Running problem

[HybridFuel]

I have a 99 cobra with a procharger p1sc, off-road h-pipe, and dual magnaflows. around 4000 rpms it starts bucking and missing under mid to heavy acceleration and the exhaust sounds terrible, it gets worse the harder i push it. i can get it to the redline without skipping a beat but thats only under super light acceleration. I've checked for vacuum leaks, there are none, i've done a wiggle test of everything under the hood, all is ok nothing loose. this problem just started all of a sudden, and seems to be getting worse. i'm thinking it feels like a partially clogged exhaust, but how common is it for these magnaflows to clog up? I need some ideas??? please help!!!

 

[COBRA90GT]

Magnaflow mufflers utilize a straight through design, and since you have no catalytic converters, I highly doubt anything is "clogging up" inside your exhaust.

You might want to start checking your sparkplugs and consider doing a compression/leakdown test just to be on the safe side. Has the car been tuned? What kind of chip are you using?

 

[HybridFuel]

double platinum plugs brand new last week, compression within specs, strong vacuum @idle. someone mentioned imrc's. does this engine even have imrc's? i cant see any actuators or anything. I cleaned the maf, no luck, i believe the car was tuned but that was before i bought it. like i said, all was well then all of a sudden it started to act up and it got worse, i made no changes to provoke this....

 

[COBRA90GT]

The 96-98 snakes were the ones with IMRCs, whoever told you your '99 had them was misinformed...I'd start with examining the plugs, were they properly gapped (seems like the last thing was changed prior to your problems)?

 

[TenorPlayinGuy]

I have a similar problem with my 87 five-oh, I just bought my vacuum gauge to check for my prob. But im sure it has to do with my EGR system somehow. I get drops of water shooting out my exhaust when its cool outsite. Water tends to evaporate really quick with this 98+ degree weather in cali. Not to jack your topic but What have you tried so far.

I also dont know what the pull of vacuum is supposed to be around for this stock motor. Any help on this?

 

[calgarycobra]

I have a similar problem with my 87 five-oh, I just bought my vacuum gauge to check for my prob. But im sure it has to do with my EGR system somehow. I get drops of water shooting out my exhaust when its cool outsite. Water tends to evaporate really quick with this 98+ degree weather in cali. Not to jack your topic but What have you tried so far.

I also dont know what the pull of vacuum is supposed to be around for this stock motor. Any help on this?

Won't a vacuum test be useless with a procharger blower installed?

 

[TenorPlayinGuy]

in a sense. but you still have vacuum. It runs your brakes, EGR system and what not. Its just MADE a different way.

 

[99SVTAddict]

Sounds like you just added the plugs and then the problems started. Sounds like spark blow-out to me.

What heat range and what gap are you running the new plugs at??