My 1992 F-150 4.9 liter with 267,000 miles finally started giving me trouble. It has been in the local shop for 1 week after I troubleshot it for 3 days.
When you power brake the truck it starts shuttering as if it were a grounded spark plug wire.
When the truck is idling it is fine.
When the shuttering starts the mechanic say he can see the miss-firing jump from one cylinder to another randomly.
New distributor with new Hall Effect sensor was installed,
New plugs
New distributor cap
New rotor button
New wires
New ignition module
New coil
New fuel filter
New fuel pressure regulator
New O2 sensor
Checked coolant temp sensor
Checked idle motor plunger
Checked throttle position sensor
New MAP sensor
New computer (found the blown blue capacitors on the board)
The truck has no codes or stored codes.
Every sensor is working
Fuel pressure is good
All spark plugs are firing
Fuel injectors are switching on and off and are lot clogged.
Compression is good
The truck is at a very reputable mechanic but I think he would be open to any suggestions.
Any suggestion on what to check next would be appreciated.

 

Too much EGR?

95 F-150 4.9L missing/bucking while cruising

 

Roader,
Thanks for the information but I installed a piece of brass between the intake and the EGR to block off the EGR exhaust into the intake. I purchased 2 EGR gaskets mounted the first gasket on the intake then the brass block off plate next another gasket and last bolted the EGR back on.

Thanks,

Gregg

 

One thing I did not do when I installed the EGR block off plate was I did not drill the 1/8 inch hole in the center so mine is completely blocked off. Could not drilling the 1/8 inch hole be my problem?
Thanks

Gregg

 

Not enough EGR? The normal EGR fix is to restrict EGR flow, not block it completely. Restricting EGR to a 1/8" opening fixed the partial-throttle bucking on my 300, but completely blocked EGR ports caused partial-throttle bucking on my Accord.

 

Thanks Roader,
I will have the mechanic drill the 1/8 hole in it tomorrow and see if that fixes it and report back.
Gregg

 

Gregg, you type way faster than I do!

 

plug off your vacuum brake booster vac source and try again.

 

I will be stopping by Thursday evening to talk with the mech. I will ask him to try that if he has not done this yet.

Thanks,

Gregg

 

Mine has a stumble/studder when you first take off, like it's hitting a deadspot in the throttle (Possible TPS Sensor failing).

Will be watching this thread

 

I lean towards the clutch for the violent shuddering, and the stumbling is not giving it enough gas (off idle). That's my fifty years of driving experience.

 

Even in Idle, it does it..

It has nothing to do with the driving aspect, it's just a "Dead spot"..

 

My 95 has the same dead spot as Wesley. Subscribing

 

I wanted to give everyone an update on my truck. While at the mechanics it got to the point it would run for about 20 minutes then shut off like switching the ignition off. You would then wait about 25 minutes for it to cool down then it would start back up and run and cut back off. Well the mechanic got tired of messing with the truck so I finally got it home.
I did a little testing myself today because I'm suspecting it could be the pickup in the distributor even though the mechanic installed a new distributor.
From a cold truck I started it up and it ran for 21 minutes then shut off.
It took 26 minutes for it to cool before starting back up and ran for 7 minutes.
I then immediately blew compressed air on the distributor for about 30 seconds.
The truck then started back up. So the truck kept running for 30 minutes while I let a fan blow down on top of the distributor and blew compressed air on it. After running for 30 minutes I removed the fan and stopped blowing compressed air and the truck continued to run for 7 minutes. Even though the truck has a new distributor on it I feel I have proved that the Pick-up circuit is overheating and cooling back down and allowing the truck to start. By blowing cool air on it I was able to keep the truck running.

My plan is to by another new distributor and try it. What do you all think.

Thanks for any help.

Gregg

 

Take the dizzy out, get receipt for that one, and take it to the parts house.....bite bullet, buy another, NEW one, not remaned....or pull the distributor back out, and replace the stator with a Motorcraft one instead. Not BWD, MPI, or off brand.