I purchased the van about six months ago. Looking through parts/service reciepts he gave me I found that the fuel pump is a cheap Airtex E7144M purchased by former owner from Rock Auto March 2017.
The pump always wines but the whine increased one day last month and turned on the check engine light within a few seconds, setting code P0171 System Lean bank 1. I replaced the inline fuel filter and cleared the code. It hasn't set the code again but since then it has been having occasional intermittent miss at idle as well as while accelerating. I checked the fuel pressure today which was 42lbs (Specs are 58 +/- 5lbs). Could this low fuel pressure be causing the intermittent miss.
I use my friends Matco Maximus 3.0 HD Diagnostic scanner to look through the data stream but can't find anything suspicious. No DTC's. Misfires are detected intermittently across all 6 cylinders at idle but not stored in misfire history. Engine doesn't idle roughly though. Miss under load is more noticeable but not detected/recorded by scan tool (weird).
I took it to the local shop and they also scanned it and experienced the same symptoms but were unable to give me a diagnosis.
Any ideas before I spend over $300 to put a Denso fuel pump in it which I really can't afford (I'm former industrial equipment mechanic/electrician but since 2014 I'm a 1 arm/1 leg amputee with a disability check to live on).