krazik

from 8-9k my exhuaust is making a poping/puttering noise

"pa-pa-pa-pop" noise

and when I looked in side my exhaust it isn't all black sooty like usual, it's all greyish.

Am I running too lean?

After this last weekend at buttonwillow raceway, SilverSurfer noticed the same thing in his exhaust. Tho he isn't noticing the puttering. And Davepk after the event started getting second 02 sensor errors (check engine light) after this event.

I know both dave and I used the 100 octane gas which I have done plenty before.

I am concerned... my track day is next wednesday.

naishou

What sort of noise does the pope make? Is it a kind of quiet mumble?

krazik

I have the HKS exhaust, but yes it is mixed in with the exhaust tone.

you can also feel the car hesitate when it goes off.

gregstevens

I think it was those brake ducts you just put on. I have heard of that happening before...



Well, if others were having the same troubles on the same gas, I would bet that had sometime to do with it. I would reset the ECU and see what happens. Take both leads off the battery and cross them for about 1 minute. Then see what happens...

And I am trying to weasel my way out there, but it's not looking good. I'll keep you posted for sure...!

davepk

hmmm... My OBDII scanner says that my secondary O2 sensor heating circuit has a fault. The engine seems to be running normal even though the check engine light is on... I called Chuck at Menlo Honda and he indicated that he has never seen an O2 sensor on an S2000 go bad...

josh3io

krazik...i have my AFPR set to a leaner mixture, i'd like to compare notes.

John MI blk/blk '01

O2 sensors can trip codes when you have a exhaust leak before the sensor. This can cause your car to run extra rich because the sensor is reading a lean condition. Another possible cause sometimes is the result of a blown head gasket and antifreeze in the exhaust will kill the sensor. Doubt if it is either of these because your OBDII scanner would have picked up some other fault.


John

shingles

Is it during a shift? If it is, it's probably just the exhaust... my crx does it often. You shouldn't heard detonation through the exhaust... think marbles in a tin can sound.

-Shing

krazik

nope... I can rev it at idle and hear it. It definately never did it before.

ultimate lurker

Too many variables, too...many....variables <squeezing temples with fingers>

O.k., first, let's look at the exhaust popping and assorted symptoms on krazik's car.

1. Popping/stuttering/hesitating at high rpm

- Doesn't sound like detonation to me. Only very serious detonation causes hesitation and if you've been experimenting (revving up, etc.) your engine would probably be dead by now. If it was a misfire though, I think you'd be throwing a code.

- Other possible causes - exhaust leak, ignition problems (pull your plugs and check them).

- Recommended courses of action - Examine spark plugs for unusual deposits or wear (such as a missing anode/electrode) or cracks. Also clearly define if it does it during acceleration, steady throttle or on deceleration (or any combo of the three).

2. Greyish deposits in the exhaust pipe

- Typically a car running lean really doesn't leave any deposits. Totally stock S2K's often have very few deposits in the tailpipe. A medium greyish or tan color (depending on gas and plug type, platinums can take on a strange color) on the spark plug usually means a decent mixture. In the exhaust though....

- Possible causes - lean mixture?, fuel type (although Silversurfer apparently did not use the same fuel as you Krazik?), exhaust leak (getting some extended burning in the exhaust?), unknown.

- Recommend course of action - clean the insides of the tips thoroughly and put a fresh tank of your normal gasoline in. Observe the results after normal driving as well as high rpm driving (if you dare).

3. Popping, stuttering when revving at a stop. Am I interpreting this correctly? I didn't realize we could rev our cars to the limiters when stopped, or is it occuring sooner? Detonation occuring during no load revving is rare and would require a very lean mixture, to the point the car might not even rev past a certain point. Not saying it couldn't be lean enough to just get to the point of stuttering, popping while still revving, but it is unusual.

Possible causes - exhaust leak, ignition, gasoline, etc.

Recommended course of action - unknown

In terms of the O2 sensor, I agree with John MI. If you had actually killed an O2 sensor with contaminant, you should be getting something beyond just a failed heater circuit code. There are codes for low voltage as well as slow response from the O2 sensors. Slow response is the usual result of antifreeze contaminant, provided that you don't kill it outright.

Like I said, too many variables. But since you're not getting any codes krazik, I'm going to rule out an actual misfire (but check the plugs anyways). Additionally, I'm going to go out on a limb and say it isn't detonation. Because if it was the computer would be pulling out 10-12 degrees of timing given your description. If you still detonate after that, your mixture is really lean. The ECU should detect that and give you a code too. The only way it wouldn't is if it only occured at WOT and had something to do with fuel delivery - a bad pump, injector, etc. But detonation so bad as to make your car hesitate _should_ trip a misfire code. And a sudden degradation of the fuel system seems unusual, especially one that only applies at the very top end.

Nope, my uneducated guess is the same as John's. You don't hear detonation out the exhaust. And exhaust leaks do cause popping and stuttering. Even if a car does it on the overrun or between shifts (my CRX does it occasionally), it will get worse if an exhaust leak develops. I'd suggest examining your exhaust for cracks, etc.

Good luck. Sucks to have problems so near an event (I'm pulling some pieces off my CRX to fix this weekend, so I know how you feel).

UL