY.

4. Check for vaccum leaks and such.

 

Car has 81k miles, 10k on the new shortblock. The only difference is in the loss of engine power... electrical stuff is fine, lights don't dim or anything, no shaking. It just doesn't accelerate nearly as quickly as it once did (biggest difference is at upper rpm's) and as I mentioned, it won't rev past about 5.2k RPM even in neutral.

Fuel filter was changed like 15kmiles ago, that should be okay. I've gapped the plugs like 3 times, no difference there 02.gif I'll get some B12, I haven't ran a can in a while. Is there a common source of vacuum leaks? I haven't moved anything on the intake or IM. I'll check some of this stuff when it's light out.

 

maybe fuel pump or an empty fuel tank?

 

I had something similar to this on another customers tiburon he ran leaded race gas and it caused the cat to come apart and clog up the exhaust. Upper rpms sucked car could barely go over 50 up a hill. Replaced the lower cat with a high flow and did an obx header and cured all the problem plus ran better then before. Just an option to check its only a few bolts to drop the lower cat if you have one.

 

If the cat was clogged that badly wouldn't he have a CEL though?
Odd problem indeed...

Probably check fuel filter or the cat.

You seem to know what you're doing, so I'm guessing if you replaced the plugs/wires that you did it correctly.

 

That was the wierd part it would have a cel for a sec then go away.... I went thru the same steps hes doing until a piece shot out the muffler in my shop thats how i figured the cat was messed up...

 

What mods do you have?

How's your air filter?

 

Is your Tib MAP based or MAF based?

Some Tibs have only 1 oxygen sensor. (My Tib has only 1 catalityc after the flex pipe and 1 O2 sensor before catalitic). So it will not throw a CEL if there will be something wrong with a cat. (Now I'm driving without a cat at all nana.gif )

 

^ Mine's also MAP based. I'll have another look but I'm pretty sure it has a sensor before the cat & another one after it too.