Code 41/91

[FoMoCo17]

Are there gaskets on the cross-over tube on the back of the head???

Also, if a KOEP Test is performed after 3 minutes and either Code 41 or 91 or present, it couldn't be from the Thermactor System could it because at this point, the computer has diverted the air to the converters from my understanding or atmosphere ... Is this correct? Do not want to fight and pull this tube off looking for a clog when it doesn't really come into play. Anyway of checking it w/o pulling it off that anyone is aware of???

 

[Blown88GT]

KOEP? Do you mean KOEO? You must be reading the Continuous Memory codes, i.e. 41-C.

There are 3 categories of codes:
O - KOEO, Key On Engine Off
R - KOER, Key On Engine Running
C - CM, Continuous Memory

Disconnecting the battery will clear CM codes. My code reader can do it, too.

No gasket. I was able to test for blockage by attaching a length of hose where the diverter valve hose connected to the hard line. Then blow through it. Thought about pulling that hard line, way too much work for nothing.

I went through the same Wild Goose Chase as you. I did find a bad TAD valve, but it solved nothing. I read your other thread, my ordeal is not unlike yours. I've got a thread going too, it's a big one.

Mine wasn't setting any codes at all, until I replaced the distributor yesterday, needed the PIP, only, but distributor wasn't rebuildable. New dist (PIP), has same road symptoms & other new erratic ones, however, it set Code 14-C, bad PIP. Must get replacement distributor today. Obviously, they don't test these things before leaving the rebuild factory. Cardone is the rebuilder. Don't really want to spend $300 for a distributor: Ford, MSD, Accel, etc.

Go back to Old School Basics: Air, Fuel, Spark. Need all 3 to make Fire.
However, in your case, since it starts & dies, & you've replaced many parts, I'm going to say it's the damn PIP, just like mine. The PIP (Profile Ignition Pickup) is responsible for way more than it should be: engine rpm, crank position, cylinder identification. See Probst p.71. Could also be the TFI, p.120. The TFI is effectively an amplifier for the PIP. Don't expect OBD-I to be that precise, it was the first attempt at engine control management. I suspect it just doesn't have enough time time to get the code for the other side before the engine dies.

Most mechanics replace both the PIP & TFI. I have 2 TFI's, get same results with either one, which indicates they are good.

I have found, that if it's related to electrical in any way, there are few experts. I've seen engineer's eyes glaze over when trying to explain electrical issues. Electrical can do Mechanical but not vice versa.

BTW, you probably should have posted this in your other thread. I feel your pain. My supercharged engine is virtually back to stock & problem still not solved.

 

[FoMoCo17]

Thanks for the "Like" did find that the TFI module was acting up at 2500 rpm but only on the IDM circuit where I could visually watch the miss as it occured with an LED testlight. The PIP and SPOUT looked great. Tomorrow I am taking top end off to solder the 10 pin salt & pepper shakers since over the weekend I noticed it ran a bit better when I twisted and moved these connectors. I had cleaned them and seperated the terminals several times to no avail. Now, they will be fixed once and for all and potential intermittents eliminated. I am solving each problem as I find it once and for all cuz this is getting old. And, they are hard to find. I just got a heat sink for the TFI off a Cougar since this appears to be why Ford had to settle on a class action lawsuit a few years back. And, they never fixed these modules but only relocated them which only partially helped the problem. So to recap: 2500 miss was due to faulty brand new MSD TFI. Spoke to Manager there last week and explained about the Class Action against Ford ... he/they were unaware of this ... imagine that!!! And they source modules from Transpo with the original problem in it just like the ones from your local auto store like Advance. Second problem is these 10 pin connectors ... they shall be removed and connected with soldering and that problem will be gone. The, the computer should be seeing everything. Computer looks VERY reliable so far in all of my tests and its own self-checking feature. I still may have a vacuum leak that I just cannot find and I have done everything imaginable ... but if one is there, I will find it because this car is getting fixed one way or another. Hope this helps you and others ...