OBDII Scanner Codes P0303, P0300: how f***ed am I?

My engine was shaking unusually at low idle and displaying the check engine light, so I killed it and ordered a code scanner. Yesterday, scanner installed and paired to Torque Pro, I cranked the engine. The first scan took over half an hour to complete, and either returned no errors, or I didn't understand the controls- 27 sensors, all green. Strange thing, by the time it was finished, the engine was idling smooth. I chalked it up to bad gas, and was fix'n to take the truck in for an alignment this morning, only to discover it was idling rough again. I repeated the ritual ritual with the scanner, this time discovering the Fault Codes button and mashing it immediately, producing these results:

Pending Fault, P0300 - Powertrain, Random/Multiple Cylinder Misfires Detected

and

P0303 - Powertrain, Cylinder 3 Misfire Detected

It's a '98 small 1st Gen- 2.4L, 2RZ-FE I4 engine, 185K miles. For most of its life, it has had almost zero maintenance performed, aside from oil changes and filter changes and cleaning. Why? Ignorance. A little under two years ago, it had the radiator and hoses, thermostat, trany, differential, and engine oil, oil and fuel filters, clutch and break fluid, spark plugs (I believe) and all belts replaced by a shop, after which, it was driven only a couple thousand miles. It has never had the timing chain (chain, not belt) system replaced or cylinder heads gapped. A few months ago, I replaced the steering rack myself, easily the highest challenge level repair I've ever undertaken. I installed a tracking device for an insurance deduction about 6 months ago, after which the battery drained below ability to crank. Having removed that tick, then ran the truck repeatedly around the 'hood and idling for these scans, it is now cranking and charging without issue.

While looking for where to start the diagnosis, my brain melted down, and is throwing its own error codes now. Any reflection on where and how to start trouble shooting will be appreciated... as soon as my brain regains the capacity to think.

 

Check your spark plugs

 

Sounds familiar. You're not fucked, but your injectors prolly are.

I would replace all four injectors with ones rebuilt by Motor West in Canoga Park, CA (747-888-9768). Been there, done that...

 

At this point a leak down test or compression test.

I wonder if the valves were ever checked?

 

Will do- plugs and ignition cables first.

Are the injectors difficult to swap out without damaging? If so, after the plugs, I might rotate the injector to test- does that sound like a good or bad plan?

I've never "check" the valves- to what do you refer? If the sparks, ignition cables, and injectors don't demonstrate fault, I'll opt for the leak down test you've suggested.

Thanks all, for the kind feedback.

 

Yes thats a good idea to rotate the injectors, if the problem carries over to another cylinder then the problem was from your injectors

 

Easy things first.
Swap plugs 3 with plug 4.
Swap coil 3 with coil 1.

See if the misfire follows one or the other. Or stays the same.

 

My advice is worth exactly what it costs you.

Slow down. Start at the beginning.
The beginning is fuel, air, spark, bang.

Check plugs, and ignition first.
Random multiple cyl and cyl 3 more than likely means exactly what it says.
Multiple cyl misfire with no.3 being consistent misfire.
Check and or replace plugs and wires unless they are less than 30,000 miles old, then just check them.
If problem persists move in a logical order one thing at a time.
Slow down.

It is only a machine, and it can be fixed.

 

I checked the resistance of my injectors before ordering replacements. Five of them had about 15 ohms resistance, and one had 25 ohms resistance. I replaced all of them and the problem was fixed.

I have a 6-cylinder engine. I think you can unplug the injectors on a 4-cylinder engine without taking everything apart, but not having a 4-banger, I don't really know for sure. Just pull the plugs and measure at the injectors, not the plugs.

 

Here's a fun fact: my '98 2.4L 2RZ-FE engine has two coil packs connected by a spark plug wire sets to the plugs; HOWEVER, some variants- particularly those destined for California's emission regulatory environment -are said to used the coil-on-plug ignition scheme.

Coil-on-plug ignition "coil packs" are easily identified by the low profile boxes with wires clusters plugging in to them located directly above your spark plugs. The spark plug wire arrangement typically features a round boot capping the aperture housing the spark plug.

 

Ran the scan again, this time only getting the P0303 error- so no general, random misfires, but only the specific #3.

Removed a couple spark plug wires and had a real WTF?!? moment. Here is what I saw, looking down at the #3 plug:




The plug wire was wet all over, including under the bottom seal, the entire plug receptacle grimy, with liquid covering the plug end. I sampled the liquid with a cotton swab- slight smell of chemical, but refused to light when a flame was applied. So, I wondered if this was unique to this plug, and pulled the wire from #4- it was covered in mud! Well, brown, mud-like stuff was all over the rubber plug seal, including inside the outer plug end, around the o-ring- and this on the #4 that hadn't appeared in the scan report.

I really have no clue how mud and liquid got up in here, other than just driving on the free way. Houston can be a really, really wet city- I'm sure I've driven through standing "water", but nothing up over the axles in the last 2 years since the plugs were replaced. I'm trying to imagine water and mud somehow being driven past seals on both ends of the wire plug, and the rest of the engine compartment not being covered in mud. Can you make any sense of that?

I guess I should be happy the spark plug doesn't seem to be passing water to the cylinder. I haven't checked to see if the spark plug will come out yet. Do you reckon it's safe to clean out the cavity around the spark plug with carb/metal parts cleaner?

 

#1 and 2 were dry. I sopped out the muck, sprayed in carb cleaner, cleaned out the #3 and 4 spark plug wells, reassembled, cleared the error codes, and ran it again. Running smoother, no error codes generated. There is a high pitch something in the vicinity of the #3 plug; listening through a tube, it seems louder near-but-not directly over the plug well- I wonder if it could be something else. I'll replace the spark plug wires, but am concerned that replacing the plugs will drop debris into the cylinder, as there was a thin ring of corrosion or baked on grime around the base of the plug I couldn't remove.

 

looks like oil from your spark plug tube seals leaking, how the hell would mud and water get in there?

 

X2. Needs spark plug tube seals. The proper repair would be valve cover gasket set, one that includes spark plug tube seals. Spark plugs and wires. PCV valve and grommet while in there.

 

Yet, that is exactly what I found- water and mud; it didn't seem like water whipped into oil. There is a gap between the top of the plug tube and the cover- I'll take a picture.

 

Coolant and oil mixed together can look very much like mud.

Have you checked the radiator ??

Getting any smoking at all?

 

The radiator is all topped up, replaced along with coolant and hoses when the plugs and spark wires were, 2000 miles ago. No smoke. From what I can see (which is limited) the seals could be intact- at least they are THERE. The OBDII scanner failed today- lasted for all of 5 days.

 

I'm on board with all that. When I have the cover off, will I be able to inspect the valves and pistons through the spark plug aperture? Can I just jack up the rear end and manually rotate the wheels to position the pistons? Is there some reason I shouldn't polish the outside of the cover when I have it off? What tell-tale signs should I be looking for when the cover is off that might explain the condition of the plug wells?

I know, that's a lot- most of this is still dark magic to me.

 

Why are you convinced it is mud and water? Most likely scenario is you have a failed spark plug tube seal and what you saw is oil. Why it didn't light on fire IDK but I would still lean towards it being a tube seal and not water/mud somehow getting into your engine. I believe those 4 cylinders are pretty easy to open up and replace the gaskets. That's a cheap and quick place to start IMO.

 

The "mud" didn't feel like any oil I'd encountered before, nor did the fluid. I very much prefer the explicable plug tube seal to the unlikely driving of water and mud from the road past the wire plugs. Maybe moisture accumulated in the sump, vaporized, and condensed in the plug tubes. If I take the cover off, and instead of seeing the familiar sheen of oil, there is hydrated oil "mud", I suppose I'll have a coolant leak to worry about. Can that be addressed without pulling the engine?