I vote for the " burnt valve" theory because of the absence of a cat and lack of backpressure

 

Haven't tinkered with the injectors but in a way it makes sense. You're gonna need alot of fuel to start, then once you get running, you don't need as much. So I bet the firing pattern for the injectors changes once it senses the engine is running. I'm gonna try the cam timing idea and then we'll see what happens.

 

The injector firing is "batch", so check the stator

 

the only stator i know of is on the distributor. is there another for the fuel injection or does it kick it all?

 

Your posted compression readings do not indicate a burnt valve, or any other top end problem. The sooted plugs sound more like a fuel or air problem.

Check your MAP sensor, it will cause a lean or rich condition. Make sure the vacuum reading to it is the same as the reading from another port at the intake. Low vacuum to the MAP will cause a rich condition.

Pull the hose from the MAP while the engine is idling. The engine should load up or stall. If the idle does not change when the MAP is unplugged, you probably have found your problem.

Check all hoses and vacuum ports for a broken or disconnected hose or cap.

Clean and check the intake air sensor.

Check the readings on the coolant temp sensor for the ECM, not the one for the gauge. It may be bad, making the computer think it is 5 deg outside creating an overly rich condition.

Unhook the plastic intake tube from the throttle body and start the engine to make sure there are no restrictions in the intake system.

Is your battery good? If you have to jump it off the voltages may be too low to operate the ECM correctly. Check the battery voltage with an OHM meter when idling. It should be 13.5 or better.

How is the cap and rotor? Check these good for wear, cracks, corrosion, or arching marks.
These are a few things that I can think of that may be worth looking at.

My cat is empty inside too, but the engine runs fine.

 

Checked the MAP sensor, both by unplugging it and putting it on an identical engine in my truck. Both MAP sensors check out fine (that's good to know) and both engines loaded up when the MAP sensor was unplugged.

The Air Charge Temperature Sensor was removed, cleaned, and tested, and fell within the established criteria set by Ford. The Engine Coolant Temperature Sensor unit is brand new because we were getting an ECT out of Range code from the computer. This corrected that. We will be installing a new O2 sensor soon.

Cap, plugs, wires, and rotor are all brand new from my recent tune up and I haven't found any evidence if its arching, and there's definitely no corrosion in the system.

Did finally notice something out of the ordinary. Usually what tests good on my truck tests good on the Bronco, except tonight when I was checking over some vacuum lines, I finally found a difference between my truck and it. On the left side of the engine (facing it) is a red vacuum tube. When I unplug it from my truck (which I presume to be healthy since it's been well taken care of, and has no codes) the truck says "no, nuh uh." and stalls. When I unplug the same line from the Bronco, it basically says "well hang on, we'll just crank the rpms up and it'll be alright." So...I've found something, I just don't know what it means. Any suggestions? Where does this vacuum line go, and what does it do?

 

Since you have two engines to switch parts out with, try changing the whole dist. The pickup could be bad.

Last ditch effort, change the computer.

You have to find the problem soon, you're running out of things to check.

 

Hot d@#$ we've got somethin now! I changed out the distributor on the Bronco today with mine and boy she really fired up. Still missing at high rpms but she blew a bunch of crap out the back end and really revved up there. I haven't seen it this happy before. So its time for a new stator. I'm wondering if the cats are plugged up because of all the raw fuel that got dumped down in em? Maybe that's making it miss a bit. Either way, I know what I'm doing tomorrow!

I really need to get an exhaust system put on that thing. I can't hear. WHAT?

 

Good Deal. With a new dist. and the timing set, you should be good to go.

After you blow the crud out of it with the foot to floor method it will probably run like new.

 

Well I rebuilt the distributor and put it back in. Its not missing out anymore but it cuts out above like 2500 rpm. I noticed when its idling, and I plug the computer back in, it retards the timing a bunch. Probably 10-15 degrees AFTER top dead center. So I'm gonna pull the codes on it and take a look. I'm almost betting its an electrical connection to a sensor somewhere because every connection I've come across so far is BAD. I swear they left the hood off this thing outside for a year or something. I dunno why everything would be corroded this bad.

 

So I put the code reader on it again tonight. 21 and 33. ECT sensor out of range, and EGR valve not closing properly. So i took the connection loose and once again tested the resistance across the plug (not the sensor) and the voltage, and compared that to my truck and ended up with identical numbers. 18.6kohms and 4.62V . The sensor is brand new and tests within specs. So I started it up and let it run for a good long time, shut it off, and ran the code scanner again. 21/33/42/12. I fixed the 12 code once already. And everytime I scan the computer I get different codes. One time it'll be a 67, the next time i scan, a 42 and the 67 will be gone.

I've tested everything short of getting one of those wiring books from Helm, which I'm gonna go ahead and order. I'm getting sick of chasing ghost codes and I'm starting to think the damn thing is bi-polar. One minute its happy, the next it wants to kill itself.

 

Well everybody, I got home from college for the weekend and decided to tinker with the gray wonder. I tested a few things, and then pulled the computer on it. Funny, the label says "For 3.0L Mercury Sable only". Cool! It thinks its a Merc. Just to be safe, I took the computer out of my truck, and on the back it says "For 3.0L Mecury Sable only." Well...so much for that.

Played around with it some more and noticed if I apply very little throttle, the engine will rev way up to probably around 3 or 4 grand, then something will change in the engine and it'll drop at least 500 rpm. Then you'll hear it change again and the engine will rev up, and it'll just keep doing that more and more. If you try to give it more gas, the rpm drops, the engine starts missing, and the computer adjustments become more noticable. It acts like its getting too much fuel ALL the time and there's no way I can lean it out unless I create a vacuum leak somewhere.

I'm still constantly getting code 21 and code 33, and sometimes a code for the HEGO sensor. Even though they're brand new, the computer says they're bad. So I'm going to guess its in the wiring somewhere. Problem is so far everything's checking out to be the same with my truck, my truck runs and this thing doesn't. The only thing I'm left with is either the timing is out of wack on the valves, or it needs a valve job...or both. Can't get into that for a few more weeks. And if that doesn't fix it, I'm DEFINITELY out of ideas. Does this ring a bell with anyone? Thanks for your help.

 

You may have already tried this and I missed it.

Have you checked the Throttle Position Sensor? That could cause the problem you have now.

With key on, engine off, you should get a reading of around .97 volts at closed throttle, and just under to just over 5 volts wide open throttle.

With key off, TPS unplugged, check the resistance and make sure as you open the throttle the resistance changes smoothly.

 

No you haven't missed it. I tested that yesterday (before your post actually) and it tested good. To be sure, I put the one from my truck on it, and it didn't run any different.

It really acts like something in the fuel system cuz it always sounds like its running too rich. I dunno if its the computer telling it to do that or if its something wrong in the fuel. It is getting a little bit better over time, which is interesting. Maybe it just needs a good hard run. But first I need to plug up a few exhaust leaks, like the big one under the cab!

 

Well for those of you who still paying attention to this lovely old thread, I got slowed down because college started back up. So I'm back to working on it this weekend.

After swapping the computers with my truck and Bronco to see if it was the computer, I determined it wasn't. I also got a fuel pressure gauge setup on the truck. When idling, it runs about 35 psi. When revved up, it drops to 32 psi. If you unplug the fuel pressure regulator, it runs 40 psi always. I'm not sure why the regulator is pulling it down to 32 psi, but I know if you create some sort of a vaccuum leak, the pressure will bounce up to 35 and the engine runs pretty good. Not sure what that's all about...almost acts like its working too good.

Still not running right though. Hope to get a new exhaust system put on it soon and replace the EGR tube that rusted in two. Maybe then we'll have something figured out. Thanks for all your help guys. I'll keep working.