I have a 2000 F-150 with the 5.4 Triton and I recently replaced 6 of the 8 spark plugs (I know, but I ran out of time to mess with it and had to drive it like that) as well as the corresponding COPs. It was surging before and killing my fuel mileage but after working on it, it will idle fine (~800 RPM) but when I sit at a stoplight in drive, it will idle at about 450-500 and incredibly roughly. Today it killed the truck. I was able to restart it, but it’s been idling like that regularly for the last week. It would do it before every so often but now it’s every time. Is it just the fact I only did 6 of the 8 or is it something else? Thanks in advance

 

Scan it for codes and tell us what it says.

 

How did the 6 that you took out look? Spark plugs can tell you a lot about what's going on in your engine.

 

Motorcraft plugs
Motorcraft or denso cops
anything else.....start over

 

No visible damage other than discoloring of the ceramic and the firing end of the plug. The gap was pretty big, but those plugs had been in for 80k miles. Didn’t see any major issues other than just standard wear.

 

My guess - vacuum leak
Check and make sure you reconnected any vacuum lines that may have gotten disconnected.
PCV hoses in place? Did you reconnect the MAF sensor?

 

Another potential issue. It doesn’t seem to sag RPM as mush in revere and it’s noticeable but not severe when it’s in park. I was on my way to work this morning and when I was coming to a stop it would sag down to about 250-300, put it in park and it would shoot back up to 700-800 then repeat the cycle every time I had to stop.

 

Alright.... this is good and all, but have you read the codes yet? We're all throwing darts here until we get solid feedback.

 

All of these codes start with “P” but it’s
0125
0442
0136
0156
1131
1151
0302
0171
0174

I’m going to start by cleaning my MAF sensor

 

When does the surging occur? You've only mentioned it idling in gear. Is that the only time it does it? And by "surge" are you talking about a "rolling idle"?