burningwrek

well I just installed my new cam and adjusted my timing and the increase in throttle response and all around power was amazing (I have a sensitive butt dyno). so I've been enjoying the new peppy-ness of my car when one day I notice that it doesnt feel quite as peppy. that same day, I also noticed that somehow the pipe between the muffler and the cat had disconnected from the cat and all three screws were missing. my check engine light came on, flashing the code for my o2 sensor. it had been several days since i installed the cam and set the timing.

so this is what I'm thinking:

a) my timing is slowly setting itself back to stock because maybe I didn't properly reset my ecu or something after adjusting the distributor and isn't quite as advanced as I had originally set it (can this happen? I'm not sure, someone help me out). or

b)my exhaust leak has resulted in a decrease in back pressure on my engine thus resulting in a slight loss in low end torque. the presence of the outside air is what I think is setting off my o2 sensor.

thanks for the help Honda homies!

dogfood

I don't think your ecu can change the distributors timing, it's bolted to the head ya know. I don't know what to tell you about the second though. Bolt it back up and see if that solves it.

murtnabila

I don't think you can have too little back pressure.

burningwrek

well I know the distributor is bolted down but I thought that the ecu could make mild changes to the spark in order to produce the best ignition timing.

on the exhaust, i tried bolting it back up but I'm having a hard timing torquing it down good. I've tightened it up twice and I still hear metal vibrating during idling sometimes. is there supposed to be a gasket between the cat and the piping?

burningwrek

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by murtnabila &raquo;</TD></TR><TR><TD CLASS="quote">I don't think you can have too little back pressure.</TD></TR></TABLE>

too little back pressure on a n/a car = now low end power

murtnabila

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by burningwrek &raquo;</TD></TR><TR><TD CLASS="quote">

too little back pressure on a n/a car = now low end power</TD></TR></TABLE>
WRONG! There is NO such thing as too little back pressure. You are talking about the velocity of airflow. If you need more back pressure stick something in the piping and see if you get more low end power?

burningwrek

so whats the point of putting an aftermarket exhaust with a bigger diameter pipe on the car? why not just stick with the ole 1.5 " or whatever pipe rather than going with a 2 1/4" pipe? anyways, it doesnt matter, someone <U>help me with the original question.</U>

crashN2u

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by burningwrek &raquo;</TD></TR><TR><TD CLASS="quote"> is there supposed to be a gasket between the cat and the piping?</TD></TR></TABLE>

What kind of exhaust do you have? All of the exhausts I've owned had a gasket.

kommon_sense

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by murtnabila &raquo;</TD></TR><TR><TD CLASS="quote">WRONG! There is NO such thing as too little back pressure. You are talking about the velocity of airflow. If you need more back pressure stick something in the piping and see if you get more low end power?</TD></TR></TABLE>

yes there is such a thing as too little backpressure.. Not everyone wants all their power at redline... Perfect example, take a straight through exhaust like a magnaflow (which I've used). Poor bottom end, good top end. Take a chambered exhaust like an rsr ex*mag (which I've also used). Much better bottom and midrange response.

Car was extremely frustrating to drive with the low-restriction straight thru exhaust as a daily driver.... Don't even get me started on bumper to bumper traffic.

Anyways, to the original poster. Reconnect the cat and reset the ecu. Be sure to use some anti-seize on those bolts.

murtnabila

I think we can argue the backpressure thing for days so I'll make a new thread in tech! Let this be a bump for this topic.

STIBungy

Why even run a header then? The bends cause some disturbance which causes some back pressure.

murtnabila

https://honda-tech.com/zerothread?id=931740 to argue backpressure leave this thread to <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by burningwrek &raquo;</TD></TR><TR><TD CLASS="quote">well I just installed my new cam and adjusted my timing and the increase in throttle response and all around power was amazing (I have a sensitive butt dyno). so I've been enjoying the new peppy-ness of my car when one day I notice that it doesnt feel quite as peppy. that same day, I also noticed that somehow the pipe between the muffler and the cat had disconnected from the cat and all three screws were missing. my check engine light came on, flashing the code for my o2 sensor. it had been several days since i installed the cam and set the timing.

so this is what I'm thinking:

a) my timing is slowly setting itself back to stock because maybe I didn't properly reset my ecu or something after adjusting the distributor and isn't quite as advanced as I had originally set it (can this happen? I'm not sure, someone help me out). or

b)my exhaust leak has resulted in a decrease in back pressure on my engine thus resulting in a slight loss in low end torque. the presence of the outside air is what I think is setting off my o2 sensor.

thanks for the help Honda homies!
</TD></TR></TABLE>

burningwrek

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crashN2u &raquo;</TD></TR><TR><TD CLASS="quote">

What kind of exhaust do you have? All of the exhausts I've owned had a gasket.</TD></TR></TABLE>

well i have a gasket between the cat and the header but not one between the cat and the piping that runs to the muffler. I'm not sure if theres supposed to be one there because I can't remember. its been years since i put that exhaust on. its a custom exhaust with a high flow cat and ebay muffler. i think one of the bolts must have broke and the others slowly worked themselves loose and fell off somewhere. if i had a gasket i guess it fell off somewhere too. so is there supposed to be a gasket ?

*header* -&gt; *gasket* -&gt; *cat*-&gt; ?gasket?-&gt; *piping* -&gt; *muffler*?

burningwrek

well i went by the honda dealer to pick up the valve cover bolt i broke earlier this week and I asked the parts guy and yes, there is a gasket between the header and the muffler piping. so i picked one up and I'll let you guys know if it fixes the problem.

93civicdead

how do you reset your ecu cause i think that might be the same problem with me and the screws fell out of mine too.....

crashN2u

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93civicdead &raquo;</TD></TR><TR><TD CLASS="quote">how do you reset your ecu cause i think that might be the same problem with me and the screws fell out of mine too.....</TD></TR></TABLE>

Pull your battery cable off for 5 or 10 min. Don't remember how long exactly. Or pull the fuse for that long.

burningwrek

well me being the goofball that I am, I forgot that a stock exhaust gasket for a civic won't fit my 2.5" exhaust. so i made my own exhaust gasket out of gasket material and rtv. I just cut out to patterns on the gasket material and made an RTV sandwich! yum! the checkengine light is still on, but then again I haven't reset the ecu. it still doesnt feel as torquey as it did before, so maybe my timing is a lil off.

murtnabila

u know with the check engine light on your ecu will run in limp mode. That's probably why you are feeling the motor to be weaker than b4.

burningwrek

so how can i reset my ecu? someone said just unplug the battery for 5-10 min. if I do that, will my CEL turn off? and will the timing advances I've made be permanent? thanks for the help 4banger friends!

Deemeetree

How is the timing slowly going back to spec? I don't think the ECU controls the ignition timing as in other cars. If you advance, it's advanced. Have you checked your timing with a timing light to see at what degree your motor is on?

Yes, most people pull the battery terminal for 10-15 minutes and most say it resets your ECU.

But, definitely look into the CEL. Resetting your ECU is only going to postpone the CEL coming back on.

burningwrek

i checked the timing the other day and the pointer was pointing towards the middle of the three marks grouped together, but isnt it supposed to be pointing towards the one mark (TDC) alone by itself like this?
right now my camshaft is advanced 5 degrees so i figure I'll turn it back to 3 or so and then adjust the distributor with the timing light to get it to point at the TDC mark. btw, the timing light gun i have isnt the one with a digital read out or a dial, it just simply strobes so I can't get an exact number as to what my timing is.

the code being shown for my CEL is for the o2 sensor, so i figure either I've still got an exhaust leak that isn't noticable enough for me to hear, or I'm not getting a great burn due to the whacked timing so unburned fuel is getting dumped into my exhaust past the sensor.

another question: once the problem with the o2 sensor is corrected, will I have to reset the ecu to get the CEL to go off or will it go off on its own if everything is running normally? thanks guys

even91civic

reset ecu (reseting the ecu will not harm nothing but the stereo settings) disconect the battery for 30 seconds and code will be gone adjust timming to stock and tune it from there how you want it but when moving the distributor it takes very little movment to get 1 deg. of timming about 1/16 of an inch or so hope this helps if o2 sensor code comes back do a tune up you may have a miss that is not noticeable at idle only under load causing raw fuel to get past the o2 and giving you a code and yes the ecu does change the timming but only off of a set base line that you set so it will never go below what you set it at my car will advance the timming to 36 deg. by 3000 rpm but make sure you are setting the timming correctly by locking out the computer hope this helps

burningwrek

can you please elaborate on how you can lock out the computer? and do me a favor and use some punctuation please. thanks!

burningwrek

also, if I havent properly locked out the computer, what will that mean since I have already adjusted the distributor? my camshaft is advanced 6 degrees and my distributor is turned towards the firewall as far as it will go and it seems to be running alright, except I just dont have as much of a punch downlow as I used to have when I had first installed the cam. I don't think I am misfiring or something because when the engine is under load it seems to run great. the tires bark during gear changes and the accelaration seems good in the top end. thanks for the help guys.

burningwrek

ok well I spent all night messing with the timing and I'm beginning to think that its NOT the timing. I don't think the timing has anything to do with my car feeling a little bit sluggish at low rpms (i know its a d-series and its sluggish down low anyways, but not THIS sluggish). I think I may still have an exhaust leak despite my best efforts to seal the connection between the cat and the piping. it still sounds kind of buzzy when I'm accelerating. would an exhaust leak cause a bit of sluggishness down low? I also reset the ecu and the CEL is gone for now but I'll post tomorrow if it comes back on.