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-   -   What could be wrong if im only getting 40mpg in my 1990 CRX HF? (https://ecomodder.com/forum/showthread.php/what-could-wrong-if-im-only-getting-40mpg-5419.html)

dylanu 10-06-2008 11:02 AM

What could be wrong if im only getting 40mpg in my 1990 CRX HF?
 
i never go above 50mph. i only do 100 percent city driving and i always follow the shift indicator light... what could be wrong and what can i do?

TestDrive 10-06-2008 03:03 PM

Here is a six step program for you.
  1. Realize that more throttle means the shift indicator light will come on later (with the engine at a higher RPM).
  2. Be very gentle with the throttle so the shift indicator light will come on sooner (with the engine at a lower RPM).
  3. Realize that the guy that designed the shift indicator light assumed that you would mash down on the accelerator just like you've been doing until now.
  4. Learn to anticipate the engine shift light. The engine shift light means - "Hey stupid, aint you ever going to shift this thing up?" It does not mean, "Ok, now it's finally time to shift up."
  5. Turn the radio off so you can hear what the engine is doing. If you shift too soon (at too low an RPM) and then accelerate too hard, the engine will knock and shudder. If you hear any of that starting to happen, down shift; gently accelerate to a little higher RPM; then shift up and try again.
  6. Install a tach so you can see what RPM you're at instead of guessing based on MPH.
  7. Bonus Step. Pay attention to even the slightest up or down hill slope of the road. When the road slopes down hill, there is less load on the engine and you can shift even sooner; use even less throttle. When the road slopes up hill, you'll need to shift later and it will take at least the tiniest bit more throttle to accelerate.

dylanu 10-06-2008 03:28 PM

thanks for the info about the SIL! I think i realized my problem was i have been babying the gas too much. since ive owned the car i have never pressed the gas pedal in more than halfway. if im wrong tell me. and also the car has a tachometer, thats what i do watch and try to shift before or at 1500rpm

Ford Man 10-06-2008 04:53 PM

I always go easy on the gas and usually shift at about 1500-2000 RPM's. I always let completely off the gas going down a hill that is steep enough to keep my speed where I want and take advantage of DFCO (deceleration fuel cut off) then as soon as I hit the bottom of the hill I accelerate lightly before losing any momentum to keep the speed up. I also try to keep 100-200 feet between me and the car in front of me that way when they lightly brake I can just let off of the gas and coast and lots of times never have to use my brakes at all, that way I not wasting energy I've already used. If you are driving in an area where the speed limit drops let off of the gas in time to get down to the new speed limit about the time you get to it then you don't have to brake to slow down. By using these techniques and driving about 50-55 MPH I'm getting almost 45 MPG combined city/highway on my '88 Escort with a 1.9L 4 speed manual transmission. The old EPA rating on it is 37 MPG combined. A vacuum gauge might also help you then you can see how much load you're putting on the engine. I have noticed since I put one in my '88 Escort that sometimes I can ease off the gas just slightly and still maintain the same speed, but the engine vacuum may go up 3-7 in/Hg meaning the engine is running more efficient. My '88 Escort also has a shift indicator, but I don't pay any attention to it. I shift as early as I can without loading up the engine. A bad oxygen sensor can cause mileage to drop 25-30%. How long has it been since the car had a tune up? Bad plugs or wires can cut drastically into your mileage. Check all of your vacuum lines to make sure none of them are cracked or off that can cause a large drop in FE. Be sure your tires are up to a least the maximum sidewall pressure and check them about once a month. I always try to check mine the first week of each month that way I know when they were last checked. Jack the car up at all four corners and roll the wheels with your hands to make sure they are rolling freely you could have a brake dragging, a bad wheel bearing or the wheel bearings could need repacking. Try to time your traffic lights so you never have to come to a complete stop. I've read that it takes about 20% more gas to get a car moving from a dead stop than if you can keep it rolling. If you haven't run any injector cleaner through it lately it might be a good idea dirty fuel injectors don't give a good spray pattern and cost you FE. I noticed you're in Charlotte, we're practically neighbors I live in Mt. Pleasant over in Cabarrus county. Good luck.

dylanu 10-06-2008 05:18 PM

Quote:

Originally Posted by Ford Man (Post 65599)
I always go easy on the gas and usually shift at about 1500-2000 RPM's. I always let completely off the gas going down a hill that is steep enough to keep my speed where I want and take advantage of DFCO (deceleration fuel cut off) then as soon as I hit the bottom of the hill I accelerate lightly before losing any momentum to keep the speed up. I also try to keep 100-200 feet between me and the car in front of me that way when they lightly brake I can just let off of the gas and coast and lots of times never have to use my brakes at all, that way I not wasting energy I've already used. If you are driving in an area where the speed limit drops let off of the gas in time to get down to the new speed limit about the time you get to it then you don't have to brake to slow down. By using these techniques and driving about 50-55 MPH I'm getting almost 45 MPG combined city/highway on my '88 Escort with a 1.9L 4 speed manual transmission. The old EPA rating on it is 37 MPG combined. A vacuum gauge might also help you then you can see how much load you're putting on the engine. I have noticed since I put one in my '88 Escort that sometimes I can ease off the gas just slightly and still maintain the same speed, but the engine vacuum may go up 3-7 in/Hg meaning the engine is running more efficient. My '88 Escort also has a shift indicator, but I don't pay any attention to it. I shift as early as I can without loading up the engine. A bad oxygen sensor can cause mileage to drop 25-30%. How long has it been since the car had a tune up? Bad plugs or wires can cut drastically into your mileage. Check all of your vacuum lines to make sure none of them are cracked or off that can cause a large drop in FE. Be sure your tires are up to a least the maximum sidewall pressure and check them about once a month. I always try to check mine the first week of each month that way I know when they were last checked. Jack the car up at all four corners and roll the wheels with your hands to make sure they are rolling freely you could have a brake dragging, a bad wheel bearing or the wheel bearings could need repacking. Try to time your traffic lights so you never have to come to a complete stop. I've read that it takes about 20% more gas to get a car moving from a dead stop than if you can keep it rolling. If you haven't run any injector cleaner through it lately it might be a good idea dirty fuel injectors don't give a good spray pattern and cost you FE. I noticed you're in Charlotte, we're practically neighbors I live in Mt. Pleasant over in Cabarrus county. Good luck.

thanks for the help. i do all those techniques. in multiple forums theyve told me about the tune up so i guess thats my problem. and yeah im in charlotte. do you know if there are any crx or mpg meetings around our area anytime soon?

some_other_dave 10-06-2008 06:42 PM

Also get the alignment checked, particularly if the car wanders or pulls to one side or the other.

I think there was an SC CRX meetup a couple of months ago; you can check the "Meets!" thread over on The CRX Community :: Index .

-soD

NeilBlanchard 10-06-2008 11:31 PM

Hello,

Since you do mostly city driving then tire air pressure is key: what pressure do you run, and what is the maximum listed on the side wall of the tire?

Grill blocks may help the car warm up more quickly, and if you do get to 35-45mph, then it can help with the aero, too.

Do you shut it off for stop lights?

azraelswrd 10-06-2008 11:49 PM

Pure city driving?

+Idling
+stopping at stops/lights
+accelerating from stops/lights
+cold engine status
+low tire pressure
+excess dead weight

...are things you should address or fix. At lower speeds, tires, engine condition and driving styles have the most impact on fuel economy. If you don't already, get into the habit of anticipating any and all stops and either gear-coasting or neutral-coasting to where you need to be. Also consider a route that is more conducive to fuel sipping. I used to take the shortest distance but the idle times wasted more gas.

50mph sounds rather "hot" for pure city driving. I rarely breech 45mph on the straightaways in my routes and even then that is too fast at times especially when traffic gets thicker. Consider slowing down a little more, but offhand, 40mpg just with 100% city driving isn't really that bad. I get about 38-42mpg in city (depending on traffic flow).

Feedback monitoring device like the MPGuino or vacuum tube should also help.

mrmad 10-07-2008 12:34 AM

I have a 90 HF and my commute puts me at 75% fwy/25% city. My HF is averaging ~43mpg, probably because I'm driving too fast, but I would think it would be pretty difficult to get an HF above 45mpg on 100% city driving.

Raysp30 10-07-2008 02:16 PM

Good results on my 89 HF
 
I bought my 89 CRX HF over the summer. Previous owner was getting about what both of the other HF owners above have mentioned, between 41-43 mpg.

I will agree that driving habits help tremendously, but with the HF, it was designed for efficiency (High Fuel economy). When driving the HF, your goal is to always shift before you see the light come on, as long as you are driving on a flat surface. So in the first post made, you are doing the right thing by shifting according to the light. On other cars with shift lights that would be a different story.

The main thing I would suggest would be a complete engine tune-up. I am currently getting 53-55 mpg city/highway and I expect that to improve with other modifications.

My suggestion -- engine tune-up, including Oxygen Sensor replacement, idle adjustment if necessary, Hot Air Intake, partial grill block, and inflating to the max tire pressure you are comfortable with.


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