Sidewaysste

I've just got my 2007 LQ9 in my project car running, it starts instantly and idles no problem. I can't get it to rev up though, either in neutral or when attempting to drive.
It'll rev up to 1500rpm or so but over that it cuts and drops back to idle. If I keep my foot on the pedal it revs up and dies back to idle, revs up and dies back.
I don't know what year the TAC module and pedal are from as they came separately. I'd wondered if that might be causing an issue but the pedal actuates the throttle plate accurately enough from closed to wide open. Plugging in My OBDII scanner only shows o2 and evap faults. The readout on the scanner shows the throttle position at around 18% at idle and I can get a full sweep reading with the engine switched off.

,I've connected in the brake light switch and the TCC switch and I've connected the CPP switch to C1 pin 35 in a clutch released Normally Closed, 12v fed/ Clutch pressed, Open circuit configuration as that's what the wiring diagram suggests it needs.

Does anyone have any thoughts on what else might be causing the issue?

jimmyg

Have u tried another pedal? The corvette pedal is around $80 . What ecm/ harness are u using?

Sidewaysste

Parts aren't common over here in the UK so trying another pedal isn't an easy option. I'd assume the pedal itself is electrically the same across all years as it's essentially just two potentiometers. Also the fact that (engine not running) the throttle plate responds accurately to the pedal suggests to me that the pedal is ok. I'm willing to be corrected though!

The ECU and harness is the standard one from an 2007 chevy silverado that's had the VATS and rear O2 sensors switched off. It's the blue and green plug type.

jimmyg

I would post over in the pcm/ tuning section . Your likely to get a better response. So the TB opens and closes fine with the key on ,engine off?

jimmyg

If u don't get a response, you can email
PSI conversions. Guy helped me out a lot when I put mine together . U might just have the wrong pedal. I know some have to be repinned to work with certain ecms

Sidewaysste

Thanks, I'll post it over there. Yeah, the TB opens and closes fine key on, engine off.

Sidewaysste

Bit of an update. Unplugging the MAF makes no difference.
It appears I have an 03-05 throttle pedal. Looking into wiring diagrams it appears that the TAC module is the same for trucks from 2003 on (same part number), but the throttle pedal is different in that the early (metal, 03 - 05) pedal has 3 variable resistors, whereas the later (plastic 06-07) pedal has 2 variable resistors. I've unpinned the 3rd resistor but it hasn't made a difference.

I've had the engine running with the maf off so I can see the throttle plate moving and it IS moving proportional to the pedal and the scantool readout correlates to the actual position so I'm doubtful the throttle or TAC module is at fault.

The only thing I can liken it to is a bad fuel map that isn't providing enough fuel.

pdsq98gt

Sidewaysste

I'm not sure about fuel pressure, but I had wondered myself. I've just ordered another gauge kit so I can test that in a couple of days.
The map sensor appeared to be ok on a pre run check - it was reporting 101kpa. I'll confess I haven't checked it with the engine running.

jozw30

Sidewaysste

Hi Joz,

I've checked the wiring diagrams and it suggested that the pins B(purple) and D(tan) required swapping over. I tried this but then the pedal stopped responding at all and it threw error codes.
Would you mind asking your harness builder for more information please?

I've checked fuel pressure and the MAP sensor and they're both fine.

jozw30