Most dont know that too much lateral movement within the distributor shaft can translate into idle fluxuations and issues idling and FYI the TFI module isnt the only thing prone to overheating ...;- The Halls Effect sensor is inside the EMI/RF chamber where the spark is hot n heavy and the heat combined causes issues when the magnets in the pickup dont detect the reluctor wheel good enough too or if theres been too much damage to the distributor shaft bearing due to camshaft walk...
If you pop the distributor cap and attach a magnetic indicator base to a spot that it will attach to and just touch the rotor with the tip ,zero it out then twist the rotor back n forth youll see the amount of total runout .
When you look at the bottom of this distributor from my 88 Mustang LX you can see how much aluminum was worn away causing my issue...My runout was at .038" and my bottom bushing had alot of side play too..I got it with 202k and it never saw a T-Chin replacement either and after doing the required maintenance it was running killer..
Tolerance limits are between .005" and .015" of lateral travel.
While youre there you should also check the T-Chain deflection for excessive slack and that requires a hefty 1/2" socket wrench and a cheater bar to turn the crank back n forth to see the slack..
Back n forth tolerance shouldnt have any more than .050"..If you have more than .050" freeplay in your crank before the rotor tip moves you need a new timingchain..........
View: https://www.youtube.com/watch?v=4_f5ukZVri8&t=1s
I bought a new distributor off AutoZone and set it in place tightened down the holddown bolt and checked lateal runout again with the digital dial indicator and this time the runout was set at .030" from thenplace that made it.
I pulled the gear and the collar and shimmed it until I got .005" on the new distributor and the thing was purring like a baby tiger as I had to pull the shaft and shim the upper part until the lateral slack was at .005"..
I also did the TFI module relocation at the same time and for close to two years the things been running pretty sweetly...
When the distributor isnt within specs and good the timing becomes erratic and this not only causes the TFI module to get a lil hotter than normal and cause running and idle issues but it does this to the ECU itself aswell from all the recorrecting it ahs to do to stay in sync.
So if your vehicle has over 130k miles and youve never done the recommended T-Chain replacement along with new waterpump and thermostat plus new front crank seal between 80k and 120k chances are youre gonna also need a new thrust plate installed especially if its a 5 speed model...Just installing a new distributor to replace one that had too much lower bearing side play wont fix the issue it will be just a temporary bandaid.
My 351w in my worktruck has 255k miles and has had two T-Chain replacements along with waterpump ,T-Chain and seals and each time the Timing Chain had alot of stretch and comes with the territory when theres a manual transmission present in a 4200lb vehicle with a 1 ton payload limit..I also replace the $13.00 thrust plate aswell for added insurance each time too......
Nobody really takes the time to realize the camshaft spins twice as fast as the crank and that all the springs combined create a rotating force that takes alot of exertion to get it moving and that job is given to a single chain up front....
If they designed engines to have two t-chains one front and one rear then the forces would be more equalled out but have alot of pressure to turn it..
My 351w has like 80lbs of spring pressure closed and like 250lbs open on just 1 valve and theres 16 of them along with 16 lifters and 16 pushrods with 16 rocker arms rocking at 1.6:1 ratio.....
Nothing lasts forever and somethings gotta wear down...........LOL
Good Luck
