Quote:
Originally Posted by tw
The difference between crap Liberty gas and Shell gas would (for example) result in maybe an 8% difference without any noticeable change in idle smoothness. If your numbers are as reported, then Liberty gas should have caused a noticeable mileage difference. The fact that you saw no difference is troubling.
In another event, a tank of Mobil destroyed my fuel injectors. I knew something was wrong due to a slight roughness in idle. But the resulting mileage change was from 32 MPG to about 27 MPG in that tank. And 24 MPG in the next tank. (Honda replaced those injectors for free). In that case, diagnostics never reported a problem.
In another case, a problem with an EGR valve kept causing a check engine light. No mileage change. Symptoms that helped me trace the problem to a hard and not easily diagnosed problem. (BTW, EGR valve is not connected to the idle system; so did not affect idle. And that failure was unique so as to not affect gas mileage.)
Examples of different failures that do and do not result in mileage changes. And that isolated the problem quickly to a shorter list of suspects.
Assuming that 5% coincided with road conditions (heavy traffic, summer open road driving, etc), then is we can assume you have a problem traceable to the idle system and that does not affect the other 'normal operation' system.
BTW, remember Cloud's problem. That was also traceable to the idle system and that would not cause mileage changes. That mechanic had one clear advantage. The Civic's diagnostic system pointed exactly to the defect - which that mechanic refused to address. An example of why some people just refuse to learn good diagnostic procedure.
Now, with Shell, what is happening? What are the latest symptoms?
|
For the last two months we've been putting nothing in it but Shell. No improvement. I put a bottle of fuel injector cleaner into it. No change. Still a rough idle after it warms up.
So I bought a CarChip Pro so I can monitor RPMs and other stuff.
I just started it and let it idle for 8 minutes or so. I didn't touch the accelerator. The first 4 charts I got are below. It started off fine, and the idle got progressively rougher, until at 8 minutes in, the roof liner started vibrating it was so bad. Then it was dinner time, so I turned it off.
Chart 1 is RPM. You can see it gradually slows down. I didn't touch the accelerator ever.
Chart 2 is the throttle position. I had no idea what this would show, but here you go. It shows little when you don't step on te gas.
Chart 3 is the first of several oxygen sensor readings it can take. I ahve no idea what this means, but this is O2 B1, S1
Chart 4 is also an oxygen sensor reading. It's called O2 B1,S2, whatever that is.
I'll have to double check the shop manual, but if I recall correctly, it should read between .1 and .9 volts. It goes a little below .1 volts.
There are a whole bunch of other readings I can have this make, but you can only do 4 at a time, and you have to take it out of the car and hook it up to a PC to change what you are monitoring.
It's a neat little gadget.