so i've been chasing an o2 problem and have decided i'm stumped. when i log my o2's they show anything from .003 to .010 and don't move. i've checked the wiring harness for grounds...all good, power to the sensors...good, continuity with the all the o2 harness wires back to the 60 pin connector.
i've tapped the back of the o2 plug so i can check voltage with a meter while i'm logging it. (don't know if this is the proper way to check this or not.) But this is what i have found. battery voltage on the heater wire and ground matches my log. however, when i check the signal wire back to the ecm, at startup, i'm getting 1.2xx volts and that drops gradually down to .8xx volts and fluctuates at that voltage.

i'm wondering if i'm just missing something in my payload that's not letting my hego's log correctly or if there's some other problem i've been overlooking. FWIW the o2's are the 3 wire bosch units and are new as of last week. i've attached my tune and log (just a driveway idle)

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

Oh man, not to scare you, or to say the same thing is going on here, OR to put you to sleep but it's sounding pretty familiar except for being on the exact opposite side of the spectrum. Have you came across this yet? http://eectuning.org/forums/viewtopic.php?f=2&t=17228

It was never "really" solved other than just forcing OL from that point on without looking back, but I did have to deal with it again when I eliminated the harness entirely and it screwed things up that it shouldn't have.

Hopefully someone has a better, easier answer!

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1986 Mustang LX, 1997 Explorer Long Block, GT40P Heads never pulled off s/b, Professional Products Upper/Lower intake and 70MM TB. Converted to MAF using A9l GUFB strategy, 03-04 Maf, Scotty Brown custom is now installed, this thing ROCKS! TFS springs/retainers/pushrods, BBK LT Headers and Xpipe, Dyno Max welded muffs, UD pulleys, Polished/Coated 4.30 gears, Z-code T5, Moates Quarterhorse, Binary Editor. 11.78@113.91 mph at Milan Dragway, 11-18-12. 1.56 60FT best. 329RWHP/353RWTQ SAE

make sure the hego ground pin on the ecu is grounded good

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http://www.efidynotuning.com/ford/

yea, i have read over that a couple of times now....along with everything else i could find with the phrase "HEGO" mentioned in it...haha. did you ever try changing out the ecm to see if that was the problem? or did ya just leave it in open loop?



i've checked pin49 (if memory serves) and it's connected directly to the battery. along with all the other grounds in the wiring harness that come from the ecm. the battery is grounded to the engine block, the block is grounded to the frame and the frame is grounded to the body...no paint, soldered connections and star washers everywhere.

FWIW, the computer is a reman unit from autozone.

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

I've never swapped ecms. I'm perfectly happy with the way it runs in forced OL. Does it by chance run VERY badly when it is warming up or anytime the ignition is shut off then turned back on? Say like, you start it, it runs fine right at first and then about 30 seconds later it starts running crappy for about 2 mins and then it's like a switch is flipped and it's all good? Or you're going down the road, turn it off and restart it and it does the same thing or no?




Actually, that's just another similarity here. Mine is also a black reman I bought on eBay many years ago, not sure where it was originally from though.

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1986 Mustang LX, 1997 Explorer Long Block, GT40P Heads never pulled off s/b, Professional Products Upper/Lower intake and 70MM TB. Converted to MAF using A9l GUFB strategy, 03-04 Maf, Scotty Brown custom is now installed, this thing ROCKS! TFS springs/retainers/pushrods, BBK LT Headers and Xpipe, Dyno Max welded muffs, UD pulleys, Polished/Coated 4.30 gears, Z-code T5, Moates Quarterhorse, Binary Editor. 11.78@113.91 mph at Milan Dragway, 11-18-12. 1.56 60FT best. 329RWHP/353RWTQ SAE

it actually doesn't run too bad at all...hot or cold, start and restart. i just want it to do "what it was supposed to do". this is an off road vehicle and i'm usually a LONG way from the trailer, so i want it to act as "stock" as possible. the only problem i have with it at the moment, is it has a rich backfire (popping) when i snap the throttle shut.

i have a line on a factory ecm to borrow so i'm gonna give that a shot this weekend to rule out the reman. i'll let ya know what i find out. i'm curious to find out now that i know we have that one thing in common.

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

popping through the intake is due to being lean not rich, a rich backfire is usually due to an ignition fault that results in the muffler getting filled with fuel and it explodes when an ignition source and oxygen get thrown into the mix, you will not mistake it

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http://www.efidynotuning.com/ford/

it is in the exhaust, and as of right now, i've just thrown some timing at it so it will run, i haven't spent much time on it yet. in the log the timing drops to 18 (when the backfire happens) then jumps back to 24 when the throttle snaps shut. i just haven't worked with that part yet.

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

Man, I got excited when I thought I saw the popping through the intake since that is EXACTLY what mine used to do when it was still looking at the 02's during warm up since it was reporting 2.4volts (beyond possibly rich) so it was pulling all the fuel, I figured your's would be opposite since you were showing low o2 voltage. I was kind of expecting to hear yours was running pig rich at first.

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1986 Mustang LX, 1997 Explorer Long Block, GT40P Heads never pulled off s/b, Professional Products Upper/Lower intake and 70MM TB. Converted to MAF using A9l GUFB strategy, 03-04 Maf, Scotty Brown custom is now installed, this thing ROCKS! TFS springs/retainers/pushrods, BBK LT Headers and Xpipe, Dyno Max welded muffs, UD pulleys, Polished/Coated 4.30 gears, Z-code T5, Moates Quarterhorse, Binary Editor. 11.78@113.91 mph at Milan Dragway, 11-18-12. 1.56 60FT best. 329RWHP/353RWTQ SAE

actually going back and looking at an earlier log...<100 deg ECT it's running in the low 12's but it's also following the LAMBSE there too. my lambse are 11.9 at startup dead cold and the AFR's are around 12.3. however, mine starts in open loop....even though i've got closed loop enabled...

another point that's probably worth mentioning is that if i unplug the o2 harness, it still "logs" the same voltage....well pretty close... .003 vs .0075

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

It's going to start in OL, it won't go into CL until several conditions are met, one being minimum hego switches detected, and if it TRULY isn't switching as interpreted by the eec vs just not showing correct in the log then it won't ever see CL.

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1986 Mustang LX, 1997 Explorer Long Block, GT40P Heads never pulled off s/b, Professional Products Upper/Lower intake and 70MM TB. Converted to MAF using A9l GUFB strategy, 03-04 Maf, Scotty Brown custom is now installed, this thing ROCKS! TFS springs/retainers/pushrods, BBK LT Headers and Xpipe, Dyno Max welded muffs, UD pulleys, Polished/Coated 4.30 gears, Z-code T5, Moates Quarterhorse, Binary Editor. 11.78@113.91 mph at Milan Dragway, 11-18-12. 1.56 60FT best. 329RWHP/353RWTQ SAE

that's why i enabled it...just to see.

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

did u ever check the hego ground pin?

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http://www.efidynotuning.com/ford/

I think he initially said he had, but if not, don't be afraid to splice into that thing at the o2 right to an additional ground, and also at the ecm, right to the kick panel or something close to where you have it mounted just to make sure. When I was trying to eliminate the ground as a suspect I ran "trial" wires straight to the battery - post just to verify.

I'm very curious to see what happens with the other ecm.

Do you know what year the harness is, specifically the 02 harness? Which one of these represents your 02 harness?

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1986 Mustang LX, 1997 Explorer Long Block, GT40P Heads never pulled off s/b, Professional Products Upper/Lower intake and 70MM TB. Converted to MAF using A9l GUFB strategy, 03-04 Maf, Scotty Brown custom is now installed, this thing ROCKS! TFS springs/retainers/pushrods, BBK LT Headers and Xpipe, Dyno Max welded muffs, UD pulleys, Polished/Coated 4.30 gears, Z-code T5, Moates Quarterhorse, Binary Editor. 11.78@113.91 mph at Milan Dragway, 11-18-12. 1.56 60FT best. 329RWHP/353RWTQ SAE

Yes i have and it goes directly to the battery negative.

My o2 harness and injector harness came out of an 89 grand marquis.the main harness is a FMS harness and was new when i put it in. Of the pics you posted, mine is the top photo (1990.jpg)

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

Ok, I don't have a clue on differences in the marquis harness or the FMS for that matter. Different jumpers and what not. Now, I know you said you back-probed the o2 return wire back by the sensor itself, have you back-probed it at the 60pin connector yet to see if it is "putting in" a reasonable signal to the eec? Or wait, I seem to remember you stating you checked continuity back and were good, cancel that last thought if so

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1986 Mustang LX, 1997 Explorer Long Block, GT40P Heads never pulled off s/b, Professional Products Upper/Lower intake and 70MM TB. Converted to MAF using A9l GUFB strategy, 03-04 Maf, Scotty Brown custom is now installed, this thing ROCKS! TFS springs/retainers/pushrods, BBK LT Headers and Xpipe, Dyno Max welded muffs, UD pulleys, Polished/Coated 4.30 gears, Z-code T5, Moates Quarterhorse, Binary Editor. 11.78@113.91 mph at Milan Dragway, 11-18-12. 1.56 60FT best. 329RWHP/353RWTQ SAE

Battery negative is not always the best place. Same place as EEC ground is probably better in this situation.

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1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

ground is obviously not an issue, does the o2 report rich at wot?

ive had an issue like that once when i opened the ecu a cap had been leaking at the edge of the qh on the ecu board, i replaced both the caps and the o2s worked fine ever since

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http://www.efidynotuning.com/ford/

Both harnesses are the same, i've just taken out the transmission part of the o2 harness since i dont need it. The main harness is a new ford motorsport.



I have not checked The WOT voltage. However i just picked up an unmolested a9l, so i'll give that a shot and pull mine apart to see if anything is out of place....i'll know something this evening.

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

In a fox body, the EEC ground went to the driverside inner fender. Which also had a ground strap directly from the battery negative.

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89 Coupe- Canfield 195's, Holley Systemax II, CI cam, 24# Inj, 05 Slot MAF, 75mm TB
BBK 1 3/4 LT's, 3"Exhaust, 3"Spintech's, T-5 Trans, QH 1.4, AEM WB, BE/EA: A9L-GUFB

okay, so let me be the first to admit i'm a bone head. some how i was counting my 60 pin connector backwards or upside down or in some other manner than the correct one to get to pin 49. that being said i now [i]really do[i] have a hego ground and surprise...they work.
i'd like to send an embarrassed thanks out for everyone's input on this.

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A9L, Tweecer, Innovate LC1, 351W +.030, world products Windsor Sr iron heads, professional products upper and lower intake, stock TB, 94/95 MAF, 30# ford injectors EV1, shorty headers, comp roller cam 214/220 .507/.507 @.050 114 LSA, 1.6 roller rockers. C6 auto into an atlas 4.3 transfer case. it's in a jeep with ton axle housings 5.13 gears and 43 inch swamper sx's. approximately 5500#

yeah. My point was just that ground, in the sensor world, is a return/common feed for providing sensor signal to/from the computer. the more direct you can connect it to the computer, the less change of an issue. just going to ground/battery does not always provide the least resistance.

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1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm