Help me kill my fickle woman...
 

Car model: Honda Fit Sport; 2007

Attempting to make: Engine kill switch

Background information:

I have had this Honda fit for about 6 months. She's been relatively good to me. Occasionally, in the right circumstances she would jerk for no reason. I finally decided to take her to the dealership because there were some "pending codes" on my scangauge.

They scanned it with a computer and found nothing wrong, but told me I needed to "let it out" on the interstate every once in a while. So I did it as soon as I left the dealership...

The jerking was immediately being duplicated, and the car threw an error code. I immediately took it back to the dealership. The technician (who was pissed to see the car again 45 minutes later) told me that some carbon may have gotten into the engine that built up from me "puttering around town," causing a misfire I RARELY go above 2k RPMS, and the jerking normally happened above that point.

Things to keep in mind: Every time I would do an engine off coast (EOC) via turning the key, the check engine light would start blinking. I posted that problem here, and many suggested it might be a cylinder misfire. The Honda manager stated that this was the problem. When my mechanic took the spark plug out, he showed me where there was UNBURNT FUEL on the spark plug. This was @ 80K miles and the sparkplugs that he took out were aftermarket NGK iridiums, implying that they had been replaced before, and therefore there should be nothing wrong with them this early.

The mechanic said that it was quite possibly caused by be doing EOC. I have seen explanations on kill switches this forum that would lead me to believe he was right. I have read that using the key to engine off coast can keep spraying fuel into the engine.

Which method should I use to build a kill-switch for my honda?

I am attaching pictures of all the fuses in my car.

Lastly, but most importantly, THANK YOU! I haven't been EOC'ing and my gas mileage is plummeting by about 10mpg.

Honda Fit Cabin Fuses

Honda Fit Engine Fuses

Files are too big to attach to post...

I'm not familiar with Honda but I would reasonably suspect that the flashing MIL after EOC is caused by an ECM conflict of seeing vehicle speed sensor input and no input from the cam sensor or crankshaft sensor.

If the jerking is caused by misfire, two things can happen. The camshaft position sensor will command retarded ignition timing, and the 02 sensors will command lean as they are in a HC rich atmosphere.

When it is jerking, look at the short term fuel trim (stft). A negative number indicates a rich fuel mixture and a positive number in excess of 10 indicates a lean condition. These numbers would be very useful to know to make an accurate diagnosis

all of the symptoms you've described can be caused by your EOC method. Cycling the key on many (though not all) vehicles will cause the fuel pump to automatically prime the system by turning on full blast for 2-3 seconds. if your system is already pressurized, this can cause an overly rich mixture at restart.

excess fuel can cause stumbling in many forms:
carbon rich egr (ie: blockages, unburnt fuel into intake, etc)
fuel on the spark plugs (misfire, incomplete burn, etc)
AFR's richer then even the "optimal power" band of 12.5:1 (fuel pooling, incomplete burn, ignition retardation, etc)

Best bet for EOC kill switch is dependent upon the make, model, and year of the vehicle... options include but are not limited to:
-Fuel injector cut-off
-Crank/cam angle sensor
-distributor/coil
-EFI fuse circuit
-fuel pump (mainly mechanical injection diesels, not gasoline engines, for the very reasons stated above)
-intake block off (again, generally a diesel application, and usually only in the case of emergency!)

as far as your particular application, it may be tough, as these newer engines have a LOT more monitoring perimeters, and can throw codes under many more conditions then older generation vehicles, and depending on whether the code is active/passive, may end up throwing your car into limp mode, and then the FE really sucks! (not to mention, if you know you're running on a passive code, a more detrimental active code may rear its head just by coincidence, and you'd have no idea that's happening, and then you're left walking!)

As far as the tech saying to open it up every now and then, I couldn't agree more! on-ramps to interstates are the perfect opportunity, as entering in the flow of traffic at speed is generally much safer (and more convenient) then entering in at a lower speed.
Benefits:
-Detergents in fuel will help clean intake valves/runners
-higher piston speeds help blow out built up carbon on piston surfaces
-prevents cylinder walls from forming ridges near the head
-helps keep EGR system clean by allowing additional purging
-helps clear blockages from Catalytic Converter, muffler, etc.

I'm not advising that you red-line it at every intersection, but that little fit engine was designed to be let loose every once and a while!

It was most likely caused by a misfire. That's the code I managed to get it to throw after "letting it out"

The crankshaft position sensor has been replaced in the last 3 months. Is there a way to stop this from happening?

It is no longer jerking. I have stopped using EOC because I'm too scared to have this happen again :(

Also, I'm losing power steering for about 3 seconds (I believe it's electric, because in my other cars it was gone completely until the engine was restarted)

AND WE HAVE OPTIONS! THANK YOU SIR.

Still lost, however :(

Going to repost the links to my fuses in case anyone has some ideas.

Honda Fit Cabin Fuses

Honda Fit Engine Fuses

And here's what I'm seeing from the pictures:

IG (Ignition?) fuse under the hood.

IG COIL fuse in the cabin

Other possibilities:

IGP

IG FUEL PUMP

IG HAC

IG METER

After searching:

The user WeatherSpotter has suggested to try using the Ignition Coil Fuse to perform EOC. Does anyone have any experiences, or even vague thoughts on why this will or will not work?

Here is the link I found...

http://ecomodder.com/forum/showthrea...ime-22409.html

EDIT:

I'm beginning to believe that this topic might have been better placed in the modding section. I'll let it sit for a few more days and then delete/repost if need be.

Have you read the wiki page on kill switches? Engine kill switch - EcoModder

the idea is to kill power to the injectors while leaving everything else on. the engine and ECU will think you stalled it with the clutch. the engine keeps turning till the gas is burnt up (spark is still on) but no additional fuel is added to the cylinders. re supply power to the injectors and the car stays off as the ECU sees 0 rpm. bump to restart.

this thread may also help:
http://ecomodder.com/forum/showthrea...tml#post199155

you need to find the wire from the ECU to the injectors then you can duplicate my switch. check Honda forums for a master wire diagram set (my matrix forums had one for me) and start looking for the wire you need.

try this diagram:
Wiring Diagram
you want to add your relay in line with the yellow/black wire after it combines the injectors but before it merges with anything else.

I edited the picture of the ECM wiring you posted with a marked place of where I think your talking about....

http://img201.imageshack.us/img201/1498/ecumap.jpg

Is that correct?

Also, after reading the wiki, I'm not sure where the camshaft position sensor would be... (But I know I have one)

that is the exact right spot. now you have to find it on the car :)

Opening it up once in a while is a good idea - as long as you don't do it so often you kill your FE or do damage to the engine.

For me, coming home from my parents, there's a very hilly stretch where I can climb to heat the engine up AND rev it out a bit on the hills. Of course, I can let it DFCO down the other side of the hill so my FE doesn't suffer a bit! (Mileage is usually exactly the same if I go this way or the flat way ... plus the flat way is more miles).

The other thing is the engine will "wear" in and be more used to the lower RPM. Then if you end up selling it to someone who drives it much more spirited, they're going to notice that it may be carboned up and the "wearing in" causes it to burn oil , etc if revved out.

I'm not sure I believe the mechanics statement.

I used to perform regular key-off-coasting with my Cavalier, and had no problems at with this method.

The Insight now has a FAS board installed, which removes power to the injectors, effectively stopping the motor, and I still have no issues using this method.

I sometimes get a hesitation in acceleration when again turning the motor back on, but it is a brief pause, probably due to the fuel circuit pressurizing again.

And one can not "see" fuel vapor on a ceramic plug tip, since the fuel quickly evaporates with such a small film thickness. You may however see the carbon residue however, but this would be after running the engine and then depositing enough carbon to actually "view" it. Engine turners used to use this technique for setting carburetor jetting 30 years ago.

Jim.

It's hard to tell, really. My CEL would blink when I was EOC'ing and I've had to replace 2 parts that would be associated with damage related to EOC'ing via key-off.

The spark plugs that were fouled undoubtedly had an incredibly low amount of mileage on them and I have heard theories on this forum about keying off resulting in fuel being sprayed into the engine. (These were dismissed by naysayers, but it appears to be true in my case...)

It was the same with my older cars. I lost power steering, but didn't care. For some reason this car just doesn't like me.

So, is this when you key-off? Or...? I'm not sure what a FAS board is called and I'm not that technically sound

Hmmm. This hesitation was an incredible amount of jerking and wasn't JUST after turning the motor back on.

I feel like it's hard to tell. I guess it could have been carbon but I dunno. I feel like he would have been able to tell the difference between the two? Maybe I'm putting too much trust in my mechanic.

-

Not attempting to be harsh, but I've taken WAY too much information on this forum as truth, only to find out it's not true.

Found the ECU. It's behind the glove box for any other honda fit owners.

Will post full details when project is completed.

Feel free is ask questions.

Okay. First question.

When you built your switch, you put the cut just past the junction.

Do I need to do that as well?

I just left myself enough room to re splice it I'd I needed to. It's up to you where you cut it.

Thanks for the reply.

Remind me not to answer any more of your posts!

Jim.

Just curious, but are iridium plugs suggested for that engine? I would bet no, and what is probably your issue. Iridium plugs are great for turbo'd engines as they resist the heat better, but on n/a engines they can cause problems.

Well my gut was wrong, ngk iridium are Oem with that engine.

Iridium conducts well, and it's the second hardest metal with a very high heat resistance, so it's perfectly suited to spark plug use in any kind of engine. All we need it to do is put a spark across a gap. When using an iridium plug, you can widen the gap a little to increase the surface area and temperature of the spark. This improves the initiation of combustion.

I wouldn't blame the plugs for the hesitation, unless you're getting a true misfire condition.

I installed a kill switch in August by cutting the wire from the ECU to the main fuel pump relay. You can do it this way, but it will trip the vehicle immobilizer and you'll end up having to cycle the ignition to reset that before starting. My MIL flashes if I kill the engine with the switch (cutting the fuel), but not if I turn the key off and on. The MIL disappears after several seconds of EOC in either case, and doesn't reappear when the car is bump started. 2005 Civic, BTW.

If you figure out a way around the immobilizer, I'm dying to know, and I know at least one other Honda owner on this board is too!

if you look at the diagram posted above, it you cut the wire not in the spot listed you will kill the whole fuel system, not just the injectors. you also kill power to the immobilizer and then need to cycle the ecu. just killing the injectors will not cause the issues listed by vman455.

Well, well, well. It appears that I now understand what I need to do. However, I still have a few questions. But first, let's start with the materials list.

* denotes a question involving the item

(1) Momentary Switch, Normally Open

(2) 5 pole relay - Bosch 30 Amp

(3) Inline fuse holder - 20 Amp

(4) 15 Amp Fuse (for holder) *

(5) 16 gauge wire

(6) Ring Spade for Ground *

(7) Male and female spade connectors *

(8) Are there any other materials I am missing? (I already have solder and a soldering gun)

Questions:

Do the above items look right? Are there any items I am missing / don't need / got the wrong amperage on?


Regarding item (4):

Is 15 amps the right number? According to this diagram, the wire appears to be 15 Amp. Is that correct?

Regarding item (6):

How exactly does one find a ground? I never understood this in grade school, and to this day I am still confused.

Regarding item (7):

I was thinking of putting spade connectors in when I splice into the wire. That way, if something goes wrong, I can just unplug the relay and slip the two ends of the injector signal wire back into place.

Would this work or am I missing something?

WeatherSpotter had some complicated circuit board that I didn't really understand.

Again, thanks for all the help and thoughts fellas. I am grateful.

And my apologies to Mr. 3-Wheeler. Your car is awesome. I wish I knew how to make that aeromod, and make it look that sexy.

Regarding item (4):

Is 15 amps the right number? According to this diagram, the wire appears to be 15 Amp. Is that correct?

"Always size the fuse / breaker to the cable"
- I'm not endorsing 15 Amps as being the right number - I've only glanced over your questions to answer some.. but - 15A cable, 15A fuse. Where you use two sizes of cable, 15A for some, 10A for some, then at most, a 10A fuse.

Regarding item (6):

How exactly does one find a ground? I never understood this in grade school, and to this day I am still confused.

"In DC circuits, ground is the negative terminal. In car electrics, typically (check yourself) - the ground terminal of the battery (negative) is typically connected to the body, and so the entire body is connected to the ground of the battery. Some can be positive though, so Check!"
Or what I'd do is find black and check it has continuity through to ground - and that is what I'd use!

Regarding item (7):

I was thinking of putting spade connectors in when I splice into the wire. That way, if something goes wrong, I can just unplug the relay and slip the two ends of the injector signal wire back into place.

Would this work or am I missing something?

"Wire the relay fail on. That is, your relay has 5 wires, the coil on that you switch, and a Normally Closed side, and a Normally Open side.
Wire your circuit such that when you switch the relay "ON", the circuit to the injectors are broken, when you switch it off, or, for example, the wire is broken, the injectors just keep going as the relay is OFF."
There's stacks of info on automotive 5 pole relays on the net :)

You can fuse it smaller, say 5 or 10 amps.

spade connectors is exactly what i used and they are a great way of making the car immobile when parking for a while, just pull one apart and the car will not start :). but they are just as useful to have if your wiring is messed up or breaks then you can put it back to normal.

Your car is a Neg (-) ground system. so any bare metal on the car is a ground point. you know how a flashlight battery has a + and a - end? you could call the - end the ground. this works for most DC systems. AC (house current) its a different thing but for your car the ground is just another name for the neg connection.

I reckon' I'm a bit confused now...

What exactly am I looking for? Am I going to have to crack open the ECU? for some reason I thought the diagram was of the wires leading up to the ECU, now I'm pretty sure that's not the case.

I see a few connections but I'm still not sure what exactly I'm looking at in the diagram...

Googling for PGM-FI Immobilizer system location puts it where the ECU is, if my sources were accurate.

You do not need to open the ECU. The diagram is of the wires leading up to the ECU. so you just need to splice one of those.

...Bump. @HilseeJ - did you ever get it sorted out?

I just bought a Fit and will be implementing some sort of kill switch.

Try as I might, I am unable to find a write up. If it doesn't exist, I'll create it.

So, using the PGM-FI system wiring diagram previously linked by Weatherspotter, I realize I need to find this Yellow wire with black stripe. I’ve popped the hood and poked around. It seems to me I’m going to have to start opening up the harness covering and poke around until I find it. The diagrams I’ve found so far do not make it clear to me how far upstream of the injectors I can go before the next junction for another fuel system component which I do not wish to electrically open – I’m guessing the IAC would be next, but do I care if it’s circuit is open? I would think immobilizer would be close to the PCM and I should then have quite a bit of junctions and options to try and pick off an easy one. Here is a link to “Wire harness Locations”. I’m guessing those other two up front are for fan and temp sensors which should also not be critical, right? I’m thinking about going in right in front where the harness comes down and around the intake – see photo. Thoughts?

hondafitjazz.com/manual/A00/HTML/CTL/IMGFRAME.HTML
Here is the main harness diagram which I believe contains this 12v+ yellow/black wire. (sorry, I don't have permission to post links yet)

I tried attaching a mark-up of where I'm thinking of playing Operation first - need to churn out 4 more posts first.

Hopefully you can copy paste this into browser for pic
dl.dropboxusercontent.com/u/58915303/2008%20Fit/IMG_20150420_114802_resize_markup.jpg

Thanks,
JL

instead of under the hood, look behind the glove box, getting at the ECU is much better then doing it under the hood. I found mine by looking up the pin out (plug configuration) for my ECU. If you can find yours then find that plug and wire and the hard part is done.

my mod is still working well.

Thanks. I actually looked there first, but I was worried interrupting yellow/black wire there would kill immobilizer and was, therefore, not the preferred method.

I did it at the ECU (about 4" past the connector) and had no issue.

by interrupting the signal, your not doing anything different then the signal to shut it off when the key goes to off. If you try it and it has an issue, undo it and it should reset. Try it first by "having a loose wire" (run the car and pull the wire out of the plug... if it shuts down put in back in and try to start. if it does then you got the right one.

I can give it a whirl. Sorry if I'm being dense and/or stubborn - I guess I'm a little hesitant to start pulling wires just yet without understanding quite what I'm doing.

Which wire, then, are you suggesting I pull from the ECM? Based on the diagram you linked in post 7, it seems to me that the Yellow/Black Wires are actually powering the ECM itself downstream of the PGM-FI 1 Relay. I downloaded an ECM/PCM pinout, but for the life of me cannot find the link. I found the two yellow/black wires at the ECM - so I'm willing to try yanking them.

I anticipate I'll get the same issues as this guy, "P0685, which is "ECM/PCM Power Relay Control Circuit/Open.""
hondafitforums.com/showthread.php?t=716

You need to find the wire diagram for your car, each is different. If you have a ECU Pin out ill be happy to look it over with you and help find the wire :)

you will love having a kill switch.

I bought a 2008 Honda Fit.

Here is the ECM pin-out diagram:
fitfreak.net/forums/fit-engine-modifications-motor-swaps-ecu-tuning/24616-ecu-diagram.html#post297286

Here is the same link to the fuel system wiring schematic you shared in post 7 of this thread where you said, "you want to add your relay in line with the yellow/black wire after it combines the injectors but before it merges with anything else."
hondafitjazz.com/manual/A00/HTML/00/SAA2E00000000000000EBAT00i019.HTML

I bought a 2008 Honda Fit.

Here is the PCM pin-out:
fitfreak.net/forums/fit-engine-modifications-motor-swaps-ecu-tuning/24616-ecu-diagram.html#post297286

Here is the wiring schematic for the subsystem we need which you linked in post 7 of this thread which I believe is the appropriate one:
hondafitjazz.com/manual/A00/HTML/00/SAA2E00000000000000EBAT00i019.HTML

grrr - my last two posts were blocked. I need to hammer out a couple more so I can link.

yay 5 posts. I'm a big boy now.

It is a 2008 Honda Fit Sport – same as OP


I believe this link which you shared is the correct electrical subsystem schematic

I think this is probably a wise statement from a wise man ;)


Here is the PCM pinout:
ECU Diagram - Unofficial Honda FIT Forums

edit: and here is the marked up photo I took yesterday showing the intake manifold and injector harness junction where I'm thinking of going Edward Scissor-Hands.

Does the 1st gen Fit have a fuse that's specific to the injectors? My kill switch has been back burnered all to hell, but it involves breaking the circuit with a Fuse Buddy. My post is #106:

Kill Switch (EOC): Where did you install your activator? And what did you use?

I would not do it in the engine compartment, the heat and water will short out your mod. if you back the wire bundle back through the fire wall the same wire should be avalable for cutting.

just re read the thread.... :) yes the diagram posted looks like the right one. post #8 has the spot marked that you need. and for your car it does look like the engine bay might be your best bet.