So my car is always fluctuating in performance. It has good days and bad days. I'm trying to find what it is thats causing it. But for the most part the biggest thing is the throttle response. After the manifold swap it was good but needed some tweaking. Now its not. But then again I may be missing more low end torque which would explain the low city MPGs. Someone tell me if that makes more sense? Ill floor it and I can feel the air coming in cuz my exhaust is loud enough, but theres not enough fuel mixing in.

I think I'm going to invest in a better exhaust system. Header all the way back. But before I do I want to see if there could be anything else. The manifold swap introduced a better and slightly bigger air flow from the F23 manifold.

Someone suggested resetting the fuel trim. I disconnected the battery for a while but they said that it really can only be done using a scanner. That true?

And I think my timing may have something to do with this too that I'm still trying to understand. "Timing Advance" is whats being read. Typically it should be at 15. Its at 9.5 and sometimes goes back to 15. Its random. But the RPMs do not change with the timing. Id think it shouldnt really ever go below 15.


To add a little more...
Under the hood- although my header is wrapped it gets pretty hot. My engine temp is 200 degrees and my exhaust is pretty loud. Some days louder than others. Could there be a crack somewhere? And its opening up under certain circumstances? Say at the header?

Could a crappy exhaust- maybe a crack or something- cause the timing to be low and that loss of throttle response?

And if so what do you recommend for new exhaust? I'm looking for something that is a bit more moderate. Good sound and power but something that makes it so I can sell when I'm done with the car. Like a performance exhaust with a sleeper muffler?

 

I believe the timing is fixed on the 97 Accord; distributor not adjustable.

A cracked exhaust manifold or heard can affect the O2 sensor, causing it to sense excess o2 (lean condition). This might cause engine stumble as fuel delivery would be increased attempting to gain correct fuel/air ratio and cause reduced performance (lower MPG). However an engine code for O2 sensor performance or excessive positive fuel trim should be set.

Exhaust leaks can be detected by adding something to intake that causes exhaust smoke (top end cleaners do this). Look for smoke around the exhaust manifold. May need to elevate car to locate leak.

good luck

 

Ok. Ill check that out. I had issues with the p1297 and p0171. p0171 being lean engine code. and I think the 1297 (low ELD voltage) was from bad battery terminal connections. They havent come back but I'm suspecting my exhaust may have a crack that opens up randomly.

Could a cracked exhaust cause the timing to drop? or is that indirectly related to o2 sensor readings?

 

Exhaust leak might be directly related to O2 sensor readings. The O2 sensor actually measures the oxygen DIFFERENCE inside vs. outside. So an exhaust leak blowing onto the outside of the O2 sensor will throw off it's reading. Of course that depends on the actual location of the leak... And oily crud dripping onto the outside of the sensor can also throw it off.

Lack of oxygen on the outside of the sensor will cause the same signal as excess oxygen inside the exhaust pipe. So the ECU will think it's lean when really it's not.

Try this for the exhaust leak? Have someone hold a big old rag over the tailpipe when the engine is idling. Not so much to stall the engine, but it'll greatly increase the exhaust backpressure. Now any tiny leak will make a lot more noise, and maybe it'll be easier to find when you're up front listening for it.

Also, grab the valve cover & rock the engine back & forth. (gloves so you don't burn your hands) When you're actually driving, the engine will move around within the flexibility of the engine mounts. This movement will flex the exhaust system & maybe that's what opens up the leak?

 

Ok. So perhaps a leak at the manifold could cause an issue. The o2 sensor is right before the cat under the car though.
I notice it is actually somewhat worse with the silencer on. So there may be a leak. Maybe just a bad gasket though and the exhaust is escaping out the head. Which would cause the high engine temp since under the hood would be hotter? My engines still running at 200 degrees.

...

I bought the gasket. Its worth a shot cuz the old one does look pretty bad. Exhaust going out the head at that spot and then going under the car to the o2 sensor? Causing varying readings and both things causing my car to perform differently randomly? On top of that while the muffler is quieter the car itself is louder with the silencer.

Mechanic looked at the catback too cuz I had to have the calipers changed. He said he didnt see any issues with the exhaust. So I guess its gotta be the header or front pipe? If it is the exhaust. But there is issue with noise difference and varying torque. Ill try the test there to see if its just when the engine moves.