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 2to 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 in a search....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.

 

This probably isnt the problem, but trying anyhting helps.

I had almost hte same symptoms when I did my intake and exhaust. It would run awesome till ~2500 and slow way down, enough to make me lurch forward in my seat. Then after ~3200 rpm it would pull hard again. I cleaned my filter, checked for leaks bla bla never found it out.

Then I took my TB off to port it. I did my P&P'ing and noticed my MAF was covered in dirt after only 70k miles on the car. So i cleaned my maf, IAC and TPS, cleaned my intake tract out and put it all back together. After that, I havent had any more problems with it cutting out in the powerband like it did.

based on the MAF being my problem, maybe it needs to be calibrated better for the increased flow of the intake and tb? or it could be dirty like mine? Just an idea, a longshot but i hope it works.

 

Sounds like your TPS is bad. Did the new TB come with a new TPS?

 

Well, last night I put the stock TB back on w/ the TPS and IAC. Cranked it up, no codes, nothing.

Drove it down the street, and it was like having 50 hp back. NO bogging, nothing. I mean it really jerked my head back, it was unreal. I drove the crap out of it to. I drove about 30 miles or so. No problems, NO more power loss.

So I can only assume that FAST tb wasn't meant for the car. I am thinking it's where it has a cable issue. If it would be possible to to make the cable a little longer, and put the throttle cable in the bottom bell hole, and the blade stay shut, it would probably be alright.

Any opinions?

 

Those are great ideas, but the thing is, the MAF is less than 3 months old, and the filter is a K&N FIPK, and it's new. It's also covered by an Outwears pre-filter, so it will look like new at all times

 

I'd like to post an engine pic after this install, how do I do that?

 

Someone mentioned trying the FAST TPS sensor that comes w/ it. Mine didn't. Those are optional, but it mentions in the directions that I can use my stockers. Could that be an issue?

 

Only if the stocker was misstakenly installed improperly to the new tb.

 

Nope, stockers were installed correctly. The only difference is that the IAC makes a 180 on the FAST unit.

Al, are the senors that come w/ the FAST, the same as the stockers you would order from Auto Zone, or the dealer?

 

Don't know as I'm running a stock ported TB.

And I read in GMHTP today that when putting a Holley TB on a FAST they had to use a Holley supplied throttle cable bracket because the cable end wouldn't reach the hole. And they stated that the bracket doesn't mount where the stock bracket does.
Maybe you should go over the TB install instructions and check for relocation instructions? dunno just a thought.

 

The instructions mention "adjusting" the cable. That is all they basically say.
There is no way to lengthen the cable on our cars. It would need to be about 1/4" longer. I just know when I put the stocker back on, it drove like a bat outta h***. So, until I find out what is wrong w/ this thing, I'm leaving the stocker on.

Thanks for the input.

 

Did you do a TPS reset when you installed the new TB? It's either the TPS thinks the old throttle body is still on the car or the cable isn't long enough. That's my guess at least.

 

I think the cable isn't long enough. I haven't ran into anyone that had the 78/78 set up yet, and been able to ask them about it. I think putting the stock TB back on, and the SES light and the driving issues going away proves the TPS isn't the problem. I am going to go down to my tuner's shop, Jeff, at CAM, to see if we can play w/ it a little more.

Thanks for the replies...

 

The 78/78 was a bad idea. You could have just gotten an LS6 intake manifold and been just as satisfied, but saved a few hundred $$$.

What happens when you do heads/cam and you absolutely know that the intake manifold is robbing you of power? huh? huh? huh? huh?

 

You must think I paid full price It's all in who ya know, I got away w/ a deal to die for, so the decision was easy enough to make

I have a cam in the car, just not heads, reason being, it's so hard to focus on the LT1 or LS1 when this new BAD **** Camaro is coming out I am saving the $$ for *THAT* car. Who will care about a stroked and poked LT1 or LS1 then? Not I