Hi,

Hoping someone on here can help point me in the right direction to solve this problem once and for all.

I've got a 95' Ranger extra cab 4x4, 4.0L, manual transmission. A couple of years ago it developed an annoying bog condition. This bog only happens when I lug the engine a bit, or if starting on a hill, or if I floor the gas pedal. When this happens I can sense a definate hesitation or bog, feels like one cylinder dies for a stroke or two. I can't see anything on the tach when this occurrs. It runs fine as long as there is no heavy load on the engine.

In an effort to source out this problem, (and some others) in the past couple years I've replaced the following components: IAC, DPFE, EGR valve, EECS components, engine coolant temp sensor, cleaned the MAF, replaced intake manifold gasket, replaced valve cover gaskets, cleaned the throttle body, replaced coil pack, wires and spark plugs, replaced fuel filter, air filter, I change the oil and filter every 5000kms.

The only thing that's ever made a difference was replacing the spark plugs (autolite DP's). After spark plug replacement, all the symptoms vanish, and the truck runs great, BUT, the annoying bog slowly creeps back after about 4 months. I've replaced the plugs about 4 times now. First thinking I got a bad one, then messing around with the gap, minimum to maximum in the range specified. Nothing works and the damn bog comes back.

I have a code reader and have checked for codes, nothing, and this situation never triggers a CEL (I wish it would). I have checked for vacuume leaks and found nothing. I'm really thinking this has something to do with spark, as new plugs solves the problem, albeit temporarily. Another thing to note is the plugs look really good when I take them out of the truck, no excessive oil or carbon, or burning, they all look good.

I'm really at a loss as to where to go next, can anyone offer any advice?

 

Have you checked and/or replaced the Throttle Position Sensor?

 

I've read here that it's best to stick with single platinum plugs, like the factory used. I'd really like to say it's a candidate for a dirty MAF sensor or a vacuum leak too, but it looks like you pursued those. A dirty MAF sensor, as we know, can deliver a lean mixture as it senses an invalid, lower than actual airflow. Buy no more sensors until they are proven bad, such as by doing pinpoint diagnostics on a suspect sensor.

*Are you 150% convinced there is not the slightest chance there could be a vacuum leak? And what color are the plugs when you pull them?

 

Hmmm sounds like a problem I had with my 91 with the 2.3. I mean the engine is low on power to begin with, but I had semi's beating me off the line.

I replaced the DIS module on my truck because of an internal problem with it. It was shutting off 2 cylinders randomly at a lower RPM. Once it got up around 3500 it was fine. I pinpointed the problem being this module, replaced it, and it's been running like a top since. Even with 311,000 miles on it right now.

Now lemme stress that this was with the 2.3 4 banger. The DIS module controlled two coil packs because it was an 8 plug design. If you even have the DIS module (which I'm sure you do because you stated that you had coil packs,) then I would have it looked at. I honestly don't know the location of it on your truck, but mine was mounted on the front of the intake manifold behind the alternator or a/c pump, depending on the truck.

Hopefully this gives you a place to start. I think some auto parts stores can test these DIS modules...

 

Thanks for the replies, Throttle position sensor has not been replaced, but I've never had any other problems that wold lead me to believe it's bad. Cowboy, my plugs are sort of a greyish-brown colour when I take them out, but not a lot of deposits, I would say pretty clean, all cylinders are the same. Is there a difinitive way of checking for vacuume leaks? I've inspected the lines as exhausively as I can/know how to do. I am surprised about your comments on the DP plugs, I was originally turned on to them from reading posts from this forum, is the consensus now that DP plugs are bad?

 

From what I understand the DP plugs arent bad its just that they dont show any advantage over a regular plug. Have you checked your fuel pressure? Injectors may need cleaned? I dont know man...just throwin out some possibilities.
Good Luck.

 

When my Throttle Position Sensor failed on my '94 3.0 L ,v6, 5spd 2wd. the throttle response was sluggish even after a full tune up. It didn't log any codes until the my truck started to not return to idle for 7 to 15 seconds after my foot came off of the pedal( it made driving real interesting). It is easy and relatively cheap to replace and eliminate as a possible source for your problem. If you change this part be sure to reset your vehicles computer and drive it 10 or more miles to allow it to relearn the system with the new parts. Hope this helps...

 

The prior owner of my Ranger, (95, ex.cab, 4x4, 4.0 hmmm) had SP plugs in when I bought. The wear factor was something else when I replaced with DP. The anodes were gone in half of them. I almost took pics.

What rear diff do you have? I have the 3.27 and I have to fight to keep the rpms up. First feels too high and I have to watch the tach or I'll run around under 2000 rpm all day.

 

The wear on the DP's is not bad at all when I've taken them out to inspect them (in my opinion). Certainly not excessive. I'm not sure what rear end I have in this truck, but I am sure the problem is not back there. The problem dissappears with installation of new plugs, then creeps back a few months later. For that reason, I'm sure it has something to do with spark/ignition, but what?? has me stumped.

 

From your description of there being no codes, it sounds like the computer isn't able to monitor whats going on.

So I suppose it might be helpful if we could narrow down some more conditions that exist, that make the problem worse or better.

When this began a couple of years ago, did it come about suddnly, after some event, or slowly over time????

Is the bog condition worse in damp/wet weather & better when it's cool & dry, or maybe better when it's warmer, worse when it's cooler, in other words, is it weather driven in any way ????

Do you notice any changes when the engine is cold, partly warmed up, or fully warmed up????

When you replaced your wires, did you use OEM or aftermarket????
Are they routed correctly, as Ford had them & are all the wire looms intact????

Did you butter both ends of the of the spark plug boots inside & the outside of the plugs ceramic insulators, with dielctric grease????

Is the top of your coilpack clean & are there any signs of chips or cracks any where on it????

 

This sounds like high resistance in the ignition system. The Key being you can put in new plugs and it runs ok for a few months. I had this once and it was wires. In your case you have already replaced these so I would look at the coil packs.

 

Did anyone read the post I made a while back? I'd look at the coil packs, but you have to remember that the coil packs pick up a signal from the DIS. I'd say pull the coil packs off and make sure they are grounding out well to the bracket. If that doesn't help, then I'd have the DIS module looked at, as they have a history of going bad.

 

I am not familiar with the DIS system, where/what is it? Paw Paw, I have OEM wires installed, as well as an OEM coil pack. There is no difference in hot or wet weather. When it's really cold, I would say that the symptoms are a little worse. The symptoms just seemed to creep up little by little, much as they do after a few months of new plugs.

 

Ok good feedback on the weather, begining event & replacement parts questions.

Looks like this one is gonna be a little more difficult to pin down, as we don't yet have many definitive clues to work with, other than it goes away for a while after you replace the plugs.

So for now maybe we should detail this area to death!!!!

Well DIS= Distributorless Ignition System. It consists of the OEM coil pack & spark plugs that you've replaced, a crankshaft sensor, the computer & all of the interconnecting wiring.

The computer takes inputs from the crankshaft & other sensors & determines when & for how long to squirt the fuel injectors & when best to fire the spark plugs.

As Handyman has pointed out, the coilpack needs a good clean, solid connecting ground, so it doesn't produce a weak spark that could get blown out under load.

The reason I ask so many questions about the weather, is, if you live, say, along the coast where you have plenty of salt spray & or humidity, then both those conditions may call for some extra attention to detail, on the High Voltage side of things, to help prevent a condition called high voltage "Flash Over", from condensation on the coil packs suface, inside the plug wires boots, or accross the plugs insulators.

My then new, 99 4.0L developed a stumble under load, during wet conditions, that was traced to flash over, from a cracked #6 spark plug insulator.

So my thinking was sort of leaning towards maybe a weather condition related problem, that would probably take some time to begin & would likely change with time & the weather conditions.

Then thinking about what changes, or what is moved, or other wise fooled with, when you replace the plugs & the problem goes away for a while, but not long enough for the plugs to be worn & you've said they aren't fouled, then seems to me, one is left with, plugs & spark plug wires, both of which are new, OEM, high quality parts, so the likelyhood of them being bad right out of the box, isn't high.

So then seems to me we're left looking at their high voltage electrical connections & surface conditions around them as possible suspects for flash over.

So have you checked to make sure the coilpack doesn't have any cracks anywhere, is squeeky clean on top along with the insides or the wires boots & plugs insulators & you have buttered the insides of all the clean spark plug wires boots, on both ends & the spark plug insulators, with a good dielectric grease, like a GE or DowCorning product & have the plug wires routed as the factory did, in their looms????????

I did all these things, plus sprayed the top of my cleaned coilpack with silicone, so condensation wouldn't cause electrcal leakage or flash over, on top. You can spray it with a water hose now & it doesn't even know it's wet!!!! LOL

When we've eliminated those questions, then I suppose it'll force us to revisit & test elsewhere, like plug wire resistance, having the coilpacks output tested & fuel delivery, fuel pressure, throttle position sensor, MAF cleaning ect, ect.

So until we get better clues to look elsewhere, lets detail the high voltage end of things, so they can be eliminated.

 

Thank you pawpaw for considering my idea. LOL. Well you've basically covered everything I was going to say, so no need for me to post anything until we get some feedback!