I did all the maintenance and wanted to check the electrical timer.
So I draw a line to mark the current position of the dizzy and loosened (just to make sure I can loosen it when it is cold) then tightened 2 out of 3 bolts.
Then of course shorted the thing under the dash and get it to warm up and tested the timing - it was on the dot. So made no adjustment. Stopped everything and tightened the dizzy and done with it.
Of course I ran the car at 3k rpm for about 3 minutes to get the radiator fan to come on. The next gas tank fill, I only got about 20miles - I used to get better than 22 maybe 24.
There had been a few more full tanks but involved some freeway driving and got 24/25. Currently it probably used 9gal and shows 192 miles on the trip meter. I am wondering if my attempted tuning worked against me?? Any tips? All the parts (rotor and … from Acura) are new and I did one at a time just to observe the difference - all positive except the last one which I am unsure. Is there a service that will take care of this issue? What is it called?
BTW: I recall in 2000, I had a 86 prelude - took it to a private Honda shop and they recommended to change the rotor among other things. The mileage dropped drastically from about 27 to 20 (from memory) or less. Mechanic said it will get better when the winter goes away but it never did. I don’t have the car anymore. I still wonder why? Are factory settings are far superior or …? I removed my dizzy on my 87 Integra and put it back but no issue with gas mileage.
I presume you mean “ignition timing” when you say “electrical timing”. What was it you shorted out under the dash exactly? Is that a procedure specific to your car, setting the ECU in some kind of test mode?
So you made no adjustment to the timing or anything else and you think the mpg has decreased as a result of some unanticipated consequence of fiddling with it? I think it is more likely nothing has changed, including the mpgs, and you haven’t made enough mpg measurements yet – or didn’t record enough before to establish a baseline – to verify on average the mpg is the same as before you fiddled with the timing.
In other words I don’t think your timing adjustment worked against you. It had no effect is all.
@GeorgeSanJose - yes “ignition timing” - yes setting the ECU to test mode - one rational explanation is that my driving habit has changed.
Before summer, I drove my kids to school which is at 5-7miles away. Now it is 2 miles away. Perhaps the car is not getting warmed up to operate at optimal.
@insightful: at this stage, I would want to take it to a shop for any further adjustment. Question is is there a machine/deterministic way to adjust so that it guarantees to give better mileage? I hear when they change stuff, they have some fancy machines to tune - not sure if these are common or inexpensive?
Yes, mpg will definitely decrease at lower engine temperatures. There’s not much you can do about the length of your trips, but one thing you could do, make sure the dash gauge for coolant temp is reaching the temp it is supposed to when the engine is completely warmed up.
Maybe, maybe not. Advancing timing should increase mpgs. Listen carefully for engine knock. Your timing light will tell you if you can do it (at least at idle). However, it does sound like your driving pattern change is mostly responsible for your poorer mileage. Also, more than 2 degrees advanced might throw on the check engine light.
Don’t advance the timing, its not just the ignition timing but the injector timing as well. The camshaft position sensor is inside the distributor where the ignitor used to be. If you move the distributor, the the computer thinks the engine is in a different position so it affects the injector and ignition timing. But the knock sensor will retard the ignition timing as needed.
“Dizzy” – apparently nick-named that because it goes around in circles very fast – is a common term for the distributor. It’s a more common in Great Britain than the USA I think, but still a pretty common term here, at least in my area. I was at a fast food joint last month and was admiring another customer’s older truck in the parking lot and he told me he as having some trouble with his “dizzy”. Then another guy joined the conversation, I guess he had an older car too, and was complaining about the difficulty of balancing his dual “SU” 's … hey, dizzy and SU in one day, maybe folks fixing their old cars is becoming more popular!
@circuitsmith - Are you sure “I’d try changing it if it’s older than 6 years”?
Thermostat is about overhearing right?
I have the factory thermostat - it is a 1999 car with 100k
I can also tell you that my 1987 integra had the Thermostat changed against the advice of the mechanic - either it was factory or it was changed by the previous owner in 1998 or so.
I called a few shops - a good m/c talked about O2 sensor but advised against since there is no check engine light. Another said performance testing, emission, valve adjustment. About 25k miles ago, I did the valve adjustment. Another said use Chevron gas and not the one from Costco.
It feels strange to me as I do not thing that any of the above are an issue. It is still strange to me why my Prelude lost mpg drastically after the mechanic changed the rotor and cap.
Your loss of mileage is not dramatic. Dropping to 15-17 mpg would be dramatic. Your loss can easily be due to a change in driving habits as you already have mentioned. But, I’d try the thermostat change , especially if you still have the factory t-stat. The spring does fatigue and alters its performance, forcing longer warmup time. The ECM will run a richer mix until the engine warms up, so that too can cause your drop in mileage.
@oldtimer 11 - thanks for the important info. The one in there is from 1999, the factory installed.
Is there a way to check the O2 sensor? I feel older parts are more reliable than newer since, even if they are Honda, they are being made cheap (there is a recent recall on Honda/Toyota air bags - a Japanese company had them made in Mexico).
@texases: “thermostat is stuck open” - could you elaborate a bit it more? What other things will it do if it is stuck open - over heating?