PLEASE HELP - I am tryin to help my grandpa fix his 89 F150 4.9. It idles very rough (Cold or hot) and bucks / kicks on acceleration. To date I have changed the: Plugs, Cap, Rotor, Wires, Fuel Filter, O2 Sensor, Egr Valve Relay, Throlle Pos. Sensor, Thermostat (195),Ignition Coil, Ignition module, Etc. I also cleaned and checked operation of (All good I believe): Egr Valve, Mass Air Flow valve, Temperature Sensor, and ran a bottle of Techtron fuel system cleaner through the system in hopes of breaking up any valve carbon. All no good. I'm far from and expert but I'm tryin. I need some help please. Gramps doesn't have any money for a repair shop to fix this and he's basically stranded the way this is running.

 

Check for vacuum leaks , Also get a read on the fuel pressure & see what it says . Do you know how to access the diagnostic trouble codes ? How did the problem begin ? If you look around the engine bay & the radiator support you will see various ground wires , Its very important that all these grounds are clean & secure .

 

Thanks Paul: It's a bit dark right now so I'll try the ground check in the A.M. The problem seemed to start after I changed the plugs, cap and rotor (And was stupid in putting some of that .99 s.t.p. fuel junk in the tank for him. First I thought maybe I messed up the firing order on the cap but rechecking that proved o.k. (B.T.W. - The only thing I'm not positive of is if the wires are back onto the posts in the proper place. I know the order is correct (And I'm positive I took them off 1 at a time and tryed to match positions as I replaced them.). Is there some way to tell if they are in the correct spots. Some kind of marking that signifies cylinder #1 on the cap. I looked the cap inside and out for some markings and there are none on it. So it has me wondering if the whole order might be off by 1 space. Doubt it, but as I said, I'm pulling out my hair right now. I also did verify that the store gave me the correct plug number and gap settings. Anyway, looking forward to any more assistance that can be offered. I'll post if the ground check helps.

 

The firing order is 153624 clockwise rotation . If you have a Ford distributor cap the No 1 position is indicated , I even think most aftermarket caps for those engines are marked to show No 1 too . Another thing to check is to make sure the plugs are tight , Those engines use a tapered plug & sometimes even though they seem tight they may not be so double check them , Esp the No 6 plug because its the hardest to access . If all this started after you replaced the plugs , wires & cap then its a safe bet either you are one wire off or you have a loose spark plug .

 

I GIVE UP GUY'S. I took it to a shop to help retrieve the codes. Came up code 41 - O2 sensor constant lean. (And I watched how he jumped the plugs out to get the code. Next time I'll know how to do it myself.). Considering the O2 sensor was replaced 2 weeks ago, it's fair to eliminate that. BUT I CHANGED IT AGAIN (Was under life time warranty so what the heck.). Still the same. Shop mechanic said most likely I've got valve problems or a dead cylinder. Told Pop's it's time to bury the old girl and get another motor. Thanks anyway for you help Paul. I'll be a board regular from now on.:*

 

If you got code 41 there is a test procedure to determine what the problem is , Just because that code , or any code for that matter , is stored , that doesnt nessecarily mean a particular part has failed . A good mechanic will take the time to do some tests before they condemn a part regardless . If the O2 sensor is saying its staying lean all the time , The Pinpoint Test for that code says to first check for any unmetered air leaks , such as an intake leak . If the engine gets too much air it will set Code 41 because the engine is getting more air than it needs , the O2 Sensor doesnt know the difference . Check for any vacuum , intake leaks . The lower intake gaskets on those engines are very prone to leaks . If your Grand Dad cant afford a new vehicle & we can help you repair his then all you need is a little know how & aimed in the right direction to repair it .

 

Hi Paul: Just to put this one to bed as they say: You were absolutely correct. It was a duel vaccuum leak - 1 gasket related - 1 hose related. I was over that thing for hours looking, feeling, and listening but I couldn't detect the leaks. Luckily the shop only charged $150 dollars to repair (Which is a lot for pop's, but better than $20,000 for a new vehicle.). I'm amazed how poorly such a small thing can make a vehicle perform. But it makes sense now. The cpu was richening the mixture to compensate for the extra air thus the crappy performance. Wish I was better at troubleshooting. Could have saved him the money. But he's happy with what I did accomplish. Anyway thanx again for your assistance.

 

Yvonne , Thanks for letting us know the results . It always helps to get feedback , that way everyone can benefit . Cheers.