I have a '93 with a 5.0 and it is surging. I am possitive it is not the tranny. I can have the truck in neutral and bring up the RPM and you can hear the engine rpm changing. What would cause this? Thank You in advance.

 

Mine was doing the same thing not too long ago and I had guessed it was a half-clogged injector. I but some injector cleaner in my next tank and the problem cleared up before I could look into it and take them off myself.

 

Got to be the most p*ss poor description I've read in a long time. Put a little effort into it! You want it to remain the same? Turn the engine off. The idle won't budge!

 

Is this any better?? With the Truck in neutral or park. I can place my foot on the gas pedal, depress it a little bit, to BRING UP THE RPM hold it in a steady position and the engine RPM fluctuates up and down. I can also feel it when I am accelerating steadily up an incline or hill.


We are all on here to help each other and learn new things, not be jerks and put people down!

 

Calm down, he's just kidding and giving you a hard time, that's what he does. haha You could start by checking the plugs and wires, a bad plug or wire could make the truck shudder and buck, and noticeably alter the rpm's. This will get worse with load. The injector thing is possible too. I had bad wiring going to one injector and when it would cut out I would get terrible surging, the truck would buck pretty bad.

 

I can have the truck in neutral and bring up the RPM and you can hear the engine rpm changing. What engine doesn't change sound when RPM when increased? Sorry if I came off a little abrasive, but the statement left alot to be desired as far as describing a drivability problem. Your re-statement of the problem, you must admit, gives us a lot more to work with. So, lets see if we can collectively figure out your truck's problem! The first thing that comes to my mind is a blatant Vac leak. Then, check fuel pressure at the rail including bleed down time & Error code scans. Manually: https://www.f150forum.com/f10/how-re...es-obdi-10907/ or the easy $22.77 method w/ digital numeric display & memory: http://www.handsontools.com/Equus-In...ol_p_5574.html I sincerely hope this helps or at least points you in the right direction w/ minimal unnecessary part purchases during the adventure. See.... I only sound like a righteous *sshole, but I lack the conviction to carry out the complete transformation!

 

Ya you were right. The first description did suck. I did a diagnostic on the truck using the jumper wire method and nothing came up. Is there a specific problem area to start looking for a vacume leak?? You know A common area where people tipically find leaks. Thanks

 

If you did the scan properly , you would get at least get 1 pause 1 pause 1 (meaning 111). this tells you there are no active codes. If you are only getting the surge above 2K, that's when Vac from the EGR solenoid actuates the EGR valve and the EGR Valve diaphragm might & could leak. Below that RPM. the Valve is not activated, and no Vac is present at the Valve. A surge at idle is another story. A lot of this stuff is not that easy to describe or explain, That's why almost all my posts end up edited at least once.

 

honestly sounds like a fuel problem, I'd check your filter and lines as well as checking how the fuel pump sounds and builds pressure. My older truck did the same thing up hills, I would have to floor it just to creep up them. I changed filter and was a sweet after, no problems after that.

 

The surge could be Air, Fuel, Fire, or exhaust. Start with one one the three and work to eliminate the possibility. Get a good vacuum gauge or pump with gauge and check the vacuum. You can manually activate the throttle under the hood after you remove the cover from the butterfly valve. WATCH FOR MOVING PARTS WHILE WORKING ON A RUNNING ENGINE. A vacuum leak will be a low reading on the gauge at that RPM range. Typically the vacuum should be around 16 or so inches. A gauge that bounces indicates engine problems, typically valve issues. A gauge that slowly loses vacuum is usually clogged cats. If the vacuum is steady and the rpm fluctuates then check the next item on the list. As you basically eliminated the Air and exhaust from the equation.