'95 3.8L dropped a cylinder?

Discussion in 'SN95 V6 Mustang Tech' started by Desert Stallion, Jun 27, 2005.

  1. So my sister's '95 coupe decided to take a dump this morning. It sounds like it's dropped a cylinder or two, and absolutely stinks of gas from the exhaust. It also seems to be puffing steam out of the driver's side pipe (I converted it to dual exhaust for those wondering), but it's not steam like coolant vaporizing as it lacks that sweet smell and isn't 'wet', but like I said it reaks of gas. There's also no coolant in the oil or oil in the coolant.

    I replaced both head gaskets 5-6 months ago. About the only issues the car's had is a random miss since she bought it a couple years back from my aunt, a muffler with a hole in it curtesy of the transmission shop that ******* up the clutch the first two times they tried to replace them, and the clutch the I replaced after my sister bought it. It also has a new IAC and coil pack.

    So anyway, I'm waiting on the motor to cool down before I pull the plugs to see what they look like.

    Any ideas? That little voice keeps saying the head gasket blew, but the lack of coolant and oil mixing and the strong gas smell don't mesh.

    Thanks all.
  2. A compression test will give you a good idea of whats goin on. My original motor only lasted 80K thanks to Ford engineering, but it knocked and smoked.
  3. Okay, updates...

    -compression test shows that 5 of the 6 cylinders are between 168-180lbs. The #6 cylinder is at 143-145.

    -the plug from the #6 cylinder was wet and smelled strongly of gas when removed. The liquid evaporated withing a minute.

    I still haven't seen signs of leaking coolant. All of the plugs looked good except for the aforementioned #6 plug, but after the gas evaporated it looks normal.

    So, I either have a leaky head gasket that's letting water into the cylinder but not the oil, or I have a bad valve/guide, or I have an injector that's failed and is flooding that cylinder.
  4. Or that plug might not be firing for some reason. Check the ignition too.
    It sounds like there's a lot of gas, though. Maybe the injector is failed open.
  5. You could put a tad bit of oil in that cylinder with the low pressure and test it again. If it jumps up to about what the others are or more with oil in it, its a sealing problem.
  6. Make that a teaspoon of oil and if compression comes up to about norm its a piston ring problem. The valves won't be affected by adding oil so that could still be an issue.
  7. One cylinder flooding

    Current clues point to a non firing cylinder. Check for spark and change that plug. Lower compression could be due to gas washing the cylinder walls of oil.
    this is cheap as you can just swap plugs with another cylinder and see if the problem goes with it.
    Second might be a stuck injector, Little more work but the next step up the check the cheap stuff first. I had this problem and it turned out to be the idiot that changed my plugs took the money for platinums, put in Autolite
    cheapos and didn't get one plug wire seated properly on the plug. Idled fine but acceleration sucked, smoke out the back and an occasional "WOOF" that sounded like a gas fire in the exhaust.
  8. Well, to answer all your suggestions in order:

    -Checked all the plugs and wires and all appeared okay
    -injector checked out okay and seals tight when not firing
    -compression was the same wet or dry
    -the compression tests were done with the injectors unplugged so there was no fuel being introduced to the cylinder(s) to affect compression readings. Also, my experience has been the opposite of yours with spark plugs. In every car I've owned that had platinum plugs, the plugs would cause running issues sooner or later. I stick with Autolite coppers because you can't go wrong for a buck a piece, not to mention they take to power adders Helluva' lot better than platinum plugs, though that's not an issue with this car.

    At this point, I'm thinking it's either valve guides or head gasket, though there's no over-heating issues to suggest a head gasket. :bang:
  9. My theory is that the injector is failing. I know a guy that had a 4.2 had poor fuel economy and smelt like a gas. The injector failed and was flooding out a cylinder. Thing is that the truck threw a code that one bank was running rich. I know you said the injector tested out ok, I'm curious what you did to determine it. Also, if a valve guide was bad, wouldn't you be oil fouling the cylinder and not washing it was gas?

    Could that cylinder be running rich because of lack of air flow from carbon build up in the intake? Could a defective EGR cause this?