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WEAK CYLINDER

edited November -1 in Repair and Maintenance
I was told that I had a weak #4 cylinder in my 98 Windstar Van..can anyone explain what that means..mechanic was kind of uncertain ..could not tell me whatelse to look for or check...
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Comments

  • edited June 2007
    It usually means that that cylinder has lower compression than the others for some reason, like burned valves, worn rings or blown head gasket. It might also mean that its not producing its share of power for some other reason like a bad plug, plug wire, fouled injector etc.

    How many miles, what are the symptoms, how does it run, smooth idle?
  • edited June 2007
    Your mechanic tells you that you have a weak cylinder but is not certain why?
    Some more info about the vehicle would help, but if you legitimately have a weak cylinder (low compression is generally what this means) then you should have a slightly rough idle that may smooth out (depends) when the throttle is opened.

    If your mechanic did not perform a compression test then he's wild guessing.

    Low compression is usually caused by piston rings, cylinder head valve, or possibly a faulty head gasket.
    Any of this is easily diagnosed.
  • edited June 2007
    If your van has the 3.8 litre engine I would bet that you probably have a blown head gasket. It was a common problem with that van. How many miles are on the van? My head gasket went with 84000 miles on the engine right after the extended warranty ran out. Even though I pulled over right away when I saw the temp gauge spike it was too late 4000 worth of engine damage. I must say though Ford did the right thing and purchased the van back from me.
  • edited June 2007
    We need more information. Exactly what were the symptoms and what did the mechanic do. If he's commenting on a compression test, that may be an inability to hold pressure or an inability to achieve sufficient compression, each with causes of its own. If he commented based on his "reading" of a spark plug (like one plug crudded up or damaged from too much heat) then the possible causes would be different. If you have one cylinder misfiring, that's a whole different range of possibilities.

    While my first suspicion is that he was referring to compression, it's hard to tell from the info provided.
  • edited June 2007
    My van has 196,000 miles..have replaced plugs twice, replaced wires. replaced PVC and hose..have not changed injector yet..going to change fuel filter this week..(due)..engine runs pretty smoothly and at times you can feel a little rough while driving but smooths out..temperture is normal..don't burn any oil or shows and excessive smoke..
  • edited June 2007
    My van has 198,000..with the 3.8 engine..only maim problem I've ever had was broken shaft in my transmission..it's been a reliable car since I brought it new in Oct. 1997..
  • edited June 2007
    All the mechanic did was a dianostic test with instrument reader..I don't think he did a compression test on the # 4 cylinder..that's the cylinder that keeps coming up on the reading..my engine light has been off for the past couple weeks but it came on yesterday after about 50 miles of straight driving at 55-65 mph..at normal temp. I'm going to take the car to Advance Auto to have the computer read and get the code numbers. thanks for the info
  • edited March 2008
    WHAT ENGINE is in your van? C.I. displacement? 4, 6 or 8 cylinders? Transmission? (Auto or standard). HOW MANY MILES? A pressure test of the cooling system quite often reveals a blown head gasket by several pieces of evidence. A competent mechanic can do this test and explain what results he got. Get a compression test done on all cylinders. They should all read within 10% of each other. I typically take the mid-range reading and add or subtract 10%. If that is true, then a mechanical failure of internal engine parts can be set aside for the moment. If the van has around 100K miles, time to do a fairly thorough check-up on the van. Check the injectors for their properly-specified resistance readings. If one is way out of whack, then replace just that one injector. Injectors don't necessarily relate to compression, but what the heck---might as well do this check to reduce potential future surprises. At $80+ a pop per injector, just don't tear all of 'em out and replace them all. If the injectors are all within specs, then it's time to check out the rest of the fuel and electrical systems. You just might have only one injector that needs replacement. But start with a compression check on each cylinder. Have whoever does the work write down his original findings. Then YOU can determine what the proper compression range is for that specific engine. Might be as simple as a stuck oil ring. A couple of teaspoonfulls of Marvel Mystery Oil in that cylinder left overnight just might be all that you need to free up a sticking oil ring. After putting the MMO in that cylinder, just crank the engine 1 revolution. That'll get the MMO up against and into the oil ring. Though the compression rings are supposed to control the compression, some of those have been known to stick. Either way, MMO just might be all that you need. MMO won't help with more major component break downs like the valves,head gasket, etc. A shot of (a couple of teasponns) of regular motor oil poured into the weak cylinder will give you a clue as to the functioning of the compression rings. Check the weak cylinder, add the motor oil, re-do a compression test on that cylinder, and if the compression comes up and then drops after a few revolutions, then it's probably rings or valves. Eliminate the easiest thing first and move on down the list. But a thorough compression test is where you start. If your guy can't/won't tell you why you have low compression, find someone who WILL tell you and continue troubleshooting until he can pinpoint the most likely cause. For instance, a cooling system pressure test will help determine warped head/blown head gasket situations. Then get into the more difficult troubleshooting aspects until you've either eliminated or repaired what REALLY needs to be done.
  • edited March 2008
    I hope they solved the problem by now, this thread was from last June.
  • edited March 2008
    Evidently, prohandy doesn't know what a HUGH [b]PITA[/b] it is to simply change the spark plugs in a Ford Windstar. Doing compression checks on all cylinders has to be as much fun as sleeping in an iron maiden. Maybe less.
This discussion has been closed.