91 Ford F-150 5.0 113,000 miles owned for 2 months replaced plugs and wires had a fuel system service, use hi grade fuel it runs smooth yet on acceleration it seems to struggle. Weak in regards to power. When I first start it in the morning it dies the first time and after that it is just fine. The check engine light comes on and off intermittently yet it stores no codes to tell me what is wrong. Oh and I replaced the tranny. Can anyone Please help.

 

Check and make sure your timing is 10*BTDC. Un-plug the SPOUT connector first.

 

i baught a code reader from autozone for 29.00 it brung up my codes when there was no light on also check juice can on fenderwell might be rusted out.

 

What is a juice can? Sorry I am not familiar with that.

Thanks

 

its a can usually on passanger side fender well with 2 vacume lines running to it.looks like a large juice can not sure if youre truck has one or not but might be worth a check

 

Thanks for the heads up. I'll keep you posted.

 

There are actually TWO of those "juice cans" if he has cruise control. The one on the left fender is for the EGR/AIR systems. The other, if he has cruise control, will be down near the frame rail on the left side (driver's) near the rad support. They are vacuum reservoirs to keep things from going wonky and dropping out when the throttle is opened up and manifold vacuum drops. There is actually a 3rd reservoir under the dash to operate all the A/C and Heat servos. There should be a white tube going in next to the AC lines into the box where the Evap coil is.

Check all those little plastic lines for splits and cracks. Depending on where you live, the environment is not so nice to that plastic. Quickest way to check for leaks is to disconnect EVERYTHING from the vac tree and cap off the nipples, leaving ONLY the MAP sensor connected. If the engine smooths out you at least know the leak is not on the intake plenum or manifold, and not the EGR. If you want to check it a bit closer on the intake plenum, cap off the EGR with a piece of steel can between the EGR valve and the plenum. Check vacuum with a gauge, just to make sure. It should be close to 20 inches Hg at idle. I personally wouldn't settle for anything less than 18. Don't forget the Evap Recovery line. It goes in right between the venturis on the TB. Best place to hook up the vacuum gauge when looking for leaks. Hook the lines back up one at a time starting with the brake booster line, and keep checking that vacuum. That will at least start you on the right line if you see a change in vacuum.

If the vacuum isn't at least 18 inches with everything disconnected and the EGR capped, take the PCV loose from the valve cover and cap it too. If it's still less than 18, you probably have a leaking plenum or intake gasket. The plenum gasket is a relatively common failure on the 5.0's with 100K+ on them. Have a look at my gallery, and you'll see what I found after two stealerships gave up on it.

 

Did You Get A chance To Check It Yet

 

have not had time to mess with it next week I will and let you know what happened. I set the timing it was about 10 degrees out it runs better as far as power goes although I have an engine knock i guess it sounds like it has bad gas in it if you know what i mean so I put super unleaded in it to see if anything changes.

 

Im having a similar problem with my '95, no acceleration especially on hills, check light always on. turned out to be the TPS on my '93 with a 4.9 straight 6...im wondering if it could be the same.

 

yeah mine used to do that before i set the timing back to 10 (4.9 I6)...but if your doing that u might as well set it to 12 BTDC gives a little more MPG and low end torque