Bad miss at 4500 rpms, running rough

[92laserRS607]

Sooooo, yes I have searched....and searched and here is where I am at....The car idles pretty well, surges when hot. When revving at a stand still it starts missing at 4000-4500. When driving it runs well until you mash the gas and hit 4500 it starts missing bad, and bucking a little bit. All I have done to it is a 2g maf and unnecessary vac lines removed. I just did a boost leak test and had a VERY small leak at the J pipe, but I noticed a considerable amount of noise coming from the bottom of the intake manifold. I couldnt tell exactly where it was coming from, but if I had to guess Id say IM gasket. Also I have a boost gauge and Im only hitting about 8 psi when I can actually get it to boost. Soooo long story short, is my problem just a boost leak? or do I have ignition problems? Any help would be GREATLY appreciated. Also I tested the coil pack and it is within tolerances.

also I have ngk bpr6es at .28, ngk wires, and my ecu looks fine.

 

[slickers111]

My money would be on the intake gasket.

 

[92laserRS607]

Yeah, ughhh I remember doing that job on my old talon and it was a pain in the ass. You think the blown gasket would make it miss and buck that bad? I guess its not all that bad if the gasket fixes the problem.

 

[92awddsm]

Fox the obvious problems first. If it still has issues, do more troubleshooting.

 

[92laserRS607]

one more thing, I cant hear a whistle while its running, and my vac at idle is a solid 18, and I remember when my IM gasket went on my talon I could hear it whistle while running...you guys think it could be an injector seal leaking? even though ive never heard an injector with a bad seal make noise during a boost leak test..

 

[92awddsm]

one more thing, I cant hear a whistle while its running, and my vac at idle is a solid 18, and I remember when my IM gasket went on my talon I could hear it whistle while running...you guys think it could be an injector seal leaking? even though ive never heard an injector with a bad seal make noise during a boost leak test..

Was there any leaking at the injectors during the blt?

 

[92laserRS607]

Not that I could see/hear, but I was rushing and had a moron helping me that knows NOTHING about cars....I think im just grabbing at straws here because im about positive the noise was coming from underneath the IM.....the strange thing is ive NEVER heard a boost leak make that much noise. I couldnt get the pressure over 10 psi also

 

[92awddsm]

Not that I could see/hear, but I was rushing and had a moron helping me that knows NOTHING about cars....I think im just grabbing at straws here because im about positive the noise was coming from underneath the IM.....the strange thing is ive NEVER heard a boost leak make that much noise. I couldnt get the pressure over 10 psi also

Did you eliminate or plug the vacuum lines that are attached to the bottom of the intake manifold brace?

 

[92laserRS607]

ahhhh, glad you brought that up...I bought the car from an long time dsmer and he did the vac elimination before i purchased the car. Today while doing the blt, I had the battery off and noticed the 4 vac nipples under the IM were uncapped except the one closest to the motor. The only line that had a cap on it had a crappy cracked cap that was hardly holding up. I was under the assumption that those lines could be left uncapped when doing vac line elimination, am I mistaken??

 

[92awddsm]

ahhhh, glad you brought that up...I bought the car from an long time dsmer and he did the vac elimination before i purchased the car. Today while doing the blt, I had the battery off and noticed the 4 vac nipples under the IM were uncapped except the one closest to the motor. The only line that had a cap on it had a crappy cracked cap that was hardly holding up. I was under the assumption that those lines could be left uncapped when doing vac line elimination, am I mistaken??

Check the opposite ends of those lines and see where they go. Make sure non of them are connected to a vacuum source.

 

[92laserRS607]

they are all eliminated, when I took the battery off i saw 4 vac nipples open, no lines attached. except for the one closest to the engine that had a cap on it.

 

[92awddsm]

they are all eliminated, when I took the battery off i saw 4 vac nipples open, no lines attached. except for the one closest to the engine that had a cap on it.

Those 4 lines come out of the opposite side of the manifold brace on the driver side. Look at those too and see what's attached or if anything at all is attached.

 

[92laserRS607]

ok gotcha, Ill check it tomorrow and update.