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BigBob, Shop Manager/Technician
Category: Car
Satisfied Customers: 4838
Experience:  Shop Manager with 25 years experience
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2001 Mazda tribute: V..The check engine light started coming..cylinder

Customer Question

I have a 2001 Mazda tribute, 3 L., V-6. The check engine light started coming on and going off, sometimes every couple of days , sometimes weeks apart. Had my mechanic put diagnostic computer on it, said cylinder 4 missing. He changed the coil pack on the front, far left cylinder and it seemed ok for several weeks. Then the light came on again twice for several days and off again. Computer still says cyl 4 missing. Did he get the correct cylinder? He said their computer only showed the firing order but not the cylinder numbers.
Or can it be something else, i.e.,a defective sensor?
Thanks, XXXXX XXXXX help.
Submitted: 8 years ago.
Category: Car
Expert:  BigBob replied 8 years ago.

Did they change the driver side coil or passenger side?

Customer: replied 8 years ago.
Passenger side - front left as you are facing the open hood.
Expert:  BigBob replied 8 years ago.
That is the correct cylinder.

Did they change the spark plugs?

Customer: replied 8 years ago.
Spark plugs were changed Aug '06. We pulled the plug, seemed ok, it was dark but not appreciably burned.
So, no, haven't changed the plugs recently.
Oh yeah, only have 68,000 mi on the vehicle. I only drive about 15 mi. 3 times a week and approx. 50 mi on the highway every weekend.
Expert:  BigBob replied 8 years ago.
Check compression on cylinder #4. If ok try swapping the coil from cylinder 4 to one of the front cylinders and redo the Key On Engine Running (KOER) test. If the code changes to the cylinder where the coil was moved to, replace the coil. 1. Do a running compression test on cylinder #4, and compare the reading to the running compression readings on one or two of the other cylinders. To do this, remove the Schrader valve from the compression gauge (from the part that screws into the spark plug hole), install the gauge into the cylinder to be tested, disconnect the COP, start and run the engine at idle. monitor the gauge needle. The needle will typically be bouncing so rapidly that it looks like a blur, but note the high side of the bounce, see if it is consistent and compare it to the good cylinders. The results will vary depending on the gauge itself and the length of the hose, but on average, the running compression reading is usually about half of the cranking compression reading. If the cranking compression is good, but the running compression is low in comparison to the other cylinders, this usually indicates a valve train problem, such as a worn cam lobe, a broken valve spring or a valve sticking. Install a vacuum gauge and observe the needle. A regular, evenly spaced downscale flicking of the needle indicates one or more burned or warped valves. Insufficient hydraulic lash adjuster clearance will also cause this action. The vacuum gauge should read between 15 and 22 inches depending upon the engine condition and the altitude at which the test is performed. Subtract one inch from the specified reading for every 1,000 feet of elevation above sea level

let me know if I can help further.

Good luck,

my information is not free, I have to pay for it, please don’t forget to accept, I don’t get paid until you do, because you made a deposit does not mean you have paid

BigBob and 3 other Car Specialists are ready to help you
Customer: replied 8 years ago.
Bob, we appreciate your expertise and suggestions and have Accepted. However, upon further inspection by an additional mechanic, the opinion is that a valve train problem, such as a worn cam lobe, would not create an intermittant check engine light. So, trying the simplest remedy first, we are going to change the spark plug or plugs and see if that solves the problem, or at least, the indication of a problem. After that, a change of spark plug wire or wires will be our next try if needed.
Thanks again.   
Expert:  BigBob replied 8 years ago.
Thank you, XXXXX XXXXX know how it goes.