no idea whats wrong...help!

[RedEclipse17]

I just replaced the head on my 90 gsx from a parts car and got the timing belt on and everything, but it runs like crap...it idles smooth but when you're driving it when you get to about 4500 rpm it hits fuel cut. It does it throughout every gear when you get it that high. Obviously somethings wrong but i have no clue...no vaccum leaks that i can find, it does hold boost which is the factory 7 psi or so. It does run rich though which im thinking the timing could be off. just havent gotten around to putting the timing light on it yet... the only mod it has is the k&n cone filter but it just doesnt run like a dsm should...any advise would be great...thanks

 

[oldman]

How did you look for vacuum/boost leaks?

 

[95blackGsTurbo]

Stock boost is more than 7psi. Running rich is probably from a boost leak. Boost leak test it and get back to us.

 

[talonalex92]

buy a boost gauge while your buying or making your leak tester also.

 

[Talesin]

Uh, he's referring to the stock '7' psi that the stock guesstimation gauge usually will read out on a 1G with a hacked MAS.

Buy a proper boost gauge and install it. The stock cluster gauge is crap... the ECU guesses based on airflow@rpm and controls the 'gauge', there's no sensor to check what the real manifold pressure is.
Also, being *able* to hold a boost level does NOT mean you don't have boost leaks. It just means that the turbo is pushing more air to keep that pressure level, even as some air leaks out around whatever.

You need to build a boost leak tester (as described on vfaq.com) or buy one, and do a proper boost leak test. It's the only way to actually do it. You can't just guess that you don't have a leak. And if you're reliably getting fuel cut? Very, very, very likely, especially in the situation as described, that you have a boost leak. Especially the running rich bit... extra fuel to compensate for that metered air that... isn't there any more. :b

 

[RedEclipse17]

I do in fact have an aftermarket boost gauge installed and hooked up correctly. I'm not 100 percent sure i dont have a boost leak but im going to do a test on it when i do get the time. At idle the gauge reads around 25 in. vacuum pressure or whatever and stays consistent. But I just wanted to throw the problem out there to see what i would get in response about the rich condition...i'll do the boost leak test and get back...thanks

 

[talonalex92]

theres no way your car is holding 25'' hg of vacuum. thats just nonsense!

 

[RedEclipse17]

ok did a leak test and to my surprise the gasket where the turbo connects to the intercooler piping was missing a chunk...simple fix but cant get the gasket right now...once i get that replaced i'll do the test again and see if anything else is wrong.

 

[oldman]

ok did a leak test and to my surprise the gasket where the turbo connects to the intercooler piping was missing a chunk...simple fix but cant get the gasket right now...once i get that replaced i'll do the test again and see if anything else is wrong.

Just because you found one, doesn't mean there is only one leak, continue the leak test after you fix that gasket until you're able to show 20psi on your boost gauge during the leak test. BTW, make sure you put your shift key to good use before you get a warning.