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Old 10-19-2010, 10:10 PM   #299 (permalink)
Grrr :-)
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Join Date: May 2008
Location: Levittown PA
Posts: 800

Cherokee - '88 Jeep Cherokee
90 day: 19.44 mpg (US)

Ryo-Ohki - '94 Geo Metro Xfi
90 day: 50.15 mpg (US)

Vger 2 - '00 Plymouth Grand Voyager SE

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Originally Posted by dcb View Post
what have you tried?
... damn I tried hard on this post and STILL found 3 errors before the 3 section. Grrr I am a sloppy typer :-) fast but sloppy :-)...

Well the simple stuff was obviously not it so I won't bore the group with everything I tried :-)

It was suggested that maybe I had carbon build up which was increasing compression (though I thought that was GOOD for ethanol??)

SO I seafoamed the engine again and also cleared out the EGR again just to be sure. there was a tiny bit in the EGR as expected (I clean that thing twice a year) and there was minimal smoke from the seafoam (I am aggressive with it) I scoped the cylinders and they were quite spotless inside including the tops of the heads (borrowed a video scope Very cool gadget I want one :-)

It was suggested my compression might be low. SO I checked that again 185 on all 3 170 dry 185 wet (very very good compression numbers for the xfi) anything over 155 and within 10% of each other is considered do not do anything to repair.

It was suggested a vac leak might cause the problem. I was not sure how a vac leak could "tell" what kind of gas was in the car but anyway I bought a nice vac tester and used it. as mwebb stated I should have 19-20inches and no flutter. I confirmed this is what I have so vac is good.

I did a full tune up. new pcv all new filters good quality wires NGK (only plugs suggested for the 3cyl) original quality plugs all carefully gapped. cap rotor etc.. etc...

I seafoamed the oil twice and used only good quality 5w30.

I changed the trans oil and installed the recommended Syncromesh.

All motor mounts are good. Coil is good. I have 4 so just for the heck of it I tried all 4 in case more than 1 was somehow bad. No change)

There is a sensor on the firewall I want to say IAC ?? I forget will have to check but I swapped that out too just in case since someone suggested try that.

I cleaned up the throttle body (did not need much is was pretty squeaky clean) and the injector and ALSO installed my backup injector just in case maybe it was out of adjustment or fouled to where cleaning would not help. No change.

Someone suggested maybe I had crude in the gas tank. logically this can NOT effect fuel economy with an "under pressure" EFI system that these cars use (its run or don't run) so I dropped the tank anyway and inspected (spotless) no residue or crude. I changed the sock filter on the fuel pump since I was in their anyway even though it was clean.

Alignment was suggested and ignored since it would effect both fuels equally (I am waiting till I do my front end to get it aligned since alignments around here are VERY expensive $90) I am upgrading the brakes to the newer 95+ brakes with better cooled rotors and calipers and will also change the tie rods inner and outer at the same time and replace a control arm while the one on their is new I don't like the look of the boot so I am proactively replacing it since I got one really cheap. All of that will require an alignment so I am waiting till I do that work to get the alignment and again the alignment will effect both fuels equally.

Someone suggested maybe it was stuck in cold loop. This was not logical since I was getting 50mpg (in cold loop I would be getting closer to 30-35mpg) but either way I flushed the entire system when I replaced the radiator and installed new thermostat and hoses. Never overheated still never overheats. In fact it runs cool enough that I think I have more toes and fingers than the number of times that aux fan has turned on this summer even in the heat we had.

The way the car is geared and the size tires I have on it probably result in me being pretty close to the 3.52 final gearing.

The car has plenty of power that I almost never tap into. In fact except when passing (which I almost never do and can not even remember the last time I needed to) I try to never take it above 2500 rpm and cruise at 2200-2400 rpm (no more than 48-50 mph.)

the max speed limit on any part of my commute is 50mph.

I don't know how to test the computer if thats even possible for a regular person. I do get the rated fuel economy when I use E0 which indicates to me its functioning properly. I was getting 55mpg which is the cars rated "combined" fuel economy and my commute would qualify as combined or slightly more toward highway.

I tried acetone. zero impact on fuel economy either way.

I replaced the entire exhaust when I bought the car (that is one of the things it needed to be road worthy) so its brand new front to back except the CAT. I do not think its clogged because I have no codes no bogging and great fuel economy. also this should effect both fuels so would be irrelevant in the equation. Short of some evidence to the contrary I can not justify the expense of replacing it "just to see" as it is nearly $100.

The Timing is advanced as far as possible without risk of damaging the engine. even at the current setting I get teeny tiny wee pinging here and there so I should probable retard it a little bit but for now will leave it alone.

I probable did a little more but can not recall at the moment.

Besides the fuel economy the car runs "perfectly" and I mean perfectly.

I DO notice some small differences with E0 over E10. the car seems to idle a tiny bit smoother and sounds just slightly different. Not enough to hear in a recording but enough that I notice.

the 3cyl is already a pretty "shaky" engine by its very nature this smooths out JUST a tiny bit on E0 (but I admit this could be totally imaginary)

I tried a few higher power accelerations and my gut says it feels like it has a bit more power on E0 (and on the washed gas) but people said this might be the residual water from the washing but I noticed this extra power was also present on pumped E0 (no water washing) it also "feels" like I can shift sooner which would jive with the increased power.

This could still be imaginary though. I have no means to actually test this or measure it with any reliability or consistency.

During my normal barely their accelerations I notice no physical or audible difference between E0 and E10 and if there is a "gas pedal" difference its to small for me to notice. I take about 30 seconds to "get to speed" the car can do it in less than half that but I drive for FE not speed.

What else should I try?

you name it. if it makes sense won't blow up my car and does not cost a fortune I will try it :-)

Last edited by Nerys; 10-19-2010 at 10:21 PM..
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