1990 Galant GSX cut off at 4,000 RPM'S

My car has an eratic idle and when I go down the road the rpm's get to about 4,000 and the car bogs down and wont go past it. But if I hit the gas really hard it will go all the way up no problem (not in gear). sometimes I can get it to go past while driving but most of the time i cant. I have a 90 GSX and the guy that i bought it from told me that it needed an o2 sensor and the car would run great. Since then i replaced the o2 sensor, fuel filter (under the hood), the spark plugs, the idle air controll module, and the thermo valve and a lot of vac hoses, and also the air filter. I had the car checked out and i was told that the fuel pressure is normal (measured from the fuel filter under the hood.) and the car still has the same problem. I have no clue what the problem is and no money for trial and error. Please help...

I will get myself a Data logger if I were you. You will need it in the long run + it's really useful. Ask somebody that knows how to use it if you dont but I would really wanna try to learn it.

either the timing belt is off, or the ECM has a leaking capacitor, requiring repair or replacement.

Thank you, i pulled out the computer and found out that it is infact bad.
Much appreicated though... https://www.thegalantcenter.org/styl...ult/tongue.gif

Yah pretty much the same thing was hapenning to my 90 Talon. It took me forever to figure it out. But as soon as I opened up the ECU I could see leaking capacitors actually corroading the board. Crazy stuff.

Probably a good opportunity to modify the ECU if you have a good amount of solid mods.