Ford Ranger / B-Series :: 1994 - Sputtering / Back Firing / No Power

Background - I just got done changing a few things... Exhaust Manifold/gasket, battery cables, valve cover gasket, oil cooler gasket and hoses, power steering pump and hoses, and ball joints. Most of this has nothing to do with the issue that came up as I am driving it back to return it to her.

While out on the freeway, I initially notice subtle power losses and surges. These quickly escalate into almost total power loss with back firing, sputtering and much more noticeable surges in power. The check engine light was turning off then on a few times before pretty much deciding to stay on.

So I nurse it back home on back roads due to its inability to maintain freeway speeds. I proceed to check everything I touched paying special attention to the exhaust manifold and surrounding area. The new manifold came from the j/y and was barely used so I had initially just stuck with the O2 sensor that came with it; I changed this to the one the vehicle had previously been employing as it was not exhibiting these symptoms until after the job was done. I also double checked all the hoses, intake tube, wires and connectors; everything is connected.

From here, I research the method of pulling codes on OBD-1 vehicles by making the check engine light flash. It flashed a 111 and a 172 at the same time; the information I could find said the 111 means everything is normal, and the 172 suggested O2 or MAF. I am reasonably sure the O2 is not the problem so I focused on the MAF. Disconnecting it while running seemed to improve the way it idled so via the process of deduction, which also included the consideration of typical symptoms of MAF sensor failure, I proceeded to replacing the MAF sensor which amounted to little improvement.

At this moment in time the check engine light has not returned but it is clearly not in a drive-able state of being. It actually seems to have ever so slightly improved though.

Additionally, the symptoms only exist when the engine is hot and has been driven; it drives normally for 5-10 minutes until it gets to operating temperature then it starts to crap out. After changing the MAF sensor, I let it idle for 20 minutes and it was fine until about 2 minutes into the test drive.

Speculation - I am thinking spark plugs could also be a culprit as its has been forever since a tune-up but the sudden onset of this condition make me doubt this a little; it also has 8 plugs so even if one or two crapped out it should still run better than this I would think.