prob NO one can fix

Sounds like it's not getting enough fuel. I would change the filter first, then if that deosn't work, get a cheap fuel pressure gage, the type that goes on the fuel rail fitting. Check to see if you have good fuel pressure, if not it is your pump. I say this becuase your ignition SHOULD be OK given the things you have said and a lean O2 reading is usualy a fuel system problem. Other posibility could be bad O2 sensors, or wiring to them, but start with the filter than check fuel pressure.

Did the guy replace the Maf? Maybe its just a dirty maf. You are setting timing with the spout out correct?

5.0's dont have knock sensors.

The spout only allows or locks out the EEC from advancing the timing. As the spout in/out is changing the timing, then it is working and so if the TFI and hall sensor in the distributor, so rule these out. Also should be able to rule out the EEC too. What i see is that with less timing it runs better (spout out), and your EEC is throwing lean o2 codes, these are symptons of a fuel problem. If the ignition was week you would get rich o2 codes, not lean ones, unless the engine was not firing at all. there is the far out posibility that the FPR is stuck open or that the diaphram in it has a leak, But these are really rare occurance items on any vehicle and nearly unheard of on 5.0's.

That leaves me back at filter and pump. these things can change quickly, so unless you have checked them since this problem appears, they could be bad.

If the problem is not in the supply system, then it could be in the injection wiring, bad ground possibly. You could check the orange wire at the back of the intake to see if it is connected good and also check the wire condition.

Also, I would suggest you run the EEC through a complete cylinder ballance check, just to make sure you don't have a bad cylinder or injector. If you do not know how to perform this, read your manual. Basicaly you do a KOER test and at the end of the test you hit WOT momentaraly, the EEC will cycle through shutting down one cylinder at a time. Then give you fail codes for the cyliders that do not pass. (are not contributing at 85%) then if you WOT again it will retest at a 75% threshold, you can repeat this test a total of three times, if a cylinder fails on the third test, it is not contributing at all and has either zero compression or injector has failed.

What grade of fuel are u using?
When the spout is connected, the computer adjusts timing according to throttle position,air intake(maf), coolant temp,and barometric pressure. If youre running 87 octane, thats not enough, especially if the motor has carbon buildup on the pistons. Set the timing to 8* and put the sprout in, and check again.

The SPOUT is the EEC's way of modiying the timing. When it is out the EC can not change timing and as the distridutor has no means of this (no vac. or mech. advance) then the timing will be whatever the base timing is set at ALL the time. With it in the EEC can advance the ignition, and will advance the ignition the minute you install the spout. From your symptoms your having it appears you engine does not like to run with any advance at all, this is not normal. So the engine does not 'like' advance and the O2 indicates lean, both of those symptoms corespond to not enough fuel.

The orange wire on the back of the motor is the injector ground.

The EEC ground is near the EEC, easy to find when you remove the kick pannel, but not a problem here as the EEC has shown no indications of malfunction. Thowing codes, manipulating ignition timing, and running engine, even if poorly, would all indicate the EEC is functioning fine.


Now, if you engine is runing "really, really good" with the spout out, there could be a completely differnt explenation for this all. It could be that your timing is way-way out of whack... This can occcure when the harmonic damper goes bad. The outer ring of the damper will spin and the timing marks will be incorrect, even though you time it to the correct mark it will not be anywhere near where you are setting it.

OR the timing chain could be bad (streched) and jumped a tooth, not likely though... I have seen an engine run off a tooth, but not for long before the chain gave out all together.

ive gotten bits and pieces of this thread, so forgive anything i missed.

the MAF wire is clean, right? its being dirty can cause lots of detonation.

do you have a FP gauge mounted so you can see FP when you get detonation?

is the EGR still hooked up (removing it w/o burning a chip, Tweecer'ing it, etc, can cause detonation)?

remember, at WOT there is no lambda input (for helping with diagnosis perhaps).

you are getting a good spark at higher rpms (or where ever the detonation occurs)?

if you suspect a lot of build up in the chambers (artificially raising the compression ratio), a lot of guys have had good luck with products like Seafoam (i cant attest to them, as i have not used them).

those were the couple random thoughts i had. i suspect they have been thought of already, but i wanted to hit them again in case not all had been hit.

good luck.

I've got two suggestions:

Replace the TFI. They're cheap. There's a slight possibilty it could be sending garbage to the rest of the ignition system.

Install a fuel pressure guage that can be read from inside of the car while you are driving. Your fuel pressure is fine when running at idle but it may help to see what's going on with the fuel system and particularly the fuel regulator as throttle settings and vac pressure changes over the range of the power band.

make sure your timing is not a couple of teeth off

sillyg said:

make sure your timing is not a couple of teeth off

Click to expand...

Silly, if you mean that the dizzy gear/rotor position could be off by a tooth or more, this is a bit of a misnomer.

as long as the dizzy has physical clearance to move (for adjustment), one cannot be a tooth off. now if you got to where you could not physically move the dizzy because of interferance (the TFI hitting something, etc), a restab is in order. short of that, the dizzy can be adjusted to correct having stabbed it in 'a tooth off'.

i think this is where you were going and you knew this, but i wanted to expand and clarify a little.

HISSIN50 said:

Silly, if you mean that the dizzy gear/rotor position could be off by a tooth or more, this is a bit of a misnomer.

as long as the dizzy has physical clearance to move (for adjustment), one cannot be a tooth off. now if you got to where you could not physically move the dizzy because of interferance (the TFI hitting something, etc), a restab is in order. short of that, the dizzy can be adjusted to correct having stabbed it in 'a tooth off'.

i think this is where you were going and you knew this, but i wanted to expand and clarify a little.

Click to expand...

You beat me to it.

...and he already said his timing was at 10*. Makes no difference how it's stabbed.

I am really starting to suspect you Harmonc damper is bad. You say you have run spout out at 20deg. base timing and it ran good. That would rule out timing chain and should rule out fuel system too. How far up can you run the timing befor you have a problem? Sounds like the damper has spun, or there is a problem with the EEC and SPOUT circuit. Either I would not rule out.

Sorry for questioning things so much, but without all the info it looked like a fuel problem. It's realy is difficult to diagnose anything your not working on yourself with the proper tools, and imposible without a lot of information. Keep it coming, someone will figure this one out I'm sure.

Reminds me of this old story, about a little old lady who takes her car to the mechanic and says, "whenever I drive to the store and get Strawberry ice cream my car won't start, but when I get Vanilla ice cream it starts just fine"

So the mechanic drove with the little old lady to the store for Strawberry ice cream.

Come to find out whenever the lady got Strawberry ice cream the stockboy had to go back to the store room to get it and it was hand packed ice cream, and it took longer then just getting the Vanilla that was in the cas ready to go. That was just enough time for her car to get a vapor lock!

Moral of the story: Don't dismis the symptoms/conditions no matter how far fetched they may sound, and you can get to the root of the problem untill you get some strawberry ice cream...

the EGR: at cruise/part throttle, it allows spent (inert) gasses into the chambers to cool things down and improve fuel economy. the puter knows when the EGR is active (gasses being passed into the chambers) and dials in a ton of timing (the diluted mixture is not as volatile as when these gasses are not being introduced).

some guys remove the EGR function, but dont 'let the computer know'. so now there is no dilution in the mixture, but there is a ton of timing being added (the puter still thinks EGR gasses are being introduced) - result is detonation for some.
the reason i brought this up is to address the timing issues. you seem to run alright with locked out timing, but not so when the puter can modify it.

if the EGR is leaking, that can diminish the idle. a common test is to apply vac to the EGR - if the idle diminishes or dies, the EGR was likely alright. if no change is noted, there is a problem which should be addressed.

i will add that quite a few guys run locked out timing. it is very common with forced induction on foxes and on stockish SN cars (they are very prone to detonation). it is a bandaid, but if it works........... (some guys like to run 20-25* -sometimes more, locked out timing).


as Jd has brought up, i would give the balancer a real good once over. you dont want a compromised one on there. the outer ring does slip (timing marks dont seem correct for the performance of the vehicle). also, the outer ring can shift on the inner hub (appears that the balancer wobbles). the elastomer between the two rings being deteriorated is often a sign of a bad unit.

i agree that if the motor runs alright one way (Locked out timing) but not with puter advance, you have narrowed down a lot of systems. again, why i suggested the EGR as it is one major thing that has timing advancement built into the puter mapping.

i would not go to a dealer. they are good for newer stuff. i would hit a local stang shop if i HAD to go to a shop at all. it sounds like you have a good working knowledge and it is just gonna take some more time and tweaking to get it figured out.

my two cents. good luck.

Hissn50 may be on to something there. And the EGR system is prone to problems too. You should be getting codes for this though. If it was not operating at all (stuck open/closed or EVP sensor not connected) it would throw a code. But that does not say it could not be some kind of anomily with the sensor and such, as the EGR does have a big effect on the timing.

For that matter so does the TPS and the BAP. Do you have a source for a spare TPS and BAP sensor.. like a friends car. Swap them out just to eliminate them from the issue and while your at it you may want to do the same with the EGR and vaccum solenoid that operates it. I would not buy anything for parts untill you know what you need or you must, otherwise this could leave you broke, and thats the surest way I know to discurage you from fixing and/or owning a 5.0.

Again, the right tools could likely diagnose this much easier. May want to take it to a truely compitent shop, not Ford unless you must, but a local tuner shop, hopefully someone with late model Ford/Mustang experience.