My car had a rought idle and ran like **** and got about 10mpg so I checked the tps and somehow it got out of spec down to like .32 volts so I moved it up to about .55. I would have went a little higher but when I tried to set it a little higher the voltage jumped to like 1.5volts instantly. Yet If I slowly moved it up the voltage moved up fairly progressively. The TPS sensor is only 9months old. My car has never run right after the head swap it's been significantly slower and getting worse mileage, TBI does suck!!

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305TBI FireBird, Holley Intake and TBI, Headers, Torquer Heads, Gears. Best E.T. 15.08 at 92.5, 0-60 6.45.(Before Heads)Summit cam purchased 204-214, to be installed "soon". And maybe a TPI swap,

 

Replace the TPS. Inside is a pair of contact points that slide over a thin carbon resistor. It doesn't take much to wear down the carbon layer. The ECM depends on smooth and accurate voltage readings that come from the center tap.

Maybe there's some characteristic about those heads that's making it impossible for the ECM to maintain exhaust oxygen levels. It can only adjust fuel mixture, EGR, and timing so much before it throws its hands up and goes into "diagnostic mode".

In my very humble opinion, I would've just yanked all that stuff off and built me a SBC that would look at home in something made before 1973 (I sure miss my 1972 Impala). A basic Q-Jet and HEI is all you need to start with. Everything after that: cam, heads, headers, etc., is gravy!

[This message has been edited by jrr (edited December 20, 2000).]

 

Sounds like you need a new TPS to me! I've read up on the TPS quite extensively due to mine messing up! Changing the heads wouldn't have any change on the TPS! I think another problem you have is that you're running TBI! But I'll warn you, if you have a high mileage engine and you switch to TPI, make sure it's properly setup or you'll get even worse gas mileage! My car has roughly 190,XXX on it and I only get about 10 MPG, where I was getting nearly 21 MPG!!

Just a little advice for you as well! IF you decide to switch to a TPI setup be careful what cam you put in the engine! I have an '86 Trans Am with TPI and I went to change my cam and found out some very interesting things! The cam MUST have a 112 or 114 Lobe Seperation Angle due to the runners! Comp cams makes some specially designed cams for the TPI setup and those are the ones I would recommend using, otherwise your performance will go to ****!!

 

The car doesn't show any codes though. What would the car being in diagnostic mode do exactly to performance ( Iknow it would be worse but how). Thankx