5.8 supercab. Had trans rebuilt to correct shudder. Transmission is now fine but I still have a miss and seems to have a shudder type vibration when engine is not loaded while driving. When this occurs if I kick it down it will smooth out, also, at idle you can feel a miss if you put your hand in front of the tail pipe. Had it tuned before getting the trans rebuilt an even gave the mechanic the correct wiring routing for the plug wires. After the tune it gave a MAP code. They replaced the MAP pick up and when it was finished no codes were visible. I bought it about 3 weeks ago and when I test drove it there seemed to be none of these problems. The longer I drive it the worse it seems to get. Have another appointment next Tuesday with the garage where it was tuned. Any suggestions as to what I can have them check? Thanks, Jack

 

Make sure your wires are routed correctly. Good diagrams on this thread:
https://www.ford-trucks.com/forums/6...e-routing.html

The shake you're getting might not be transmission related, in fact if it is happening at regular driving I would suggest it is somewhere else, perhaps u-joints. Generally your transmission shudder is going to happy at TC lockup, not always though

 

More information, while I was making the appointment with the garage I left the truck running (about 5 minutes) and my neighbor who just happened to be there picking up his car, said when I pulled out in front of him the truck smoked (grey smoke) for about 1 mile after I pulled out then cleared up. I also just checked the gas gauge and I used over a quarter of a tank to go about 35 miles (front tank) after picking it up from the transmission rebuild.

Skandocious,I gave the mechanic a copy of the wire routing diagram before they tuned it last week and they said they did it according the the diagram. Now afraid to take it anywhere for fear I might cause more problems.

 

I've been going through everything I can think of that may have caused this. The only additive I put in the truck is Seafoam. I put it in both gas tanks. I don't know if it could cause the vibration and smoking problem. Now both tanks are near empty and I'll refill without additives. Does anyone remember similar problems with Seafoam? Thanks again, Jack

 

Seafoam in the tank shouldn't cause a vibration but its very likely that it was causing that smoke.

 

Umm, maybe if he's running the truck with a mix of 1 quart of gasoline to a tank full of Seafoam. What his neighbor described as grey smoke may have been black smoke and white ash. The cats will build up ash which loosens when they cool (assuming there's not a lot of oil vapor in the exhaust) If he used 1/4 tank to go 35 miles, that's LOUSY fuel mileage, even for a 5.8 with 4.10's in the pumpkin.

Did you check the Fuel Pressure Regulator to see if it's leaking into the intake? The fact it smooths out when you step on it says one of two things: A.) It's getting too much fuel burn at light throttle and opening the throttle helps it burn, or B.) you have a vacuum leak somewhere that's worse under light throttle. B would not explain the smoke, though. Seafoam will mix with the fuel, and you'd have to put a lot of it in the tank to see the truck smoke. I poured two cans in mine, and watched for smoke, and saw absolutely none. A leaking fuel pressure regulator will make it smoke like a coal fired locomotive, and give you horrible fuel mileage. That covers two of the symptoms. If it's leaking bad enough, it may also cause light throttle miss. Pull the plugs, and see if any of them are blackened with soot and fouling, but do that AFTER you check the FPR. Disconnect the vacuum line at the plenum and drop it in a cup to catch the fuel if the FPR is leaking, and keep it off your engine. Spilled fuel is dangerous, especially while doing any kind of testing that may ignite fumes. Jumper the Fuel Pump Test connection on the DCL to make the pump run continuously, and turn on the ignition key. See if any fuel comes out the vacuum line. If it does, you need an FPR.

One other thing I'd do is run a compression check to make sure all 8 are within 20-25% of each other. Compression imbalance can cause some vibration as well as low RPM missing.

 

Found a Master mechanic that works for Ford and does repairs at his home on weekends. He's going to look at it for me. I'll post the problem and fix. Thanks Jack

 

Just thought of one more thing that I did. When I bought the truck it was on the rear tank and I filled the front and rear tank then added Seafoam, ran the rear tank low and switched to the front tank and ran that for awhile before getting the trans rebuilt. After getting the trans done it was still on the front tank and it just came to me that I didn't have the problem when test driving it on the rear tank before I bought it up until I switched to the front tank. Won't be able to drive it until morning (family dinner) to check it. Any Thoughts?

 

Bad news I guess. The mechanic drove it today. List goes like this, when tune up was done one of the plug wires was touching the exhaust manifold so it was burned and sparking, next, idle was searching and high. He noticed that as soon as I got out of the truck while he was sliding into the drivers seat. Test drive indicated a bad U joint. He said probably the front one. After the test drive he popped the hood and found a wire rigged to hold the idle high. As soon as the idle slowed down a noticable slight knock showed up . His guess is a rod or bearing. I guess I'll get some estimates on a rebuild and go from there. Thanks for all your help. Jack

 

Damn dude... Get ready to break that piggy bank Sorry to hear it. On the bright side, it sounds like your mechanic knows what hes doing. Good luck with all that. Keep us posted.