94 Ford Ranger Running Rough, Seeking Advice

I pulled the fuel rail and the lower intake manifold. You can see coolant in the lower intake manifold in the cylinder 3 port. Most of the gasket came off the lower manifold and onto the top of the motor. The gasket around ALL of the coolant ports looks kinda crappy to me, but the gasket around all of the intake ports themselves looks to be ok.

I also took picture of the bottom of the lower intake manifold. You can see how the bottom of the manifold looks different around the cyl 3 port. It looks as if some of the coolant is stuck to the bottom of the manifold as well. But that’s only around the cyl 3 port. The bottom of the manifold looks normal around all the other ports. So perhaps the lower intake manifold gasket was simply leaking around cyl 3, and the coolant made its way in there?

I’m hoping the lower intake manifold gasket was simply leaking around those coolant ports. I realize I could also have a cracked head or head gasket. It puzzles me as to how this coolant would have gone UP the intake manifold instead of just down into the oil. I’m going to drain the oil to see if there’s any coolant in it. But checking it on the dipstick it appears to be fine. I’m going clean the manifold up really good and check for cracks. It appears to be just a simple manifold gasket failure, but I guess I won’t really know until I put it all back together and see if I’m still using coolant.

I’m also wondering why cyl 3 would have the dead miss. The coolant itself wouldn’t do it right? Maybe that fuel injector was clogged, allowing the coolant to build up in that cylinder. I can’t think of any other explanation.

I completed the repair a few weeks ago. I thought I’d post the results to keep the forum search function valuable.

The intake manifold gasket was very brittle when I removed it. It was leaking coolant into the oil, and into the cylinder 3 intake runner. I replaced it, the cylinder 3 fuel injector (not sure it needed the injector, but I had one on hand already so I put it in), the thermostat (because why not), and I did an engine flush (motor medic) and changed the oil twice after the repair.

There was coolant in the oil, though I couldn’t see it initially. I left the oil drain plug out while I had the lifter valley open and dumped a few quarts of oil down there to “rinse” out the engine. That’s when I saw the coolant in the drain pain. The coolant in the oil must have been the cause of the clacking sound I had. After the repair, engine flush, and oil change, the clacking sound has disappeared completely, there is no more misfire, and the vehicle is running like a dream. I checked the cyl 3 spark plug after the repair and it was initially very white (probably from burning off all the coolant that was in that cylinder). I changed it and checked it again after a few hundred miles and it looks normal. I have a feeling the catalytic converter might be clogged because it was burning coolant for so long, so I’ll have to get my hands on a gauge and check that sometime soon.

The only odd thing remaining after the repair is the temperature gauge on the dash. The truck never used to run hot, the temp needle would often sit between 1/4 and 1/2 the way up the temp gauge when the truck was warm. Now the needle doesn’t even reach 1/4 of the way up the gauge. It’s just barely in the [normal] range on the gauge. The upper radiator hose is getting plenty hot when the truck is warmed up, so I’m thinking the coolant temperature sensor may be faulty. I did remove it when I took the intake manifold off and cleaned it. I’ll buy a sensor on my next purchase from rockauto and see what replacing it does.

Thanks to everyone for their help and guidance!