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Old 07-07-2006, 08:47 PM   #1
shirpa
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coil stress test

dealer said have oil in coil, causing misfire. also said coils should be replaced in pairs, has any heard of this, thought they are all independant, why in pairs
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Old 07-08-2006, 12:42 AM   #2
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Re: coil stress test

Did they mean pairs, or all of them at the same time? Many times it is suggested that all coils be replaced at the same time. I hope they meant once the oil leak is fixed. If the oil leak doesn't get fixed, the new coils will foul soon as well.

If they really did mean pairs, then they may be referring to the fact that when cranking the engine for startup, a pair of coils fire simultaneously until the PCM determines cylinder ID and knows which cylinder of the pairs is on the power stroke. This will occur for the first 6 revolutions of the engine at startup, or if there is a failure of the CranKshaft Position (CKP) sensor.

-Rod
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Old 07-09-2006, 01:21 PM   #3
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Re: coil stress test

never heard of coils being replaced in pairs, take it somewhere else
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Old 07-09-2006, 06:25 PM   #4
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Re: coil stress test

Well, it's often recommended that all 8 coils be replaced at the same time to avoid multiple labor charges. If the coil failed for a reason (oil leaking into the plug well, extreme heat, etc) chances are good that the others are not far behind.

When I had my Taurus SHO, I replaced individual coils when they failed. About every 4 months I was replacing another coil, never the same one twice.

-Rod
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Old 07-11-2006, 12:43 PM   #5
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Re: coil stress test

I must tell you that yesterday I had my ignition coils replaced - all 8 of them. I cost a little under 1000 dollars. They also replaced my spark plugs. This is insured for a year. I didn't take it to the dealer but had I taken it to the dealer - the labor would have been thru the roof. When my car was under warranty I was having them replaced as they went out. They said that according to my warranty they couldn't replace them all. But the guy at the shop yesterday said, it's usually better to replace them all because you will be constantly repairing them. And that could get expensive.
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Old 07-11-2006, 01:53 PM   #6
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Re: coil stress test

Thank you for the follow-up. Did the shop that replaced them make any mention of signs of oil on the coils? If not, you may want to ask. If the plug well seals are leaking, this $1000 will only be temporary.

-Rod
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Old 07-11-2006, 02:40 PM   #7
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Re: coil stress test

Rod - I spoke with the mechanic that worked on my LS and he said there was a little oil on my spark plugs but not on the coils - he also said only 2 spark plugs were functioning - the others were burnt out. Make sure people are aware that the spark plugs might need to be replaced too - I love my ls but it can be expensive to repair.
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Old 07-11-2006, 05:14 PM   #8
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Re: coil stress test

Keep an eye on the plug wells. If the oil leak gets worse, you will want to get it fixed before it starts taking out the new coils.

As for checking spark plugs, that should be a given when checking the coils as there is really no additional labor to check the plugs when the coil is out, but I will try to remember to point that out in the future.

How many miles were on the plugs when they were replaced? More than two almost had to be functioning for the car to start and run. If you did manage to keep the car running on only 2 cylinders, then you'll want to keep an eye on your catalytic converters. Six cylinders' worth of raw fuel getting dumped into the exhaust would certainly cause the catalytic converters to get VERY hot. If you notice decreased power, no start, rough idle, one of the first items you should have checked is exhaust backpressure. Since your car uses OBD-II you will probably get a flashing Check Engine Light (CEL) if the catalyst efficiency drops too much however.

-Rod
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Old 07-11-2006, 10:07 PM   #9
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Re: coil stress test

Quote:
Originally Posted by carlos80
never heard of coils being replaced in pairs, take it somewhere else
dealer serviced car, when stopped at light with ac running car jumps out of idle couple of times in a few seconds then returns back to idling smooth. what could it be? had sparkplugs changed, coil asy valve cove, gasket. dealer said o.k. ITS NOT. afraid to bring back, already cost me about 1000 in LABOR.
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Old 07-11-2006, 10:12 PM   #10
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Re: coil stress test

Quote:
Originally Posted by shorod
Did they mean pairs, or all of them at the same time? Many times it is suggested that all coils be replaced at the same time. I hope they meant once the oil leak is fixed. If the oil leak doesn't get fixed, the new coils will foul soon as well.

If they really did mean pairs, then they may be referring to the fact that when cranking the engine for startup, a pair of coils fire simultaneously until the PCM determines cylinder ID and knows which cylinder of the pairs is on the power stroke. This will occur for the first 6 revolutions of the engine at startup, or if there is a failure of the CranKshaft Position (CKP) sensor.

-Rod
rod sent you message, wasent sure how this forum works , figured it out now, wish i could figure my ls problem . what do you think? think dealer robbed me for 1500 parts and labor, sent you the details.
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Old 07-11-2006, 10:41 PM   #11
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Re: coil stress test

If the the valve cover gaskets were leaking, and the plug well seals were letting oil into the plug wells, the dealer did not perform work that was not needed. Unfortunately, it would appear that is not the only issue the car has.

Have you used fuel injector cleaner in the fuel tank on a regular basis? If not, get a bottle of fuel injector cleaner and add it to the tank. Drive the car for 100 miles or so and see if that helps. I suggest adding 1 bottle at each oil change. I've seen it solve some pretty wild engine "problems." I can only imagine how many issues are prevented by using it regularly!

Does the idle issue only show up with the A/C on? Does the car idle fine with the A/C off? If so, I would start by checking the Idle Air Control (IAC) motor. The IAC is supposed to open with the A/C on or when other items put an increased load on the engine. If it is not functioning properly, it could cause idle issues.

Also, inspect all vacuum lines and hoses. Make sure they are all connected and in good shape. Others on this forum have discussed issues with the PCV vacuum hose cracking. Search the forum for details and check for the issue on your car.

Another potential problem could be a malfunctioning Exhaust Gas Recirculation (EGR) system. The EGR valve should close completely when the car is at idle. If not, it can cause issues such as you describe, or even cause the engine to stall. It's not that uncommon for the EGR pintle seat to become contaminated and not allow the pintle valve to close completely. If this is the case, one can often use a good throttle body cleaner to clean the deposits from the EGR valve and passages.

If you have access to a scan tool with a datastream function, that could greatly aid your diagnostic search. Monitor the air fuel ratio on the two exhaust banks and see if they appear to be affected by the stumble. If so, do they tend to go rich or lean? Rich and you probably have either a spark or vacuum issue. Lean and the problem may be in the fuel system (filter, pump, or injector).

With the scan tool, you could also monitor the coolant temperature and see if it seems realistic. With a warmed up engine, you can expect the coolant temp to be somewhere around 200 degrees F. If significantly different, you may have a bad thermostat or coolant temperature sensor. Out of spec coolant temp readings would cause the Powertrain Control Module (PCM) to alter the air fuel ratio to a less than ideal ratio.

-Rod
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