hello I have a 2003 dodge Durango with a 4.7 engine. drove it to the doctors office and came out and suddenly it runs really bad. I have been noticing a bit of a missing at idle and as I accelerate every now and then but it always cleared up. but now its not at first the time it has not cleared up here are the codes I am getting po172 this makes sense if two coil packs are really down. po351/po355 are the next coeds. I took a test light and removed the connector to the coil one and started it and I got a light and I repeated the step on coil five and got a light. also getting code po121 could this have jumped trimming I know I should investigate the coil packs is there a way to test the coil packs or do I just replace them and trust the codes
benny

 

I'd try swapping one of those coil packs with a known good one and see if the problem follows the coil.

 

amazon has a set for 59.00 I wonder if they are any good