My trucks playing with me I got a 1999 f150 4.6l v8 I started misfiring, stalling, rough idle, jerking trans, I pulled codes got 1 random misfire, 5 and 6 misfire codes, 2 egr codes, 3 trans codes, 2 o2 codes so I started with the basics checked spark, wires had spark, plugs were good, then I checked fuel pressure it was a little low 20 psi low so replaced fuel pump no changed, switched fuel injectors 5 and 6 to 1 and 2 no changed in codes, vacuum lines are good no leaks sprayed with carb clean all around vac hoses no change, next i disconnected exhaust to check for clogged cats, no change, now i decided to check compression on 5 and 6, only 20 psi lower then the rest, so I put little bit of oil in spark plug hole no change in compression, so I decided to pull the heads, took heads out sent them out to get check, machine shop said leaking intake and exhaust valaves, did a valve job on the heads, installed head with new head gaskets and bolts, also installed new timing chains guides and tensioners, put all back together put new plugs wires intake gaskets, throttle body gaskets, put truck back together and fires it up runs great, 2 days later doin the same original misfire problem, so switch fuel injectors back again, started truck, runs great no codes but egr and o2 codes, so drove truck for a whole week ran great all week trans ran perfect could barely tell the truck was on, end of the week friday night started misfiring AGAIN, so I let it sit over night and next morning runs great wat the hell!!! Seems like when I drive the truck for a while it starts and when it cools down it stops I drove about 50 miles and started misfiring almost as if somethings getting to hot and causing it to run like crap, new pcm only 4 months old sorry such a long post any help ideas im at a dead end rode

 

Sounds like you may be chasing down a few demons. It would help if you posted the exact codes you're currently getting. There are a lot of O2 and EGR codes.

Remove the throttle body and clean the EGR ports. Last one I did was a 2001 F150 4.6L and I spent at least 30 minutes digging out what looked like charcoal. It doesn't have to be pristine, but it needs to be clear. Might as well change your EGR valve while you're at it.

A misfire when hot can often be caused by a failing ignition coil.

Fuel pressure spec for your truck is 28-45 PSI when running, and 35-45 PSI with the key on and engine off. Something overlooked at times is the fuel pressure with the key off. Hook up your gauge and turn the key to the run position, then turn it off. If you rapidly lose pressure, you may have a sticking injector.

When you changed the fuel pump, I'll assume you also changed the strainer or you used a new assembly. When you had the fuel tank out, did you notice any rust on the inside? If so, the fuel strainer rapidly clogs with rust. The only real solution to that issue is to replace the tank.

For future reference, a 20 PSI difference in a compression test generally doesn't warrant any sort of repair. With a compression test, you're looking for consistency. If the difference from your highest reading and lowest is within 10%, that's excellent. I consider 10-15% to be very good, and 15-25% is still acceptable. I have no idea what your numbers were, but if your highest reading was 180 and the lowest was 160 for example, that's 11% difference. 160 high and 140 low is 12.5%. 140 high and 120 low is 14%. Anything below 100 PSI is unacceptable.

The chart below shows the maximum variance permitted in the service manual. The numbers shown reflect a 25% variance.



And for the more obvious things. I'll assume that you're using the correct plugs and they're properly gapped. Motorcraft finewire platinum or Autolite XP is ideal. I'll also assume that your wires are not damaged or old. And of course, fuel filter not overdue for a change.

 

New coil packs and wires.

You can't just "check spark"

 

Ok thanks for the input yes everything ive put in my truck is new new plugs wires, fuel pump, strainer, coil packs are new, replaced my egr valve and dpfe sensor, cleaned throttle body, cleaned egr ports (completely clogged), new fuel filter, only thing thats not new is fuel injectors and I was thinking about replacing my vacuum hoses kind of old I also wondering why its misfiring on 5 and 6 only ive and I cant get it to act up unless I drive it for a long time in order to check it last time it happened I was on the highway about 30 whiles away from home was goin 45 in a 70 speeding limit with pedal all the way to the floor

Today its running great no pronlem only codes im getting are o2 and egr codes ill post codes up later

 

How about posting the exact codes?

 

Here the codes im getting
P0300
P0305
P0306
P0750
P0755
P0743
P0133
P0153
P0401
Just started acting up on me right now on the highway

 

Wow.

Random misfire
Cyl 5 misfire
Cyl 6 misfire
Shift sol A
Shift sol B
TCC circuit
Bank 1, sensor 1 failure
Bank2, sensor 1 failure
EGR insufficient flow

So first thing, your check engine light has been flashing I presume. Don't drive when it flashes. That's how cats are destroyed.

Secondly, I can only assume these codes and issues started at the same time. But if you're the type that will drive indefinitely with a check engine light, you may very well have multiple issues and the help I can offer is pretty limited without having the truck in front of me.

If this did all occur at the same time, I'm thinking chaffed wires, bad ground, or faulty PCM. If it weren't for the trans codes. But that's not to say other components aren't fried as a result of driving it in that condition.

Sorry I can't be of more help.

 

All those codes at the same time is indicative of a blown fuse. I don't remember exactly which one. I think it may also have something to do with one of the large multi-wire connectors through the firewall.

 

See my transmission codes only come on when it starts misfiring when its not misfiring trans runs great shifts good and all im gonna install my old pcm to see if it solves my problem ive looked at the wire harness behind the motor because I kno they get melted some times and short components out but no sign of that also got a new code today. P1451
Only thing I can think of is wiring issue

 

Do check all your fuses first. I'll take a stab - check fuse #23 under the hood.

 

Update I disconnected my injector connector for 5 and 6 and my truck has no change, checked fuel injector connector on 5 and 6 with noid light an did not blink, compared with the rest of the injectors all the rest blinked, now I had 2 choices either look up wire diagram on all data or just replace my pcm, I replaced my pcm with the origional and reprogrammed it, and is running great now but ima put it to the real test tommorow ima get it hot on the highway