Engine misfire why?

I have a 1997 ford f150 with 4.6 v8, and keep getting a misfire no matter what I do, I have put fuel injector cleaner in, changed the plugs, changed the wires, changed the corresponding coil pack to the misfiring cylinders (2 and 4), I tried the screwdriver to the ear trick to make sure the injectors were clicking which they were, I am stumped at this point and would like my fuel mileage to be at a normal rate

Haven't heard any whistling from a vacuum leak, and I have suspicion of the intake manifold gasket leaking but is there a sure fire way to know?

I changed the intake manifold gaskets both lower and upper along with the throttle body gasket, the outcome was an even worse running motor, I have much less power than before and the valves float much more often, could sealing the leak at the gaskets have allowed another leak to arise? It's way beyond my knowledge, please any advice you have would be much appreciated

Ob2 says cylinder one misfire while l drive. How do you correct problem? How do you do a compression check on cylinders?

This ole truck is cursed, new plugs and wires, cleaned MAF, cleaned EGR valve, using higher octane fuel. But the slight miss comes and goes to the point where it’s unreliable. In the morning three miles is fine until it warms up and it will start to miss enough that the dummy light blinks. Please help me good mechanics. I could replace the MAF, and EGR. Which one is it?

Engine warm misses when started give it gas it stops what could it be? I replaced plugs, wires, distr. Cap, rotor buttom, idle control, mass air sensor, fuel filter

Front engine seal leaking which seems to cause all cylinders to misfire.

I need help diagnosis of obd1 port. Customer has changed plugs, wires, coil, distributor, idle air control valve, fuel pressure regulator, map sensor.

I have a 5.0 1990. It started having a bad miss about 6 months ago. I changed the plugs, wires, cap, rotor, coil with no change.

What it does is when starting cold it seems to run OK. I can start off and after about a mile to mile and half it then seems to start have a miss almost like a dead cylinder or something. It does not miss under full pedal and also if I keep the rpm above 2200-2400. It has now started to spark knock a little and lose power when going up hill even with the RPM up.

I thought it may be the trans as it seems to miss or maybe it was the converter bumping or something as it seemed to happen when the trans would go into OD.

I took to trans shop and they said the trans seemed fine but it had a miss.

Someone said maybe a ignition module or something.

In a nut shell if you are going down road after warmed up when it goes into OD with any kind of pull at all it starts a bad missing/jumping like motion. Only does this under load. Even when warm it runs smooth (mostly as it does have alot of miles). Is has a slight miss when reving up up but the bad miss is when driving under load, makes the truck actually bouch like with real bad vibration like in motor/trans area.

It has to be something that changes after warming up.

Any ideas?

Merlin2021,

The check engine light has not been on. Is there an easy check for the 02 sensors-egr-PCM. I know what you mean looking for vacume leaks. This has got to be something simple but finding it my not be.

Thank you.

Merlin2021,

I unplugged the 02 sensor with no change. I did find a vacuum leak yesterday that I fixed but it had no effect.

The motor starts good, idles smooth, takes gas well no bogging or missing. The only time there is a problem is when the truck is going at speed for the trans to go into OD and the converter locks up, it then has a vibration almost like a drive-shaft, when it comes back out of od or at high rpm in od it does not seems to did it nearly as bad.

The trans guys told me twice the trans is fine, but with it only doing this when it goes into OD at a low RPM and when you start giving more gas it then either misses or something is virbating, I had a van that would sometimes kill a plug and with the dead cylinder it also feels the same.

I know this is long winded but this is driving me crazy. I don't have the money for a complete shop check out so I have to try to do it myself.

I appreciate your help very much.