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No acceleration even at WOT

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Old 06-14-2018, 09:54 PM
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Default No acceleration even at WOT

I just completed installing everything on my 92 Z28 6.0 LQ4 swap, recently I took the PCM to a tuner to change it over from DBW to DBC and figured I'd take it for a test drive today. I could not get it above 20 MPH the car just wouldn't accelerate at all, even at WOT it wouldn't move the car it just sounded like it wanted to turn off. I am running open headers and the idle is also rough. I'm not having any vacuum leaks, I've also put new spark plugs in, and I'm not getting any codes when i scan it. I'm not entirely sure whats going on here any ideas?
Also My current mods are:
torquer V4 cam,
Ls6 Intake,
! 7/8 headers,
241 heads,
4l80e trans.
PCM and harness is a 0411 out of a Yukon Denali and added the IAC and TPS wires for DBC

Last edited by demontrey; 06-14-2018 at 10:07 PM.
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Old 06-14-2018, 10:10 PM
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Has it been tuned for the cam?
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Old 06-14-2018, 10:23 PM
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When i had it sent out the first time it had the tune for the cam and the rest of my mods put in it. I couldnt get the DBW stuff to work so i changed it over to DBC, I took the PCM to a different tuner this time to change the tune over to DBC and he didnt ask for any of my mods so i assumed he didn't need to change anything over but the actual OS
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Old 06-14-2018, 10:31 PM
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Originally Posted by demontrey View Post
...he didnt ask for any of my mods....
There ya go......
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Old 06-14-2018, 11:08 PM
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Well dang I didn't even think about that, i assumed the values stayed the same and you could just change it to DBC without deleting anything. Im going to take it down there to him tomorrow to fix it then thanks guys I'll update the post tomorrow when its done.
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Old 06-15-2018, 04:00 PM
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So i came back form the tuner today and it had a p0121 code because apparently the tps was disabled in the tune so he turned it on i still wasnt getting any codes when i scanned it so i found it odd. Howeber I'm still getting the same issue as before any other suggestions?

Edit* I've also checked the voltage on the TPS from idle to WOT and there's no jumping of volts and it's reading .49-4.40 so that seems to be fine at least

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Old Yesterday, 07:35 AM
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"I could not get it above 20 MPH the car just wouldn't accelerate at all, even at WOT it wouldn't move the car it just sounded like it wanted to turn off. "
Something in the tune is still seeing the DBW file, and putting it into limp mode.
Maybe, have the "tuner" start w/ a fresh cable drive tune?
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Old Yesterday, 07:48 AM
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I agree with the above statement. sounds like something is still not adjusted to convert to DBC.
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Old Yesterday, 01:17 PM
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Might just take the car to a dyno to get it tuned so they can see whats happening in real time but its $500 and might be a while before i can do that. So I did a fuel pressure test and im getting 60 psi at idle, but when i give it gas the fuel pressure goes from about 60 to 40 rapidly also when i turned it off it held pressure i will post a video of what its doing
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Old Yesterday, 01:21 PM
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could be a bad fuel pressure regulator. I'm at work but i'll post my short vid I took of my fuel pressure doing a short WOT pull if interested.
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Old Yesterday, 01:27 PM
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low fuel pressure

heres the link to the video

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Old Yesterday, 01:32 PM
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Originally Posted by fst100 View Post
could be a bad fuel pressure regulator. I'm at work but i'll post my short vid I took of my fuel pressure doing a short WOT pull if interested.
Yea if you could that would be great
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Old Yesterday, 01:44 PM
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Old Yesterday, 01:45 PM
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after watching your vid, doesn't appear to be fuel pressure regulator related like mine. it's being controlled or 'throttled'. i'd lean back to something in the pcm is my guess.

edit that chatter towards the end gave me the shivers
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Old Yesterday, 02:13 PM
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yea its pretty odd ill have to just wait to take it to the dyno then hopefully its just a bad tune
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