I've got 2004 4.7L V8 all stock with 90,000 miles. Been a fantastic truck up till yesterday. Started up great and took off, after about 500 feet it started to lose power and could feel the vibration from missfire and check eng light came on. I drove very slow about 1/4 mile to gas station. Took a reading and got the P0300 code. It would start up fine and idol but was missfiring. Giving it gas made it worse. Towed it back to house and went to work.

1st - Replaced spark plugs w Champ Copper and cleaned throttle body. Plugs were very dry and electrodes almost gone. It started right up but idol still missfiring. Giving it gas made it worse. Spray a little starter fluid in throttle body and would rev right up.

2nd - Replaced the PCV valve, it was very dirty. Also put some Sea Foam injector treatment in the tank. Now it will not start. Can hear the fuel pump come on and cranks fine. Seems to almost start but no go. If I spray starter fluid in throttle body, it starts right up for about 3 seconds and dies.

My guess is I've got a fuel delivery problem. What should I check and in what order?

Because my problem happened so suddenly, I'm thinking it's the PCM. I've seen a few others on this list go through several checks and end up getting a referb PCM to fix the problem. Anyone got any better ideas?

Thanks!

Mark

 

Just had my wife start the truck as I was spraying starter fluid in throttle body. Started and ran OK as long as I was spraying short bursts into TB. Stop the spray and motor would die in 2 or 3 seconds.

I'm not getting fuel but not sure why? What should I start testing?

 

The PCM controls the fuel pump relay. It is pin 85 on the relay. You should see this energize for 3 seconds when you turn the switch on and should come on and stay on while cranking. I kind of expect its your PCM based on the way it started to fail. If your fuel pump or relay went out it would run for a little maybe start to misfire a little but quickly die and most likely never start again.

 

Thanks, I think it might be PCM as well.

I found two places in Florida that sell them. Auto Computer Exchange at $171 and All Computer Resources at $208 and both come with Lifetime Warranty if I send back my old PCM. Anyone on this list know anything about these two company?

 

Update: Just before I ordered a new PCM thought I would test to see if my PCM was sending a signal to injectors. It was, so now I was thinking fuel problem? I took a sample of the fuel and found LOTS of water in my tank! Proceeded to drop the tank and dump all the gas, then cleaned it out by hand. The fuel pump had corrosion on it and the filter was very dirty so purchased a new pump. I put all that back together and removed all my fuel injectors. They were all cooked from the water. I put 5 gal of gas in the tank with a gas additive called Quickcare the boat people use for water in the tank. I used the new fuel pump to flush all the fuel lines clean. Then installed the new injectors. Once the system filled up with fuel, she started right up and been running great!

The water came from one of my boat tanks that I rotate into the truck to keep the boat fuel fresh. I will be checking the boat fuel before I ever do this again... I had about 1 gal of water in 10 gal of gas!

 

Well glad that got solved.... you should put dry gas into your fuel tank for the next few fill ups to make sure it's all out of there...

1/10 is about average for a boat... that's one of the reasons why they don't put ethanol in the boat fuel b/c it binds with water and then gums up everything very quickly... might want to check out your boat too... little bit of dry gas additive goes a long way.