So i have been a long time watcher of your videos i find them Educational and entertaining. But i have an issue and would like to ask a question....or two.

What I have is a 1993 Ford F150, it has a 4.9l 300cui Inline 6 Great engine. 5spd manual trans.

The truck has been very reliable and a strong runner for years has about 180k on the engine still running strong up untill about a year ago. I was going down the high way and i droped a gear and went to pass and all of a sudden it started Bucking and misfiring almost as if it was flooding, and every once in a while it does. It is a fuel injected engine and had never had this issue untill one day out of the blue.

I have done a full tune up on the engine, new wires, cap, rotors, plugs. with no fix

The engine only does the misfiring and bucking when you try to put it under load and go above about 2500 RPM. When it is just idling with no load and you rev the engine it will not misfire Much if at all But when you are driving down the road (unless you really gingerly ease into the throttle) above id say 2500 rpm it will misfire and flood abit. and if you try to go from a stop to hard acceleration if will missfire and flood. only if you ease into it slowly can you take it above 2500 RPM

years ago i put duel stacks on it and took off the Catalytic converter and mufflers. and it still has the o2 sensor in its original place. The only Codes that i have gotten from the engine are that there is insufficient flow to the EGR Valve. But i have been getting that code for about 5 or so years now ever since i took out the Catalytic converter. And the engine issues that i am talking about only just poped up a year ago.

Since then i have replaced spark plugs, wire,cap,rotor....just recently it has had a new fuel pump and a new filter, I have made sure the timing is right.

I am not 100% it is the EGR valve just because of the timing of the misfire issue. I am not ready to give up on the old girl she is a good running truck and i have done alot of work to the truck and it is a family heirloom.

But i do have a theory and i want your opinion.

in the 2016 Christmas season i put Christmas lights on my truck and ran them through a power converter from my battery, And through that time i am well convinced that i have Cooked my alternator, it will keep a battery charged But anytime that you put a significant load on it the volt meter will drop immediately, significant load meaning headlights and anything else be it AC, heater,wiper blades ECT. So i know i need to replace the alternator.

Could Low voltage output from the alternator Cause the engine to have misfiring issues under load. I can to this hypothesis last night when i was running the headlights and the engine seemed to start flooding and misfiring more then normal???? I value your ideas and hope to hear back from you.

My other thought could be that maybe it has Jumped time on the gears But my Uncle said that if it had done that i would likely have the issue all the time vs just at higher rpm. I just want to fix it i miss driving the truck.

Thanx Chris.

Comments (1)
No. 1-1
ScottyKilmer
ScottyKilmer

Editor

unfortunately it's SO old, the on board diagnostics is basically non existant. So an old pro is needed to manually test everything from fuel pressure to injector on time to ignition oscilliscope readings. good luck