1994 explorer 135K miles/ engine stumbles

[felixxer]

I start it up in the AM and feels like it runs on 5 cylinders.
Sometimes it straightens up after getting warm.
Sometimes not.
No check engine light comes on.Terrible mileage even on highway.
Anyone have an idea?

 

[Centaurious]

First question is 'What state of tune?' these trucks have a wasted spark ignition and eat plugs twice as fast. Use Autolite double platinum plugs and good quality wires, I recommend NAPA lifetime plug wires because like the plugs they see twice as much wear.

Just because you don't see a check engine light does not mean there are no codes. Most codes do not cause a check engine light. Read the KOEO, CM and KOER codes. Post them here for help identifying problems.

Intake leaks are known problems. Intake to head for water passage leaks, intake to lower injector seals are not common but happen, upper intake to lower intake seals can leak, Intake tube to MAF sensor housing or throttle body can leak.

Best of Luck

 

[Dora 1993]

whats the condition of the plugs/wires?

 

[larrydd999]

X2 on plugs and wires, I keep records of mpg and whenever it starts to drop off I change the plugs. Say what you want to, however, almost anything is better than the old distributor cap and rotor system with the points that always seemed to need adjustment or replacement.

 

[luvmonterey]

Codes? Could also be a failing coil pack. Also, what is “terrible mileage”? I still have my window sticker and it says 12-18 and 15-23. I’m lucky if I average 17-18.

 

[96eb96]

All of the above and don't forget about the cracked head problem with these engines. K seal and new plugs seemed to have completely fixed the problem, sounds similar to what the OP has.

Without knowing history on the truck it is hard to say. Probably a tuneup is in order.

 

[Centaurious]

1994 was pretty much past the head issues thankfully. Unless it is a barn queen with no miles it either has the good heads stock or has seen them replaced by now.

The first gen problems are few and well known, thankfully we never had the SOHC 4.0 and it's timing chain issues to deal with.

 

[Rhaegal94]

Mine would intermittently hiccup when I came to a stop. The short story: I ended up changing the spark plugs (even though one mechanic told me they were OK) and spark plug wires. I used Motorcraft spark plug wires and Autolite spark plugs. Hiccups stopped and I find my start ups to be pleasant.

 

[96eb96]

Mine would intermittently hiccup when I came to a stop. The short story: I ended up changing the spark plugs (even though one mechanic told me they were OK) and spark plug wires. I used Motorcraft spark plug wires and Autolite spark plugs. Hiccups stopped and I find my start ups to be pleasant.

A new coil isn't a bad idea too, the v6 coil interchanges up till 2011, and is around 35$ for a new Ford unit. Mine was cracked. With new ignition components my truck starts instantly and runs like new. I also had a coupon and got Iridium TTs, they are an improvement over the Motorcraft finewire (They are dual finewire, great for waste spark!).

I'm pretty sure though I had a base engine issue because the K-seal stopped the misfires, but it would happen occasionally again on cold soak. The plug was ruined from the coolant. After a tuneup it is gone for a few thousand miles. The plugs are now dry and clean.

Cracked heads are not uncommon. They sell a ton on Ebay. They crack between the valves and if its bad it could drop the guide.