I've got a 151/4 TBI in a winter driver Fiero that ran fine for years. I "unswirled the heads, enlarged valves, bowl, and ports this past spring. Also installed a mildly improved cam. Engine ran fine all summer until the car was struck while parked.

Fast forward two months (the time it took to find replacement parts and fight the perp's insurance company) and after body assembly it runs extremely lean just off idle position.

MAP is new; TPS new and idle position voltage dead on 0.85VDC; TPS made adjustable and set to various positions to cure problem - no help; fuel and air filters new; fuel pressure adjusted from 11 PSIG to 26 PSIG with little effect; new oxygen sensor installed; distributor replaced; IAC removed, cleaned, and lubed; throttle plates aligned, CTS in perfect range; ECM reinitialized more than once; new injector, fuel return line clear. Ignition timing has been adjusted all over the place with no improvement. Exhaust is not plugged. PCV valve is new; EGR is cleaned and operating (disconnected for testing); and the new intake/TBI/head gaskets aren't leaking as best I can tell. Hoses and plumbing are intact.

If I force backup fuel mode, the engine runs great but is defineitely on the rich side. This proves to me that the ignition is reliable, and fuel is the problem. I suspect that I've altered the intake enough to take the normal fuel requirement at cold temperatures off the PROM's fuel map. The cam grind is not tha much different than stock, but the increased valve sizes may have amplified the effect.

Any insights?

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Later,
Vader
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"No matter how hard you try you can't stop us now"
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Sounds to me like you use a use a chip with a bigger "pump shot" to compensate for the lean condition and the cam you have in there now. I don't know.. just an idea.

 

Vader, give Pablo a shoot. He's extremely knowlegeabe about TBIs and buring a PROM for them. You might even want to make a post in the TBI section if you haven't done so.

I looked at all that you have done, and everytime I thought of something, you said you replaced it. So I too agree with your thinking that you need to alter your fuel maps for your TBI to compensate for your mods.

Wish I could help you more.

 

Shoot glen.. i know a little, but extremely knowledgeable? i think not hehe

I responded to you on the tbi forum vader