When my car is idling, the engine will shake my car, almost like its misfiring. But then it will idle smooth and then shake again. Could this mean one or more coils going bad? or maybe my MAF? Or do I just need a tune up? (probably could use one of those anyway) Its got 120k... 00 V8
intermittent shaking
- Thread starter Dacket
- Start date
Rifleman@LaymansPC.com
Well-Known LVC Member
I'd start with the plugs. I just put a new set of Bosch Platinum IR Fusions in and it cured an occasional bounce of the engine during idle. Inspect all the coils as you go. Look closely for hairline cracks in the plastic housing as well as hard spots in the rubber boots. Make sure you use dielectric grease both in the threads of the plug as well as sqeezing a gob up in the the end of the coil boot where it seats on the plug. Loads of folk skip this, and it extends the life of the coils and plugs preventing the oil and water from ruining things as quickly as well as ensuring all the power gets used making spark.
I would also check vacuum lines and EGR functions. If the EGR valve isn't closing properly (it should be fully closed during idle) and allowing exhaust gasses into the combustion cycle during idle it can cause rough idling.
I would also check vacuum lines and EGR functions. If the EGR valve isn't closing properly (it should be fully closed during idle) and allowing exhaust gasses into the combustion cycle during idle it can cause rough idling.
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If you've never had to replace coils now might be the time to pop the coil covers and see if there is any oil in there by the plugs. Of course they do also fail over time from heat. At first you will see a rough idle and for me it was just once and a while ,at first, and then you will just see worse and worse performance. Btw, it's better to find and fix the problem before then or you could end up damaging other parts of your car. If you can rule out coils then you might want to post some more specifics about the problem.
I guess I will just have to start replacing my coils and plugs then before I can rule those out. I'm not that experienced with engine work, but I am extremely interested and a quick learner. (and thank god for the internet)
Rifleman@LaymansPC.com
Well-Known LVC Member
More money than I have to put into a set of wheels.
If it's just a daily driver, typical service is to only change bad ones, I've seen Ford COP units last over 200k miles, never a full set, especially a set of 8.
Point is, why put out money on something that's not going to improve things if it doesn't correct the issue. Plugs at that milage surely need changed as they've exceeded the 100k mile tune-up interval that the motorcraft platinum plugs call for. New plugs would make an improvment whether they fix the shaking or not.
I would possibly pick up a coil when getting the plugs, and if changing the plugs doesn't smooth it out, then test the new coil on each cylinder and rate it for better or same by the rate of shakes in 10 seconds or a minute or whatever.
It's impossible to diagnose a car over the internet, one persons shake is another persons shimmy. If it were my money, I'd go one step at a time to save on money, plugs first, coil or two if needed. I would not change all coils on a whim.
If the plugs are changed, and a new coil or two makes no difference on any combination of cylinders, then it's time to start looking towards something else like the EGR I mentioned earlier.
I'd be willing to bet some money at odds that the plugs will cure it.
If it's just a daily driver, typical service is to only change bad ones, I've seen Ford COP units last over 200k miles, never a full set, especially a set of 8.
Point is, why put out money on something that's not going to improve things if it doesn't correct the issue. Plugs at that milage surely need changed as they've exceeded the 100k mile tune-up interval that the motorcraft platinum plugs call for. New plugs would make an improvment whether they fix the shaking or not.
I would possibly pick up a coil when getting the plugs, and if changing the plugs doesn't smooth it out, then test the new coil on each cylinder and rate it for better or same by the rate of shakes in 10 seconds or a minute or whatever.
It's impossible to diagnose a car over the internet, one persons shake is another persons shimmy. If it were my money, I'd go one step at a time to save on money, plugs first, coil or two if needed. I would not change all coils on a whim.
If the plugs are changed, and a new coil or two makes no difference on any combination of cylinders, then it's time to start looking towards something else like the EGR I mentioned earlier.
I'd be willing to bet some money at odds that the plugs will cure it.
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Thanks for the advice. I will probably do that. Is it hard to get to and change the plugs and coils? Last time I changed spark plugs on a car was on an 85 chevy caprice classic 305 v8. lol That was easy, this looks a little more complicated.
Coils and plugs are wear items. With your mileage and lack of history on the car just go to Ebay and buy a full set of coils for $160 or so. Then replace all 8 spark plugs. Before that I would check if you need to change the valve/cam cover gaskets. It all can be done at once. It's a big job but not beyond us shade tree mechanics!!
Here is a set on Ebay for less than $150 with free shipping!
http://tinyurl.com/l25a7d
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Here is a set on Ebay for less than $150 with free shipping!
http://tinyurl.com/l25a7d
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Rifleman@LaymansPC.com
Well-Known LVC Member
At that kind of price I guess it would be worth the saving of hassle in testing. I'm used to most Ford COPs costing about $50 each locally... That and I'm just a geek who likes to do the whole "process of elimination" testing.
Yeah the stealership charges $80-120 each for these coils. I have a full set of coils and plugs with only 200 miles on them. Plus the gasket set if you need it(also only 200 miles). I have the coils and plugs for sale for $120 plus shipping, worth $214. The gasket set was $120 new from the dealer and I will let that go for $75.
LsUnV2
Dedicated LVC Member
is there any way to tell if your coils are going bad without a cel??
Rifleman@LaymansPC.com
Well-Known LVC Member
Dealers are supposed to be able to "load test" them, whatever that means...
Not sure if they need the car or you can just carry in a box of old coils though, you'd need to call them and ask.
Not sure if they need the car or you can just carry in a box of old coils though, you'd need to call them and ask.
Rifleman@LaymansPC.com
Well-Known LVC Member
check the coils for resistance with an ohm meter
From my understanding that is only accurate for "dead or alive" and load testing is supposed to stress them to test for intermittant issues.
2000lson20s
LVC Member
I get the same shake as you but also when I'm driving if i am in the 1500-1800rpm range in any gear it will also shake. Only code i got was the Idle air control and I just replaced it today and same problem and code. WTF ohh and yeah for about $20-$40 more you can buy the whole set of coils on ebay then it would cost you for one local
Rifleman@LaymansPC.com
Well-Known LVC Member
I'd first ask if you made sure everything was clean inside throughout the intake? Could just be a flow problem.
How old are your spark plugs and if you've pulled them to inspect for signs of misfire (discoloration or uneven wear of the electrode) on any of the cylinders? I typically pull them all out, lay them side by side in the orientation they come out, and compare them side by side. They should look identical. I've seen many plugs partially misfire, but not create a misfire CEL, after a couple hundred miles of driving in such a scenario there should be visable differences in the coloration.
How old are your spark plugs and if you've pulled them to inspect for signs of misfire (discoloration or uneven wear of the electrode) on any of the cylinders? I typically pull them all out, lay them side by side in the orientation they come out, and compare them side by side. They should look identical. I've seen many plugs partially misfire, but not create a misfire CEL, after a couple hundred miles of driving in such a scenario there should be visable differences in the coloration.
joegr
Dedicated LVC Member
check the coils for resistance with an ohm meter
The typical failure of the LS coils is a high voltage insulation breakdown issue. That won't show up on an ohm meter. Some dealers do an off-car stress test with very specialized test equipment. Others "scope" the coils on the car.
"scope" = look at the voltage waveform on the primary (low voltage) side of the coil with an oscilloscope.
If warranty isn't paying for it, my opinion is that it is cheaper to just replace them all. However, if you have a Ford specific scan tool, you can look at the misfire counts for each cylinder and come out pretty good by just replacing every coil with a count greater than zero.
Always replace the spark plug when you replace the coil. An internal problem in the spark plug may have caused the coil failure.
joegr
Dedicated LVC Member
Use anti-seize on the plug threads. I would also pull the boot off of the coil and put some dielectric grease around the plastic that the boot pushes over.
Well considering that the serpentine belt that I replaced the other day looked like it was from factory (9 years old) I'm willing to bet that the plugs and coils are as old as the car. I haven't removed any of the coils or plugs yet, I'm not really sure how to do it yet. I looked over the tech article a little. I probably will just replace all the plugs and coils anyway just so I wont have to worry about those.
I also really need to replace my tires, that's going to happen next weekend.
I also really need to replace my tires, that's going to happen next weekend.
Rifleman@LaymansPC.com
Well-Known LVC Member
I got a tube of stuff called "tune-up lube" at Advanced Auto a couple years back when I did plugs on my wife's car that claims to be anti-seize and dielectric all in one.
The boot pulls off the coil? SWEET! joegr is full of usefullness.