Hello, my 1994 F150 5.8L needs some help!

It doesn't start unless I disconnect the air intake and give it a shot of ether (even then it has a hard time lighting up. However it will start without ether when the engine is up at running temperature. Once running it will idle (a little rough) and has some hesitation with acceleration. It really lacks power! When I drive it and step hard on the pedal it revs up and starts to bogg and jerks/surges with minimal power.

Given the above symptoms I thought it was a fuel issue so I changed the fuel filter and had the fuel pressure checked at the rail and it was up to specks.

My next thought would be replacing the cap, rotors and wires (and possibly the plugs too). Any suggestions?

 

it might be possible that your timing chain could have too much slack in it and allowing it run at idle but try putting in the stuff like you said cap rotor bug and wires along with new plugs. and while you're at it change the fuel filter that's in line plus get a bottle of injector cleaner and pour it into the tank

 

Yes, absolutely change the plugs too. With a new plug check for a strong blue/white spark at a well grounded plug. Having changed the cap, rotor, plugs, and wires, and you see a little yellow spark that is an indication of a weak coil.

Also, when performing a tune up it is very important to set the timing. I suspect the poor performance may be caused by the base timing being retarded. Follow the directions on the sticker inside the engine compartment. SPOUT will need to be disconnected.

Poor idle quality is an indication of possible carbon build up on IAC Idle Air Control motor. Clean this, and the throttle body, with plastic safe throttle body cleaner.

Check for vacuum leaks using propane gas. Here is a pic of such a set up:

http://oldfuelinjection.com/images/v...enrichment.jpg

Since propane burns clean you wont see any smoke if there is a vacuum leak. Watch a tach instead for increases in engine rpm's. Propane is far superior in detecting even the smallest of vacuum leaks, and avoids corrosive residual from aerosol methods.

Check that the EGR valve is receiving no vacuum at idle. The EGR valve should be serviced every 60,000 miles to clean carbon build up, and assure good seating of the valve when closed.

Feel free to ask questions. Please post updates.
Cheers.

 

This is great....thanks for the advice fellas I will start trouble shooting soon! Alright I will change the plugs and have a look at the timing chain. I will look for vacuum leaks as well. You'll have to excuse my ignorance....what does EGR stand for (is it some sort of Gas Regulator?)? If it is a Gas Regulator then by checking the fuel pressure at the rail should eliminate that right?

Thanks again for your input!!

 

EGR stands for Exhaust Gas Recirculation. It is part of emission controls. The valve allows a metered amount of exhaust gas to enter back into the combustion chamber during the burning process. This cools the combustion temp., and thereby reduces the formation of Nitrogen Oxides (NOx). When NOx is released into the atmosphere a chemical reaction occurs with ultraviolet light producing tropospheric ozone, commenly refered to as "smog".

Typically, vacuum is used to open the EGR valve once the engine has reached operating temp., and above idle speeds.

An EGR valve that is open at idle will cause a rough idle, and stalls. There must not be any vacuum to the valve at idle at anytime. Sometimes carbon build up on the valve seat will not allow the valve to close even when there is no vacuum applied.

So no, the EGR valve is not part of the fuel delivery system; the fuel pressure regulator is a different componet not part of emission controls.

But, while we are on the subject of the fuel pressure regulator another check would be to pull the vacuum line from the fuel pressure regualtor, and make sure there is no fuel present at that vacuum line. If there is it means the diaphragm inside the fuel pressure regulator is ruptured, and should be renewed. You stated that the fuel pressure is within specs', however, it's a simple, easy check just to make sure. The fuel pressure regulator is located on the fuel rail.

 

Great, thank you very much for the in depth information. I fixed 90% of the problem by changing the cap,rotor,wires and plugs. One plug was not firing at all...I pulled the plug off it was badly corroded.

It starts and runs "good/ok" but it has a mis every now again. At approximately 1500 rpm or so it has an occasional mis. It appear to run better at higher RPM.

Any more suggestions. I have just done the cap,rotor,wires,plugs and checked the EGR for fuel vapour. I haven't done anything else yet.

Thanks again for the insight

 

Hook up a vacuum gauge, and read the needle when the miss occurs. Here is a pic of vacuum gauge readings.

http://www.freeasestudyguides.com/gr...m-readings.gif

What you want to look for is a fluttering needle, (bottom row middle). A needle that drops everytime the miss occurs. This would indicate, or rule out, a mechanical problem in the valvetrain like a sticking valve etc...

I suspect the cylinder with the corroded plug is the same cylinder the miss it occuring. You might try increasing the plug gap another .010 on that particular plug. This will cause the coil to put out more voltage, and hence, a stronger spark for more effective air/fuel burn. Again, that spark should appear blue/white to the eye. You can use a small piece of vacuum host to fit over the spark plug terminal, and the male coil terminal, and ground the plug well, and watch the spark.

You want to make sure the EGR valve is not getting any vacuum at idle.

The fuel pressure regulator, on the other hand, is no fuel at the vacuum line.

Look forward to more updates.

 

First of all thanks again for your information and patience.

Yes the Vacuum hose on the EGR has suction at idle. However, I'm not sure wether it makes a difference wether the engine was warm or not (it was warm in this case). Please see the attached picture so as to make sure I have the right vacuum hose

What would happen if I disconnected my vacuum hose from my EGR (besides the emissions)?

Thanks

 

Also, does it matter which vacuum line I use for the vacuum test?

thanks again

 

Until your regular responder replies, it looks like you are working on the fuel pressure regulator and it should always have vacuum on it as long as the engine is running.
The EGR valve is much larger and should be located more to the rear of the engine and most likely on the passenger side.
It may even have a large piece of tubing about 3/4 in. diameter attached to the bottom of it . That tubing should go to the exhaust manifold.