My f150 has the 300 inline 6 in it but I have had many problems with the engine electrical system ever since I got it about a month ago. right now it will stall right after I start it when it is warm and will also do this sometimes when I put it in gear but only when it is warm. I has not yet stalled will in gear unless I accelerate, then It will hesitate and try to stall but I am able to keep it from stalling if accelerate quickly or push the peddle down about halfway. other than the hesitating when I first take off it will run fine. keep in minid though, the truck runs almost perfect when it is cold. It also has a pinging/pre ignition problem that I am so far unable to fix. timing has been checked and it was only 1 degree off and it is still that way because the mechanic didn't think it was a big issue. The truck also seems to be low on power even for a 6cyl. it has much less power than the day I drove it home and I can't figure out why. I have replaced the IACV, the main high pressure fuel pump, the fuel filter, water pumper, water neck, oxygen sensor, fuel pressure regulator, power steering pump, tensioner pulley, and the serpentine belt. mechanic told me the egr valve is bad but I would like to get more opinions before I replaced it yet because i am not sure the egr could cause any of these problems. I have also run sea foam and fuel injector cleaner in it . truck is also running on premium fuel and the pinging seems to get worse the warmer the motor gets. I also had the catalytic converters tested and they tested good. the mechanic suppossedly tested the tps and said it was also good.let me know what you all think! any suggestions would be helpfull!

 

i think a vacuum leak would cause all of the symptoms you are seeing:

a vacuum leak would lean out your air/fuel mix.

so...
1. it runs better when cold b/c the choke is on, which richens the mixture.

2. you can avoid it stalling by stomping the gas- because the accelerator pump shot kicks in...which richens the mixture.

3. it pings because...you guessed it...the mixture is too lean.

check all your vacuum hoses, and any vacuum plugs.

 

"...the egr valve is bad..." What your mechanic said could very well be true. Have the codes been pulled?

 

so the mechanic told me to replace the egr , oxygen sensor, egr position sensor, and some sort of vacumn solonoid on the side of the engine just below the egr . I replaced the oxygen sensor and there was no change. I have been running premium fuel in it and the pinging is a lot less noticable but still there. The truck seems to stall more when it is cold. for example: the truck did not stall at all for nearly two weeks while it has been unseasonably warm here in virginia and I also noticed that somehow during this time period the vacumn line for the egr valve had come off. so I am not sure if the warmer weather or the vacumn line coming off the egr fixed the stalling issue but right now it runs almost perfect except for some misfire at idle ,the pinging, some hesitation upon acceration after the engine is warm, and of course being very low on power. also i did noticed a new sympton while driving down the interstate with the truck loaded down with all my lawn equipment. as you know the truck is very low on power even for an I6 in my opinion so when I am driving it down the interstate I have to keep the pedal to the floor most of the time except when I am going down hill. every 30 seconds or so the truck would suddenly lose a lot more power and I would start to deccelerate but then it will correct itself and then in another thirty seconds to a minute it will do it again, especially going up a hill. I put the egr vacumn hose back on to see if that would correct the issue but it did not, I only noticed that it seemed to happen less than it did before. This is the first time I have really towed anything with this truck on the interstate so it may have had this problem since I bought it and I just didn't notice it before because I wasn't towing anything with it over the winter. The truck does not do this when it not towing anything so thats why I never noticed it before. right now the truck barely has enough power to pull itself up a hill on the interstate. if the speed limit is 60 mph the truck will slow down to about 55 or 50 mph when going up a hill if it us unloaded and not towing anything. if it is towing it can slow down to 40 mph trying to go up a hill . The truck had way more power than this when I first bought it and I don't know what has caused it to lose power! the motor also has good compression. most of the cylinders have about 150 psi of compression , one of them has 155 and another one has 137. so I don't think compression is an issue. The truck has a c6 automatic transmission just so you know. can the egr cause it to ping and lose power? also, I put a new High pressure fuel pump on it because the old one hummed very loud but the new one does the same thing! If the turn signal is on then the hum gets louder and queiter in sync with the turn signal, in fact the pitch of the hum changes when anything electrical on the truck is turned on or off on the truck. could this be maybe a low voltage issue with the fuel pump? this truck has frustrated me to no end! and I will greatly appreciate all advice you can give me!

 

All the systems in an EFI engine must be operating correctly for the engine to run the way it should. Rather than throwing parts at it, pull the codes or have them pulled (some of the parts houses do this). Then you will know what system(s) to focus on for a fix.

 

I had the codes pulled and the oxygen sensor wasn't working and neither was the egr, the egr position sensor, and there is some vacumn soloniod that has the part where the vacumn tube plugs on broken off. so I am going to fix those and see what happens. I already fixed the oxygen sensor and nothing changed. I would still like to know why my brand new fuel pump is so noisy . sometimes the hum goes away for a few minutes on its own and then it comes back. it is especially noisy at engine idle and the noise pitch changes depending on what electrical components are on in the truck . such as the wipers,headlights, and blinkers which makes me think it is and electrical problem but I am also wondering if it could be the new borg warner fuel pressure regulator I put on it.