88 Dakota 4x4 3.9L V6 TBI. Get a code of 21, 51 and 52. O2 Sensor has been replaced twice but still says running lean and running rich. Everything from fuel filter to map sensor to temp sensor has been replace. Seems to run rough when engine is hot. Has yet to do it when cold. Kicks, bucks and backfires.
Have you connected a vacuum gauge to the intake? What is the reading and what was the variation? Have you searched for a vacuum leak by clamping off vacuum hoses and spraying throttle body cleaner on suspect gaskets?
Hope this helps.
I haven’t done that specifically but have paid quite a bit of money taking it to the Dodge Dealer. They did perform a vacuum test and it passed with flying colors.
Checking for vacuuum leaks by spraying TB cleaner or starter fluid in suspect vacuum leak areas is a good idea, as Researcher said. The engine will speed up as the fluid gets drawn in if you hit a leak.
Beyond that, your symptoms suggest fuel metering problems. Assuming you find no vacuum leaks, possibilities that occur to me are a malfunctioning fuel pump, fuel pressure regulator, and/or injector. Don’t just go changing parts, however, until you test them. Instructions to do the first two will be with the fuel pressure test kit, or at least in a Haynes manual.
Is there any merit to an anomaly called the #115 splice?