Engine Knocking under boost.

**natethegreat** · 08-23-2015

The cars top swapped with the stock pulley. I've also had the car tuned for the top swap. Anywho, put a new supercharger on last night, drove it around for a bit and seemed to drive fine. Went into boost nicely. I didn't have a knock meter up because i wasn't going to romp on it too hard. Well accidentally downshifted to 1st at 6 grand. I let off right away but after that the car would buck. Well turns out it knocks whenever its in boost. Any thoughts on what could cause this? Anything that could get knocked loose in the bay that would cause it to knock only under boost? Thanks.

**bandook** · 08-23-2015

What map sensor you have? Who did the tune? Do you know what was changed?

**Scottydoggs** · 08-23-2015

why do you guys touch the shiftier after its in Drive? dont down shift these cars, its not good for the tranny. or your engine in this case.

my guess is you broke something when you hit 6,000 rpm.

**natethegreat** · 08-23-2015

Stock gtp map sensor off a 97 i think. A local guy a few years ago when i did it, and no, i think it was the stock gtp tune with some fueling/timing changed to account for the higher compression.

**natethegreat** · 08-23-2015

I meant to downshift into second but pressed the gas too far.

**Scottydoggs** · 08-23-2015

news flash, a top swap tune is the settings changed to a gtp's, but cut some timing lol

**natethegreat** · 08-23-2015

I mean i know nothing about tuning so wasn't sure.

**bandook** · 08-23-2015

Oh...so this swap was done awhile ago? Only thing different is blower? So, it was running fine just until you drop shifted into 1st? No KR prior to this?

**Slick2500** · 08-23-2015

Cracking flexplate?

**natethegreat** · 08-23-2015

It said it had some kr sometimes but it was never was never a lot. I took the belt off and it's still doing it. 2500/3000 rpms and starts popping, and bucking, it will kind of get out it downshift and be fine then do it again at those rpms. In just barely on the peddle enough to accelerate.

**Scottydoggs** · 08-23-2015

post a vid.

**natethegreat** · 08-23-2015

https://www.youtube.com/watch?v=bspa...ature=youtu.be Hopefully this shows well enough what i mean.

**Scottydoggs** · 08-23-2015

check your spark plugs yet? that sounds like a misfire somewhat.

**natethegreat** · 08-23-2015

No not yet, I don't have tools right now but I can do it later.

**Scottydoggs** · 08-23-2015

if you have not done a tune up, it maybe over due. new wires too, cause they might break when you pull them off the plugs.

im runing 104 copper plugs gapped to 0.50 in my top swap. it seems to like em.

**natethegreat** · 08-23-2015

I'll throw some new ones in tomorrow and see if that changes things. Thanks!

**Slick2500** · 08-23-2015

Change your fuel filter.

Sent from A Galaxy Far Far Away

**natethegreat** · 08-24-2015

well put some new plugs in and took it out. I can now drive it somewhat normally. I did some pulls from a stop at max 75% throttle and only 3ish pounds of boost and it seemed to run well. There was on spike of about 8* of knock but it was just split second. It also seemed like if i started at 30-40mph itd knock more but was alot less severe. Not sure i guess. Either way ill put a fuel filter in and see how that ends up.