Major loss in performance

[Mcdougal]

I have a 97' Gst car idles rough not much but enough to notice. Problem is when im driving the car it has absolutely no power. I literallly floor it and it hesitates horribly to go pass the 2.5k rpm. Very rarely when it hits boost car runs fine for a split second but then returns to its shtty performance. I replaced spark plugs, wires, MAF. I have no CEL. car has used a lot of oil and there is abit of black smoke coming from tail pipe. I took out the throttle and there was quite a bit of carbon buildup. I also removed the engine head and the valves are full of carbon. Pls help I need to know whats going on

 

[Breezio69]

Id go with boost leak. #1 cause of most major power loss. Especially with all those symptoms

 

[ehc14]

Similar thing happened to me, had a boost leak in a couple spots.

 

[Afizzle]

spark plugs, plug wires, and a boost leak tester. if that doesnt clear it up go with a compression test and report the #'s.

http://www.dsmtuners.com/forums/articles-parts-fabrication/386650-how-build-boost-leak-tester.html

http://www.dsmtuners.com/forums/articles-420a-specific/258957-compression-test.html

btw you dont need a gauge on the BLT

 

[smoked28]

Sounds like boost leak(s). Similar thing happened on a friend of mine's 1g.

 

[Mcdougal]

Thanks you guys for your input me and a mechanic of mines decided to have the engine machined and cleaned. Start from scratch with brand new goodies and toys for my GST

 

[my dreamt dsm]

Welcome to my world. I have no boost leaks, no vacuum leaks, perfect compression, major tune up, new sensors. Nothing help. With all my mods at 10-14 psi I can not even break my tires off the pavement. Happens at the same rpm you are mentioning. Esp 2- 3rd gear.

 

[Breezio69]

Welcome to my world. I have no boost leaks, no vacuum leaks, perfect compression, major tune up, new sensors. Nothing help. With all my mods at 10-14 psi I can not even break my tires off the pavement. Happens at the same rpm you are mentioning. Esp 2- 3rd gear.

Fuel pump? Maybe its going out and simulating fuel cut when you hit boost?

 

[my dreamt dsm]

Fuel pump? Maybe its going out and simulating fuel cut when you hit boost?

Nope, I threw in the new walbro 190 last month. IDC's are good too.

 

[Breezio69]

Hmmm... not sure then? My symptoms were a little different with a boost leak. Basically anything after 5psi of boost with mine would feel like the car was "breathing through a straw", so to speak. It just fell flat on its face at any rpm.

It would also give a little buck when transitioning from any amount of boost to going to vacuum.