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1) You would need to look at scan tool PID data, particularly the fuel trims. Also, anytime you do tune ups on these vehicles, its very important to use OEM parts only, not aftermarket.
As a technician, you would also have to do a very good visual inspection and look for other issues that could be causing a drop in fuel economy.
2) Some of those issues can stem from vacuum leaks, faulty electrical portion of the ignition switch, IACV problem to even an incorrect set idle.
Here is Eric’s idle speech –
on the bad gas mileage. are the tires inflated to the right pressure? excess weight in the vehicle (junk in the trunk) the cold weather and gas blend
will drop mileage.driving habits. #2 the car shutting off. you may have a problem with the electrical portion of the ignition switch. to check it jiggle the
key to see if the engine cuts off. also check for vacuum leaks. C8-)Quoted From dreamer2355:
1) You would need to look at scan tool PID data, particularly the fuel trims. Also, anytime you do tune ups on these vehicles, its very important to use OEM parts only, not aftermarket.
As a technician, you would also have to do a very good visual inspection and look for other issues that could be causing a drop in fuel economy.
2) Some of those issues can stem from vacuum leaks, faulty electrical portion of the ignition switch, IACV problem to even an incorrect set idle.
Here is Eric’s idle speech –
+1
The OP mentioned doing some diagnostics but I didn’t see anything in the stuff he checked regarding looking for vacuum leaks. I’d definitely look at the fuel trims to start and go from there.
This isn’t a problem with my car. These are two subjects that I do not have a rational way to diagnose. This seems to pop up on OBD1 accords, where you cant connect a scanner to read sensor data without some expensive scanner.
I was wondering if the experienced techs on here would say something like, start leaning towards a fuel delivery problem, spark problem, etc…. for scenarios #1 and/or #2. I hope this makes sense.
Drop in fuel mileage. Some ideas worth checking out. Your car starts cold. Couple of thing. What is the ECU doing, because it can’t trust the reading from O2 sensor when the engine is cold. Is the ethanol in the gasoline changing O2 levels in the exhaust? At normal operating temperature, and high speeds, does the ECU stop leaning the fuel for the catalytic converter?
Anyone know?
I cannot common on the 2000s as I don’t have any experience with them but I would think they are similar. For the 90-93, I have some experience.
With the car being that old I would:
1) Question 1: gas mileage.
-Tune up which you did mostly, check the base timing then go on to check ignition timing.
-Fuel filter?
-In this old car, you almost never get a CEL for an inefficient O2 sensor. The only time you will get the CEL on is when it’s totally not working, like when you disconnect it. Or when it’s totally almost clogged. I just recently replace my O2 sensor. My gas mileage went from 28, 26, 22, 20, then finally 18. This is for mix driving both city and freeway. 2 days after I received my new O2 sensor, the code came on b/c I was messing around with the connector and did not connect back all the way. I thought it threw a code and was happy. Code 43. I replaced the sensor and now I am getting 34 on the freeway and mix driving around 29-30. My car is an auto as well. I keep my car in good shape so the timing is dead on. I never race, and try to keep every thing below 3000rpm before the next gear. You can do this with an auto if you ease the gas pedal.
-CA gas will have ethanol in it and I can’t do any thing about it. But I always use Chevron brand only.
-When I clean my EGR ports out, I also cleaned the injectors as well.
-Tire pressure. Honda recommend at 29 psi. I have mine at 30 cold and I check it every 2 weeks.
-Air filter. You need a clean air filter.
-Clean the throttle. Keep the idle speed at OEM specs. For my auto, it’s 750rpm idle, 850rpm with AC on.Question 2: Stalling when coming to a stop.
-Check your base timing. Too low of an rpm will cause this.
-Poor ignition timing some time does this.
-Check for sticky throttle.
-Vacuum leak. With a vacuum leak you also have shaking a bit.
-TPS problem. Throttle position sensor.
-I have seen bad battery connection once that did this.It some time take time to diagnose a problem but if a car this old, chances are you can find the same problem on Google.
Good luck.
The fuel mileage issue on the older Accords is often the O2 sensor getting ‘lazy’. If you’ve done all the tune up items (with Honda parts) then that would be the next logical place to go and since the older systems weren’t as good about O2 sensor monitoring it often doesn’t set a check engine light till the post 96 model years. There are other things that can cause poor fuel mileage but that is the most common one that I’ve seen.
As for the stalling issue it could be a couple of different things, the first is that Honda’s have issues with the ignition switches going bad causing the engine to shut off and the other is an issue with the idle air control valve going bad, some people clean these but I haven’t had much luck with that so I often replace them with I find a fault there. There are other things that can cause them to stall but those are the most common that I’ve seen.
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