P1131 - Engine stumbling and lose of power

[jimirig]

I have a 98 Explorer 4.0 OHV that has been giving headaches for a couple of months. During cold start, the engine idles rough almost like it's missing until I get the engine to 2500 RPM then it smoothes out. Anyway, a couple of month ago, one of the lines to the DPFE had a slice in it so I replaced the DPFE and vacuum lines. Everything ran fine for a couple of weeks and then it started acting up again. I replaced the air filter and cleaned the MAF. Once again everything ran perfect for a couple of days. Now I’m back to dealing with engine acting like it is missing during idle and sometimes while going uphill. The CEL has been throwing a P1131 code off and on. At times the vehicle smells like rotten eggs, so my first thought is the cat is pluggin up, but I would like to avoid dealing with that if all possible. I thinking I need to replace the EGR but would like to know if there is a way to test it before I waste $60.

 

[jimirig]

Fixed

Just a quick update on what I did and how I fixed this issue. After a week of checking all the stuff tha could cause a P1131.

*checked and cleaned MAF - didn't think this was an issue since it was only affect one bank but did it anyway
*checked and cleaned IAC
*checked for vacumm leaks
*checked for intake manifold leaks
*cleared the PCM

Then yesterday, I got P1131 and a new code P0133 (02 Sensor Circuit Slow Response (Bank 1 Sensor 1)). So I decided the change the upstream O2 sensor on passenger side. I put in a NTK, I believe I've read people have had problems with Bosch. The old girl runs like she got a second chance at life.