Random Misfire Codes

[Zaen]

Hello,

It's been a while since I've been on, for better or worse. I'll keep this one short(ish). About a month ago, the wife's 2004 Vue (3.5L honda engine) CEL came on about 20 minutes into a road trip. I took the next exit and checked the code nearly immediately. It was something about catalytic converter efficiency. Unfortunately, I didn't write it down before clearing it. The CEL didn't come on at all for the rest of the 2 hour trip, or at all until now.

This last week the CEL started flashing while she was on her way home. The codes that currently are happening are: PO300, 301, 302, 303, 305, 306. No PO304 for whatever reason, and nothing about the catalytic converter.

The idle is a little off, but if you drive around the block you can definitely feel that one cylinder is missing it actually feels very regular rather than random.

So far, the searching I've done convinced me to try disconnecting the O2 Sensors on the exhaust manifolds, as well as attempting a valve adjustment, to no effect in either case.

Any ideas what might be causing these codes? I've read threads that said the CKP sensor was AND was not a likely culprit. I figured I'd at least get another opinion before digging into such an involved job. (The valve job was needed before the misfire issue started)

Thanks ahead of time for any help you guys can offer.

[fdryer]

It was better not posting as this would presume not having any issues with a well running Vue. A good thing. Returning back with major misfiring implies several problems with one major warning; don't drive this Vue if the check engine light continues to flash - all the unburned fuel sets a fire in the catalytic converter to a higher temperature than its designed to handle. With a fire in the catcon, one member here found out too late that less than 50 miles of a continuous flashing cel burns out catcons. Five out of six misfiring cylinders is serious and shouldn't be taken lightly. Catcons are expensive unless you're in states ignoring emissions inspection, leaving you with misfiring problems. Disconnecting O2 sensors does nothing but increase error codes.

Mileage? A test for a partially blocked catcon would be removing one or both upstream (of the catcon) O2 sensors and driving. A diverter made from soup cans may be needed to prevent hot exhaust gases from burning nearby plastic and the exhaust will be loud but two alternate exhaust holes can allow the engine to breathe with renewed power. No change means the catcons are fine.

Crank sensors tend to fail in one of three modes; fail outright with no possibility of the engine ever firing up (starter can crank all day until the battery dies or starter burns up), fail with a fully warm engine but work again after engine cool down or intermittently at any time whether the engine is hot or cold. Older Saturns have been shown with all three symptoms. Its rare for cranks sensors to create misfiring but does occur sometimes. Before concluding a faulty one, consider if its inaccessible for immediate replacement or if its a long drawn out process of removing parts to have access to it. While considering this, consider doing the easier things; checking for fuel pressure (borrow a pressure gauge from Autozone if there's one near you), blocked air filter, worn out spark plugs, damaged coils, poor/loose connections of coils, wiring damage related to coils, etc.. I prefer to do the easy things first and eliminate them before moving on to difficult troubleshooting.

The crank sensor provides the primary timing signals to the entire EFI system by its clock signals that allows ecm's to operate; fuel pump, ignition system and injectors. The crank signals are only output when the engine is turning over during starting or when running.

[Chazberry]

Originally Posted by Zaen

(The valve job was needed before the misfire issue started)

Do you mean valve job or valve lash adjustment? How many miles on this '04?

[Zaen]

Fdryer,

I appreciate the warning! We parked the Vue after this issue started, so we're actually down to one car right now. We're not in an inspection state, but the Wife probably wouldn't appreciate a CEL that never turns off. I tried disconnecting the O2 sensors on some advice in another post.

Current mileage is 194k. I'll see about removing the O2 sensors tonight to test blockage.

I went to the crank sensor next because that was mentioned in multiple threads, and the engine feels like it's only missing on one cylinder. (IE you can feel it miss at a regular rate, directly corresponding to the speed of the engine)

The nearest tool rental for a fuel pressure gauge is about 50 minutes away, I was debating just buying one on amazon. The spark plugs looked good, but I have new ones on the way, they should be here soon.

As a quick side note, one thing I never did read was why the valves needing adjustment could cause a misfire. That seems absolutely bizarre to me.

As usual, I appreciate the help. I'll let you know if removing the O2 sensors from the headers does anything, and if I can get my hands on a fuel pressure gauge soon.

[billysvue]

Originally Posted by fdryer

Mileage?...worn out spark plugs, damaged coils, poor/loose connections of coils, wiring damage related to coils, etc.. I prefer to do the easy things first and eliminate them before moving on to difficult troubleshooting..

[Chazberry]

Originally Posted by Zaen

As a quick side note, one thing I never did read was why the valves needing adjustment could cause a misfire. That seems absolutely bizarre to me.

This Honda V6 has 'mechanical' lifters, not 'hydraulic'. Valve lash adjustment is required after 100k mi. See these threads . . .
http://www.saturnfans.com/forums/sho...d.php?t=161620
http://www.ridgelineownersclub.com/f...-w-photos.html

and Video links . . .
http://www.saturnfans.com/forums/sho...d.php?t=195027
https://www.youtube.com/watch?v=OnyqVg3nWRk
https://www.youtube.com/watch?v=iLdgivYwUiQ

[billysvue]

Originally Posted by Zaen

I never did read was why the valves needing adjustment could cause a misfire..

AS valves wear, they sink
( upward) into the head - which decreases valve lash.
If it progresses far enough, the valves lose their seal when they can no longer firmly seat into the cyl. head, which results inburned valves lower compression/no compression/misfire.

[Chazberry]

Originally Posted by billysvue

AS valves wear, they sink
( upward) into the head - which decreases valve lash.
If it progresses far enough, the valves lose their seal when they can no longer firmly seat into the cyl. head, which results inburned valves lower compression/no compression/misfire.

Correct - and the exhaust valves on this Honda motor get too tight and cause misfires. My money is on this as the cause of the OP's misfires.

[far2grumpy]

Do all codes return after you clear them?

If yes - go for things that can affect all cylinders and most common is fuel pressure or supply.

Find an old coot with vacuum gauge and knows how to use it before pursuing valve adjustment or exhaust blockage.

Forget about CKP (until you check fuel and determine intake vacuum status).

[Zaen]

Sorry for the lapse in posts, I've been putting in way too many hours at work, had the fridge start heating the food inside, and generally been getting too little sleep.

Chazberry- Valve lash adjustment, my mistake. Roughly 194k right now. I understand now it was completely pointless for me to start with this. I did so because there was a slight valve tic, and I'd read that misadjusted valves caused misfire issues with the Honda J-Series Engine. Valve tic means there was too much play, which then wouldn't cause a misfire. Feeling a little dumb over that one.

Which brings me to the cause of the misfires. Oil on the spark plugs. When I did the valve lash adjustment, I noticed the seals for the spark plug sockets were trashed, like a 300 lb gorilla used a razor blade to seat them in their sockets. And it wasn't me for once. We took it into a local shop to have it diagnosed, me not having a ton of extra time, or a compression tester or fuel pressure gauge. (and the nearest Autozone is 50 minutes away, and I don't believe they have the tools anyways. Might be confusing them with the Advance auto parts).

In any case, they said the oil in the sockets was causing issues with the spark plugs. I didn't even know that was a possibility, but I got it back 10 hours later in working condition. And they didn't even charge anything because they didn't do the work of replacing the spark plug seals. I love small town shops, way better than going to someplace in the big city.

Far2Grumpy-thanks for the advice on the ckp, I'm glad I didn't leap to that as the next problem. I just didn't think the spark plugs/oil could be the problem for how new(ish) they looked. No complaints as it's working now though. I'll replace the seals as soon as the Rockauto order gets in.

Moral of the story is: Always check the simple stuff first. Always. Thanks for all the help everyone!