[lancefloyd]

Hey, I finally got the balls to take this car out of the city and on some highway, away from all my tools (the ones that wouldn't fit in the trunk anyway) and all the security of a quick tow-ride back home. On the way to my destination, I noticed something that doesn't usually occur at street speeds (WOT 1st, 2nd, 3rd, ...lol), ..in 5th at a 60+ roll or so, when I get on it partially or almost to the floor, the car will accelerate hard (like I intend) but then buck around a little bit.

Only mods are a shimmed wastegate to around 9psi, PVC piping catback, no EGR, iridium plugs, NGK wires, K&N FIPK, and a few other goodies that I really can't remember right now...but nothing in the form of fuel or ignition control, so the factory ECU is still in charge.

The bucking isn't terrible, its not like the car hits brick walls or anything, it just doesn't pull cleanly to redline like it does at lower speeds and in shorter gears.

My guesses right now are the iridium plugs might have incorrect gap, one of the plugs might be damaged in some way, I might have a clogged injector, I might have a clogged fuel filter, I may have an AFM that is oily from the K&N, I might need timing work, or some othe stupid thing that is completely obvious to you guys but not to me.

Tell me what ya'll think.

 

[Ckanderson]

Fuel Cut?

 

[lancefloyd]

no...not THAT herky-jerky!... That happened once to me when I blew an IC hose off...scared the hell outta me. No, this is like mini-versions of that...but not nearly as abrupt.

 

[JSupra91T]

Sounds like a boost leak. And you made a catback out of PVC pipe???

 

[Shawndude]

I agree, sounds like an intake leak somewhere. It can be fairly small, and it will cause the symptoms you describe.

Hell to find though. Also check your codes.

 

[lancefloyd]

LMAO....yeah...thats what i did...

no, catback is blitz, PVC is the IC pipes...

I'll break it all down and redo it when I get back home (to all my tools..)

thanks, I'll update ya when I get the sonofabitch back home.

 

[jazz]

I have the same problem, but my car's all stock. I posted in the MKIII section and didn't even realize about the MKIII technical section. You can read up on it here http://supraforums.com/forum/showthread.php?threadid=159113

 

[MKIIINA]

do you have a auto or manual tranny?

 

[jazz]

I have a manual tranny.

 

[Cyrus]

sounds like a dead/misfiring spark plug maybe. can you hear pulsations in your exhaust too?

 

[greensupra_87]

don't know if it helps, I had the exact same thing on my n/a, there was a hole burned from my header in the intake. another word check for hole/leak in intake tubing

 

[jazz]

sounds like a dead/misfiring spark plug maybe. can you hear pulsations in your exhaust too?

I've been hearing pulsations in my exhaust for a while. They were there before i had my plugs and wires changed and the pulsations are still there.

 

[jazz]

Oh, I don't know if I mentioned this or not but my car was backed into. Could an intercooler pipe have cracked or slipped off?

 

[boostmastersdotcom]

i was reading a corvette buying guide for a presentation i was doing on the a/c system. And it said that with a uneven flowing exhaust that it means that the rings could be worn. SOmething was that is just wasn't running right or not good, can't say exactly the link is on my comp at school.

From the looks of the coil packs it's a wasted spark system, where it fires twice during the 4 cycle. So with that unburned fuels could be lite and a uneven idle could occur, or spinning the turbo wheel, but when i ran open stock dp, it's sounded like it was a cammd v8 so anything goes, i'm just reachin here, i'm waiting for an expert to put me in my place.

Timing could be it, now that i think about it. But the ecu should make up any min problems.

 

[lancefloyd]

Well,...AFTER ripping the whole top end of the car apart, from the turbo hoses to the piping that I made out of PVC, to the 3000 pipe, the ISC hoses, the famed accordion hose, all that...

I redid every thing, noticed no leaks to start with, and ended up with a tight set of connections...

STILL DID IT, GODDAMNIT. It would be especially bad during hard runs through the rpms in smaller gears this time though, so maybe I moved the problem.??

I have one theory yet to be tested. When I was removing the AFM and the K&N Filter, I noticed a film of oil on the afm body inside, and of course we all know that the AFM electronics don't like this oil. (Which leads me to ask WHY in the hell we actually use K&N's on our cars.) It makes sense to me that the AFM might be fouled. Later on tonight, I'm going to carefully open the thing if possible and clean it.