Diagnose the issue... the new game show.1 and 6 not firing 97 Ford Explorer

Ok theres nothing you win but hey its fun! :slight_smile:

Diagnostic says 1 and 6 are not firing. Car runs rough slightly. I think one of them is intermittently firing the other maybe not at all.

Possible causes according to diagnostic:

coil, plugs, injector, vacuum leak, wires (From memory)

Gas mileage is excellent. This makes me think its injectors. Failing plugs or wires would cause massive gas loss through misfiring cylinder.

Just bought this car. The seller said the wires and plugs are new. I will inspect tomorrow when I do the brakes.

Assuming they were replaced it leaves coil, vacuum or injectors.

Your thoughts? Much appreciated.

What is the actual code? A misfire code for 1 & 6 could mean one miss every ten tries, not every try.

I suspect the coil. Ford uses a wasted spark ignition system on their DIS systems. This means one coil is used to fire two cylinders at a time, with one spark firing a cylinder on the power stroke, and the opposite firing on the exhaust stroke. On the V8 engine, cylinders 1 & 6 share a coil. Get a good repair manual or sign up at Autozone.com and use the free repair guides to test the coil with a multimeter to see if it is going bad.

My thoughts exactly until I looked at manual. 1 & 6 on my 4.2 six cylinder don’t share spot.

Still could be coil. Or injectors or both.

I noticed at start up (choke) it runs a bit better. Like maybe 1 cyl better.

Have you pulled the plugs on 1 & 6 and compared their appearance to the other plugs? The plugs can sometimes tell you if a cylinder is running rich, lean, or has excessive oil saturation. There are charts online that can help you read the plugs.

You may be right that it will turn out to be the injector, but folks here rarely post their problem turned out to be a faulty injector. Injectors are robust, and pretty much bullet proof these days. An injector failure in a 97 Explorer would be unusual. Not impossible, but unusual. If this were my car, I wouldn’t assume it to be the injector until the other possible causes were eliminated. Misfires wouldn’t cause any more gas usage in that cylinder. The spark or lack of it doesn’t affect, or at most only slightly affects, the amount of fuel injected. If it were my truck, I’d measure all the coil resistances, test the crank sensor (assuming you have one), visually check all the high voltage components for cracking in the insulation, and carefully look at all the vacuum hoses, see if you find one split or that has come undone.

@bustedknuckles I went to pull the plug and it was really tight. I will lube them before I pull them. Last thing I need is a busted plug in cylinder.

I havent busted a knuckle so the job cant be done.

@Georgesanjose I dont have those tools.

BUT I do have new info. The old fashioned screw driver in your spark plug boot held near ground.

Both one and six firing strong and jumping a full inch to ground. But six seemed to be a bit sporadic but that could very well be the imprecise method I was using.

It tells me the plug is getting spark. So now its the plug or the injector. I think that rules out the coil and the line.

Also it dawned on me that it could be the onboard computer?

When it runs it seems like one piston is out just out no nothing.

The other seems to sputter.

When given gas it seems kind of to go away but not like normal.

What I mean by that is when a piston starts firing its a jump in the car and sound of the engine.

If i give it gas it accelerates fairly well and it seems to smooth out.

Any relation between 1 and 6 im missing? They dont share any head gasket. They dont appear to share space on the coil.

Im thinking of buying coil b/c its easy and I may be able to find one relatively cheap.

If your getting strong spark by that method, I doubt it is the coil. More than likely the plug or the injector. What brand of plugs are you running? I use nothing but the factory Motorcraft, and have had no issues. They are available at AutoZone and Pep Boys. Should be available near you. I don’t know if these trucks are sensitive to aftermarket plugs, but my old Toyota was, and ran best on Denso brand and worst on Autolites. Bosch were OK, but Champions were terrible. Sounds funny, but it’s true.

Also, tossing in a bottle of Techron to the gas could help if it is a dirty injector.

I dunno, in over a million miles, I’ve never had a bad injector. They’re good for 300K plus-I had over 500K. I guess you can test the injector by unplugging one at a time to see if there is a change in performance or not. You should see a huge change with one injector out.

Next I guess I would discount anything the previous owner said they replaced. If the wires don’t look brand new, I’d replace them and the plugs just as a matter of normal maintenance. After that coils.

If you paid for the diagnostics, you didn’t get your money’s worth. They should have been able to tell you from the computer if there was an ignition problem.

“They should have been able to tell you from the computer if there was an ignition problem.”

Unfortunately, it’s not quite that simple. A scan tool doesn’t have all the answers. If you get a P0306 code, it means there is, or was, a misfire on #6 cylinder. It’s up to the mechanic to figure out what is, or was, causing the misfire.

GM capable scan tools have an injector balance test, which helps to pinpoint a faulty injector. However, not all Ford scan tools can do this. Pinpointing a bad injector on a Ford is not quite so easy.

Also, the scan tool won’t tell you if a particular cylinder is receiving a good strong spark. The mechanic has to figure that out for himself.

So, in essence, the scan tool is a good tool, but it is sometimes just a starting point.

If the diagnostics say one and six are not firing, yet you see a spark on both, if it were my car, and I’d eliminated the other obvious, first thing I’d do is bring all owner’s manual suggested routine maintenance up to date, then tested the easy to test things like vacuum leaks, egr valve, ignition timing, pcv valve, fuel pressure regulator not leaking gas to vacuum hose, etc, I’d probably spray some starter fluid into the fresh air intake when the rough idle was happening and see if this improved things. If so, that would indicate some kind of lean fuel problem. If so, next I’d measure the fuel pressure. And I’d probably do a compression test on all the cylinders. This kind of problem can be tough, as it can be caused by a dozen or more things out of whack. Trying some fuel injector cleaner in the gas tank probably won’t hurt (except your wallet) but I doubt it will help. But it is fairly inexpensive and easy to do so probably worth a shot. You may need to consult a dealer or a Ford expert who has the Ford scan tool to get to the bottom of it. They could do an injector balance test to see if all the injectors were injecting the same amount of gas. Best of luck.

p.s. there’s an inexpensive gadget you can buy at harbor freight tools that makes it easy to test for spark. It inserts in-line between the spark plug cable and the spark plug, and lights up when the spark arrives.

Ok ill go with your its not the injector @bing.

Plugs will tell a lot. Gonna spray lube in the holes and try in a couple of days to get them out again.

Agreed re wires, plugs and coil. They don’t look new. So ill get them.

As for the scan it was the Auto Zone free scan and all it said was 1 & 6 misfire. Gave suggestions which we’re discussing. One oother I forget.

The miss is VERY consistent. Dirty injector, bad plug I would think would hit occassionally.

Veey strong spark. So plug or wire.

Leaks in vacuum etc would be less consistent and I would think would cause problems w 1-6.

I put in one bottle of injector cleaner. Bilden? I’m about out of gas so I will put in second bottle I bought.

No change after first bottle.

Why are you guys so sure it’s not an injector?

As a pro, I must say that a bad injector does occur from time to time, although it’s uncommon

I’ve seen both plugged injectors and injectors that had an electrically open circuit

I would have a shop perform a fuel pressure test, as well as an injector balance test. If they don’t know what an injector balance test is, that is not the shop to use

All these recommendations are IN ADDITION to any other tests

Not saying its not an injector, just saying it wouldn’t be the first thing that comes to mind. The OP did say the “diagnostics showed”, not “code scan”, so to me a simple code scan is not diagnostics. Paying a mechanic $100 or so for diagnostics should pin point it further than plugs, wires, coil, or injectors on 1 and 6 is all. So far anyway, the code scan really hasn’t revealed much except there is a miss for some reason. But guess he got what he paid for.

Yes it wasnt a full blown diagnostic.

I just came across this thread which talks about unplugging the batter which causes the computer to misread and need to relearn. The seller did say he bought a new alternator and the alternator looks new.

The seller replaced coil, wires, plugs, distributor and alternator trying to fix the missing. That leaves the computer and injectors.

Will disconnecting the battery again and reconnecting help?

Does it run differently if 1 or 6 plug wire is disconnected? If not, that confirms that those cylinders are the problem. Do a compression test, If low compression, new plugs won’t help. If low compression, do a wet test (squirt some engine oil in theu the spark plug hole) .
If compression comes up- bad rings.
If compression doesn’t come up, bad valves, head , head gasket, block or piston.

Is the engine a V6 or V 8?