Developed a miss, Looking for ideas

[Jwade]

Hello All,
My 90' Coupe has developed what seems to be an ignition miss. It acts just like a plug wire or coil wire breaking down, is the same sort of stumble. However, it only does it when it's warmed up after I've driven it for a while. I have already replaced the cap & rotor, and the plug & coil wires (even though I couldn't see them arching anywhere). The car has fairly new plugs in it, Bosch Platinums with the quad ground straps.

I'm looking for ideas here to see if anyone else has experienced something similar? I'm thinking that it could be the coil, or maybe even the ignition module, however, in my experience those 2 usually just cause the car to quit running altogether...not a intermittent miss....but there's not much else for ignition parts left to change either.

Thanks for any help you can provide!

Jwade

[Dark_5.0]

If it were me I would change the coil.

[Jwade]

Thanks for the reply, I'm thinking that will be next....it appears to be the original coil, and the car has just turned 90K. I was especially thinking this because it doesn't happen until it gets hot.

I'll give it a try!

Thanks again!

[Jwade]

I replaced the coil, and it was okay for about a day, but it has started missing again. I've pretty much gone through all of the ignition now, so I guess it's time to start looking at injectors now....this is really getting to be a P-I-T-A!!

[Capri306]

I had a similar problem and it ended up being the TFI-IV module, or ignition module in English. It would be a complete DOG after a little high-speed driving on the expressway, bogging and coughing the whole way home. You could be having the same condition. Have it checked at a parts store for free if you like, but I'd replace it anyway because the factory modules tended to die before or around the 100k mark. And yes, Ford modules are finnicky like that; they work for a while, then sputter once warm. Bad transistors (internal part) are to blame, along with bad heatsink engineering.

Have you ever changed the HEGO (oxygen) sensors? If not, those should be next on your shortlist. EEC-IV's rely heavily on HEGO signal to run properly.

After that, I would suspect a fuel pump or injector, but it's EXTREMELY hard to tell without actually hearing the car running. Is it just one cylinder not firing, or like a "lean-out" condition? Any check engine light?

I will say this once: get rid of those Bosch Platinum +4 spark plugs NOW.

[Jwade]

Thanks for the reply!

The miss is just a quick sputter when it happens....if you've ever felt an arching plug or coil wire....it feels exactly the same....definatley more of a missing cylinder, not really a bog. I was looking at it tonight, and it appears that it has the original module in the distributor, so I think you may be onto something...that may well be the culprit. I bought this car about 3 months ago, and the previous owner only drove it on occasion, so the miles were low for a 90' model. I've been driving it a lot more than he did, almost daily, and took a sudden 3000 mile trip on the HotRod Powertour in June....so it may not be used to this much driving either!

I think I'll go ahead and replace that module since it is so old.

Thanks for the advice, and I'll let you know how it turns out.

[Jwade]

BTW - Not sure on the o2 sensors...they may be original as well.

On the Bosch plugs....they were put in just before I bought the car....I'm kind of an old school type guy myself, would rather (and had better luck) running AC Delco's in my 468ci Chevelle than any Bosch or NGK BS that some guys push.

I'm interested to hear your story on the Bosch +4's? I can tell you that I would never pay that kind of $$ for plugs myself....but haven't bothered with them since they were already in there when I bought it.

Thanks again!

[lxfiveoh]

I had a similiar problem to the one you describe. I changed the TFI module, but not the cap & rotor or wires, as those were fairly new.

It started much like yours, only when warmed up. Eventually, it started to do it all the time. When the miss occurred, you could see the tach DROP for that split second. Also for that split second, it felt like the engine just died...

In my case, it was the PIP / Hall Effect Sensor. This is the "stuff" that's on the inside of the distributor that sends the signal to the TFI module.

The easy way out for me was to replace the distributor with a unit from NAPA. I simply marked where everything was pointing, removed the old distributor, and installed the new one in the same exact position. Then, I swapped over all the "old" parts (cap, rotor, TFI) and all was well.

When I spun the old distributor in my hand, you could hear that PIP just rubbing all over something in there. It was horrible.

Good luck,

[Jwade]

Hey Nelson, that is the exact symtoms I'm seeing. My tach drops for that split second too, and it acts like it loses all fire, but just for like a half second...I went ahead and bought a new TFI module this evening, the one in there now appears to be the original unit anyway, and surely won't hurt to replace. I have noticed that the hall/effect wheel has a lot of corrosion on it, not really rust, but sort of a white colored film all over it.

I think I'll go ahead and pull the whole distributor out and inspect all of its internals before I install the new module....will make it much easier to install the module anyway.

Thanks a ton for the reply!

[lxfiveoh]

No problem...let us know how it turns out.

[rdy2rn2]

i feel your pain bro and there is something that many 5.0 owners overlook or forget. the e7te heads have a hard time on their own keeping ANY plugs tight. especially the passenger side front 2 plugs. i did all that you did and replaced part after part and turned out that it was a loose plug that tends to work loose over time and exhibits the same problem. i have made it a priority to check each of my plugs atleast everyother week. what i did find that has worked thus far is a small dab at the end closest to the main body of the plug on the threads to apply a dab of red loctite. the plugs still come out, no damage occurs and the plugs do not work out.