OBD II codes.

[alg]

I have a 02 explorer slt. I get the following codes: P0301, P0302, P0303, P0353.
I checked the primary coil pack and get identical resistance readings.
The secondary readings are all 13.5k ohms. The shop manual says range is 6.5-11.5k ohms.
Since my scanner shows cylinder 3 issue I checked the resistance in that cylinder wire and it is 9.5k ohms. That is good as normal is 5k/ft of cable.
There is great spark on that cylinder with a test light.
Except for the secondary coil readings which are higher than specs (but all readings are equal) I don’t know if the coil pack is an issue.
My questions are; are the secondary coil resistance readings an issue ?
What should I investigate next, if I get feedback that the coil pack seems ok. The vehicle is not drivable as it stands.
Thanks for your feedback.

 

[Fix4Dirt]

how old are the spark plugs? not sure about the other question though

 

[J_C]

Which engine? Since you are getting cylinder 1, 2, and 3 misfire codes, I'd wonder about an intake manifold gasket leak on that bank, and use a scan tool to look at long term fuel trims.

Someone correct me if I'm wrong but since it is a waste spark system, any wire/plug/coil issue would not only cause misfires on one bank but also the other, I mean since the waste spark, shared coil is always between two cylinders on separate banks, on the SOHC 4.0L it's shared coil between cylinders 1-5, 2-6, and 3-4.

On the other hand there's the P0353. Here's one instance on a newer gen 4.0L where it happened due to wires shorting out:

Got code P0353 So I.... 2008 explorer EB v6 4.0

today, my truck was running terrible and had no power. i left it run in the driveway for about 20 minutes, and finally a check engine code came in. The code was P0353. Ignition coil C Primary/secondary circuit malfunction. i pulled the wires off the ignition coil one at a time, and on the...

www.explorerforum.com

The resistance readings don't seem alarmingly high to me, but one thing you could do is take the coil pack off and look for cracks on the bottom which is a sign it's failing. It could instead be a fouled coil pack connector, or one of the bulk connectors near the firewall. I don't think 3rd gen has a sticky topic about it but here's the equivalent topic for a 2nd gen:

2nd gen issues? Try this first!

Sometimes a gremlin can be caused by the smallest thing. There are 2 large wire bundle connectors on the firewall. Both are held tight with a 10mm bolt. Any bad connection in either plug can cause just about any issue. from bad transmission shifting, bad o2 sensor readings, no start, no...

www.explorerforum.com

 

[Mr. Alligator]

Have you checked plug wire connections?

Have you removed and checked the condition of the spark plugs, especially for cylinders one, two and three?

Any recent maintenance or changes to wires or plugs?

Your scanner is showing an issue for cylinders one, two, and three, correct?

Since plugs and wires are maintenance items, I would replace the entire set if they are well worn or aged.

 

[alg]

Have you checked plug wire connections?

Have you removed and checked the condition of the spark plugs, especially for cylinders one, two and three?

Any recent maintenance or changes to wires or plugs?

Your scanner is showing an issue for cylinders one, two, and three, correct?

Since plugs and wires are maintenance items, I would replace the entire set if they are well worn or aged.

So here’s where I stand. I replaced the plugs(they were old), spark plug wires, and coil pack.
The symptoms are unchanged. It will start, idle for a few seconds, then stall. I have read about it possibly being a vacuum leak, and looked at the vacuum hose routing diagram affixed to the hood, but am too stupid to translate the diagram to the parts. And advice? I’ve gotta figure this out.

 

[J_C]

^ Hook up a scan tool capable of live data and look at the long term fuel trim, though 5 seconds is barely enough time to work with.

At the same time you can look at the temp sensor reading, if too high it could cause too lean, as could a dirty MAF sensor. However I'm still thinking the intake manifold on the bank for cyl 1, 2, 3 based on the code, as a vac line leak would more likely affect random/all cylinders not just the one bank.

 

[alg]

^ Hook up a scan tool capable of live data and look at the long term fuel trim, though 5 seconds is barely enough time to work with.

At the same time you can look at the temp sensor reading, if too high it could cause too lean, as could a dirty MAF sensor. However I'm still thinking the intake manifold on the bank for cyl 1, 2, 3 based on the code, as a vac line leak would more likely affect random/all cylinders not just the one bank.

Looking at this engine, is the intake manifold plastic too? It seems to be. Is there a history of this whole thing cracking? Just wondering.

 

[Fix4Dirt]

Looking at this engine, is the intake manifold plastic too? It seems to be. Is there a history of this whole thing cracking? Just wondering.

the upper intake plenum is plastic, and iirc the lower is too. i havent heard really of em cracking before, but given ho wmany ford has sold, i imagine there have been times

 

[Mr. Alligator]

Both upper and lower intakes are plastic. Never heard of the plastic cracking. The gaskets, though, can leak and allow unmetered air to enter the engine (especially on cold starts).

Modern engines hate unmetered air.

Be safe and have fun.

 

[Taxhero]

You may want to look for carbon tracking on the coil packs, especially if it’s had a lot of use.

The higher resistance shouldn’t really be enough to be causing it to be undriveable

 

[Bookworm370]

From your symptoms, it really point to a vacuum leak, being you said you had to stand on the 'power' brakes. The brake booster is directly connected to the throttle body vac port with one of the biggest vac hoses under the hood. If you can't tell if there is a leak in the hose, the brake booster (not common but happens) can fail internally and you'll get the same thing. The way to test this is to remove the hose from the booster and then try to start it. If it starts and runs better, you got it. Replacing the booster is not a 10 minute job but you can get them and it's very doable.

 

[J_C]

^ I could just be lacking sleep, but I think you meant the way to test that is to remove the hose from the booster and plug the end of it.

Same can be done for any other vac line too, though rather than going to the end of the hose at the vac powered object, unplug from the manifold and plug the nipple there instead.

 

[Bookworm370]

That could work but you wouldn't eliminate if there was still a problem in the line. The totally right way to do it is to unplug it from the throttle body and plug the throttle body port. If it fixes it then put it back and now unplug it from the booster and plug the end of that hose. You've now proven that it's the brake vac system and the only thing that can be leaking (no easy way to test) is the brake booster itself.

 

[J_C]

^ But my point was, based on the prior post, all you'd be doing is making the biggest vac leak possible through the disconnected brake booster hose, not making it start and run better but rather, starting and running worse even if that wasn't where the vac leak was.

I agree, to eliminate the hose you can unplug the other end and plug the port.

However I'm still wondering why a van leak before the intake manifold gaskets, would only affect one bank of cylinders.