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curiouser and curiouser; evolution of xfi issues
Topic Started: Dec 23 2009, 06:17 PM (1,314 Views)
geonewbie
Advanced Member
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when purchased car had a stuck open EGR, clogged TB coolant pasage, timing set at 0* BTDC, faulty injector, bad alternator, hard starting, high idle etc. etc, but there was NO stored codes and NO C.E.L. commuting mpg of 36, high way 43.

removed EGR system and delt with the rest including grill block and timing at 8* BTDC. commuting mpg of 50. CEL ( #13 ) lights for 2-3mins. after about 15 mins at 55mph, until next stop then goes out.

last night moved timing to 10* BTDC and removed the intake snorkle again. today much easier cold start, faster warm up and the CEL flashed for less than a full sec. ( had to think, what was that ? ) after about 7 mins at 55mph.

now why would the ECM and 02 sensor act like this ?

this evening i moved the timing to 12* BTDC (since i had no ping ) and almost wonder if the CEL will stay off tomorrow on the way to work.

thoughts ?

steve
Edited by geonewbie, Dec 23 2009, 06:19 PM.
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nerys
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Grr

whatever your doing your "compensating" for something else would be my guess.
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Bad Bent
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Facetious Educated Donkey

Isn't driving a Geo not "compensating" like driving a BIG truck is? :dunno

Well, we will see what happens, eh.

My source says "Code 13; Oxygen sensor voltage stays between 0.35 and 0.55 volts for 30 seconds when the TPS signal was above 0.55 volts. The engine had been running for at least 40 seconds with an engine temperature above 110° F."
So based on that your next move might be to adjust the TPS. Mark it before adjusting.

"now why would the ECM and 02 sensor act like this?" I'd take it personally. They obviously have a "thing" gong on.

If I drive around town, make 4-5 stops my CEL comes on. I find some open road and rev it up to 5-6000 for 10-20 seconds and blow it out, and the light also. :D
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geonewbie
Advanced Member
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nerys,

yes, i agree that i'm compensating, i have a car in a state and displaying issues i don't like, Soooooo i'm taking steps to make it diferent. LOL

BB,

as to the ECM and the sensor having a thing going on, i'd agree with that too, since the results of the actions i take alters their presentation.

i have also heard that a missing EGR is just like a mal-functioning one and that the ECM should set that code as well when there is no response to it's commands or readings for it. trouble is, while my EGR WAS malfunctioning i didn't have any codes and now with it gone i don't have THAT code, i have the 02 code that changes it's behaviour in response to changes i make.

it has also been more likely to appear if the ambiant temp. was slightly higher, say 30* or more.

i'll drive it today and see what it does, then check the TPS again.

thnaks,
steve
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mwebb
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FOG

"Code 13;
Oxygen sensor voltage stays between 0.35 and 0.55 volts for 30 seconds when the TPS signal was above 0.55 volts. The engine had been running for at least 40 seconds with an engine temperature above 110° F."


first of all
this is not the same description for DTC 13 listed in the "sticky" above ....
but anyway


what the above description means is that
02 sensor voltage is hanging low when the engine is above idle and warmer than 110f

in short
system is lean

or
02 sensor is NFG and stuck low

or
02 sensor signal is shorted to ground WITH 350mv + voltage drop on the ground side , possible but very unlikely
.........................................................
DO NOT START WITH THE TPS
get out your voltmeter and measure 02 sensor signal at hot 2k rpm
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geonewbie
Advanced Member
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to measure the sensor do i back probe the coupling and ground to the engine ?

i really didn't think the TPS was involved in this, and pretty certain it's set correctly.

from reading it seems that the result of removing the snorkle is statistically irrelavent to mpg's directly, comments ?

many feel that more initial timing is "better" for mpg's, has anyone seen a drop in mpg on an xfi above 8*btdc ?

thanks,
steve
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geonewbie
Advanced Member
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well, got the new 02 sensor in today, no cel at any time.

seems smoother and stronger, as though it may have been slightly lean. it even cruises at 55 mph at a decernably smaller throttle position than before.

great, now on to the wheel bearings.

thanks,
steve
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geonewbie
Advanced Member
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i really would like to hear comments on the ignition advance issue if there are any.

does anyone have experience of loosing mpg moving a stock XFI from 8* to 12* BTDC ?

thanks,
steve

reason being, as stated above , last change made was to put a new 02 sensor in, with noticable results, but they seem somewhat counter intuitive to me.

car was getting steady 50 mpg before the timing change and the 02 sensor and still had a very dark tailpipe. now, with the 12* timing and new sensor car runs smoother and cruises at a smaller throttle setting, but the tailpipe is noticably lighter ( now on the grey scale for the first time) and i seem to have dropped a couple of mpg.

it occures to me that these "managed" engines are a real love / hate relationship. LOL

Edited by geonewbie, Dec 28 2009, 02:31 PM.
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geonewbie
Advanced Member
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further driving and calculation shows that i have returned to the former 50.5mpg mark, with the new 02 sensor and 12* BTDC.

this is what it was at 8* BTDC and the bad sensor, so, just as an exercise in curiosity, i'm going to drop it back to 8*BTDC and see what happens.

my experience is that there is a decernable "sweet spot" for MPG and drivability when the ignition timing is starting the burn at the point that MOST co-incides with max cylinder pressure at cruising speed, i just need to find it for THIS engine.

thanks,
steve
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Woodie
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I wouldn't make any decisions until three or four tanks of fuel show the same result. Literally hundreds of things can cause you to "drop a couple of mpg".
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geonewbie
Advanced Member
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OK, the next tanks showed that the new 02 sensor and 8* BTDC setting dropped to an average of 44.75mpg.

then, i unscientifically changed 2 operating settings at once and had a surprize.

i have had my front bumper blocked except for a 3x6 opening in front of the radiator and still running stock CAI.

i closed the bumper openings completey and took the intake snorkle off at the air filter housing and blocked the tube from the fender, timing stayed at 8* BTDC.

warm up is much faster, heat value available to interior stays more constant and the last tank gave 49.2mpg.

weather conditions have been very stable and constant during the last 4 tanks, so i'm pretty satisfied that there IS an improvement, i'll watch further and report back.

steve
Edited by geonewbie, Jan 21 2010, 03:30 PM.
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bansheetaz


i would put the EGR back on and get it working properly. especially with that much ignition advance. just because you cant hear it pinging doesnt mean its not. if a metro came with EGR, it is best to have it operational.
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mwebb
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FOG

bansheetaz
Jan 21 2010, 05:21 PM
i would put the EGR back on and get it working properly. especially with that much ignition advance. just because you cant hear it pinging doesnt mean its not. if a metro came with EGR, it is best to have it operational.
yes very correct
and
a functional EGR will improve Fuel economy as well

because when the EGR is operating

Engine size is effectively reduced by diluting the combustion chamber with inert gases
and
the operator (driver) unconsciously steps slightly down on the throttle to make up for that and in so doing
reduces suction throttling losses

and
combustion temperatures are reduced which limits formation of NOX and
can not hurt the longevity of various engine components ,
like exhaust valves
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geonewbie
Advanced Member
[ *  *  *  * ]
bansheetaz
Jan 21 2010, 05:21 PM
i would put the EGR back on and get it working properly. especially with that much ignition advance. just because you cant hear it pinging doesnt mean its not. if a metro came with EGR, it is best to have it operational.

so....... at whatever base timing, if you have to load the engine with WOT or climb in high gear to get ping to occur to the point of noticability, is it doing it at any other time ?

i doubt it, or folks wouldn't be satisfied with the "till it pings ,then back off till it stops" method. i was also under the impression that 8* total base advance ( that's 3# past stock ) is well within the safety zone.

i don't operate in either of those conditions. i drive so light footed that i upshift from a dead pedal condition before the "arrow" ( 10-20-30-40 ), never drive over 55mph. and there are no hills worth mention around here.

as to the need of the EGR, i am unconvinced yet.
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Woodie
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I too would get the EGR back to functioning condition, but don't worry about that timing. A lot of Metros came from the factory with no EGR and 10 degrees of advance. Your car could probably take a little more.
Edited by Woodie, Jan 23 2010, 05:55 AM.
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