90foxnotch

So I have done a lot of reading on this topic, and I mean a lot. I have an type-s 6mt. Since last year Ive been trying to figure out why I have random misfires. Ive read about plugs, egr cleaning, low compression, and the infamous over-rev or mis-shift on the manuals killing valves. So far I have changed the spark plugs-NGK, Cleaned the Egr valve, cleaned the intake ports, always run 93 from same gas station, and had a valve adjustment done. It is still true I need to do a compression check but I am just confused because this car pulls very strong, only uses half a qt of oil in 3k miles-192k miles on car-, and still achieves 25mpg being beat. It does not smoke and the code will cycle every few hundred miles. I have swapped coils from my friend and seems to help for a while but returns. I have checked the plugs and there is no oil. Now consistently on cold starts it will throw the codes then go away. I can hear a little rumble through exhaust but I do have PCD's, a jpipe, and mm delete. I guess I will do a compression check and see what the numbers are I just don't get why it still performs so well. If numbers are good I will do a leak down test but at this point I don't want to spend a lot of money on new engine or rebuilding this one. Any other suggestions are open- Thank you

horseshoez

iTrader: (2)

If the standard compression test yields good numbers all of the way around, then, given your symptoms, I don't think a leak-down test will give you any meaningful results.

What codes are you showing? Is it always one cylinder, or is it random cylinders. If random, I'd say you have a bad coil.

Regarding coils, OEM coils are made by either Hitachi or Denso; I would toss them if they are another brand.

90foxnotch

Thanks Shoez, They were oem coils from my fiend's other cars. And it reads random misfire po300 or whatever then lists 4 or 5 cylinders. Being a Ford guy I know not to waste money on junk coils and use oem but these were used before but I know they can last a long time. I still have to try and replace 2 coils on the front head so hopefully it will do the trick. Also tb was done by last owner at 160ish and I have never missed a shift.

horseshoez

iTrader: (2)

As a general rule on Honda engines, if one coil is going bad, the P030x error codes will often come up reporting multiple cylinders. The easiest way to diagnose is to pull the wire from one, listen for a change, replug, and try another. Once you find a suspect coil, swap it to another cylinder and repeat the test; if the misfire issue follows the coil, you have your culprit.

90foxnotch

I have done the unplugging test once before but maybe Ill have another set of ears with me to help. From previous experiences I know all coils don't go out so Ive tried using my scanner and swapping coils but it's always random-I'll update when I do the individual test again, Thank you

horseshoez

iTrader: (2)

In this case, the scanner is virtually always wrong.

90foxnotch

I still need to do the unplug test but when I had the hood open I heard a hissing sound-I knew it had to be a vacuum leak. The brake booster vacuum hose that attaches to the valve cover had a hole in it, I cut off the bad part,put it back on, cleared the codes, and now I will just wait to see what happens next

t-rd

You can barely tell the RPM change using your ears, when you use the unplug and plug back in of coil pack test. Use a scanner and watch the RPM numbers in live data.

90foxnotch

I have a pretty basic code reader, I will ask my father in-law who owns a shop if he can do some tests for me. Is there a tool to test fuel injectors without removing them?

horseshoez

iTrader: (2)

I wouldn't bother, 99.9999% odds it isn't an injector. Said another way, waste of time and effort.

RoyNeal

If all falls check the ECU to make sure none of the diodes are short circuited.

El_Cheapo

Ask him if he can scope the injectors and coils.

You can also ask to do a fuel pressure test.

90foxnotch

Thanks for the replies, I am going to take my car into shop hopefully soon. The codes came back of course, still running really well though. I will update soon when I have his scanner