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Discussion Starter #1
I have been having some strange issues with my escape. About six months ago I was stopped in a drive-through and the car seemed like it started to misfire. It almost died while idling in gear. I had no more symptoms for weeks afterward.

In the past few months, the problem has returned and gotten progressively worse, but it doesn't seem like a run-of-the-mill misfire. It will now idle rough, and miss randomly while driving at highway speeds, but this only happens sometimes. It seems to get worse after the engine warms up. I can start it in the driveway and drive it to work at highway speeds twenty minutes away with zero issues. If I then stop and let it idle or shut it off and restart it after it is warm, it will begin to miss. This is repeatable.

There are a couple other symptoms that may be related because they started around the same time. These are:
1.When it gets bad (missing at a higher than normal ratio) I have noticed that the battery light will flicker exactly at the same moment that it misses.
2. Several times in the past few months the gauges on the dash have reset while driving. When this happens, they do the normal startup thing, i.e. cycle from zero to max and then proceed to operate as normal. Everything else continues to operate while the gauges cycle.

Besides this the engine seems to operate normally. I have full power 99% of the time even when I stomp the gas. But occasionally it seems like multiple cylinders do not fire for a cycle, the battery light flickers, and then normal operation resumes until it happens again.
I have replaced all the plugs and checked the coils. I cleaned the battery terminals and had the battery and alternator checked; both checked out ok. I checked for vacuum leaks and found one at the EGR and fixed it. This had no effect whatsoever. To me, it seems like an obvious electrical issue. It’s like the voltage for the entire system is dropping to zero and then jumping right back up to normal like there’s an instantaneous short somewhere. At least this is my thinking since the battery light flickers when it happens. PCM? Dying alternator? Short? Any ideas?

No check engine codes.
 

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canuck
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The V6 is a great engine although electrical issues are the worst. I would start simple. Clean the MAF sensor, lots of good how to videos online. There should be a ground wire that attaches to the frame, or somewhere around the battery. The screw may be badly corroded, even missing, etc. Otherwise someone with more knowledge may chime in about a crank sensor possibly worn out, or with any luck an easy inexpensive fix.
 

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Discussion Starter #3
Good ideas. I'll clean the MAF, maybe even disconnect it while the engine is running funky and see if that produces a change. I did think to check ground connections, but I forget every time I'm under the hood. Seems as likely as anything. I'll report back on whether or not these ideas fix it.
 

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Discussion Starter #4
Cleaned the MAF, no change. I found two grounds, one almost directly under the battery and one on the passenger's side next to the coolant reservoir. They both appear to be in really good shape. Heavy gauge wire, no corrosion, secure connections.

I picked up a new battery just to hook it up and see if it was that simple. The new battery made no difference at all.

Running normally while cold is still a repeatable pattern. But then as soon as I stop, shut off the car, and restart it while it's warm, it starts to misfire. The battery light still flickers every time it misses. Some electrical component seems to be working normally while cold, and then intermittently failing after it heats up. The flickering battery light points to an alternator issue, but then I don't understand why it runs normally while cold and produces 14.4V every time I have checked it.

As this gets progressively worse the thing that confuses me the most is that there are NO CHECK ENGINE CODES. When an engine misfires this much you would think it should throw a code.

If anyone has seen something like this before please chime in.
 

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Try LOAD testing alternator and see what readings you get . Check wiring , plug at alternator .Would also suspect a coil/s breaking down intermittently especially when hot , but USUALLY triggers a code as you suggest , but not always .I have found the crank sensors /wiring normally fail when hot , causing none start in most cases , but worth checking .Could try changing the engine coolant temp sensor and check for vac leaks , check PCV valve and hose .
 

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Discussion Starter #6
I did perform a simple load test on the alternator. I had a friend sit in the cab and keep the engine rpm around 1500, and then flip on the high beams, blower motor, radio, etc. The regulator seemed to responded appropriately with the voltage always bouncing back to ~ 14V within a second or two. Of course I did this while everything was cold and running normally so who knows... It's charging the battery just fine but that doesn't mean it's working 100%.

A shotgun approach isn't my favorite diagnosis method but I'm going to start with replacing all of the coils. They look like factory originals and should probably be replaced anyway. They're COP coils, so coil/s failing after getting hot makes sense. I'll check out the PCV valve and hose while I've got the manifold off. Crank and camshaft sensors are cheap and easy so that might be next, although like you said there should be some non-start or complete stalling issues if that was it.

I REALLY don't want to have to replace the alternator in this vehicle. I'm sure anyone who has replaced an alternator in an older escape 3.0L can relate.
 

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Discussion Starter #7
FIXED! It was a coil, or coils, that only failed after they heated up. I noticed when I pulled the coils for the second time that there were some microscopic cracks in the plastic on some of them. Why it wasn't throwing a code when it was often misfiring to the point that it was hardly drivable is beyond me. My best guess given the symptoms is that when the coil failed it wasn't arcing to the block, but failing to spark entirely, and the back emf was f***ing with the entire electrical system.

Here's a recap of the symptoms:
  • misfiring, but only when warm
  • battery light flickering exactly when it misfired
  • gauges resetting while driving and other wonky electrical system issues
Also note that at no point was there a CEL indicating which cylinder was misfiring. The coil resistances checked out OK and they sparked when I tested them. I did these tests when it was cold, ~30 degrees F. They only failed when hot!

And the fix: 6 new coils

Hopefully this thread helps someone in the future. Thanks for all the suggestions!
 
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