1995 Rwd Ranger XLT with SOHC 2.3L in-line four.

I’ve been driving it semi regularly since this February. On three different occasions, it has misfired while under load at 60 mph. I have the UltraGuage dash reader, so I know that every time it’s been a P0304, cyl 4 misfire. The previous owner put 6 of 8 new plugs in it, and left the two under the intake manifold for me to deal with. I put them in shortly after I got the truck. All 8 plugs are nickel NGK TR5 V-powers.

The first time time it misfired, I put all new spark wires in and it seemed like that fixed the problem.

The next time time it happened, I took stuff apart but didn’t change anything... but it didn’t misfire when I took it for a test drive under similar conditions.

The third time time it happened, I exited off the freeway, stopped at a few lights, got back on the freeway, and boom, no misfires!

I checked the coil packs with a multimeter and they’re good. The passenger cyl4 spark plug has been in longer than the one on the driver’s side and has a green tip. It has only misfired on cyl 4 according to the code reader. Do I have a bad injector? Bad plugs? Any help would be greatly appreciated!

Passenger side

Passenger side

Passenger side

Driver side

Driver side

Driver side

 

Welcome to FTE.
85 reads but no replies, so will see if I can get things started. You've been busy on this puppy. I agree, spark belongs on the suspect list for a high rpm miss under load.

Good idea to post trouble codes & plug photos, so the forum can sorta do a plug read. I think I see signs that the plugs are sitting in oil & Lots of crud on the plug threads & deposits on the ground side wire & plug casing combustion chamber end, for them to be new. So, how many miles on this vehicle & is the engine using oil from bad valve stem seals, guides, or worn or mucked up /poor sealing piston rings, or the plug well seals need to be looked at maybe replaced???

If the vehicle isn't up to date on its Owner Manual "scheduled maintenance" mileage replacement parts call-out, begin there, as you may need to be working more than one problem to get a lasting result on the misfire. If you don't have an owner manual, one can be down-loaded @ no cost here, Owner Manuals (ford.com)

Our Rangers have a "waste spark" ignition system that works its components Twice as hard, as the plugs are paired together & fired on Every rotation of the crankshaft, one is fired on its power stroke & the other on its exhaust stroke (waste spark), on the next crank shaft rotation the plug pair roles reverse, the plug that was fired on its waste spark mode, is now being fired on its power stroke, the one fired on its power stroke is now being fired on its exhaust (waste spark) stroke. Also on this system, Half of the spark plugs also get a Reverse polarity spark that emanates from the ground lug side wire to the fine wire center electrode, so plug design & heat range is important, as its a tuned electrical system & All components need to be able to deal with that Double workload & reverse polarity spark & work together to provide a balanced electrical load, to work its best
All that said, the latest Motorcraft spark plug for our engine is the fine wire, iridium enhanced center electrode, with platinum pad side wire design. It's also the proper Heat Range which is important & the plugs in there now aren't that design & unknown heat range.

Have the plug wires been replaced & if so with OEM Motorcraft, or the lowest cost Aftermarket, or with ones that say in writing that they meet, or exceed the specified OEM Motorcraft ignition plug wires???
Have you tried swapping plug wires, or coil packs, to see if the cylinder miss code follows the plug wire, or coil pack???

Some beginning thoughts for consideration, let us know what you find.

 

Thank you for your reply!

Should have included mileage. Odometer read 168k when I bought it, but was broken, so I don't really know. I've probably put <100 miles on it, changed the oil with full synthetic (I think), put a Purolator filter on, and have driven it 500ish miles since then. I don't think it's burning oil. I'll keep an eye on it though.

Some of the junk on the plug threads may be the copper anti-seize I put on them. The engine block is also really gunky around the plug holes, so I think the chucks of oily stuff on the plugs is there from when I took them out. However, oil in the cylinder is possible I suppose. Could I find a leak with a compression tester? I wasn't aware that plug well seals existed. I'll look into those.

I have both the owner's manual and the Hayne's manual. As far as engine maintenance procedures listed in the Hayne's manual, I HAVE NOT done anything with the coolant system, PCV system, or fuel system. Hayne's says the PCV valve must be checked or replaced every 12k miles. Probably is past that limit. I'm guessing the coolant hasn't been flushed and the fuel filter hasn't been changed when it should have been too. Seems like all those would affect all cylinders, and not just cylinder 4. Am I overlooking something?

I replaced the spark wires with NAPA's "Spark Plug Wire Kit - Premium" made by Belden Edge. For what it's worth, they say it meets or exceeds OE specs.

I have not tried swapping coil packs or wires. My understanding is that the coil pack fires two cylinders at once, so any problem with them would cause two misfires, not one.

I read on this site the thread on double platinum plugs. I came away with the understanding that double platinums or iridiums last longer, but have the same performance as copper when they're both new. I'm willing to try new plugs though if I'm wrong about the preceding.

I think I'm going to check the PCV valve next. It's a cheap part, and seems like an easy thing to check. I've gotten pretty fast at changing plugs too, so that would be a simple thing to try if you think it would help.

Thanks again!

 

I'm not a Ford 4banger guy, so see I engaged my keyboard mouth before engaging my moldy oldy brain about spark plug well seals & your Haynes manual reply woke me up that I too have a Haynes that covers the 95 2.3 L 4banger & I see the plugs aren't installed through cam cover deep wells that have rubber seals on them like the Wifes OHC Neon 4banger, so we can forget that question & not waste time on it.

I agree probably a good idea with the unknown mileage & past unknown scheduled maintenance, to replace the PCV valve. If its mucked up & sticking or is closed, with the mileage & possible piston ring blow by, it could over pressure the crank case & force engine oil past wimpy valve stem seals, the valve cam cover seal, to weep onto the plugs & muck them & the head & engine block up. Same for the oil pan gasket & crankshaft end seals, so check what you can see for weep signs & check how it goes after the new PCV valve is installed.

If piston ring blow-by isn't bad, we shouldn't have much positive pressure trying to blow our hand off the removed oil fill cap. There is a spec for it but i don't know the number but remember it was low. Most Dealers or good engine shops have a modified oil fill cap with a pressure gauge attached that can measure it, or we can mod a salvage yard part & make our own.

Sounds like the aftermarket plug wires may be of good quality but at least measure #4 plug wire end to end resistance to see if its in spec, like 1K ohms per inch of length, 30K ohms Max & the reading should be Steady as you wiggle Both end connections.

Check the owner manual, I think the PCV Valve replacement is like 120K miles, not 12 K

More thoughts for consideration, keep us posted on what you find & how it goes.

 

Ok, I'm going to check the PCV valve and spark wires to start with. I'll report my findings.

Couldn't find anything about the valve in the owner's manual. Hayne's says to check every 12k, and replace if needed.

 

I am not an expert at reading plugs but have looked at guite a few over the years, and I don't see any major problems with your plug. It is not oil fouled and the green is likely from the copper antisieze. Antiseize gets on everything. Check the gap but it looks about right.

 

I checked the resistance. Passenger side is 6.7k ohms and driver side is 8.9k ohms.

 

That’s a great point about the anti-seize.

I’ve got the hood up, so I’ll double check the gaps.

 

The gaps check out. 0.044 on both. .042-.046 is called for.

 

The 96 Ranger PCV valve replacement is 60K miles for Normal & Severe service, as noted in the Scheduled Maintenance booklet.

The thick electrodes on those plugs may be fine for long wear but their heat sink quality won't make for a stable, hot, tough to blow out spark kernel, like the iridium enhanced fine wire center electrode with platinum pad sidewire plug makes, as outlined here, Spark Plug Mini Tutorial - Ford Truck Enthusiasts Forums (ford-trucks.com)

 

I forgot about the Scheduled Maintenance booklet. I have it in the truck, so I'll have to read through it soon.

Yesterday I took the PCV valve out, and it rattled, which the Haynes manual says is an indication that I don't need to replace it. There's a vacuum test I can do on the PCV system, but I ran out of time for it yesterday. Here in MN, it got really cold today, so I'll probably wait till at least tomorrow to do anything on the truck.

 

Are you saying that I might see an increase in power & reliablity by switching to iridium/platinum finewire plugs? If so, I guess I could give it a try.

I believe I have the same plugs in all 8 positions, but I'm only getting a misfire in cylinder four, which to me seems to indicate the plug type is not the main issue here. Correct me if I'm wrong though.

Thank you for your continued advice, I really appreciate it.

 

As mentioned in a earlier post, the fine wire plug design has long been specified on TSB by Ford as a upgrade for our vintage waste-spark ignition. I use them in all our family fleet vehicles from the 94 Taurus 3.8L standard distributor ignition, to the Wifes 2000 Dodge 2.0L Neon 4banger waste spark ignition. All give faster year round starts thats really noticeable on cold winter days as posted earlier. EDIT: I just remembered, replacing the Neon waste spark ignition Specified standard copper plugs, with the specified heat range Autolite iridium enhanced fine-wire XP plugs, Fixed the intermittent "go @ throttle-up" miss the Neon had developed. Later as Scheduled Maintenance called out, I replaced the plug wires with Autolite after market top of their line, that was USA made & supposed to be = to OEM & they have been fine. So if we choose wisely, after market parts can be ok.

Did it have the miss Before the plugs & wires were changed???

 

Lets think about this some more. Seeing as how you don't know if the PCV valve thats scheduled for a change every 60K miles, has Ever been changed & the vehicle now has 168K miles on it, says it may be 2.8 times older than specified. The shake-rattle test only says its not mucked up solid, it doesn't measure wear on the parts, like how weak is the spring, nor how worn is the pintle or its seat, so how Well is it working???. Seeing as how this item can be thought of as a controlled / allowed / calculated for Vacuum leak, if its Not operating as designed for & its down stream of the MAF sensor, so not monitored by it, if it misbehaves, it can cause the up stream O2 sensor to mis-report the amount of O2 in the exhaust & that'll have the engine computer muck up fuel trim by adding a little more fuel & that might be what I think I see on the new spark plug casing & electrodes that shouldn't be there on New just installed spark plugs.

Hope you can follow all those drill-down thoughts to just replace that part as Ford Engineering has specified, so you know that Scheduled Maintenance Replacement part will be up to date & you can inspect its connecting rubber hose & elbow, that like to bake out, crack & become a vacuum leak. Whew!!! lol

 

It had a roughish idle before the plugs were changed. Didn't drive it enough before I changed it to know whether or not it misfired then. However, the previous owner had to replace the cat because it "got filled up". Seems indicative of a misfiring condition that let fuel into the convertor and wrecked it.

After I started driving it regularly, it misfired for the first time. I put the new wires on it, and that seemed to fix the misfire, but it came back again.

This Wednesday it misfired on a stretch of freeway where it had misfired before, and then yesterday it misfired again on a stretch of 60mph freeway that had a very slight grade. Whatever the problem is, it's getting worse.