Looking for suggestions...

[93EddieBauer]

I'm having a little bit of a hesitation or "stumbling" problem under hard acceleration from a dead stop. You can feel the truck sort of shudder and the tach either will drop a couple hundred RPM's or stay steady and then it will pull hard the rest of the way up to speed. It seems to do this mostly once the engine has warmed up. I have so far replaced the ignition coil which I checked and it was starting to go bad, O2 sensors, fuel filter, cleaned the MAF sensor, and changed the vaccuum modulator on the tranny. All of which has helped but hasn't totally solved the problem. Which brings me to the last two things I can think of, the fuel pump and fuel pressure regulator. I put the pressure gauge on it and it read 33 psi at idle with vaccuum line attached (spec is 30 to 45 psi). 38 psi at idle with vaccuum line disconnected (spec is 40 to 55 psi). When you shut the truck off pressure holds at around 38 psi. This leads me to believe that it is most likely the regulator and not the pump. Let me know what you all think. I'd hate to drop all the money and time on the wrong one.

 

[Beertime9]

Have you checked your egr valve, it sounds like it is suck open, do you have a check engine light on?

 

[93EddieBauer]

I haven't checked the EGR yet. Where is it and what's the best way to check it? The check engine light has never come on.

 

[Houston at NCSU]

One more cheap and easy trick, take rag with carb cleaner (or similar solvent) and wipe out the inside of the throttle body. Just disconnect the big plastic air intake tube, hold the butter fly valve open, and wipe the oil and crap build up out. I have done this to my explorer, and both my parents cars, and it usually helps acceleration and idle quirks, but im not sure why.

 

[Beertime9]

Follow the vaccum line to a black solenoid further back from the egr. Take the cap off (it just pops off, the cap also has a filter on it, you might want to clean it too)the solenoid and there will be a little bypass vent pipe. Hold your finger over the vent pipe while the engine is idling and the egr should open, you can see the diaphram move and the idle will stumble, sometimes carbon gets inside the valve and makes it stick, carfull not to turn this stem, I did on mine and screwed it up. Also check the DFPE valve, this sits in front of the egr valve and has two high temp vaccum hose that run down to the pipe leading to the manifold. They sometimes clog up with gunk or they are broken. You can take off the egr valve and clean the stem of the diaphram, careful not to get carb cleaner on the diaphram. The thread before about cleaning the throttle body helped on mine to, I just took it off and cleaned it throughly, also ran some carbon cleaner in the vaccum side, the intake manifold has a ton of carbon on it, I plan to remove the whole thing and clean it. Hope this helps.....

 

[93EddieBauer]

I've already done the throttle body cleaning, but I will have to try the EGR before I buy any new parts.