Bad Coil ?
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Laughing Gas
Joined: Apr 2004
Posts: 819
Likes: 2
From: Northern Maine
Bad Coil ?
Is it possible to have a bad / weak coil pack without the check engine light coming on? I have a 2005 3.0 Escape with 133,000 miles. (I just had a re-manufactured transmission installed) At about 55 MPH and only after it has sufficiently warmed up, it bucks when under a slight load. If I give it enough to make it shift down, it no longer bucks. It also doesn't buck when I lock it out of over drive or when going down hill. It seems to have plenty get up and go, which makes me think that it isn't the fuel pump or a dirty filter. It acts just like my old Ford Ranger did when it needed plug wires.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
If the spark gap is too large, it can misfire under the conditions you describe. If there is an intake manifold leak, the same applies. When the engine is in OD, with the torque converter locked, and there is spark breakdown or failure, you get the same symptoms as bad plug wires.
How long ago, mileage wise, were the plugs replaced? Just because they "CAN" be left in for 100k miles doesn't mean they should. Misfire can eat the catalytic converter ...$600-900 each, or the computer, by the COP back EMF when it cannot send the spark through a large-gap spark plug are more expensive than a set of plugs. The boot on the COP can also break down, allowing the spark to jump to the cylinder head, esp if the spark gap is large.
tom
How long ago, mileage wise, were the plugs replaced? Just because they "CAN" be left in for 100k miles doesn't mean they should. Misfire can eat the catalytic converter ...$600-900 each, or the computer, by the COP back EMF when it cannot send the spark through a large-gap spark plug are more expensive than a set of plugs. The boot on the COP can also break down, allowing the spark to jump to the cylinder head, esp if the spark gap is large.
tom
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Laughing Gas
Joined: Apr 2004
Posts: 819
Likes: 2
From: Northern Maine
The spark plugs were changed at 100,000 miles and new intake gaskets were used. the gap on the new plugs were checked before they were installed and found to be correct. I should have asked if there would be any codes in the computer if the check engine light is not on. I will have the codes read anyway.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
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From: suburban atlanta
Two things you can check are the MAF and the EGR. If the MAF has a bit of stuff on it, it will not report the air intake, and may make the mix too lean, causing 'lean surge'. Or the EGR may be a little sticky and not responding exactly as commanded or quick enough?
Too much EGR can cause a miss at cruise also. Ascending a grade in top gear is the time when you will notice an ignition breakdown as that is the hardest time for the plugs to fire. Did you replace the plugs with a foreign brand, or did you use Motorcraft or Autolite. I may be wrong, but have heard reports here and there about some brands not working well, but take it with a grain of salt. Why not pull a single one and inspect?
tom
Too much EGR can cause a miss at cruise also. Ascending a grade in top gear is the time when you will notice an ignition breakdown as that is the hardest time for the plugs to fire. Did you replace the plugs with a foreign brand, or did you use Motorcraft or Autolite. I may be wrong, but have heard reports here and there about some brands not working well, but take it with a grain of salt. Why not pull a single one and inspect?
tom
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Laughing Gas
Joined: Apr 2004
Posts: 819
Likes: 2
From: Northern Maine
I'm not real sure what brand I used but they were a name brand bought at the local CarQuest store. The vehicle is a spare so I'm not going to drive it until I can get it scheduled in to have the codes read. One thing that I forgot to mention was that we (my wife and I) bought a new car in April. Our Escape developed transmission issues shortly after that. It sat for 5 months without even being started while we decided what to do with it. We ultimately saved up the funds to have the transmission replaced and are going to keep it. It sat an additional month in the transmission shop (I made the mistake of telling them that I was in no hurry for it) I am assuming that the 6 month period of inactivity didn't help the coil(s) very much.
Cargo Master
Joined: Aug 2003
Posts: 3,263
Likes: 92
From: BC Canada
I'm not real sure what brand I used but they were a name brand bought at the local CarQuest store. The vehicle is a spare so I'm not going to drive it until I can get it scheduled in to have the codes read. One thing that I forgot to mention was that we (my wife and I) bought a new car in April. Our Escape developed transmission issues shortly after that. It sat for 5 months without even being started while we decided what to do with it. We ultimately saved up the funds to have the transmission replaced and are going to keep it. It sat an additional month in the transmission shop (I made the mistake of telling them that I was in no hurry for it) I am assuming that the 6 month period of inactivity didn't help the coil(s) very much.
Check for any pending codes.... and freeze frame data..
You might consider connecting a "LIVE DATA SCANNER" not a code reader... and check the parameters on the MAF, ECT(>180*), AIC, LTFT and O2 switching voltage..... Philip
Cargo Master
Joined: Dec 2006
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From: hinckley ohio
Mine had a studder at around 43 mph it would go away if if you sped up but if you where just cruising steadily it would studder. I had the trans rebuild and had the same issue checked it with a code reader and there was a pending code.It was a coil pack that was going. it would idle fine and the check engine light was not on.
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Laughing Gas
Joined: Apr 2004
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From: Northern Maine
bmuhlabach, That's what mine is doing but at 55 MPH, and only while in OD going up a hill. I hope that it turns out to be a bad coil. My transmission was toasted for sure, it shuttered while shifting in every gear. It shifts smooth as silk now. I got a good deal on a re manufactured unit with a great guarantee. I've got too many irons in the fire and not enough money in my pocket to take it in right now (we don't drive much it anyway). I plan on having the codes read in a couple of weeks. In the mean time it is going to stay parked in my garage so that I don't ruin something else.
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Laughing Gas
Joined: Apr 2004
Posts: 819
Likes: 2
From: Northern Maine
I took the vehicle in to have the codes read but found that there were none. There were no codes in the history either. The only things that we could find was a dirty (very dirty) fuel filter and a white greasy deposit on one of the coils on the spring where it connects to the spark plug. I cleaned that off and replaced the fuel filter. It seems to be running good, at least for now.
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Laughing Gas
Joined: Apr 2004
Posts: 819
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From: Northern Maine
I thought that it might be dielectric grease too. If it was, it was left over from the factory as I didn't use any when I changed the spark plugs and it was only on that one coil.
Junior User
Joined: Aug 2008
Posts: 78
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From: Sumneytown, PA
Dan- I had the exact same symptoms on my '03 V6. Was fixed by eventually replacing all 6 coils. Some were probably good (if not most) but ater trying to access the rear coils one at a time I decided to just do them all. It's been many months now without problems. Also, the computer doesn't seem to log the miss as no codes were ever posted even after some nasty episodes.
Good luck- Jack
Good luck- Jack
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Laughing Gas
Joined: Apr 2004
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From: Northern Maine
So far, so good. I'm going to try it for awhile and see if it acts up again. If it does, I might chance replacing the front 3 coils one at a time but if there ends up being one bad on on the rear bank I will most definitely replace all three of them. I'll probably put in new spark plugs again while I'm right there.
Logistics Pro
Joined: Jan 2002
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From: suburban atlanta
I would get some dielectric grease for the boots. They will bake in place and harden making them difficult to remove... and they are not cheap. Dielectric grease is pretty inexpensive.
The plugs should be fine at 33k, and I would not touch them unless you think they are having a problem. The COP system should be a lot less susceptible to misfire as there are no plug wires that have to be routed and kept tight in place, and the only place for spark to jump improperly is to the inside wall of the plug well, or the shell of the plug.
I have seen the coils for prices that range all over the place. OEM prices are pretty steep, but there are alternatives that are not so expensive.
tom
The plugs should be fine at 33k, and I would not touch them unless you think they are having a problem. The COP system should be a lot less susceptible to misfire as there are no plug wires that have to be routed and kept tight in place, and the only place for spark to jump improperly is to the inside wall of the plug well, or the shell of the plug.
I have seen the coils for prices that range all over the place. OEM prices are pretty steep, but there are alternatives that are not so expensive.
tom
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