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I have a '90 bronco 351w w/E4OD, speed density. Motor was weak (horrible compression) so I had it rebuilt. Machinist pointed out to me all the exhaust valves were white indicating a lean condition, so I had been pondering the reason for that. The only upgrade I did prior to pulling the motor was shorty headers and K/N replacement filter. I could only afford a stock rebuild, no ported heads with bigger valves,forged pistons, or roller cam for now. The machinist advised me to upgrade to an r/v cam(federal mogul 204/214 @ .050), so I did, now with the new motor in, my bronco runs rough, and stumbles going down the road. It starts fine and does'nt stall, but it aint right. I installed the cam and timing gears, so I know it is all lined up right(marks on gears facing each other). I got it sitting at 14 btdc. Just been searching threads and checking things others had problems with to no avail so far. Is it the darn speed density system not adjusting to the cam? I do have the E4OD, which I understand is controlled by the pcm, so what are my options? Can a chip be added without messing up the E4OD? Checked for codes, and all is good. Need some advice, Thanks

 

Did you remove the EGR or the Thermactor (air pump)? those two are known to create lean conditions, but given the fact you had such low compression, i could think that alone could cause some sort of lean condition, as the lack of pressure would lead to incomplete combustion.

About the K/N filter, get rid of it ASAP and get back to the stock air filter.

 

No it is all there. Just replaced the air inj. check valves. Why would I want to get rid of the K/N?

 

Doesn't work well with these truck, specially MAF ones (if you ever plan to make yours a MAF). Now regarding your problem, apparently you did some mods, and as you already pointed out, maybe the SD setting isn't getting the readings right, a chip can be added, even though not many like the idea, i, personally, would prefer upgrading to MAF.

The parts you need for the MAF upgrade: Harness from a MAF truck with a E4OD, the top of the airbox and the air-tubes going from the TB to the airbox, i think that would be all.

 

Machinists have great ideas but if the cam you installed is not ground for a speed density system, you are going to have trouble with it. Speed density can handle changes in duration for the most part but little if any changes in separation. Cams ground to fall within speed density parameters will be noted in their specs.

14 degrees BTDC is a bit far for the speed density (when you consider that 8 BTDC is typical OEM). I've not dealt with the changes that come with an RV cam but 12 BTDC is the extreme end of anything I've ever done with a stock 302 or 351.

As for the lean condition, ANY vacuum leak has the potential to cause a lean condition... that's just physics. What is the condition/age of your O2 sensor? Age and crud will cause it to send the PCM rotten information that could cause the PCM to "think" it needs to lean out a mixture that does not need to be. There are a few other potential causes but if it is running that badly, I would suggest pulling codes and see what the PCM "tells" you. Codes can be present even if you have never had a "check engine" light come on.

 

Yeah, I have been considering both options, but the chip may be the cheapest solution. There is a guy down the road that is supposively good with fords. I spoke to him briefly yesterday and he said he'll look at my bronco first to make sure it isnt something simple, and that he can "cook" the pcm and add a chip if needed. I guess he does dynotune as well, or maybe that is part of the process. I do have the E4OD, so I hope that does'nt change things. Just kinda need the bronco, and money is a little tight.

 

Re-flashing the PCM will only go so far with SD if the cam is not an SD grind and there is no chip that will compensate for something that the equipment in the truck cannot compensate for. A chip merely changes the parameters of the existing programming. It cannot compensate for timing changes needed based upon air flow changes for the simple fact that SD does not have the capacity to make those changes.

Oh, and Encho is dead on about tossing the K&N if you make the MAF swap. You will trash the MAF sensor inside of two months if you keep that air filter. The oil-impregnated filter bleeds tiny oil particles into the MAF sensor which kills it.

 

grey streak, the exhaust is dual that had a small connector pipe connecting the two pipes together for the o2 sensor. I replaced the o2 sensor about a year ago, but the pipe broke apart, so I had the hole welded in the one pipe, and left the sensor in the other that was left, with the open end welded also of course. The o2 sensor could have been damaged during welding, and also it may not be positioned in the exhaust stream properly. Aside from the weak motor, it ran fine prior to rebuild. The rebuild kit came from northern auto parts for a '87 thru '93 351w. It had upgrade options, which included three camshafts, all of which noted might require an aftermark chip, so I guess I should have done more research. As far as the timing goes the farther I advance it the better it runs, and that is why I left it at 14 btdc. I decided to manually adjust the timing without using the light, but when I checked it with the light afterwards, it was around 30 btdc, and I aint running it like that. Yes I did unplug the spout connector.

 

I have checked for codes, and there are only pass codes, no trouble codes.

 

Was the engine at full operating temp when you set timing?

Your O2 sensor... as a result of the situation you described is it getting exhaust stream from ALL 8 cylinders or just four? That's a big deal right there if it is only "reading" 4 cylinders.

 

The computer treats all cylinders the same so it really doesn't matter how many cylinders the O2 sees.
The O2 should be positioned directly in the exhaust stream however, off to itself on a dead ended pipe isn't a good location. I'd also suggest you post the full cam specs so we can determine if it is SD friendly, if it isn't you may have to live with some drivability issues.. assuming you don't now have a bad or misrouted plug wire or a fuel delivery problem. What was the firing order of the cam you installed anyway?

 

Conanski, here is the cam specs:
Speed Pro CS1084R
351W Firing Order, Pro-2000 Performance Camshaft, Use With Hydraulic Lifters
Attributes
Cam Type : Hydraulic
Exhaust Lift (Inches) : .295"
Exhaust Lift (mm) : 7.493 mm
Exhaust Valve Lift 1 (Inches) : .472"
Exhaust Valve Lift 1 (mm) : 11.989 mm
Intake Lift (Inches) : .280"
Intake Lift (mm) : 7.112 mm
Intake Valve Lift 1 (Inches) : .448"
Intake Valve Lift 1 (mm) : 11.379 mm
Exhaust Duration : 214 Deg.
Intake Duration : 204 Deg.
Lobe Centerline (Exhaust) : 117 Deg.
Lobe Centerline (Intake) : 107 Deg.
Lope Separation : 112 Deg.
Overlap : 51 Deg.

 

I beg to differ on this point. The computer knows NOTHING about individual cylinders past the spark timing sequence. The O2 sensor reads oxygen levels ONLY across the ENTIRE engine so half the volume of exhaust gasses equates to half the oxygen found in the system from what the PCM is "expecting" to find... the O2 sensor ONLY reads oxygen levels... so it can't tell that there are fewer OTHER exhaust gasses in the mix as well. So... HALF the engine supplying exhaust to the O2 sensor designed for that engine will "assume" a rich condition and tell the PCM to lean out the mix! Best to know HOW the sensors work before assuming they won't affect things.

 

I agree with you streak. If running duals you need a decent crossover pipe with the O2 sensor inbetween, so I will get that straightened out first before I buy a sd friendly cam.

 

Sorry that's where you're wrong, the O2 does not read oxygen levels it reads air/fuel ratios, and since the computer applies the same fuel trims to all injectors the A/F ratios will be the same at the O2 sensor regardless how many cylinders it sees.