FI light and backfiring

So the VFR was running pretty well, then we synced the throttle bodies (by the book, and we double checked). The bike ran smoother (and got much better mileage) but now backfires a LOT under deceleration.

Further, on my trip up to Laguna Seca last weekend my FI light would come on. Turning the bike off then back on reset the light, and it would stay off for nearly an hour, then come on again. ...reset, and it didn't come on again in 200 miles. Then that night on the way home from dinner, it comes on.

Same thing on the way back. Nothing for hundreds of miles, then on. Reset, it stays off.

The bike seems to run fine, not like a cylinder isn't firing or anything. But the random FI light and the backfiring have me stumped.

Any thoughts?

D <- Not liking FI, I want my dependable, smooth carbs back!!! :biggrin:

PS. I've heard of "jumpering" the ECU to get error codes, but can't find it in my manual. ...anyone have a page number?

 

light

Is the light on solid or does it flash? If it is flashing, count the number of times it flashes.

 

No flashing, just a solid light. It goes off with a reset of the ignition, and may not come on again for hours.

 

codes

You need to get the code out of the ecu .

 

pm

sending pm on diagnostic plug and codes.:thumbsup:

 

Thanks for the diagnostic instructions TC. Having done that I get one blink, so (hopefully tonight) I'll pull the MAP sensor and check the connection there, clean it all up, and reinstall. ...with any luck, it's just some more of that East Coast corrosion gumming up the electrical works.

I'll post up, for future reference, once I've had a chance to pull it apart and have a look see.

 

C'mon now, are you done? It's been a couple of hours. Please let us know.

 

I'm detecting some sarcasm, but no, it's not done.

I jumped the connector and turned on the ignition and got a single blink back. According to the manual it indicates a fault either with the MAP sensor, or its wiring. I unplugged it and checked out the connector and it was nice and clean, but I cleaned it anyway, and gave it another go; still one blink!

It looks like the MAP sensor may be bad. I'm going to go price one today when I get a chance (like right now). ...I'm guessing they're not super cheap, just because that's how my luck seems to run with VFRs. lol

D

 

Well???????????????????????????????????????

DONE YET???????????????????:biggrin:

 

Haha. Actually, a buddy of mine has a VFR engine sitting in his garage, so I'm going to go over this weekend and nick the MAP sensor off it and see if that fixes the problem.

 

did this ever get resolved? I think I have the same problem...

 

Unfortunately, not yet. I replaced the MAP sensor (a $250 part) because that's what the code (1 flash) indicated was the issue. ...since that did nothing to solve the problem, I took a few days away to let my head stop pounding then sat and thought about the issue and the symptoms. I am now convinced that the likely culprit is a vacuum leak somewhere in the system; most likely at the manifold (or wherever the vacuum lines terminate under the air box).

I'm in Chicago on vacation for another day (been here for a week or so) and maybe, just maybe, I'll get a chance, and the courage, to tear into the old beast again this weekend and see if I'm right. :biggrin:

Good luck with your issue, and if you find the culprit before I do (and I promise to post when it's fixed) ...be sure to post up what it was!!!

Cheers,
D

 

Had a similar problem a few years back. Started out with symptoms similar to yours, then got worse and worse, with the bike cutting out. Took a while to find the cause - a wire from the ECM was in a make/break condition. Have posted on this forum about it if you wish to check.

 

what would i search to find that john?

 

I think my thread was in Mechanics garage titled "VFR 800 cutting out"

But I would do a search with the words "FI light" - you will turn up a wealth of problems and possible solutions.

 

Just an update, since I've been really slow getting things taken care of. I cured the backfiring issue and the bike now purrs like a kitten, but the FI light is still coming on and when it does the bike begins to surge a bit.

I'm going to pull it apart tonight and check the connections at the ECU first, followed by a multi-pin ground that's built into the harness (apparently) followed by the rest of the usual electrical suspects.

The backfiring was a combination problem, but the main issue was starter valve sync. My service manual was followed to the T when we did the starter valve sync, but what I didn't know was that late '99 models have a different ECU map than early '99 models, resulting in a vastly different starter valve sync spec. The old speck was something like:

#1 - fixed
#3 -20 (from 1)
#2 = 1
#4 -10 (from 1)

The new spec is:
#1 fixed
#3 -1.5 (from 1)
#2 = 1
#4 -1 (from 1)

Having done this (combined with the other fix, below) yielded a bike that purrs like a kitten and doesn't backfire under deceleration at all.

The 2nd fix was the air filter. I had replaced that completely shagged OEM with a K&N. Even removing the rubber gaskets from the air box & air box lid made the lid sit nearly .25" apart from the base and it leaked air between the fastening screws (tested with propane & the bike running at idle). I purchased a new OEM filter and replaced the gaskets and what do you know, the air box seals up tight as a drum (no leaking).

I don't know how much of an issue this did or didn't cause, but I have a brand new K&N filter for cheap if anyone needs it!

Tonight it's back into the electrical. ...hopefully I can find the problem as I'm supposed to ride to TX and back with a buddy next week.

D

 

Well, things just keep on getting stranger with this bike. lol Tore into the electrical again, jumping the test connector to recheck the error code gave me the usual 1 blink. I decided that, since I knew the MAP sensor was ok and I had checked it's wiring, there might be something amiss at the ECU (as was also suggested here by Capt.John).

I pulled the ECU out from the tail of the bike and checked out the connections (though without removing them) and set it down to recheck the error code; now it gave me one steadily lit indicator!

Looking in the book it claimed one of three things could be the cause, but since the error had changed with me doing almost nothing to the bike, I decided to reset the computer and see if I could get another code to pop on a short ride.

So I jump the connector, turn on the ignition, the FI lights solid again, and I remove the jumper wire ...only the light stays on. This isn't supposed to happen, when you remove the jumper, the light should go out. Then you can re-jump the connector causing the light to blink 5 times indicating that the computer has been reset; this doesn't happen!

I've repeated the process several times, always with the same result.

So, we (my buddy Tony and I) pull the connectors apart, and inspect every wire, and every connection to the ECU, all are solid. We clean every contact and reconnect. We even jump the ECU's ground-pin directly to a frame ground (vs. the ground block that is taped up in the harness in front of the RR), all to no avail, the symptoms remain the same!

In all we spent 4-5 hours pulling apart, inspecting, cleaning, and measuring connections all over the bike to make sure everything is as it should be, and everything checks out 100% ok. The only thought is there might be a tiny bit of exposed wire in the loom somewhere that causes an intermittent short; but we don't have time this weekend to unwrap the harness and inspect all the wiring.

So we button her back up and yesterday morning I go out for a 3 hour spin in the Santa Monica Mts.; and not once did the FI light come on. ...the bike purrs like a kitten and pulls like a freight train!

So I'm just going to keep riding it and see what happens. Somewhere on that bike is an electrical gremlin (in hiding) and I'm pretty sure it lives in the wiring harness between the ground block and the ECU, but I'm not opening that can of worms until the problem creeps back into my dashboard indicator lights!!! :biggrin:

D