I have a 91 F150 302 that has been having a hesitation problem in the low speeds when the engine gets warm. I've tried everything under the sun so far to fix it, but to no avail. I do have one tuned up truck though now! I have replaced the TFI module on the outside of the distributor, and that seems to have helped. I am now very suspect of the hall effect coil inside. I have not been able to find any information on the procedure to replace this little unit. It does not appear hard....take out the distributor, remove the TFI module....then what? Does the hall effect just unbolt?

Any info would be appreciated...

 

What you are calling a hall effect switch is what I have always heard called the pickup coil. Some vehicles do have a specific hall effect switch, though. Heres the bad news, replacing it requires removing the distributor and removing the shaft from it. It looks like they could have made it come out the top if they had accounted for this when it was designed. To get the shaft out you will have to Remove the distributor gear, the factory gears seem to be very brittle, you can't just beat it off with a hammer and punch (you can but it won't be in one piece when your done). At least I never could. Ford recomends replacing both the pickup and module at the same time. When one goes it usually causes the other to run hotter, shortening it life. It's not uncommon to replace a module and then have to replace the pickup sixmonths down the road. Did I replace both the last time I had a module go out? Nope, but I will probably wish I had.

 

I really doubt if it will cure your problem but I can explain how to remove it. Remove dist, rotor, module, octane rod, roll pin & gear, roll pin & collar, pull shaft out, 2 screws on pick-up coil, remove pick-up coil. Requires special tools to press the gear off & on. Comes preassembled on reman. distributors.

 

Well, I'm running out of ideas to cure my problem. What do you suggest? I am getting ready to break down and either live with it or take it to the dealer (ugh).

 

The same problem on my '92 was fixed by replacing the throttle body itself. I had a large leak in the intake caused by a bad manifold gasket resulting in a very high idle. After that was fixed and I still had idle and hesitation I replaced the high priced throttle body item. That fixed the way the engine idled and for the most part some of the lag I was feeling when accelerating away from a stop, but I also had a torque converter problem. This was my first transmission maintenance after 156K miles on the original transmission and converter so I didn't feel too bad about doing this work. Now it drives like I remember years ago. I like it! Maybe you should get a couple of opinions from transmissions shops? I went to 3 before I picked the one who gave me honest answers and a list of customers to call. Money well spent.

All that transmission talk is just to say that the fix is not always related to what seems to be obvious. I thought I could rule out a problem by looking elsewhere but instead found the real cause of the hesitation. I don't think it is your distributor either. If the engine is running the spark is getting through fine.

 

The truck runs fantastic, with great acceleration when cold. 10 minutes into the drive, when the engine gets warm, it will hesitate at the lower speeds with mild acceleration. If I floor it, it does good.

The truck is a 91 and only has 57,000 miles on it. I do need the tranmssion serviced...I was going to get it flushed. Perhaps that may help. It is just so strange to me that the problem only happens when warm, not all the time. Seems like an electrical thing to me...

 

[updated:LAST EDITED ON 14-Feb-02 AT 05:52 PM (EST)]I've got a problem too. Trying to pin it down now.

Regardless, what I have is that when I'm doing light acceleration or even holding a light throttle opening, it's like there is a cylinder that falls off occasionally. Went through the ignition, fuel injectors were cleaned and set up the same, still have the little problem. Feels like ignition, but we're looking at the fuel pressure regulator.

Earlier, I had felt like it was the trans locking and unlocking, but that seems to be fine.

 

Try unplugging the EGR vacuum line, plug it off, and test ride for a few minutes. The engine light will be on. If that helps the hesitation, you need to remove the EGR valve and install a restrictor of some sort, then reinstall the EGR valve(if it is OK and clean).Reinstall the vacuum line after the test ride, Engine light should go off.
Phil

 

It is frustrating isn't it. Doing a search on this board seems to show 302 engines have this problem fairly often and nobody seems to be able to pin it down to one particular thing.

I had a 1979 F100 I6.......maybe I should have kept it....