Hi guys, I have a 86' bronco with a 302 efi, I have recently changed the fuel filter, throttel positioning sensor, and the o2 sensor, but when i hook it up to the computer it says it is running rich, and the truck is hard to start.(it turns over and over and smells real gasey) I have to lightly push on the gas to get it to start, but then while driving it still smells real gasey, i am getting better gas mileage now that i changed all that stuff but not as good as when i got it. please help

P.S. the computer also says the Thermolacal air system is not working. What is this ?? the smog pump and cat's have been removed before i bought it and i think that is why the emmissions light is stuck on. Please help


Plesas and thank you

 

you are getting that emissions light and the thermo air code because of the removal of the smog and emissions goodies. I have my smog pump removed and the extras around it and one of my cats is gone and I get the same code every time i run the codes. I don't have an emissions light so I don't have to be annoyed by it. Lucky me!

KJ

 

The computer says its running rich because it probably is. You have "part" of an emmission system on the truck. Without the smog pump dumping fresh air into the heads and CAT, the O2 sensor is picking up exhaust gas readings that would indicate too little O2 in the exhaust. The computer is trying to compesnate by dropping the fuel coming into the engine which is why its hard to start. Once running, you have to stand on the gas more to get it moving because of this compensation so, in effect, you are having to run a wider throttle than normal to achieve the same performance hence the "gasy" smell.

 

I belive your problem is the fuel pressure regulator. The one on my 86 has gone out 2 times the first time it melted the cats, the second it was puting so much fuel pressure on the injectors it actualy hydro locked the engine.

The thermactic AIR system should not make the Bronco run rich. The AIR tube goes into the cat well past the O2 senser and should not affect its reading.

My 86 has over 480,000 miles on it (with the old injection system, It has a new one now) and most of that was without the smog pump and thermactic AIR system. It never ran rich, It never turned on the emissions light, and it even passed emisions with a good aftermarket cat.

the codes for the AIR system will not turn on the light its the one fore running rich thats doing it. Check your fuel pressure past the regulator

 

AIR injection system (which includes the smog pump) runs air into the heads at each exhaust port as well as the catalytic converters. Every 302 and 351 after 1974 had the AIR injection manifolds cast into the heads and the plumbing was via formed hoses and metal lines into the rear of the heads. So, the AIR system can affect the O2 sensor readings. Not to say that fuel pressure regulator isn't the problem, or part of it, but the emissions components are designed to work together as a complete system and removing some of them can create the kind of conditions mentioned.