99 Explorer XLT 4.0 V6 SOCH running rough

[EchoTwo]

Hey guys, I've been having a problem with my truck for a while with running rough during idle. I checked the sensors, took it to the shop to get an inspection, nothing. i was told it was a vacuum leak, one day when it was getting rougher than usual I hit the gas just a little and finally my engine light came on. Ran the code and it turned out it was an Upper intake manifold gasket (I think) and got it replaced...no change. When I got the gasket replaced though the shop told me I had a misfire in cylinder 1, couple weeks later I took it back to get that diagnosed. They say its the spark plugs and needs a tune up, so they replaced all the spark plugs and spark plug wires....the old ones were pretty bad.

So now that the setup is all done, my truck is now running even worse, I'm losing power when I hit the gas, the engine shakes pretty bad and sometimes it sounds like its revving up and down a little, it's even stalled twice but not on the road. I do not have a check engine light, just like before. Any ideas what it could be? I will also note that while actually driving the truck runs fine, it's while I'm stopped, and when I first start to take off from a light or something.

Thanks for the support!

 

[donalds]

Look at your fuel pump test it when it's acting up should be 65-72psi at all times
Look at the fuel filter to

 

[XLTrunner]

There is no specific code to indicate the intake manifold gaskets need replacing. However, codes PO171 & PO174 indicate a lean condition and is often a result of bad gaskets on these engines. Your mechanic should have replaced both the Upper AND Lower intake manifold gaskets; not just the Uppers. I would agree your next step would be to verify fuel pressure. It's a simple process and your mechanic could have easily done that while it was in the shop if he was competent.

 

[RickOTR]

My vote is on the lowers as well. Uppers rarely leak but should be replaced as a set. Did they get the plugs gapped correctly and did not get the wires mixed up. What about fuel injectors?