Guido

reset your TPS to read .35 base voltage. This will cure the blues.

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-86 IROC
Vortech stuffed EFI 406 in progress
-=ICON Motorsports=-

89RS355

Thanks! A buddy of mine is going through that kind of problem right now, and I think that might just be the answer. Just curious, but how does that work? Does the computer just use that as a baseline idle voltage, or does it think the throttle is open just a bit? Thanks!



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Jerry

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89 RS Lt Blue T-Tops T5
355 Crate, Compucam 2040
Pst Front Hotchkis Rear
Edle. TES 3" Flowmaster
Harwood hood, bla, bla, bla...
94 Z28, LT1 6M, Black
Most of the bolt-ons
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Guido

Here is how it was explained to me.

In the PROM there is a table that plots MAF voltage (air flow) vs. TPS position voltage (amount of throttle appiled). There is a preset range for this whole table. for instance say @ x rpms, Maf should be "y" and TPS should be "z". If its not in that given range it thinks that something is wrong so it tosses a code.

When you put a cam in, it generally flows less on the low end, and more on the top end. This pulls it out of range on the lower end (which is typically where the code 33 happens). If you set the TPS down, it tricks it into thinking there is not as much throttle applied therefore does not realize a problem.

I did it and cured the blues. Madmax explained it to me, maybe I can get him in here to explain it better.

Good luck!

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-86 IROC
Vortech stuffed EFI 406 in progress
-=ICON Motorsports=-

Jim85IROC

iTrader: (2)

Just to play devil's advocate for a minute, let's think about this.
If your cam is radical enough to cause your car to throw a code, you really should have a custom prom anyway. If you do get a custom prom, it should be calibrated for the TPS in the proper location, so be sure to put the TPS back to the stock location when getting that custom prom that you should have.

On my 85, I'm using the stock 305 computer and chip on my 355 with a 214/224 .442/.465 112 LSA cam. Not a radical cam by any means, but in any event I don't have any codes. My 85 came with a more agressive cam to begin with, and the computer in the 85 barely checks to see if the car is running, so later years may be more sensitive to cam changes.

Just my misc. thoughts. Respond as you see fit

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Guido

Actually Jim your on the right track. You should have custom PROM burnt for aftermarket cam.

Whats worse, I have a custom one and it still screwed with me as Ive mentioned.

Maybe they did not mess with those tables any. Im not positive. But when I set the TPS back, it fixed everything.

PureEvil