350 HRSS

I installed a FAST 78/78 set up (tb and intake). I drove it about 200 miles or so, then I get 2 codes. I get the 121 and 507. I had them erased by a Tech 2 to see if they would come back.

I drove another 10-15 miles, the SES came back on. It stayed on for about 110 miles, and then I stopped to get gas. I left the gas station, and I looked at the dash, and the SES was gone??

I get back home, and plug up the Autoscan just to see if there were any codes still there, it was showing the 121 again, but no SES light on the dash???

I looked it up in a little more detail and it supposedly means:
P0121 sets when the predicted throttle angle does not match the actual throttle angle.
P0122 sets when the TP sensor signal voltage is less than 0.2 volts.
It sounds like you have a wiring problem ( broken wire somewhere). You can count on this low voltage being lower than normal closed throttle voltage. A bad ground would increase sensor output so rule that out. It is possible that your 5 volt reference voltage took a dive so carefully inspect the wiring to the sensor. To save weight, the wiring is smaller and is more prone to breaking inside the insulation. The telltale signs of internal breakage would be a bubble in the wiring insulation. You could also have had a loss of 5 volt reference from the PCM. If so, you would expect DTCs from other sensors using the same 5 volt reference. Usually this is an EGR DTC.

I found that info on CZ28.com Can anyone help me out a little?

On the FAST tb, it has 2 places to hook the throttle cable up to. I could only get it to work in the first hole. B/c when we hooked it up to the second hole, the throttle was part way open, and there was no way to lengthen the cable.

Can anyone explain some of this to me? And it has affected the power big time IMO. It starts out great down low, but when I go WOT, it bogs for a second or two, like I am running on 4 cylinders. But when it hits the 3k RPM range, it picks up like it should.

I would appreciate any help on this. I am assuming it is a FAST quality issue, and I don't think tuning would fix it. I think it is the stupid FAST tb. I thought about putting the stock tb back on to see if the issue went away.

Thanks for any info.

ZL1Killa

iTrader: (17)

its got to do something with your FAST tb and everything that plugs into it. somethings not right there. try putting the stocker on and see if it goes away.

i isntalled a Nick Williams TB and had no problems, i went 90mm on both. didn't even have to adjust anything cept my tune. no changes to TB tables or anything

350 HRSS

Does the NW throttle body have 2 holes for the throttle cable?


That is what I was thinking, it was a TB issue. When we installed the TB, we pushed the pedal to the floor, and the throttle blade would only open maybe about 75%. I tried to put the cable in the second hole of the tb bell, but it would leave the blade about 1/2" open. And there is no way to lengthen the cable. But it really needs to be in that bottom throttle bell hole to be correct, and to match the stocker.

I have heard others had to use the first hole as well, like I did. It's a big performance loss in the 2k range. You can hold the pedal down, and when it hits around 3500 rpm it really jumps into action.

This is all very annoying. Thanks for your reply.

Anyone else have this issue?

FRDnemesis

iTrader: (19)

Yes, the NW does have two sets of holes. You had your cables connected correctly to the FAST TB. I used to have a FAST 90mm TB, but now have a NW and I'm much happier.

When your cable is in the second hole (highest up) and you put the pedal down you should still be getting 100% TPP. If it is not at 100% with the pedal down and the cable in the sexcond hole up, then it sounds definitely like the throttle cable armature is mounted in the in-correct position on the shaft, causing the eroneous readings from your TPS. So you should check your voltage readings at closed and WOT. I think the target range is .5mV -.64mV at closed and no more than 5.0V at WOT.


Something else to also consider is that you may have a dead spot in your TPS. You can verify it by turning your key on, put your SM on TPS and "Slowwwwwwly" push the accelerator down and watch the numbers climb. If they jump eratic, or your pushing the pedal down and the voltage sits constant and then jumps up, then thats it. The numbers should climb slowly and smoothly matching your pedal input.

This doesn't sound like any of the issues with the FAST TB's, it sounds like a TPS input issue.

Jeff