Temp Gauge, coolant loss, rough idle/accel

[NCTuskie]

I've got a 96' Ford Explorer V6 4.0, with a slew of problems. They may be related, or they may not, but here are the big ones in order of occurance.

ROUGH IDLE/ACCELERATION:
When I bought it last year, the previous owners said that it had problems missing. They said that sometimes it would work fine, and all of a sudden it would begin to miss. They pulled the codes and got a Cylinder Misfire, and a bad O2 sensor. I drove the Explorer for about a month before the problem occured with me. Shortly there after I changed the plugs, and it ran perfect.

Several months later, the problem began again. I had the codes pulled again and it read #6 Cylinder misfire and EGR Valve replacement. Since I had already pulled the plugs, I decided to change the spark plug cables. Once I did, it ran perfect.

Now it's been about another 5 months or so, and the problem has occured again. Instead of "fixing" itself as it has in the past, it has gotten worse, and I've noticed a dramatic decrease in gas mileage. This has been going on for about a month. I pulled the codes again, and it read a #3 and #6 Cylinder misfire.

My next step is to replace the coil pack.

COOLANT LOSS AND TEMP GUAGE:
Around the time I replaced the plugs, I noticed the temperature guage acting erratically. It would shoot to hot, then go back down. When I would shut the engine off, the temperature guage would remain in place, and remain there until the next time I turned the Explorer back on. Around this time I checked the coolant, and noticed that there was none in the overflow reseviour. Over the course of 6 months I ran through about a gallon of coolant, after replacing the thermostat, with no signs of leaks on the ground, around the engine compartment, and no smoke from the exhaust.

Also last week the temperature gauge stopped working altogether. The needle sits at low and does not move.

For now I'm replacing the coil pack and seeing what the does about the engine knocking. What do you guys think?

 

[KBarbina]

Have you checked (pr smelled) the spark plugs for evidence of coolant in the cylinders or checked compression on any of them? or seen any coolant or water in your oil? I'm just curious because of the lack of coolant on the ground the the erratic variance in the engine temperature.......and now the engine knock.....

 

[Fifty150]

coolant can trickle out the weeper hole of your water pump because of a bad seal. In most cases, that only occurs while the car is running, and the coolant will dissipate on the hot engine block. In my case, some of that coolant worked it's way into the water pump studs and caused them to rust and corrode. But if you do have a bad water pump, it doesn't run while the car is parked, so you may not see any coolant on the floor. But that usually does not result in enough coolant loss for you to not see any fluid in your overflow tank.

 

[NCTuskie]

I haven't noticed any coolant or water in my oil, and I've been through several oil changes. I did begin to think it was the water pump, but I haven't seen any signs of leakage. At times I do smell antifreeze after driving, but can never pinpoint the location. I don't know if this is constant or not.

 

[1AJeremyD]

Try doing a pressure test with the coolant and a cylinder compression test . Easiest thing to start with. If the 02 sensor is bad you could have a head gasket leak and the coolant is fouling up the sensor. The plugs could getting fouled from the coolant as well hence the misfire. Good luck with it! Keep us posted!

 

[NCTuskie]

I swapped the coil packs last night. Some of the rough acceleration stopped. However I did notice Transmission fluid on the garaged floor. I found the general area from where it was coming from. I checked the dipstick, and the level is still good. There does seem to be a delay when upshifting while accelerating, and rough downshifting.

I still haven't checked on the coolant loss issue, or the temp gauge issue.

 

[NCTuskie]

Any thoughts?

 

[pcsaav]

Had similar issue with my V8. Was losing coolant quickly but didn't have any coolant on the ground. Turns out it was the gasket for the timing chain cover. There are two coolant ports at the front of the block(in and out). I'm sure it is similar in the V6. the gaskets go bad and leak at the ports but the heat of engine evaporates the coolant before it hits the ground. I bought a gasket kit and pulled the water pump and timing chain cover. I replaced all hoses, belt, water pump, thermostat, and of-coarse all associated gaskets. At 145K it was time. It needed a new alternator so it got one of those too.

Haven't had any issues. Remember, it might not be that deep in the engine. look at the weep hole on your water pump. if the seal is bad it will leak.

good luck.

 

[NCTuskie]

Is this bad

I noticed this green wire is cut, not sure if this has anything to do with the aforementioned issues.

 

[timlagios]

thats not a wire ita a vacuum line
to the egr

 

[NCTuskie]

Update:
Took it to the shop. Head gasket and two cracked headers. Plus a cracked transmission pan.