P0305 & p0306

[TKMS1220]

My 99 Explorer started running rough and sputtering from the exhaust. Thru codes P0300, P0305 and P0306. Checked coil and spark plugs and wires, all ok. Timing OK too. I cleaned the MAF and the throttle body. I'm getting a rotten egg smell from the catalytic converter. Checked all the PVC and vacuum hoses, all OK. The intake gasket was replaced about 9k miles ago. Took to a local shop, he's not sure whats wrong, he wants to try replacing the fuel injectors for about $500 bucks. He suggested that we might want to take it to a Ford dealer. Anyone have experience with this condition or some suggestions on what to look for? Thanks

 

[rb142]

Unlikely it is the injectors. I would be very suspicious of a vacuum leak somewhere ... specifically near cylinders 5 and 6 (for obvious reasons). Check around everything again -- spray around with something like carb cleaner, propane, or even water in a spray bottle. If you find something that changes the speed (slower or faster), you have found your problem. Check all around the intake carefully, and the air inlet tube (everything after the MAF). Check the seals around the injectors. Test the fuel pressure and flow. Listen to the injectors with a stethoscope to see if they are clicking properly.

What are the conditions? Does it misfire all the time? Intermittently? Only at certain speeds? Do you have a flashing check engine light?

Deal with the misfire problem first, then re-evaluate any catalyst issues. If the misfire has been going on long enough, it could have damaged the catalyst.

 

[TKMS1220]

It starts to misfire 60 seconds or so after startup and continues at all speeds, small backfires during acceleration. The check engine light flashes and then stays on.

 

[rb142]

At least it is consistent ... which should make it easier to find.

It sounds like it is going rich. (If you have access to a scan tool, you could check the fuel trims to see if it is commanding rich or lean.)

You could do a fuel pressure drop test to figure out if the injectors are leaking. You cycle the key to pressurize the fuel rail. Then use a tool to pulse the injector a fixed amount and watch the drop in fuel rail pressure. Then watch to see whether the pressure slowly drops (from leaking). It could be injectors, but I would want some evidence before throwing $500 at it.

You also might consider doing a compression test and/or a cylinder leakage test to make sure there aren't any mechanical problems in those cylinders (or in the head gasket between them).

 

[blakshukvw]

Search for my recent thread about my Xs ignition woes. You say you looked at the plug wires but be damn sure they are not compromised in any way at all. After reading that it begins to misfire after about a minute of running, it makes me curious about the health of your ignition. My truck would run decent until it ran for a bit as well and then start misfiring. Definitely ensure your intake gaskets are not leaking around those cylinders like mentioned.
Your mechanic isn't much of one if he's suggesting you take it to Ford. He needs to run a scope on the ignition, do fuel pressure tests, check for intake leaks before giving up. Sounds like he's just guessing by wanting to put injectors in it.
Have him check that the injectors are plugged in all the way. The plastic clips that hold the plugs onto the injector are real brittle and break when attempting to unplug the injector. Maybe they were compromised when the intake gasket was done. I has to zip tie mine all to the injectors.
Definitely don't drive it until its fixed or you'll just melt down your cat on that bank.

 

[1992fordgreen]

If there is a rotten egg smell, I'd highly suspect the catalytic converters. Take a look undertneath the car after its been running for awhile and see if the cats are red hot. If they are, that means either 1: They're clogged and need replacing or 2: unburned fuel is entering the exhaust (running rich), which causes the cats to glow red hot. Both cases require the cats needing replacing most likely. Check into the PCM. Does not sound like a fuel injector issue. There is TOO MUCH gasoline entering the exhaust, not too little (or running lean).

GL

 

[blakshukvw]

Yeah probably not an injector issue as it would be lean. The cats don't necessarily need replacing at this time, they stink because the fuel that's being unused in the cylinder. Now if you keep driving it you will need new cats. Check your ignition.

 

[lobo411]

My 99 Explorer started running rough and sputtering from the exhaust. Thru codes P0300, P0305 and P0306. Checked coil and spark plugs and wires, all ok. Timing OK too. I cleaned the MAF and the throttle body. I'm getting a rotten egg smell from the catalytic converter. Checked all the PVC and vacuum hoses, all OK. The intake gasket was replaced about 9k miles ago. Took to a local shop, he's not sure whats wrong, he wants to try replacing the fuel injectors for about $500 bucks. He suggested that we might want to take it to a Ford dealer. Anyone have experience with this condition or some suggestions on what to look for? Thanks

Did you visually inspect the wires for the affected cylinders, or physically remove and reattach them? I had a misfire code after working on the engine a few weeks ago. I did a visual inspection and everything looked perfectly fine, but I still had the code. Then I unplugged and replugged the spark plug wire on both the coil and the plug for that cylinder, and I plugged and unplugged the fuel injector wire for that cylinder. That fixed it.

 

[TKMS1220]

Before sending off to the shop I replaced #5 & 6 plugs (no change). I then switched #4 and # 5 plug wires (no change # 5 continued to misfire). Checked the ignition on #5 & 6 with a spark tester, received a steady rythmic spark on both wires.

 

[ron castle]

After changing #5 and #6 plugs did you clear the codes off before checking again?

 

[TKMS1220]

I cleared the codes each time I tried something new, no change in codes

 

[blakshukvw]

Still could be the coil pack for 5. A spark tester is OK but you need to know what the spark is doing under heavy load while driving. That's where a scope comes in handy.