xXx Justin xXx

I'll try to make this informative and short.

100% stock D16Z6. Had a knocking sound, thought it was bottom end. Until i retarded timing a little and it went away. Sounds like the problem right? wrong. the car lost so much power from the amount of timing retardation it basically required running to like 6k rpms to drive at a normal cars acceleration rate.

I replaced the spark plugs (which had very burnt threads and white burnt metal tips).

The cap looks new, but it was oil filled... so I replaced the O ring on the dizzy. and cleaned out the cap.

the rotor looked burnt a little, have a new one I may put on tonight.

Plug wires look to be in good condition. I have the timing retarded a little from where it was when I bought the car (almost all the way forward) and the noise is still not as loud as it was, but definitely present.

sitting still and holding rpms steady thru the whole range it sounds like a normal engine should. push the gas a touch harder putting a little load on it and you hear a slight knock.

am i over looking anything with the ignition that could be a cause? Thanks

B serious

iTrader: (1)

the white spark plugs, plus knocking say that you're running too lean.

Retarding the hell out of the timing would help the situation but would rob you of power.

Check your fuel delivery system. Also, maybe there's something wrong with your O2 sensor. If it keeps sending out a rich signal, the ECU will keep trying to go leaner.

Fuel pump may be weak, the injectors may be clogged, fuel filter may be clogged, etc.

It's most likely a lean fuel mix problem.

xXx Justin xXx

Ok. So Ill replace the fuel filter, can I use some injector cleaner additive type stuff for those? Any recomendations? Any way to test the fuel pump? Like with a Ohm meter or something for resistance levels? Or is that just pretty much a crap shoot?

Due to the cost of O2 sensors... I'd prefer to try everything else first. Thank you very much for the response and idea of direction.

might be completely irrelivant <sp> but I think the catalytic converter is clogged a bit too. My reason for this thought is from extreme pinging/dinging/popping sounds when it is hot... for like 30 minutes after I shut the car off. Didn't know if impropor air/fuel ratio for very prolonged periods could cause something like that as a result. anyway, it will be test piped soo.. just thought that might help back another theory..

B serious

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xXx Justin xXx &raquo;</TD></TR><TR><TD CLASS="quote">Ok. So Ill replace the fuel filter, can I use some injector cleaner additive type stuff for those? Any recomendations? Any way to test the fuel pump? Like with a Ohm meter or something for resistance levels? Or is that just pretty much a crap shoot?

Due to the cost of O2 sensors... I'd prefer to try everything else first. Thank you very much for the response and idea of direction.

might be completely irrelivant &lt;sp&gt; but I think the catalytic converter is clogged a bit too. My reason for this thought is from extreme pinging/dinging/popping sounds when it is hot... for like 30 minutes after I shut the car off. Didn't know if impropor air/fuel ratio for very prolonged periods could cause something like that as a result. anyway, it will be test piped soo.. just thought that might help back another theory..

</TD></TR></TABLE>

I wouldn't test pipe it. You're only looking at like a 1/2hp to 1hp gain....and you gotta remember that you breath air. Unless you find another substance to breath so you can live, you probably want to ease off on polluting the air for no good reason.

The cat wouldn't get clogged from a lean fuel mix. Your EGTs from a lean fuel mix will be pretty hot. So the exhaust might just be cooling for a longer time, especially if you live in a hotter place.

A cat being clogged wouldn't cause a lean mix either.

The fuel pump is more or less a crap shoot as far as I know. But your problem being caused by a fuel pump is un likely.

Injector cleaner poured into the tank doesn't do much. If you want to clean them, take them apart and clean them with some sensor safe throttle body cleaner. Dont use brake cleaner.


O2 sensors aren't really that expensive. For a Z6, from http://www.sparkplugs.com, it should only be around $50 or so. But you'd have to check to make sure.

xXx Justin xXx

gotcha. yes its a little warm here (98 today, 100 tomorrow and sunday. and august is the hottest month )
one last question. If the o2 is unplugged... besides getting a cel. Does that make the ecu run the engine lean or rich?

just got married 3 weeks ago... trying to not spend money on something and end up not needing it. (already did with $145 on bottom end bearings only to figure out it was an ignition issue).

if an unplugged o2 would cause a rich mixture in limp mode or something... i could maybe rev it lightly for a sec to test for knocking with a rich mixture. and then spend the $60 on an o2. but it probably makes it run lean too.

cleaning the injectors... just take them out and spray around the jet area correct?

edit: I didn't figure the cat. would have any relevance to this problem. but I figured I would throw it out there in the event that was something that would trigger an idea.. like an added symptom

thanks again. happy friday to ya.


Modified by xXx Justin xXx at 4:03 PM 6/6/2008


Modified by xXx Justin xXx at 4:03 PM 6/6/2008

B serious

iTrader: (1)

unplugging the O2 sensor makes the car run rich. It will never come out of open loop (warm up mode) with the O2 unplugged.

VTEC will work. Nothing bad will happen. It just will keep running rich.

If it runs fine with the 02 unplugged, that may or may not damn the old sensor. Even if you unplug a good, working sensor, the car will run richer. So that isn't saying much.

Low O2 voltage means lean condition. So the ECU gives out a rich command.

High O2 voltage means rich condition. So the ECU gives out a lean command.

The O2 should be doing that switching back and forth at about 5Hz (5 times per second) during idle or steady throttle cruise or VERY slight throttle accel.

If you unplug the O2 sensor, it just has a low voltage going back to the ECU. So the car runs richer for that reason. Also, in open loop, the ECU ignores the O2 sensor. If you force the ECU to ignore the O2 sensor, it will stay in open loop.

The only way to really TEST an O2 sensor is to plug it into a Oscilloscope ($$$$$$$).

You can unplug your 02 sensor to see if the car runs better when it runs rich. But all it will tell you is that the car runs better when it runs rich.

So you still have to figure out why the car is leaning out.

Another cause I forgot to mention for leaning out would be a Vacuum leak. Got any?

Cleaning the injectors means taking them out, pulling out the little screen, cleaning that, and then spraying up into the injector. Usually, they use some sort of pressurized solvent...but the TB cleaner is a quick clean. It's not as good as having it done professionally.

xXx Justin xXx

alrighty... don't think I have any vacuum leaks. car starts/runs/idles pretty smooth. every once in a while it will seem to idle low... but I also have figured out I have some tachometer issues. that thing is accurate some times and all of a sudden it will be way off.

after hearing what you had to say i had something click to me that helped to confirm the leaning out thing. Since I bought it i have been saying that it didn't do that knocking thing when it is cold. it doesn't start until it is good and warmed up. (i guess when the ecu starts depending on the O2 sensor's input).

Thank you very much for all your insight. It has been greatly appreciated. I have built several honda's from about every angle... and here i sit on my 9th one at age 26... and still I get to learn new valuable information thanks to you. &lt;- a drink of choice for you kind sir!

B serious

iTrader: (1)

no problem, bro. Good luck.

matt j

justin thanks for the heads up, mine is still doing it a little as well, but i am going to change the timing belt and get my 1 vacuum leak fixed, i can let you know what i come up with on that. my cars spark plugs the last time i checked they were the golden brown/tan color so i have a good air/fuel so i dont know if thats the problem.