2002 Explorer misfiring

cubsfan5150 · 09-04-2009, 09:36 PM

Alright, my exploder began sputtering pretty bad the other day and I had the codes read at Auto Zone and sure enough, I had a cylinder 1 misfire to go along with my EGR high voltage that I've had for sometime. The guy at Auto Zone said to change my plugs and wires and that should fix the problem. Did that with Bosch Platinum plugs and Duralast wires. Problem still there. Changed the coil pack, problem still there. Not sure where to go from here. Any help would be greatly appreciated.

It's the 4.0 SOHC engine.

theoldwizard · 09-05-2009, 04:38 AM

Try swapping injectors between 2 different cylinders. If the problems moves with the injector, you know your culprit !

cubsfan5150 · 09-05-2009, 08:58 AM

By the way, I got the codes checked again and I ended up with a misfire on three more cylinders too (2, 3, 6), and I was told that I might have a timing problem, but the mechanic also said that the timing probably wouldn't be causing my misfire problem.

cubsfan5150 · 09-05-2009, 09:34 AM

I did another diagnostics test this morning after driving the car last night, but it only shows 4 of 8 tests done. How do I make the car do the other four tests?

TheBobsHere · 09-05-2009, 08:54 AM

You may want to clean your EGR and check the DPFE sensor, they can both cause lean AFR which can cause misfire, especially if one of the injectors is sightly off from the rest. If after solving what I'm assuming is P1401 code you still have no. 1 misfire, here are some tests to eliminate any guess work.

First, simply listen to the injector. You can do this a couple of ways, with a stethoscope, a dowel rod or long screwdriver. If you use a stethoscope simply start the car put it on and listen to the injector, if you use a dowel or screwdriver it's pretty much the same, put one end firmly on the injector put your ear on the other end and listen (if you use a screwdriver you put the handle up to your ear, not the working end lol), either way you should hear the injector clicking steadily along increasing with the engines RPM. If the injector doesn't sound right (or at all) it's time to break out the multimeter and check the injectors resistance. To do this, set the meter to measure resistance (Ω) disconnect the cars battery unplug the injectors electrical connector and put one lead on each pin of the injector, the reading should be somewhere between 10-18 ohms. If the resistance is within spec plug the injector back in and reconnect the battery, if it's out of spec replace it. Next, put the key in the on position (don't start the engine), set the multimeter to dc volts, put the black lead to ground and probe the connector with the red, one side of the connector should have around 12v (depending on battery charge) the other side side should have nothing. If 12v is found its time for a tool called a noid light, you should be able to buy ($20) or borrow one from certain automotive chain stores. Once you have the noid light, install it on the connector of the injector in question and and start the engine, if everything is ok the noid light should flash and rise with the engines RPM, if it doesn't light at all you need to check the wire that had no voltage for breaks, if it stays lit constantly look for a short to ground on that same wire. If after these tests everything tested out fine, the injector may be clogged. Remove the injector and check the filter basket in the fuel supply side of the injector for blockage/debris, if its full or blocked clean or replace the basket (available in certain injector rebuild/seal kits) and run some fuel injector cleaner through the system.

It may be a bit complicated but if you do these tests you should know for a fact if you have a problem with the injector, it's circuit or if you need to look elsewhere.

phantom_smack · 09-05-2009, 10:02 AM

Drive it basically,but I would bet the problem now is yhe Bosch platinum plugs you should have stuck with motorcraft plugs.

TheBobsHere · 09-06-2009, 05:33 AM

My Mustang never ran right with Bosch plugs, tried several tip styles and they all caused a loss of HP over stock plugs. To top things off, even though they were torqued to spec three out of eight plugs leaked around the ceramic. I now run E3 plugs, the engine loves em.

Since your misfire problem started before the plug change I again would suggest solving the EGR/DPFE problem as it might just solve your misfire problem altogether.

TheBobsHere · 09-06-2009, 05:46 AM

Here's a link on how to check the DPFE sensor. Not sure if the sensor's location is the same , but the testing process is accurate enough. Just make sure to fill any holes you make in the wires with silicone sealer.

Two notes about the test method in the link...
1: Use a a push pin rather than a safety pin as it's is smaller and less likely to short to ground.
2: Don't start the engine for the DPFE sensor part of the test unless you want to make that part of the job hotter and therefore harder.