I have a 2001 Ford F-250 5.4L V8. 117,000 miles. The problem I have been relentlessly trying to diagnose is a slight bucking that occurs under load when the truck is in overdrive. When the truck bumps up to higher RPM's it is fine but when it is around 1500-1700 RPMs on the highway it does a small buck like I'm hitting a bump in the road. I know there are many threads on this but none of them have gotten me any closer to a resolution. It also seems to have a bit of power loss when accelerating.

Things I have done so far.
-Spark plugs and COP replaced about 1000 miles ago
-New fuel filter
-Cleaned MAF sensor
-Cleaned throttle body
-New PCV
-Seafoam treatment in gas and through brake booster.

Any other suggestions?


Alex

 

I also seem to be leaking a small amount of coolant and smells a bit rich. Not sure if that helps. Also no CEL or codes are present.

 

When you say "No Codes" is it because you hooked up a code reader and it said no codes? There could be codes stored even without the CEL lighting up. Maybe P0401 or P0402.

 

By "No Codes" I meant I hooked up a code reader to it and there were no codes stored.

Alex

 

I wish I had another idea for you.

 

This afternoon I was exploring the idea that it might be a vacuum leak. While I was up in the engine bay I was throttling up the car manually and noticed that there was a loud sucking sound coming from the throttle body area as I gave the truck gas. Anyone know what this could be? Maybe a bad throttle body?

 

Could be normal, we have no way of hearing what you're hearing.

You have a mild misfire, an extremely common issue on the modular engines. You need to use a scan tool to go into the Mode $06 data and look at the individual misfire counts to pinpoint the offending cylinder(s). A simple code reader isn't going to be useful. Without knowing which cylinder(s) to focus on, you're left with simply throwing parts at the problem and hoping you get lucky (you didn't).

See this thread, ignore all the little side detours. https://www.ford-trucks.com/forums/1...bd1-obdll.html

 

Check the PCV hose, particularly at the elbow where it goes into the valve body, for a vacuum leak.

 

I'm not a mechanic, nor know what I'm speaking of here, but what if (instead of the engine bucking) its your tranny?

 

It *might* be a torque converter chatter, but it usually (overwhelmingly) due to a misfire. TC chatter is usually described as feeling like one is running over a washboard and it isn't limited to certain driving conditions. A mild misfire is extremely common as the engine experiences it's maximum load with a somewhat lean mixture which usually occurs as one is:

1. Lugging up a hill with light throttle in overdrive
2. Just up-shifted to overdrive as the speed passes through 45-55 mph.
3. Towing heavy, especially in overdrive,


That is why it is critical to DO THE DIAGNOSTICS. They eliminate extraneous concerns and help you focus on the actual symptom(s).

Here's an excellent video from Wells:

 

I have a Innova 3130 Scan tool and I still cant seem to be able to extrapolate the data from the article above. I cant find Mode $06 data. The non-continuous tests I can run are $01, $03, $10, $50, $53, $54, $55, and $56. Any help in finding the correst data would be helpful.

 

Nevermind. I figured it out. Thank you for the video projectSHO89 for the video. That was extremely helpful. Intermittent misfire in cylinder 4.... lucky me.

 

I was able to get ahold of the previous owner and he said the shop he went to used Ford Coils and NGK Plugs. Since im only replacing 1 plug and 1 coil do I need them to match the current setup? If so where is the best place to get Ford OEM plugs other then the dealership.

 

Many auto parts stores and online sellers carry them. Easy to get.

 

Back when I had a repair shop I had problems with NGK plugs in the modular engines such as the 5.4L. I don't know why, but we fixed several intermittent misfires by switching to Motorcraft plugs. My lead tech had 20+ years of wrenching on Fords and swore that NGK plugs caused problems in modular engines.