BBk 78mm throttle plenum
 

Wazup everyone. I just installed the bbk 78mm throttle plenum on my 1998 ford mustang gt 5spd, And ny car is running like crap now! wat should i do? its idleing rough and sputtering during acceleration! Wat do yall think could be wrong? Its not throwing any codes or anything! If anyone could help me out id appreciate it.

Unless you have major mods, a 78mm TB is way too big, I'm not surprised that it would make it run worse. Bigger doesn't always mean better. I wouldn't even be quick to go for a 75mm TB myself. Other than just the part itself. Make sure you hooked up all you vacuum lines, IAC, the TB stop screw is adjusted correctly. All that mess. I'd even put the stock TB back on, see if it goes back to normal, then reinstall the aftermarket part to see if it happens again. You could disconnect the negative battery terminal for a while, then see if it improves.

my car has cold air intake, true duals with no cats and flowmaster 40 series mufflers. short throw shifter, and a PI intake. it ran ok before ith factory tb and plenum, it just idle a little rough! after i installed the 78mm tb and plenum i drove it and it spurtered a little around 3000-4000 rpm. so i took it back to shop and fully cleared the ecu and drove it again. after clearing ecu it got way worse, its almost sounds like its dropping a cylinder or misfiring but its not throwing any codes! the company i bought it from said i had to adjust the tps voltage??? but it only does this when i accelerate over 1/4 throttle! if i barely push gas it doesnt do it!

It really sounds like a vacuum leak, also ckeck the EGR valve.

No vacuum leaks. Checked everyhting. Today i put the scanner on it and found i was misfiring on three cylinders so i pulled plug and they were all bad so i replaced them, and the TPS sensor with oe motorcraft plugs and recleared ecu. Fired her up and let her run for about 30 minutes before driving so ecu could adjust and relearn. its not as bad now but its still doing it! it only does this at high rpm ( above 3500rpm). The only code its throwing is Theft detected, so i checked the theft fuses and there good! Im lost here, everyhting is good, all sensors are reading correctly and no leaks, new plugs, new TPS. Wat could be wrong?? Tomorrow ima try and take it on a road test with scanner hooked up and see if it shows me any info because it only does it over 3500 rpm!! Any suggestions????

What is the trouble code number and what did you gap the plugs at?

There were no trouble codes. except for Theft default but i dont remember the code! The spark plugs are gapped at .054 which is factory specs! When I pulled out the old spark plugs there were 6 NGK's and 2 bosch! and they were filed out and 1 of em was soaked in oil from valve cover leaking! so i replaced all them with motorcraft double platinum and cleared ecu. The bbk tech line keeps saying its either a vacuum leak or my coils are going bad! but its not throwing any codes. my boss thinks it the gps tracking device the car lot installed on my car until i pay it off! because the ecu also has the code theft detected! I also cleaned EGR valve while swapping the Throttle bodies

the code im throwing is Theft Detected, Engine Disabled. Im taking bbk 78mm off tomorrow and sending it back for a full refund and im putting the factory one back on. anyone who is thinking about buying one of these 78mm throttle plenums, ***DON'T DO IT*** THEY SUCK, AND ONLY CAUSE PROBLEMS TO UR STOCK VEHICLE. THIS PRODUCT HAS ONLY BEEN ON MY CAR 3 DAYS AND HAS ALREADY COST ME OVER $200 IN UNNECESSARY PARTS DUE TO IT MALFUNCTIONING

A TB and plenum is not going to cause a theft detection code IMO. So I don't think your blaming the right thing here...

Its had that code since the day i bought the car! but I took the bbk off today and put oe back on and car runs like new! so my guess is that the 78mm caused the ecu to over correct for more airflow which fouled out my spark plugs!! but idk for sure! all i kno is the bbk made my car run like crap and it runs fine with oe on it! im sending it back for a full refund! and to anyone else who is thinking about getting one. DONT DO IT