boost leak symptoms

[dre240]

when i accelerate to about 3500-4000 rpm my car jurks back and fourth. i had a friend check the mafs and the wiring and it seems to be good for the most part. also my car is running really rich a lot of black smoke is coming out the exhaust. could this be a boost leak problem? or something else im not aware of. any comments are appreciated.

[virus77]

if you go real easy on the gas can you get it above 4k? A boost leak will do what you are describing depending on where the leak is from. Is it the correct mafs on the car?

[dre240]

i can go pass 4k but it gets bumpy. the car jurks back and fourth alot and it back fires a hole lot...lot of smoke. it is the right mafs and also i switched it with my friends and it still does it.

[dre240]

if i go fast on the gas it gets rough. if i go easy ,the car feels some what normal. i can go to redline.

[mmashburn]

have you checked your plugs to see what they look like???? could it merely be the timing??? how long has this problem been going on?

[virus77]

if i go fast on the gas it gets rough. if i go easy ,the car feels some what normal. i can go to redline.

It could be other things but good chance its a leak, one of the most common things I see in peoples cars. you have to pressurize your system with a boost leak tester and you can very easily find youre problem, heres a link to it:zerothread?id=113785

If you cant access your turbo compressor inlet to easily since its a bottom mount, you can take off your filter and hook it up to the mafs and pressurise from there, just make sure if you do it this way, you block all nipples/hoses on your intake pipe. like catch tank and other crap that goes on the stock intake pipe or you will but pressure in the valve cover and other and whatnot.

[dre240]

i thought all this was caused by bad gas. i changed the plugs they were BLACK. i changed the fuel filter. i ran the car for a few more days thinking it would clean up but it didnt. its been about a week now. would the timing make the car run rich?

[virus77]

BOOST LEAK

[mmashburn]

do you have a fmic or side mount??

[dre240]

i have a greddy front mount.

[efrain240sx]

hi sorry for butting in but I have the same problem whit my car once I get to 3500-4000 rpm in 3rd it just starts to back fire like crazy my friend told that it shoots out a 2 foot flame out throught the exhust . could these be becuase my turbo is dieing it is lieking oil.

[mmashburn]

do you guys have a boost gauge...

[efrain240sx]

yeah I have a boost gauge

[dre240]

my friend said the same thing to me. he said he saw a huge flame from the exhaust. i have a boost gauge also. im running 14 psi but not all the time of course.

[nothingFancy]

i have same problem. i run at 11psi. but the gauge goes to 9-10psi and stats dropping at WOT

[drifting240]

ok well. my car is similar to ya'lls problems...except, my car runs normal till i try to get some boost...once my needle gets around the "0" on the boost gauge it starts hesitating and wont go anywhere.... could be a boost leak or a fuel problem but i have no idea...thanks.

[Nismo_Freak]

ok well. my car is similar to ya'lls problems...except, my car runs normal till i try to get some boost...once my needle gets around the "0" on the boost gauge it starts hesitating and wont go anywhere.... could be a boost leak or a fuel problem but i have no idea...thanks.

More than likely an ignition issue. Replace spark plugs with BKR7E's and gap to 0.032", go down in 0.002" increments until you hit 0.028" or the ignition issue goes away.

[travisn]

ill second the spark plug idea. and when checkign them dont look at the color, look at the gap and how much is left of them. if the ground strap is burnt all the way back your car will run like total ****.

[fullthrtl_tech]

travis you d!ck when r u gonna get her done. I see it sit there every day in body shop, i wanna see that thing sideways. Im just bustin your balls. Its coming along sweet. Love the color

SOunds like you are loosing spark because those huge flames you are seeing are unburned fuel vapors getting ignited as they leave the exhaust

[travisn]

yea yea yea soon enough...

[dre240]

my problem ended up being my ecu. i switched it out and it worked fine.

[travisn]

must be nice to know someone else with an sr to do that with. i am the only 240 sr i have ever seen besides at heavy throttle...

[240TweakerNewbee]

I feel the need to throw my 2cents in but I had the same problem and it was definately a leaky turbo gasket comming off the manifold... the second time it was a broken bolt (causing a leak) from the header. I fixed both, now its back to

I figure; if the turbo isnt getting its pressure from the manifold then its not producing the right amound of boost that you have setup in your AFC, so you will run rich, have hesitation, and not boost all the way. I think a boost leak from the manifold side is as bad if not worse than one from the compressor side.

[jrb92se]

i had a similar problem last night i have a 92 240 with an rb25det i have an autometer boost gauge and a dna motorsport maual boost controller since ive installed the gauge the boost reading has never gone above 4psi i thought this was odd and maybe the mbc was closed to much so last night i turned up the boost on the mbc just to try it out i got the gauge to 6 psi it ran fine for about three miles then i stopped at a light and got on it a lil when i pulled away the car made power till bout 4-4500 then fell flat then instantly made power again and backfired it was very ruff almost like slamming on the brakes i got jerked foward the slammed back into the seat i immediatley pulled over closed the mbc to its original position then it ran fine