Car Stutters/Bogs out during certain rpms/load

[JustanITguy]

Hello all,

Quick backstory, spun a rod bearing YAY! I tore the engine down myself and found the culprit. I sent off the block and heads to be resurfaced at a well known machine shop here in Orlando, FL. I ordered all new OEM short block parts besides the pistons them selves as all I did was just clean them. (yes i got new rings) i put the car back together and took my time doing so. Bought a nice digital torque wrench and went to work with the proper specs.

Fast forward. Engine is now in the car and i started off with a few problems off the bat. A couple codes i chased down and i was able to get the car to start. The car had sat for close to 6 months and luckily it was on E with fuel. I put fresh 93 in the car and came across a fuel leak from bank 2 DI. So i ordered all new orings and seals for the DI's (oem). Replaced them my self and made sure i lubed them enough to not crack or break them going in.

Car is now running normally but ran into an issue where it was still throwing a DI code, I forgot what exactly it was but I was stumped. I took the crazy tow to the dealership where they "fixed the coil pack clip and DI clip on the wire harness" Car is now running again and idling fine. (side note, car did not have a registered tag and headlights on so they did not test drive it). I got the car back and started to drive it. I was able to drive it and everything felt normal. after a little bit, It jerked and the car had no throttle response and was slowing down like i had just lifted off the pedal in gear. It did this about 4 times until i towed it back to my friends shop. After checking here and there i went ahead and said maybe its the TB, so i ordered and OEM one for the ridiculous amount it is and nope no fix.

After letting it idle for a solid hour, i noticed the HPFP was making a louder than usual ticking noise. (tested that was where it was coming from with a stethoscope) After driving it down the back roads holding the pedal down WOT the car would jerk and i'd loose throttle for until it decelled about 1-2k rpms and i would regain throttle. During me holding the pedal down, and it jerking and cutting off again, i would get backfires out of my exhaust (online that is related to DI issues) I finally got it to throw a code P0087 i believe it was. everything online was related to the HPFP. So i ran a live diag with the SNAP ON code read (after clearing the code) and drove it watching the MPa and the PSI of the HPFP. MPa's stayed solid at 4.004 MPa's and the PSI during idle was around 1200 ish. While driving under WOT it got to 3400 ish. during the jerking and lose of throttle, it went to 116 psi. So i said well maybe its my HPFP. I ordered one used online for about 80$ and figured lets give that a shot. it fixed the ticking noise but not my issue.

Last desperate issue, I renewed my tag and put the car all back together (bumper, headlights and so on). I should also mention that i had put brand new spark plugs (oem) during the rebuild. The car was dropped off at the dealership and it just so happened to blow a seal in one of the DI.... So after talking to the manager, I agreed to let him change out all the DI seals and Orings, both DI fuel lines that are (one time use) there are 2 of them. also a new intake manifold seal, and a HPFP all new. They just finished it as of 1/25/2020 and i have yet to get there and pick it up. They called me and said during the test drive, they were able to get the car up to speed, but if they pressed the gas to hard, it would lose throttle response. (same issue i was having it seems) they said the only thing the car is saying is a CEL for an O2 sensor on Bank1 and then began to told me that i have an exhaust not made for the car. Currently on there is a Borla UEL paired with Nvidia N1 catback exhaust and has been on there for 2 years with no issue (followed by OFT tune for the headers). They told me their next step is to order OEM headers and exhaust to fix the CEL and they said its no guarantee to fix the problem. They don't know whats going on with it so that's why im reaching out here on the forums. Sorry for the long post.

[NoHaveMSG]

Sounds like an issue with the in tank fuel pump to me.

[humfrz]

Originally Posted by JustanITguy

Hello all,

Quick backstory, spun a rod bearing YAY! ...........Sorry for the long post.

Hello JustanITguy and welcome to our forum -

I would have sold that puppy after the first sentence of your post -

Sorry, I don't have the patience to read all of your post nor the knowledge to help you even if I read the post. -

However, I'm sure others will be along soon with some help. -


humfrz

[JustanITguy]

@NoHaveMSG, Thats what i was thinking, depending on how the car reacts when i go pick it up, i was going to test the in tank fuel pump and sending unit to see if it was dropping in pressure.