[FastGT31]

some of you may know about my car. its a 91 beretta with a 3.1. it has a solid roller cam, 3400 heads/intakes and a 3500 UIM. i also have the 65mm throttle body from the store. it has yet to be tuned but my problem is it never enters closed loop. i have a 180* thermostat (runs around 200* most of the time). i know it should enter closed loop after a few minutes at most ( i live in fl). everything on my scan tool looks normal. the only thing i could think of is that the o2 sensor is too far downstream ( i plan on converting it to a 4 wire soon anyway) or it has something to do with vacuum. im lost on this. if any of you may know what is stopping it or what else i should check please let me know.

thanks

chris

[IsaacHayes]

4 wire heated should help a lot. Unless it's wiring issue or bad O2.

You have custom headers right?

Is that cam just a solid roller or a different grind too?

[Superdave]

closed loop is triggered when 2 conditions are met, When either the cold, warm or hot timer has run out, and weather or not the coolant temp was warm enough to enable those timers.

So, i'd check the CTS.

I guess it depends on which style you went with but the one with the yellow wire runs to the ECM, the green goes to the gauge. Most 3400 swaps use the 3 wire setup.

[IsaacHayes]

Hell I'm using the 3 wire cause the sensor in the rear head went bad and is hard to get to, and I have several 3 wires sitting around LOL. When/If I go MegaSquirt I'll put a new one in the head and use that for the MS.

[1988GTU]

Do you have the ground wire connected on the trans stud near the rear (by the bulkhead) of trans? Should be two wires going to one eyelet iirc. If that is NOT there, it will never go into closed loop.