'99 Corolla P0300 Codes Issues

[dimwittedmoose51]

'99 Corolla VE with 160k on it and The onset of the rough running was sudden and not gradual according to my wife that was driving it when it happened. The CEL came on and the engine idled roughly and a was missing under load. Sometimes it idles just fine and revs normally with no load. It still has original spark plug wires (Sumimoto or some brand like that).They haven't been tested yet. Plugs were Bosch Platinum but switching to NGK Iridiums. In addition to the 300 code, I'm getting the 301 and 304 misfire code so I thought naturally it was the 1/4 coil pack. A new one didn't solve the problem. The CEL does flash from time to time and the engine does run fairly rough under load. I drove it far enough to the gas station to run a full can of Sea Foam in the tank and to mix it in by filling the tank. Some posts would have you pour it straight into the brake vacuum line with the engine idling to clean the injectors, but I haven't gotten that aggressive yet and I realize that a 3/4 mile drive home wouldn't do much cleaning if the injectors were dirty. Engine compression check revealed good news. 215-225 psi with the motor warm and throttle fully open, so I don't think it's a burnt valve and I have replaced the PCV valve with an aftermarket one from Advanced Auto Parts despite the old one still moving freely. My wife also noticed that the temp gauge on the dash was reading a little lower than normal, but with it being this cold out(0 F to 30 F), I figured that might be normal.

The plug inspection was curious as the 2/3 plugs looked fine color and carbon-wise. The #1 plug(passenger side) was very sooty and black and the #4 plug was crusty with white all over it. Wondering if I have multiple issues going on here that have nothing to do with the coil pack. I have not checked for vacuum leaks yet, but that would be another free check that wouldn't cost money, but a vacuum leak should affect all 4 plugs equally, right?. I'd rather not run the motor any more than necessary until I find the problem.

Next things to check: Cam position sensor, crank position sensor, coolant temp. sender, upstream O2 sensor. Trying to do the free stuff and eliminate one thing at a time. I will put the new plugs in first and see if that will solve the problem after I clear the codes. I've read many CEL 300 posts both here and on Corolland and nothing seems to fit my particular problem, but a lot of "food for thought" offered as it appears that even pro mechanics and dealerships get stumped by these problems.



My questions are as follows:

1. My Haynes manual(#92036) apparently doesn't have my particular coil pack set up. I have the 2 coil packs that feed the 1/4 and the 2/3 respectively mounted on the driver's side of the cylinder head. How do you test these packs for good/junk status? What are the resistance values? Or do I take a known good plug hooked up to the plug wire and ground it and run the starter?

2. The Duralast wires I bought at Auto Zone are US made but no other info offered up. Other posters have said the Duralast wires are crap. Should I take these back before I install them or get to Advanced Auto and order the Denso wires instead? There's not $5 difference in price, just a special order issue. With the dealer wires at $115, I could buy two sets of Denso.

3. I did notice that the evap valve assembly has slipped off its mounting tab, but I can't imagine that causing engine issues if the hoses are connected. Maybe it grounds through that, but I doubt it.

There's not a huge hurry here, but my daughter would like her car back!! ...and I'd get some garage space back.

PS: If anyone is curious, the Duralast Coil Pack from AutoZone was a carbon copy of the OEM coil pack I pulled off the vehicle. $89 vs. dealer price(don't have enough zeros on my keyboard to type that number in)

TIA

DM&FS

[bail_w]

if the NGK spark plugs doesn't solve the problem then spark plug wire set should be replaced asap.

[dimwittedmoose51]

Updated Info:

Checked the coil packs: the new 1/4 pack had 12.09k ohms resistance(9-16k is normal) the old coil pack for 1/4 had 11.92k ohms and the old 2/3 coil pack has 11.90, so maybe the problem isn't in the coil packs?

Then I tested the ignition wires and Haynes says anything over 25k ohms is toast.
#1 wire(the really black sooty plug) was 9.3k
#2 wire was 8.94k(normal colored plug)
#3 wire was 6.64k (normal colored plug)
#4 wire was 5.14k (really whitish looking electrode)

I realize this isn't testing under load, but I will wait until the Denso wires come in on Thursday before any further action. Still haven't figured out where the cam and crank sensors are on this motor as the Haynes manual has photos of the 97 and earlier and the 2000 and later but forgot to take a picture of the 98/99 engine bay. Any other sources for the photo info that I'm not aware of??

Thanks

DM&FS

[pdq]

I'd change your spark plugs first if you haven't yet done so. Those plug wire readings look good to me.

The upstream O2 sensor is probably due at that age. If you go with one, get the Denso, which is OEM.

[dimwittedmoose51]

As soon as I check the resistance values of the cam and crank sensors, the O2 was next on the list. Got starter problems too, so it's going to be an expensive January.

Thanks

DM&FS

[bail_w]

upstream o2 sensor:

Amazon

Amazon

You prob won't find another one "Denso" for this price.

[dimwittedmoose51]

Well, I got tired of waiting for the Denso wires and put the old ones back with the new iridium plugs. PROBLEM SOLVED!!! Not getting overly anxious waiting for the CEL to come on again, but it's been 3 days now. My daughter helped me put the Denso wires on it this afternoon, so wires won't be the worry from here on.. Maybe that new starter will come sooner now than later....
Thanks for the guidance

DM&FS