Hi guys, i have a 93TT GTO stock as as far as i know, engine has started slight misfire at 2-3k on light throttle, replaced plugs, leads etc, cleaned out throttle body, engine started hunting at idle , adjusted idle mixture, hunting dissapeared after a few days
Engine is slowly getting worse, on WOT it hestitates just does not pick up like it used to , put injector cleaner in it over the weekend, no real improvement went on club run at the weekend, car is blowing black smoke on even light boost, surges feels like not enough fuel, but i think its two rich, exhaust light came on briefly while on boost. Could i have bad o2 sensors car has 128k km jap import so could be more.

any help apprieciated

Regards
lambo

Out of curiosity, how did you clean out the throttle body? Did you take it off to clean it? Did you take anything from the throttle body apart?

it honestly sounds like you have some boost leaks, black smoke is running rich, and since I believe you just got the car, you should do a intake pressure test, you can build a pressure tester for about $15-20, and it will definately help you later on down the road, if air is escaping that has already been pressurized, the airflow sensor has already seen it and adds fuel accordingly, so it's getting a lot more fuel than it needs, that can also cause the 02's to fail prematurely......good luck

yep. sounds like boost leaks.

only you should not make a pressure tester. you should buy one from 3sx. They are made by Rob Beck, who is a super guy, and they fit PERFECT. that is the way to do a leak test... I've tried the ones that you make of of CPVC at home depot. not as good. plus the one from 3sx is only like 25 bucks, or something.

Also, make sure your boost solenoid is working, or maybe your only hitting wastegate pressure, while the computer adds fuel for more.

You also NEED a logger. that will tell you if your o2's are cycling while crusing, and what the A/F ratio is when you get on the gas. if it's going full rich that's bad. and you may be spraying down the cylinder walls with fuel, and contaminating your oil, which leads to spun bearings over long periods of time.

you said you replaced the "leads" is that the plug wires, or the coils? cause those being bad will cause misfire also.

Thanks guys for the answers, since putting the injector cleaner though the engine things have improved alot, it still has a misfire at light throttle, and if you boot it it coughs and sputters at half boost, if you put more throttle into it, then it gets up and goes like it used too.
When i cleaned the throttle body i removed it from the intake and cleaned behind the butterfly with engine cleaner it was seriously coated in there.

The leads i have replaced were the spark plug leads, i will try the boost leak tester idea, but its strange there is no sound of boost air escaping, as i'm at the bottom of the world it will take a long time to get the tester you sugested, does anyone have a plan/ drawing for a simple tester i could make up. As the injector cleaner has helped could it just be dirty injectors, just squirting fuel in and not spraying a fog so the fuel never gets burnt. also where can i find the boost solinoid to test it.

Best Regards
Lambo

ah. my bad. I forgot that. then mel is right. make a tester out of plastic.

you probably will not hear the leaks. also, if you have never tested for them, you have leaks. it's a rule of thumb with GTOs. :57: