davidis1

I have a 1990 4 door accord 4 speed automatic ex sedan. I am having problems with gas mileage and emissions. I live in Arizona where it is legal to drive up to 75 mph and the highway patrol will smile and wave while passing on the right at 90 mph in certain areas. (It's happened to me. They wave and blast by.) We don't get good gas mileage as a rule of thumb. Driving 55 would be dangerous.

We test on a dynometer here in AZ. I guess most states do these days. Not as easy to get it to pass as it once was. I have been tuning and tweaking based on gas mileage in hopes that an efficient engine might pass emissions. Did the timing belt a year ago before it originally failed. Don't have a timing light so I can only hope the belt didn't stretch when it broke in. (It's a Gates)

The O2 sensor did not give correct voltage as per Haynes. Replaced it and the car ran better but failed emissions. Also did the cap and rotor cause the old ones were visibly worn out. Wires ohmed out uner 12k. New NJK plugs for six dollars didn't hurt anything. Got a Framm fuel filter for $12 and did that. (Poured the gas out of the old one into a clear glass jar and it was black like soot.) Did the air filter and changed the oil with 5 w 30. I ran numerous brands of injector cleaner including a double dose of Techron before it dawned on me to change the fuel filter. (I wonder how effective it is to clean injectors through a dirty filter. Probably not so I ran more cleaner through the tank.)

I Fixed an idle surge problem by bleading theradiator fluid. Found bubbles. Helped some. Tightened wax fitting on fast idle thermo that helped some. IAT was not ohming in spec with Haynes numbers so I replaced it. Idle surge seems better for past day. I wonder what all that extra air in the mix was doing to my emissions test. We'll see...

I do not hear any vacum leaks and the car is running smooth now.

NO2 missed by a smidge on emissions test so I cleaned and checked the egr valve. No issues there. However I did not mention that this is a smooth running 90 accord with 252,000 miles on it and great acceleration. It idles smooth except in reverse with the AC on but I have heard that is a common problem. (Yes the mounts are all good.)

I have many questions for a well seasoned and qualified tech such as the fellow that opened up this forum. First of all, is therre a better alternative to cleaning out the egr ports than drilling out the taps? That just does not seem prudent. Bad enough to go chipping away at carbon in the intake let alone making hay out of little mettle filings. Could it be done any better if I purchased a used intake, cleaned it up and then swapped it in? I have seen them for $30 on Ebay. I am not having driveability problems but have heard that clogged ports may be a factor in the NO2 problem.

I have recently become acquainted with the intake air bypass valve. For an experiment I took this out of the loop by removing the bottom portion of my air filter box. I kept the filter in place by means of a wire tie. (I am definately not ASE certified! HA!) Lo and behold, my decrepit gas mileage went from 18.5 mpg to 22 mpg (combined city and highway). (Sounds like it went from bad to not good, right? Remember I'm driving an automatic in the city and the government says I should be aiming at 24 mpg combined.)

So do I take out the IAB for the emissions test with IAB removed? Would it help to burn 20% less fuel during the test? Maybe not since it measures stuff in parts per million, right? And if I do, should I disconnect the IAB solenoid? Would that give useful feedback to the ECU to stop trying to run the valve?

Does a car of this age necessarilly have to have it's injectors cleaned ultrasonically to get the best performance? There is a shop around here that will do the injectors and rails for $100. They will also replace the O rings for that, too. I guess I'll have to do the seals myself. If I could get another two MPG for $200 it would pay off in less than two months of driving. What do you think?
It looks easy enough to pull the injectors on this car but how can you tell by looking at them if they need a bath?

Thanks for your input.




Modified by davidis1 at 1:22 PM 4/27/2006

Ross 2.0

Since you drive the crap out of your car anyway I say that you just need to make sure the transmission has fresh clean ATF-Z1 and the tires are propperly inflated. I doubt your EGR and ports are clogged at all with the thrashing it gets on a regular baisis. But your gas mileage is definately off even with your driving habits. When your about 500 miles away from your next test have your induction system cleaned (BG or use Honda Top Engine cleaner).
It won't hurt to run a tank of premium gas every once in a while either.
Hope that helps some.
I'm not a smog technician so it's hard to go any further in detail as to what you need to do to pass the sniff test.

davidis1

What is BG? I Guess Honda Top Engine Cleaner is just a Honda part that is similar to Sea Foam top engine cleaner. I have never used any of these.

Do you recommend using in PCV throttle body vacum line as well as crankcase? I am extremely hesitant to put a strong detergent in the crankcase when I already have a valve cover gasget leak. It is leaking heaven knows where else to the sum of about a quart every 6000 miles. Very nice for a car of this age. It also does not burn any oil. A thin layer of varnish may be contributing to sealing the rings. Who knows?

I do not know what the intake manifold really looks like inside. If I popped off the EGR and filled the EGR intake with top engine cleaner and then drove the car around my unsuspecting neighborhood, would that do a good job on the EGR ports? Maybe I should just rev the engine to 2500 rpm until the white smoke goes away.

Do you have to look at all the timing marks to really know if it's correct? Or will a timing light tell all? Guess I have to get one. This gas mileage is unacceptable.

Thanks for the help. I would not have thought of the cleaner on my own. I thought it was a gimmick!

...Dave