I hate to add to the already numerous random misfire threads, but I've been chasing this problem for almost a year now and it's getting quite frustrating.

My car is a 2004 6MT with almost 140k on it.

First off, the misfire ALWAYS happens at idle or low load/RPM. I've NEVER had the CEL flash/turn on WOT or high RPM. The codes are always P0300 through P0306. It has never been less than all six cylinders. However, sometimes the light will just flash and not set off a code.

What I've done so far is change the spark plugs (NGK Iridiums) and coil packs. I've also replaced the battery with an Optima Yellowtop (which I hope to return since it didn't fix the problem).

The next thing I was going to do was check fuel pressure. I rented a pressure gauge last weekend only to find out the hard way that our cars don't have a schrader valve on the fuel line. I understand I have to put a T in the line somewhere, but where?

Obviously I'm open for suggestions on other things to check. I was planning on checking compression as well.

Thanks in advance.

 

SKIP EVERYTHING ELSE

and just do a compression test and a leak down test.


Six speed + random misfires = I'm positive that its been over revved.

 

Checked compression. The rear head doesn't look great, but when I took the spark plugs out (which I installed at 18ft*lbs maybe 10mo ago) they were noticeable loose, and one had a little oil blow back. I think I had put a little too much anti-seize on them and they had blown out a bit. A friend of mine who's a Honda service technician said Honda doesn't even recommend putting anti-seize on the plugs. So I wiped off what was on there and reinstalled at 20ft*lbs. The car ran noticeably smoother after putting everything back together.

Anyway, back to the compression test. The values for the rear head are concerning, but if I had bent valves from a missed shift, wouldn't that bend the valves on all 6 pistons at that kind of RPM?

 

i have the exact problem with my car right now! been going on for about 8 months now.i just posted a forum about it to.. iv been told to replace coil packs and plugs as well. nothing more frustrating than this problem

 

spec for spark plugs is 13ft-lbs. Who did the compression check?

 

I would be very concerned. If you really want to diagnose what is going on, you need to perform a leak down test, this will check the integrity of the valves, rings, etc. Those static compression numbers are very low on the rear bank. You definitely have serious issues if the numbers shown are accurate. Also, it is not a given that all the valves would be bent if it was over revved.

 

Just thought I would update this. I installed a set of heads from a 2008 base with 15k on them a few weeks ago. New timing belt, new plugs, new water pump. Car runs like a champ now!

 

did u inspect the old heads when u removed them? was it bent valves?

 

Yeah they were all bent to one degree or another. All the exhaust valves were white too.

 

Uh, you might want to get another friend And you way over-torque your plugs....



2004 TL Service Manual^^^^^

 

Interesting. Wonder why they were backing out so easily then. I did only torque them to 13lb*ft this time around.