car runnin rough... need help please.

[PresTeeJ88]

Hey guys so this just started a couple weeks ago but my car wants to die out when you accelerate then step on the brakes. It drops RMP very very low and sometimes even dies out. The car dropped vacuum down to about 14in when it's warm and only about 10 when its cold. It idles just fine. Has very bad gas mileage like 20-21 on the highway. And I can't really use the cruise control because instead of staying at a constant speed it goes up and down about 3mph so that would give it even worse gas mileage since everytime it goes down it has to speed back up and the car goes into boost. If anyone has any ideas for me please let me know. this thing is killin me.

 

[markdr7]

I had this same problem a week ago myself. It turned out that I had bad boost/vacuum leaks. I did a boost leak test and found out that I had a bad throttle body gasket and that I was leaking around my BISS screw. I fixed those and it made a big difference. I would try a boost leak test on yours thats probably what it is.

 

[GRAVEDIGGER]

+1 for the boost leak test You must start with that first, because:

no boost leaks = a happy car

*also a tune up is a necessity if it has not recently been done*

 

[markdr7]

Something else that might be worth doing, is running some seafoam through it. I did it and it makes an awesome difference, feels like it gave my engine new life. You can do a search on here to find out more information on it. It'll make your car smoke like crazy for a few minutes but it's worth it.

 

[PresTeeJ88]

Yeah I was thinkin of doing a boost leak test or taking it in because I don't have any idea how to do it. also just an fyi my air/fuel gauge never reads rich when clearly it must be runnin rich with that bad gas mileage. and I did recently do a tune up (beginning of the summer)

 

[PresTeeJ88]

One more thing I wanted to make note of. I am making full boost if that matters. around 12~13psi out of the stock turbo.

 

[markdr7]

A boost leak tester is easy to make. It only costs a couple of dollars. Heres the link to make and preform the test.

IC Pipe Tester

The air/fuel gauge is not really the most accurate gauge. I have one also but it's better to go with a wideband gauge rather than the narrow band gauge that we have.

Also try checking out vfaq.com you'll find answers to alot of your questions there. Between doing a search on here and the vfaq.com you should be able to find a answer to almost all of your questions and directions on how to do things such as the boost leak test.

 

[markdr7]

One more thing I wanted to make note of. I am making full boost if that matters. around 12~13psi out of the stock turbo.

You could still have boost leaks even though you are running full boost. You almost definatly have some leaks. Once you get them fixed you'll notice your car just performs better in general. In the case of my car, fixing my leaks mine quite a bit more
powerful. It pulls alot harder now.

 

[PresTeeJ88]

definately gonna try that boost leak first.