Well I got the EGR and Throttle Body off, but couldn't get the Plenum off yet. It seems there is a Torx fitting holding it on in addition the the hex-bolts. I'll pick up the required torx bit today to remove the Plenum.

The EGR valve had a lot of deposits in it, but after using a hand vacuum pump to test it, I determined the valve was working properly. I cleaned it up as best I could using the Sea Foam product you guys recommended.

The tube running from the top of the intake manifold to the EGR valve has a bunch of gunk in it to. I'll remove and clean that as well when I get the Plenum off.

Interestingly, the port in the Plenum where it connects to the EGR valve was completely clogged with deposits. I used a screwdriver to try to chip away at some of it, but it was difficult with the Plenum still attached to the top of the motor. Also, I didn't want to risk damaging the Plenum by gouging it with the screwdriver. I'll get it throughly cleaned up when I get the Plenum removed.

The throttle body was in good working order with no deposits.

On another note, I bought all the gaskets to put this thing back together, but do not know if any gasket sealer is required. I would guess no since there is no oil or fluid running through this system, but not totally sure. Any recommendations?

I don't know if a clogged Plenum port would even cause the power loss problem I'm having, but I guess I'll know when I get it all put back together!

 

Gasket sealer is probably not nessicary but would be good as an extra precaution. Plus it holds the gasket in place so you can get the parts back together which is great if you're doing it alone. I usually use Indian Head gasket sealer for parts that don't have fluids running through.

 

I would not use gasket sealer on the plenum gasket. If you ever have to take it off again its a mess to clean up and the alumimun plenum walls are pretty thin and you can damage them pretty easy with a gasket scraper. A much better way to align the gaskets and plenum, and keep them in place during assembly, is to get a couple of slightly longer bolts with the same pitch and thread as the plenum hold down bolts. Grind the heads off these longer bolts and use them as insert them in a front and rear bolt hole, and use them as dowels when putting on the new gasket and the plenum.

As far as that middle torx head bolt goes, the best thing I've foind for that is to make a tool by welding a T40 tip onto a ten inch rod, then weld another piece accross the top to form a t handle.

 

Have you checked out your fuel system at all? Check for pressure and make sure the filter is good.
-Johnboy

 

I got the Plenum off. The EGR port was indeed completely blocked with carbon. I got that all cleaned up. I reinstalled the plenum and replaced that torx fitting with a regular hex-head. (I can only imagine that the reason Ford used the torx was to disuade people from doing their own work!)

I ended up using no gasket sealer on any of the gaskets. I spent 2 hours removing the old gasket and sealer from the top of the intake manifold. I'd like to avoid that in the future. I did end up with a few small gouges in the aluminum, but I don't know if they could have been avoided.

I got the whole thing back together and it seems to run great! However, I'll need to get some miles on it tomorrow to see if my problem has been solved.

I immediately noticed that the truck runs much better when initially applying the gas pedal. Before, the truck would bog, then "take off" when you added gas from a complete stop. Now it "takes off" very quickly, with no hesitation. So regardless of whether or not I've solved the original problem, at least I succeeded in improving overall performance.

 

Johnboy,

I had some other unrelated (or related) fuel problems so I ended up replacing the Dual-Function Reservoir (contains the filter), Fuel Pump and Fuel Pressure Regulator. I have thought about getting a fuel pressure guage, hooking it up, and driving around until my problem manifests itself, then checking the fuel pressure. If cleaning the EGR, Plenum and Throttle Body do not end up doing the trick, I might give that a try.

I have always thought in the back of my mind that it might be fuel problem. It won't surprise me if that is indeed the case. However,I don't know what else to replace. I know the low-pressure pumps in the fuel tanks work fine, so what else is there? I guess I'll have to dive deeper into the fuel and electrical systems if the power loss is not solved.

 

Well, I put about 35 miles on the truck today with NO power loss! I'm very happy, but I must admit, I'm keeping my fingers crossed. It really will not suprise me if this problem resurfaces. I find it hard to believe that a clogged Plenum port would cause this problem, but I'll take what I can get!

 

Smaller things can cause big problems.....

 

Glad that worked for you....feels good, doesn't it?

 

Yeah. Feels awesome. Thanks for all the help guys. I really appreciate it!

 

Here's a quick update to this issue. Cleaning out the plenum worked great and the truck is still running perfectly. I think I found the cause of the clogged port. I recently brought the truck in for a new exhaust system and the technician pointed something out to me. It turns out whoever installed the old exhaust system used some sort of home-made collector assembly. (I think that's what it's called....the section of piping that goes from the exhaust manifold to the catalytic converter.) Basically, the diameter of the piping was of too small and the angles were all wrong. The guy told me this was probably causing a ton of backpressure. After the new exhaust was installed, I noticed an immediate improvement in throttle response and top end (60-70 mph). Before, when I let off the gas at highway speed, the truck would slow down so fast it was as if I had hit the brakes. Now, it slowly "coasts" as is slows down. It was almost like I had an Jake Brake on the truck! I'm no pro, but the new exhaust has made a huge impovement in my engine's performance (it also looks and sounds great!)

If anyone is interested...I replaced everything from the exhaust manifolds back. I think the 2.5 inch collector/catalyitic converter assembly was made by Magnaflow (could me Flowmaster though..can't remember). It hooks into a Flowmaster 1 inlet, 2 outlet turbo muffler. The dual pipes go out the sides at a 45 degree angle with 3 inch stainless steel tips welded on (tips are 22 inches long so you can't see where they're welded on). It was a bit pricy at about $850 installed, but I'm keeping the truck for a long time and it was worth every penny to me.

Anyway, this was just a good lesson to me that doing things half-@ssed, can cause serious issues later on. The crappy exhaust that the previous owner had skimped on almost ruined the truck. If it hadn't been for FTE and especially ri_truck_guy I probably would never have figured out this problem. Thanks for everything.

 

I am having a similar problem on my 89 F250. I will start digging into my EGR and see what I find. Thanks everyone for these tips.