I have a 96 Ranger with a 3.0 and unknown miles as the odometer stopped working some two years ago. The service engine light has been on for some time when I pulled the codes all I got was the P0401 EGR code. I honestly did not feel like dealing with it since the truck is not being driven very often. A few weeks ago she started running really rough so I figured ok I guess I'll do something with the EGR. I got a new DPFE sensor as I was sure that was what it was. Before installing it I pulled the codes again. In addittion to the P0401 I was now getting a P0306 code as well. I replaced the sensor then started checking the #6 plug and wire. The plug was as pretty as the day I put it in a year ago. The wire however had a burn on the side of it were it was resting against the pipe for the egr. I figured great easy fix. Pulled a wire off one of the parked trucks at work (it just had a tune up so the wires were nice and new just waiting to be used) and put it on. Still runs rough and the check engine light started flashing. Pulled the codes and got P0300. Decided to drive around the block to see if things would clear up. They didn't and got worse. the light went from blinking to stedy burn. Got her back home pulled the codes again and got P0306 and P0303. It seems putting on the new wire only made things worse. It's raining tonight so I couldn't get much further. These are the two cylinders at the back of the engine. I have no idea if this means something or not, but thought I would throw it out there. I would like some advice on what to check next.

 

I should add that a year ago when I did the tune up in addition to replacing the wires and plugs I also replaced the cam position sensor, syncronizer, cleaned MAF, replaced all the filters (air, fuel, ect), serviced rear end, transmission, oxygen sensors both, fresh paint, tires, seafoam treatment, and all four shocks. The truck has probably had less than 5000 miles put on her since then. Regular oil changes every 3000 miles as well.

 

Any ideas, anybody? I've gotten out of the habit of working on things with spark plugs.

 

Well the P0300, random multiple cyl misfire could be a number of things from spark, to fuel injectors, to compression, but with the P0303 & P0306, whch says the computer is unhappy with those two cylinders for some reason.

It would seem to me with the plug wire thing you found on #6 & the weather conditions you mentioned, kinda makes me want to lean more toward an electrical problem with plugs or wires.

So if we back up to the point that you last reworked the igntion system with plugs & wires, did the CEL come on just after the rework, or somtime later????

If it came on shortly after the rework, maybe there is a problem with the new wires, or plugs, just because they are new, doesn't automatically make em good. I've seen bad brand spanking new ones, right out of the box.

You might have damaged something on installation, like chipped or cracked a plug insulator, or maybe didn't route the wires as the factory had them. Or maybe damaged the wires insulation, on installation, on those two cylinders.

Seeing as how you say it was raining when it was acting out, flash-over would be a possbility too, so did you apply a good di-electric grease to the plugs insulators & inside the plug wires boot's, on both ends, of all the plugs & wires????

If you think moisture may be part of the problem, you could try wetting those two wires down with a spray bottle of water & see if you can get it to run rough when the wires or plug boots are damp.

Are the plugs & wires OEM, or at least OEM quality, or are they some inexpensive off-brand????

You say it hasn't been driven much, so how old is the gas, thats in the tank???? I'm thinking maybe dirty, varnished up injectors.

Just some thoughts to ponder.

Let us know what you find.

 

Thanks for the info, I'll check those things out. The plugs and wires were OEM or better according to the packaging. I paid extra to get the pro-fit performance wires. The plugs I were of equal quality as well. I had no problems after the tune up and she ran very well until a few weeks ago and only had the P0401 code. When she started running rough I pulled the codes and got the P0306 code along with the P0401. The gas in the tank is not that old, but I'll try a fresh tank as she is about empty. I noticed this morning when I moved it that there was an odor of fuel at the pipe. I'm figuring that this may mean that the fuel isn't being burnt. I have to put the old wire back on tonight before the boss notices that I yanked the new one out of one of the work trucks. As for the rain I doubt that was a factor since it started raining after I took it out for the ride and got the codes.

 

Well on the rough running part, you may have more than one problem.

If you still have the P0401 code, check out the EGR systems VSV, as it supplies the ERG valves operating vacuum pulses, at the direction of the computer.

So if the VSV is faulty, or it's operating electrical signals from the computer are corupt, it'll cause the EGR valve to act out & can cause engine operating problems.

Have you done a end-to-end resistance check of the #3 & #6 plug wires????? Can you see any electrical breakdown at night on any of theplug wires????

On the non operating speed-o, if your ABS light is on or the ABS system is acting up, or if you have cruise control & it's acting out, a good suspect would be the rear ABS speed sensor, located in the top front of the rear differential casting.

 

The egr code is gone and has not come back. The number six wire does have a small burn in the side. When I replaced this the only thing that changed was that now I got a P0303 code along with the P0306 code. Went to check the wires with the multi meter and found that the meter was dead. I do not see any sparks coming from the wires in the dark. Swapping the wires has no effect. I still get misfires and codes P0300 first then P0306 and sometime P0303. There is a smell of fuel coming from the exhaust. I'm wondering if the coil may be going bad, but wouldn't that effect all the cylinders and not just randomly shut down number 6 and 3? I'm going to get a new meter, check the wires, and then if they check out grab a spare plug and check for spark.

edit: I also tried swapping sparkplugs around still the same codes.

 

The general all inclusive misfire code P0300 could also mean you have misbehaving fuel injectors in those two cylinders.

Could be anything from a dirty, sticking, leaking injector, to electrical problems with an injector.

Seeing as how you've mentioned smelling raw gas in the exhaust at least twice now, maybe it's time to check those two misfiring cylinders injectors out.

Maybe try running a real good fuel injector cleaner through it, like Chevrons "Techron Concentrate Plus? at the specified one ounce per gallon treat rate, in a tank of Chevron, or Texaco gas & run most of the treated tank out.

That combo will yield a 10X increase of Techron detergent in the mix. It'll also tidy up the intake valves & combustion chamber deposits.

AutoZone has a $3 rebate on the 20oz size.

If that doesn't work, check the injectors resistance & make sure it's between 12-16 ohms.

If that checks out I'd consider pulling those two injectors & inspect the pentil for deposits or damage & their spray pattern.

If they are really dirty I'd think about pulling all the injectors, checking their resistance & if ok having all of them professionaly cleaned.

Just some more thoughts to ponder.

Let us know what you find.

 

How long on average do injectors last?

 

CHeck the distributor cap / rotor I believe the 3.0 still has one and it may be having a problem. Check your wires for resistance anything over 7000 ohms should be replaced. I don't care if they are new out of the box I have seen bad ones. I have fixed several vehicles with p3xx codes by power cleaning the injectors.

 

Thanks wtroger, but my truck does not have a distributor it's all electronic. I have not gotten a new meter to check the wires, but I have switched them around and even grbbed new ones off a truck at work that's running fine and still get the same codes. The problem does not follow the wires. I'll try the injector cleaner and see if that helps. I did however just do the seafoam treatment to the truck with no results, but I will try the techron and see if that helps.