Mdirollo

I have a 97 Accord EX wagon, 4 speed automatic with 55k on the odometer. I bought it used 10 months ago with 48K. Have had poor gas mileage since I bought it and of course the guy I bought it from doesn't want to know anything about it. I've since had it tuned and the timing belt done using only OEM parts (Honda). Still getting the same poor gas mileage, usually 18-20 mpg, best was 23 mpg and that was an anomale. Took car to dealer and got the usual - "Can't find anything wrong". Too bad because I like the car and it runs very well. I'm looking for any advice or ideas to help remedy the problem. EPA estimates for my car are 23 city/30 highway. I'd be grateful for the 23 ANYTIME. Anyone out there with ideas/comments/suggestions? Please help or feel free to write me direct at: mdirollo@sbcglobal.net. Thanks to all !

P_Adams

Refer to the Gas Milage thread.... I made a suggestion for the both of you.

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Mdirollo

Thanks for the suggestion. I understand what you're saying and have asked the dealer about the O2 sensors. Of course, they're standard reply that there would be a fault code if there was a problem with them. I think they're worth replacing because I've invested quite a bit of money in this car with the intention of keeping it a long time. Now I'm about ready to sell it due to this gas mileage problem. So, I guess a little more effort is warranted before I bail out. Do you recommend changing both Oxygen sensors? Also, I've read that it is recommended to clean out the EGR ports? Do you agree? Lastly, where can I find this "SeaFoam" product? Thanks for your help and suggestions. Regards, Mark

P_Adams

Apparently some of the guys have found it in places like Autozone - there's a thread in here from maybe last week... let me see (pause)

Heres a thread on egr valve (there's others)
https://honda-tech.com/zerothread?id=1398643

and here's one on SeaFoam
https://honda-tech.com/zerothread?id=1391117

That should get u started.

Most major auto manufactures have the same product thru their parts dept. Whatever they call it, it's all the same; a de-carboning agent.

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amckee

You will not gain 10 MPG by replacing the O2 sensors. Period.

P_Adams

Period..... hum.
Ok, what happens then when an O2 sensor, because of carbon buildup, sooting or electrical failure starts sending a signal indicating an overly lean condition? The ECM compensates by going rich to get it into range.
Of course there are other sensors that can cause this (ECM engine temp sensor comes to mind) but the system would set a light as the system failed to go into closed loop; and you'd have code(s) available. (which Mdirollo has not made mention of)
True, 10 mpg may be a bit of a stretch, but what do you (amckee) suggest?
He asked a question; I gave him an informed suggestion, since he's pretty much touched all the correct typical bases.

amckee

Vacuum leaks would be the first place I would start. 18 to 20 MPG is more than a lazy O2 sensor. These sensors are capable of trimming the AFR , but not to this extent by themselves. He may have more than one problem and granted your suggestion may be one of them, but, I would start with whats free and work my way up to whats expensive. I really meant no hostility toward you with my last reply, and I appreciate some of the finer detail you put into your post that many others do not know or don't take the time to include. When I hear of a 4 cylinder Honda getting that kind of mileage without any noticable performance loss I think big fat air leak or many small ones. The O2 would think the TPS was more opened than it really was. The MAP would think it was on top of pikes peak.

d357r0y

How about:

compression/leakdown test

tire pressure

dragging brake (faulty caliper)

Just some suggestions, my 5speed wagon (with 165K) gets 30mpg around town.

Mdirollo

Thanks for the suggestions to one and all. I've done a compression test, which comes up great for all 4 cylinders. Tire pressure is always vigilantly monitored. As for a lazy caliper....hmm, I guess that could be a possibility. But, I suspect, it's either a vacuum leak, dirty EGR passages in manifold, faulty egr valve or maybe sluggish O2 sensors (my 1997 EX car has two). I just don't understand why I shoudl be having this problem on a car with only 55K original miles. The dealer has done a preliminary check and did not find any fault codes whatsoever. I don't have the tools to check the O2 sensors or the vacuum lines, so it looks like it's gonna be another trip back to the dealer ($$$$). I want to keep this car but this problem is forcing me to consider getting rid of it...have only had it 10 months and it's been poor on gas since I bought it (had 48K on the odometer 10 months ago). As I said, I really dont want to get rid of it - especially since I've put some money into it over the past few months (you name it, I did it). Anyway, any past or future suggestions are appreciated.

amckee

Your car averaged 7000 miles a year during it's life. I think it's safe to say that these were putt around town miles that carboned up the ports and heads and maybe even your exhaust. Cars prefer long stretches at highway speeds over around town shifting under 3000 RPM.