Ignition coil testing / misfire

1996 V6 Sport explorer, 219K miles, no engine work yet.

Been getting a misfire code on cylinder 6.

Got spark plugs changed at dealer. Changed the wires myself. (Both long overdue). Noticed that some of the old plugs were showing 'lean' white-ish stuff on them. I'm getting pinging when going up hills also (maybe that intake manifold problem that people talk about).

As wires and plugs were new, and code later came up again, I decided to test the ignition coil. It's the original one, after all. Seemed to be the next logical thing to do. Primary resistance checked out OK. It tested secondary resistance of approx 13.5K.

As this is supposed to be 6.5K-11.5K, according to Haynes manual, I purchased a new ignition coil.

First I purchased a Wells ignition coil, the new unit tested 12.7-12.9K secondary resistance. As I read such bad stuff about Wells ignition coils and it seemed to be out of spec, I decided not to install it, and returned it to the store.

I then purchased the Motorcraft one. This one tested 13.2K secondary resistance.

I then purchased some 10K and 20K resisters from radio shack. Using the same multimeter, these all check in easily in spec (+/-5%), eg. the 10K resisters test at 9.69-9.67K, and the 20K resiisters test at 21.3-21.4K.

So, that seems to validate that the multimeter is working OK.

So, is the spec on this part off, or whats the deal?

I'm guessing that the new motorcraft ignition coil probably won't do anything to help...but thinking of installing anyhow, as it would be a pain to return back to the store (bought mail-order).

If the new ignition coil doesn't help, what's next....thinking a visit to the dealer for them to look at injectors/hook it up to whatever tools they have? I did read about the camshaft sensor, and another sensor that might be pertinent.

Paul

Reply to
Paul Scrutton
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Wooah...that's a 22K resister by the way, that checks in, in spec (not a

20K).

Paul

Reply to
Paul Scrutton

Interesting, I just re-read my Haynes manual on this section, and noticed that in Fig 7.2, where they show the secondary resistance being measured on a motorcarft ignition coil, they have a pciture of a multimeter, and it shows 13.19 being displayed on it's digital display.

The chapter specs say 6.5 to 11.6K ohms though. And the description on the checking procedure clearly says 'The resistance should be listed in the Chapter Specifications'.

Anyone know what the Ford manual says?

Paul

Reply to
Paul Scrutton

I wouldn't spend too much time agonizing over this reading..... The correct way to test this would be with a spark tester at the plug end of the wire - I have seen many bad coils ohm good.

I see no mention of a compression test - this is one of the most basic tests that we can make and indicates whether we can expect the motor to run smooth or not. That you have received a misfire code without any mixture codes makes me want to see some compression numbers.

If you take it to a shop for diagnosis, I would suggest refraining from trying to direct the diagnosis. There is a logical progression to timely diagnosis (read economical) and flying from pillar to post will only add to the expense.

HTH

Reply to
Jim Warman

Thanks for the tips Jim. I haven't done a compression test, and it might just be that the engine is getting old at this point, and is getting low on compression. I might have to go out and pick up the equipment to do this, or get it done.

While we are talking about that, does anyone have acceptable numbers for compression on this engine (V6 pushrod)?

Paul

Reply to
Paul Scrutton

Depending on altitude (remember to hold the throttle wide open when performing the compression test) I would expect anything above 110..... when performing a compression test, we are more concered about even readings than the pressure itself (though the pressure does figure in).

Reply to
Jim Warman

Hey I have a 98 Explorer with the 6 cylinder OHV. It is doing the exact same thing. Cylinder 6 misfire. I don't think it is your compression for that reason. Have you had the test done or figured out what has caused it yet? I replaced my plug wires and plugs twice. It fixes it for a while and then it starts cutting out on me. Eventually my engine light comes on and the code reads cylinder 6 misfire. The only think I can think of is the coil.

Thanks David

Reply to
david824

Hey I have a 98 Explorer with the 6 cylinder OHV. It is doing the exact same thing. Cylinder 6 misfire. I don't think it is your compression for that reason. Have you had the test done or figured out what has caused it yet? I replaced my plug wires and plugs twice. It fixes it for a while and then it starts cutting out on me. Eventually my engine light comes on and the code reads cylinder 6 misfire. The only think I can think of is the coil.

Thanks David

Reply to
david824

I'm getting this also (same cylinder)...I'm wondering if it could be fuel injector?

Why wouldn't compression cause it?

I changed plugs/wires, and bought a lamp type spark tester that you hold near the wire, which indicates that all 6 wires have spark, so seemingly eliminates the coil. Although I'm not convinced that this spark tester can tell me whether the spark is good or not, just that there's some.

I was going to check the fuel injectors next, and then compression after that.

Paul

Reply to
Paul Scrutton

Hey I think I might have found the problem. It may not be the sparkplug, coil, wires or compression after all. The intake manifold gasket might have a hairline crack in it causeing a leak over cylinder 6. I know these explorers are notorious for having the intake manifolds bolts come loose in the back, causing them to run poorly. I was talking to a guy who owned a chevy and his was doing the same thing our explorers are doing and that was his problem.

David

Reply to
david824

Wow awesome. I also have the ping monster going off also, so did need to retorque the intake manifold bolts down too. That was going to be another task I had lined up to do.

I didn't expect them to be correlated, but this makes some sense.

Now what I need is a good reference for figuring out which bolts I need to torque down. I know there's a lower and a upper manifold. Do you have to remoive the upper manifold to tighten the lower, or can the lower manifold bolts be tightened without removal of the upper?

Quizzingly yours,

Paul

Reply to
Paul Scrutton

I have no idea, I haven't even tried it with mine yet. I need to get a torque wrench and some specs first. I asked a local mechanic about it, and he said that it sounds like the intake to him also. He said that he would just go ahead and replace both the upper and lower intake gaskets while I was at it because its under $20 and if there was a problem with the gaskets it will be taken care of. If you get yours fixed before I can get mine done, please let me know how it runs.

Thanks, David

Reply to
david824

I have had the pinging problem with my 1993 Explorer Sport. This vintage Explorer motor had a "weakness" in the intake manifold gasket which would let water leak into the #5 cylinder if the lower intake manifold was not properly torqued.

You can tell this by pulling the #5 spark plug and looking for a whitish coating on the plug tip. This is what was causing my pinging.

To torque the LOWER intake manifold bolts, you need to follow a torquing order and gradually torque them down one cycle at a time until the full torque value is achieved.

I believe the final torque is supposed to be about 20 ft-lbs. In the Haynes manual, the value is given in in-lbs.

Gradually retorque the bolts in a pattern (given in the Haynes manual) to avoid cracking the intake manifold. If you crack the manifold, it'll probably be some big bucks (I think I recall sombody saying $300 for a new manifold).

And, even if the new gasket is only $20, it is the labor to put it in that is the $$$ - I've heard quotes of $350 for labor since lots of stuff must be removed to pull the manifold.

Be aware that the most rearward bolt cannot be seen, must feel around for it.

And, I've found that my bolts tend to loosen up every two or three years, so you may have to go in and retorque again.

Plus, remember that you may have to change the #5 spark plug if it's coked up since the carbon build up is what's causing the ping.

I believe that Ford redesigned the manifold on the '96 model, so this only applies to the 1995 and earlier model as far as I know.

Reply to
Tommy Wood

I'll report any progress, if I make any. So, far my web-browsing leads me to believe that it is not absolutely necessary to remove the upper manifold to get at the bolts for the lower manifold. But a swivel socket may be needed. It would appear that it is a lot easier to get at the lower bolts if you do remove the upper manifold though.

The Haynes manual does have torque specs and the order in which you torque them. I might try and tackle this later this week. Been putting it off for about 3 years now....time to bite the bullet.

I plan to torque the lower and upper bolts and see if there's any improvement.

Paul

Reply to
Paul Scrutton

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