These are the two parameters that matter most when it comes to SD and those aren't really that radical so this cam should not cause much problem.
You stated in the first post that the engine idles fine but stumbles under load, that potentially points to a high voltage ignition problem. Are the plug wires new and are they routed away from one another and metal engine components as much as possible. The wires for plugs 5 & 6 in particular cannot be run parallel to one another in close proximity because those cylinders follow one another in the firing order and an induced pulse will cause a misfire.

 

No it does not. It ONLY understands oxygen levels. The chemical reaction that takes place in the sensor when it reaches operating temperature reacts to oxygen levels only. It is this reaction to the oxygen levels that the PCM uses to determine fuel/air ratios. O2 sensors ARE comparators. But they compare oxygen levels between the inside of the exhaust pipe and the outside of the exhaust pipe! This is why you need to keep these sensors clean and clear of foreign materials both at the tip and around the body of the sensor. The only reason they have the additional wires is so that the heating element in HEGO versions can pre-heat rapidly and work effectively BEFORE the exhaust system reaches full operating temp.

Furthermore, if the O2 sensor functioned as you say, there would be no need for more than one type/configuration of O2 sensor. Every engine could use the same sensor because it could compare oxygen and other gas levels regardless of what the volumetric capacity of the engine was. This simply is not true because each O2 sensor is designed to operate based upon known oxygen levels within the exhaust range of engines with certain volumetric capacities. This is also why you can't just slap any O2 sensor into any vehicle or any engine. Yes, several four-cylinder engines may utilize the same sensor but the volume they flow is relatively similar and within the range that a given O2 sensor can function properly. The same may be true for any group of engines that flow similar capacities simply because that particular O2 sensor will "read"/react to the oxygen levels so as to give the PCM a satisfactory information stream.

 

Well if by level you mean the ratio between oxygen and fuel then yeah, but if you mean the volume of oxygen then no you're wrong. Can you produce any 3rd party information that says an O2 sensor measures the volume of oxygen in a gas mixture? I can't.. but I can find all sorts of stuff that says it measures the ratio.

 

regardless about the o2 sensor. the issue with the motor currently is the cam. 35-255-5 is a great cam that will work well on sd efi.

 

The sensor cannot measure anything BUT oxygen levels... so it has no way of "knowing" what the level of ANY other gas or particulate in the exhaust. In order to have a ratio you have to be able to measure more than thing. O2 sensors cannot measure anything but oxygen. Its physically impossible because the chemical reaction that takes place in the sensor ONLY reacts to oxygen! Don't know how many ways there are to say it. The computer takes the oxygen level information it gets from the O2 sensor and adjusts fuel/air mixture based on known values that produce the appropriate ratio of exhaust gases for the engine in question. If you want third party information look up how an O2 sensor actually works!

The ONLY comparison the O2 sensor does is the differential in OXYGEN level between INSDE the exhaust system and OUTSIDE the exhaust system. This differential should fall within certain known parameters no matter what the conditions. It is this known range that the computer uses to determine the changes to fuel/air mixture by basing the reading it gets from the O2 sensor on this known range. The O2 sensor can do this because the chemical reaction is greater in the presence of a greater level of oxygen and vice-versa. I see no point to further argue this or justify something I have taken the time to understand with someone who has not, and merely wishes to argue the point.

By the way... I'll go one better here. If you know how an O2 sensor works you will know and understand that it is entirely possible for an engine with a vacuum leak to run RICH!

 

Well I have welded a good O2 sensor cross over pipe in. It is a little bigger than the little stock pipe, but it will work better. It still runs rough, but I think the O2 sensor is damaged. One of the vents on the sensor had been somehow pushed shut, I could see a mark where something hit it, and I decided to blow it off with comp. air, and when I did white crap came out of it, so I better get another one, even though I dont think it is going to matter. Conanski, the bronco does idle rough and stumbles going down the road, and the plug wires are new, and I have them routed acording to a ford diagram I found. It shows how to rout the wires to avoid crossfire. The plug wires are new Auto Zone duralast wires,with plenty of wire dividers. The coil is about a year old, but that does'nt mean anything. I am thinking about getting a high perf. coil, cap, and wires. I have thought about trying a colder plug in case the compression is alot higher than stock. I was told that a cam with a center lobe angle that is less than 114 wont work with sd, and the one I have is 112, but I am still trying to get out of having to change the cam out, but it may be the most economical solution. comp cam $175 plus shipping. I would love to convert to maf, but I dont like messing with ecm's and splitting the wiring harness. I'd be a nervous wreck trying to do it, but I can do the mechanical.

 

90bronc, what tranny do you have in there currently? that will determine how easy going to maf would be.

the stock ford coils are great so no need to change but if you do go msd. get some 9mm ford racing wires and run a regular copper motorcraft or autolite plug.

good luck and keep us posted.

 

I have the E4OD, so I guess I cant use the mustang ecm. Replacing the crossover pipe improved the situation, but it still idles rough and stumbles/surges going down the road, just not near as bad as before. Chip guy is out of town, so I cant talk to him 'till next week. I would feel like a complete jackass if I replaced the cam and it still ran like crap. I guess I should get a new O2 sensor, and high perf. cap, rotor, and coil, so I can open up the gap a little. I may have a fuel problem also, I have 30psi running, but only 18 to 20psi with key on, and it should be at least 35psi with key on. Bad regulator maybe? I soake the injectors in a can of carb cleaner, before I put on new seals and reinstalled them, so I hope I did'nt mess any of them up some how

 

Don't go throwing parts at it when you have specific clues to run down first. Cycle the key off>run>off>run a few times without starting it to see if the pressure can build to something closer to spec. Also, pull the vacuum line off the nipple on the fuel pressure regulator to see if there's fuel on the wrong side. You could also have an injector stuck open that's pulling the pressure down so see how fast the pressure falls off with the engine not running.

 

That's what I will do. I was ignoring the fuel pressure, but I was using a tire gauge to check it, so I will be running down to harbor freight to buy a tester, and stethoscope to listen to the injectors, or at least the ones I can get to. The stethsoscope will let me now if they are cycling, but it wont tell me anything about flow. I cant start just throwing parts at it.

 

What firing order do you have them routed for and do you know that the cam has that firing order? Did you try the other one just to see if it makes any difference?

 

I think you are confusing levels with ratio, there is all sorts of documentation that appears to make it sound like the O2 sensor measures the amount of O2 in the exhaust but what they really mean is the amount relative to other inert gasses or in other words the ratio.

See.. that's not possible either because no part of the sensor is outside the exhaust for reference.

I don't seem to be convincing you that I'm right here and I'm not trying to pick a fight or **** anyone off, just trying to dispell what appears to be a misunderstanding. I will gratiously accept it if it turns out I'm wrong.. but right now I'm convinced I'm right.

If your line of thinking is correct then one of these engines should not run correctly if the O2 sensor were to be located such that it only sees one side of the engine.. as it would when positioned in the collector of a longtube header for example. BUT... I have that exact setup on my truck and not only does the engine run well.. it runs perfectly well and passes tailpipe emissions tests. I also have a wideband O2 sensor that I can install on either side of the motor(have welded in sensor bungs) and it shows me that both sides produce the same 14.7:1 A/F ratio in closed loop. If an O2 sensor measured anything besides ratio this simply wouldn't work, but it does. You don't buy a different sensor for a 4.9, 5.0, 5.8, or 7.5l motor in these trucks the same one works in all of them, and you don't need to buy a different one when you turn a 5.0 into a 347 stroker with a big cam and heads. That's because the volume of oxygen in the exhaust is irrelevant, all that matters is the ratio between O2 and other gasses.

 

diagram is for 302, but firing order is the same. Cam is 351w firing order 1-3-7-2-6-5-4-8.

 

That is a good diagram for a stock 5.8 or '94+ 5.0, but just to rule out the possibility that you accidentally got a cam with the old 5.0 firing order(**** happens) swap the wires for 3 and 5, and 7 & 4 to see if it makes any difference.

 

I'll try switching the firing order, but I am not sure that the engine will run any better. Please correct me if I'm wrong, but I believe the crank is made for specific firing orders, and that puts the pistons where they should be for each specific firing order, and if that is the case it would probably run worse, even if the cam is not made with the proper firing order. I checked the fuel injectors with a stethsoscope and they are all opening and closing, and I used a fuel rail injector cleaner about 9 or 10 months ago, so I suspect they are spraying properly. I checked the fuel pressure with a f.p tester, and it shows 35psi key on and about 37psi running, and when I pull the vacuum on the regulator, the pressure jumps to over 40psi, and the regulator does'nt appear to be leaking, so I am running out of stuff to check. TPS maybe? I had the block on a stand, and I was very meticulous about sealing the lower intake, as well as the upper intake when the motor was in the truck. Changing the cam will be a last resort