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Engine Knocking - Additional Information

Here r some details my husband omitted.

  1. The first reading of computer showed 2 codes. One for cylinder 3 and one for cylinder 4 missfiring but "check engine light" never stayed on-just flashes when problem (knocking) occurs then goes off. Mechanic replaced all sparkplugs, problem continued. Mechanic replaced #3 coil, added premium gas, and Techron, problem mildly reoccurs intermittently, with "check engine light" flashing, then going out. Brought back to mechanic after coil changed and computer reading showing #3 cylinder missfiring even though that was corrected. All else appears normal in car when happening, temp guage fine, Also when knocking, missing, etc., the "check engine light" flashes on and off, but does not stay on. Problem is intermittent, generally happens at speeds over 55mph, then gives smooth ride. Afraid to use for long distance driving at this point. Sometimes smoke pours out of exhaust when knocking, other times doesn't do it. Prior to any problems, oil & filter was changed about 5 days before, and valve cover replaced on same day.
Reply to
iconlarry
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There's a big red flag right there. Why was the valve cover replaced?

--scott

Reply to
Scott Dorsey

IN late January, I started to smell an oily/smokey like smell inside the car while driving it, of course not regularly, but enuf to want to bring it in and have it checked. Mechanic said gasket needed to be replaced. But fine to drive until repaired. Basically it stopped doing it, and I brought the car in when the weather got a bit better here on March 18. On that date I had the oil and filter changed it was about

40 miles overdue, receipt reads 4 qts. 10w 40 oil, and the valve cover gasket was replaced on that day.

On April 4th, brought car in for: loud knocking, kind of bucking, engine light flashing on and off, only on highway, local driving no sign of problem. Mecanic read pending codes misfire of # 3 & 4 cylinders. Replaced all spark plugs. After sparkplug replacement still had flashing "check engine light", code read misfire #3. So had #3 coil replaced next day, tested, still knocked but much more gently, flashing light when knocking only, code reads misfire #3 same as before. So from March 14 to April 5 recap: oil change 4 qt. oil filter change Replace valve cover gasket new spark plugs replace #3 cylinder coil had front brake pads & rotors replaced (very necessary) I was aware of brake grinding, rust, etc. had a few hundred miles to go, but had work done-car was also due for inspection in April. car idles soundlessly. Any leads you may supply would be appreciated. Thanks again.

Reply to
iconlarry

Misfire messages can mean bad spark plugs, bad plug wires, dinternal short in distributor if it has one, bad coil or ignition unit, blown head gasket, cracked head, and perhaps others.

It could be bad, or not. You have to work through the possibilities carefully. Trouble shooting, not parts replacement, is the better way to go usually.

Reply to
hls

Sounds like a dirty valve problem to me, or a broken spark plug wire, or a fuel delivery problem...or cylinder #3 isn't getting proper compression during firing cycle. (intake-exhaust valves for cylinder

3 not seating fully with block).

Replace spark plug wire.

Get 1/2 tank gas, add 1 bottle GUMOUT =and= 1 bottle TECHRON. Run until near empty.

Put full synthetic oil in engine and let that remove engine deposits, while Techron and Gumout goes after fuel delivery system. Get Techron FUEL SYSTEM CLEANER, nothing else, except for hi-concentrate GUMOUT.

I had this problem, and solved it myself.

Lg

Reply to
Nicholas

I'm not suggesting anything. There are a lot of things that could be causing your problem. But just to let you know: if someone had left a socket wrench inside when they closed up the valve cover, it would probably have symptoms like you describe.

Whatever the problem is, the computer codes are indicating an ignition problem, but in fact the ignition issue might be a symptom and not the actual problem.

If it were me, I'd pop the valve cover and check the lifters myself. I'd also pull the plugs on the cylinders producing the errors and verify by eye that they have a nice hot spark.

Intermittent problems are no fun for anyone, because as soon as you start looking for them they go away and then they come back when you aren't prepared to look any more.

--scott

Reply to
Scott Dorsey

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