Hello all,

Took a video of an issue I've been having pre and post engine rebuild/tune. Engine was rebuilt by Lucky 7 and tuned by Nelson. While idling, a quick and slight jab of the throttle will cause the vacuum gauge to rise toward zero and the car will stumble and almost die. The idle is set a bit high in the video but is now set to 900rpm, car is basically stock with all emissions in place.

Checked the VTA1/2 ranges which were within factory spec, also replaced the throttlebody Oring but I'm no expert so any help on what else to look is much appreciated!

 

Have you checked the TPS?

 

It's like the accel enrichment isn't working. With the engine off, key on, if you look at the sensor check screen and watch the TPS values do they both go up nice and smooth?

Do you have a way to save the map for the PowerFC (datalogit)? If so I'd do a reset on the PowerFC and see what happens. Also it may be worth looking at the enrichment settings compared to the stock PFC map and see if something's up.

I'm assuming it's only a hard jab on the throttle that makes it do that. If you slowly raise the RPM I'm assuming it will rise up and not stall out?

Could also be a dirty ISC or something.

Dale

 

The builder and tuner should be fixing this problem free of charge.

 

VTA 1 and 2 is the tps.

all of the things i was going to say, minus the ISC since i dont have one. i would suggest watching your AFR when you do it and see if it goes super lean. it may just be a bad spot on the map. to better help, knowing if it only happens with jabs or when you throttle up slowly is important. also, turn off o2 feedback and see if that helps. also do all the things that dale said. realistically, the tuner/builder should be doing this troubleshooting free of charge as adam said. you were given an incomplete product and whether or not it was like this when you got the car back or it just started, he should take responsibility and fix it. have you brought this issue up to him? does he know youre having problems?

 

Thanks for the help all, mentioned to lucky7 at sevenstock but it's difficult being about 5 hours away from them otherwise it'd be back there asap.

Rechecked the TPS voltages after warming up the car and it looks like they're still good. Did notice that VTA2 topped out about 2/3rds of the way opening the throttle, not sure if that's normal but otherwise they're nice and smooth.

closed open
VTA1: .56v 4.40
VTA2: 1.07 4.97

I'll check the ISC next, all the throttlebody stuff is original and hasn't been touched or adjusted.

 

It did this before and after the rebuild when running on the PFC base map so I'm not sure. I'm really just blipping the throttle, if you do it lightly/quickly enough it stumbles and almost doesn't catch itself.

 

Well, stop doing it then

 

Problem solved, user error.

 

RCCAZ might be into something here. :P

Its normal to have the TPS voltage top out at 2/3rds full throttle. My brand new TPS and my old one did it. The one thing I noticed from the first video was when you blipped the throttle it looked like it just didn’t catch itself. This can be from the throttle dashpot not working right. The dashpot is a little dampener for the throttle plates that slows the closing of the plates. This helps prevent the plates from slamming closed and starving the motor of air. If you open the throttle body and the little white plunger of the dashpot is sticking out about an 1/8 inch, then the pot is bad and needs to be replaced.

Matt

 

You need to load the map and also put this post in the correct forum.
I say that the injectors map or the 2 acceleration maps might be bad.

 

Did some more searching and that looks like the issue, you'd think this would be something that would have been tuned for I have a datalogit, just never hooked it up and had to order a new usb adapter. Also the ISC and the dashpot were working correctly.

Will post up in the PFC forum if I need anymore help. Thanks!