sr backfires/misfires at full throttle??

[mxsx25]

the only mod really done to the car is an hks wastegate and to my understanding it is set for 10 lbs, also has an apexi boost controller but i initilized it so it shouldnt be affecting anything...

anyways, under part throttle the car revs all the way up fine, but once i put it to the floor it starts to sh*t all over the place lol... any ideas?

[Z U L8R]

vacuum/boost leak. a small one. possibly an intake gasket or hairline crack in the manifold, maybe a leaking injector-manifold grommet *shrug

i'd start by checking intercooler couplers for rotting/cracking, and tighten the clamps while you're inspecting em.

Dave

[sliEighty]

boost leak... i had the same problem

[91drftr]

my friend had the exact same problem, wec also thought it might be boost leak problems or fuel but to make long story short the last thing we did is that we switched out the spark plugs with some new ones and that did it, we were flooring it all over the streets no problem, its been running great ever since.....:cool:

[mxsx25]

say it is a boost leak... besides visual inspection, how do i go about pressure testing the system for leaks?

[vutony]

make a cap w/ nipple and use air comp to fill air into the system
listen for leaks or at idle spray carb cleaner and if idle fluates, theres the problem

at wat rpms does it misfires
i had this problem last week

usually misfire relates to coilpacks, coilpack harness, ignitor, or grounds
for me after confirm all those parts were in working order, i finally decided to swap a new engine harness which fixed the problem (motor misfires after 5k or 5500k)

[Sonic Motor]

3 letters, T P S

[vutony]

yes, i forgot

check timing

[mxsx25]

yeah it ONLY backfires/misfires under wide open throttle acceleration... around 4500 to 5k... im gonna get her to buy some new plugs and then if that doesnt do it... ill swap the coils out of mine and see if that does the trick... also, she has one of those cheap ass ebay fmic's and i honestly wouldnt doubt if that P.O.S leaks threw the welds and what not... so we'll see, thanks for the help guys! keep it comin!

[Synicals13]

its crazy cuz i just got my car up and running again and i have the exact same problem. With the exeption that my car is running rich due to the bov.

Im gonna switch out the spark plugs tomorrow, i'll let ya'll know how it goes.

[SixSpeedSleuth]

Check the spark plug gap as well as base timing, and what others have suggested, boost leak.

[mxsx25]

i put bran new plugs in, and swapped the coils out of my own car (which i know are all good and near new) and still the same fu**ing problem! she has a p.o.s fmic so maybe thats leaking, i havnt figured out how to pressurize the system to test for leaks yet, anyone got a pic on how they did so? it must be that since it only does it under full boost/ full throttle

[SixSpeedSleuth]

i put bran new plugs in, and swapped the coils out of my own car (which i know are all good and near new) and still the same fu**ing problem! she has a p.o.s fmic so maybe thats leaking, i havnt figured out how to pressurize the system to test for leaks yet, anyone got a pic on how they did so? it must be that since it only does it under full boost/ full throttle

Were the plugs pre-gapped? I had a similar problem of the car breaking up/misfiring in the upper rpms, checked my plugs (gap was way off), gapped them to .028 and that immediately fixed my problem. But, if that does not fix it, it def sounds like you have a boost leak somewhere.

[unicoladron]

i put bran new plugs in, and swapped the coils out of my own car (which i know are all good and near new) and still the same fu**ing problem! she has a p.o.s fmic so maybe thats leaking, i havnt figured out how to pressurize the system to test for leaks yet, anyone got a pic on how they did so? it must be that since it only does it under full boost/ full throttle

i've been researching on how to make one myself. this should do the trick. the two different links go about it in two different ways. have fun!

http://www.vfaq.com/mods/ICtester.html

and

http://www.stealth316.com/2-pressuretester.htm

have you checked timing yet!? it takes like 5 seconds. also make sure your TPS is calibrated right. if you don't have an FSM PM me, i have it hosted on an FTP server.

[Z U L8R]

ngk bcpr7es or bkr7e gapped at .028 ftw

Dave =]

[mxsx25]

im going to go out and make a pressure tester today thanks to unicoladron! great how-to's on those links... as well as check the plug gaps and what not...it must be a boost leak i think though...we'll find out today if she's leakin! thanks for the help guys!

[mxsx25]

so i just made my own pressure testing device... and i found boost leaks from the bov itself , the flange, the tb gasket, the vacuum ports coming from the intake manifold...and little hoses, so alot of them... and to top it all off, as im writing this messege, my dad comes up and tells me he backed into the side of the car in the garage :rl: with the tahoe.... well heres some pics...

in the picture below, the places where i felt a leak coming from are circled... im curious about the one with the arrow going to it though, its all tweaked and such, are those removable? i dont want to break them or something in case they arent..
http://i12.photobucket.com/albums/a211/wgurschick/camera044-1.jpg

when i pressurized the system air was going crazy out of that little hole i have circled on the bov?? is something supposed to be there? it seems like thast how it always was?
http://i12.photobucket.com/albums/a211/wgurschick/camera045-1.jpg
my little contraption worked quite well
http://i12.photobucket.com/albums/a211/wgurschick/camera038.jpg

[mxsx25]

anyone have any advice on these pics?

[dingwing]

i had the same problem with my car. i dropped my gas tank and pulled out the fuel pump and the little filter on the fuel pump had little metal peaces in it:eek:. i replace the fuel pump and my car has been running fine since then.:bigok:

[mxsx25]

damn it could be so many things lol

ill just do everything then!

[vutony]

plug them up
i have my fpr, bov, boost gauge connected to the tb

as for the vac leak test, i have it capped off to the intake (not hotpipe)

[duffman1278]

I have mine to the intake as well, works good to catch any leaks on the hotpipe. I ended up getting 2 for in that area.

[mxsx25]

the bolt on cyl#3 coilpack was broken and i was told that may be a problem due to having a bad ground...?
http://i12.photobucket.com/albums/a211/wgurschick/camera049.jpg

i got one of the vacuum ports out, but the other broke... drill and remove? or just thread a bolt in to plug it up?

http://i12.photobucket.com/albums/a211/wgurschick/camera051.jpg

also, the greese on the flange leeds me to beleive that there must be a leak at the flange? anyone have any thoughts on this..
http://i12.photobucket.com/albums/a211/wgurschick/camera052.jpg

[mxsx25]

so i fixed the problem, not sure what fixed it though since i did a couple of things... i made sure there were no more boost leaks for one, plugged an open nipple which was after the maf yet before the turbo, and realized there was a broken bolt on the #3 coil pack so i fixed that and then installed a diy grounding kit for the coils and she purrs like a kitten at all times, all i have left to do is recirc. the bov becuase it almost wants to die on decel after heavy throttle... anyways, thanks for the help guys

[jskateborders]

If the grease at the flange of your bov is due to a leaky bov, you have a bigger problem than a boost leak

[mxsx25]

yeah there might be a bad seal on the turbo but im not too worried about it RIGHT this second, she bought a gt2871r with the .60ar housing so that will bolt up but im not about to put that on with stock injectors (the kid that told her to buy it said it was an easy bolt on and drive project) lol i wish, we'll see what happens