Nope.. the crank is the same for all 5.0's so the firing order comes down to the cam.

 

Never mind this I'm mixing up different posts.

 

And once again you are wrong. The body of the O2 sensor undergoes the same chemical change that generates an electrical impulse when it heats up and since it is OUTSIDE the exhaust pipe it produces two separate (and different) reactions/electrical impulses. That's why the body of the sensor sticks out so far from the exhaust pipe! You don't really think they would build an O2 sensor that bloody long just for the heck of it do you? Especially when space around exhaust components in that area is at a premium in most vehicles anyway! (And if it was shorter a standard deep-well socket would fit over it after the wires rotted off). This is why an O2 sensor covered in mud, road tar, and grime will cause fuel efficiency/economy problems. I have now basically explained the entire operation of a functioning O2 sensor and if I need to I will quote chapter and verse from a publication with more authority than mine but I really don't see the need.

Yes, the ratio of oxygen to other gasses is the concern but for the PCM, NOT the O2 sensor. The PCM is already programmed with the known information of the other exhaust gasses based upon the fuel it is telling the system to deliver. The PCM has no need for information about gasses created when fuel burns because it already knows how much fuel is being put in there and based on that, the calculations for the known by-products of the combustion cycle are rather simple! It needs the variable information about the oxygen level to determine how to adjust fuel delivery and how to adjust spark timing to prevent detonation and provide the cleanest engine performance possible under any given set of circumstances. The O2 sensor, no matter how hard it may try (or how much you may want it to) cannot and will not be able to discern ANY element level other than oxygen because the chemical reaction that happens within the metal of the sensor simply is not affected by anything else. That's why its call an O2 (oxygen) sensor! This is also why you can "fool" an O2 sensor by feeding propane into the intake... the exhaust gas content changes AND differs from normal engine operation but the ONLY thing the sensor knows is that the amount of oxygen in the exhaust has diminished (displaced by the propane). The PCM determines the RATIO once it has information from the O2 sensor about the one variable that the PCM has absolutely NO control over... the amount of oxygen in the system.


And for the record you aren't upsetting me at all. I've studied this particular topic in such great detail that I write these responses with a grin and a giggle... because I DO know how an O2 sensor works.

 

Gentleman please, O2 sensors all over the world are just besides themselves knowing that you two are splitting hairs in order to establish their specific technical make up, operation, and the optimum conditions they should be exposed to. Just keep it simple, unless you go carb, you have to have one unless you want it to run like crap, and it should be exposed to all cylinders. The stock pipe has the O2 sensor placed to where it is exposed to the exhaust from all cylinders. If you run dual exhaust, maybe it does'nt matter if you have the O2 sensor sitting on only one side, but anyone serious about performance will definately have a crossover pipe, and if they do they might as well put the damn O2 sensor in the crossover pipe. Now I appreciate everyones advice on my bronco, but please just drop the O2 argument

 

OK I stand corrected on one point, the O2 does reference atmosphere to determine the relative O2 content inside the exhaust.. to me that is still a ratio but lets not continue that argument. My original objection here was about the need for the O2 to see all cylinders, and I stand by the statement that it doesn't. On these trucks all cylinders get the same amount of fuel so the relative O2 content inside the exhaust will be the same if the sensor is seeing all cylinders, half of them, or just one. Of course injectors get dirty over time and if one starts flowing more or less than the others it could be good that the O2 measures the collective output of all cylinders so that some compensation can be applied, but when everything is in good working order it's not necessary.

 

Ok I have switched to the comp cam 35-255-5, which is speed density computer friendly, and I still have a rough idle. Vacuum guage stays around 18in, but does fluctuate a little. Prior to changing the cam, I checked the fuel pressure, both key on and running pressure, I placed a stethsoscope on all the injectors, and they were all "clicking" so I assume they are working, although some of the injectors may not be spraying good (I used a fuel rail inj. cleaner about a year ago). I checked for codes, and there are'nt any fault codes. Could the valve springs not be stiff enough cause a rough idle? It does'nt smooth out when I raise the rpm's to around 2000 the motor still dances a little. The comp cam does have a little more lift than the speed pro rv cam I had in it. Let me know what you guys think

 

is your spout connector plugged in.

have you pulled the IAC off and cleaned it or replaced it?

i just got my motor in and running and after setting the timing i forgot to plug the spout in and when i reved the motor the idle fluctuated and wouldnt hold steady. plugged the spout back in and all better.

 

No codes at all? Even when everything is fine you should get Code 11 or 111.

 

Yes I plugged the spout connector back in, and I do get a code 11 in koeo, continuous, and running, but I hope I have found the problem. I found some vacuum leaks by spraying starting fluid around everything. There is a slight leak around the front of the upper intake where it mates to the lower intake. and a much bigger leak coming from the egr valve. The egr valve is not leaking from the diaphram, but from where the valve shaft goes down into the valve body. I have applied a vacuum to both the diaphram and the flange area of the valve, where it bolts to the upper intake using a little plate I cut and drilled and placed a barbed fitting where the hole is in the valve body, and I can hear the air sucking through where the little shaft goes through the valve body into the exhaust side of the valve. The problem is I have bought two new ones and neither one holds a vacuum where it bolts to the intake, even when I put my thumb over the exhaust side of the valve. First I used a gasket, and then I used rtv between my little plate and the valve. Should'nt a good valve hold a vacuum at the outlet?

 

The new egr took most of the rough idle out, but it still isnt as smooth as I would like it. I will pull the upper intake off and put a new gasket on it, I reused the gasket that was on it because it looked good and was only a couple of weeks old. Other than that, I will have to keep checking different things and hopefull I will get it smoothed out