99 Bird lacks power and backfires on acceleration

[urloozn]

Hello boys and girls! I haven't been on here in a while since I ride a Honda and it doesn't give me any trouble!

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.....until now. I just bought a Triumph Tiger and now my lovely wife has inherited the Blackbird. I put 46k on it and she's been riding it for about two months now with no trouble.

Then the 'event' happened.

We were on a ride with some friends. That morning I had gassed up the 'Bird then walked over and gassed up the Tiger with the same hose and the same gas. About 75 miles in, the 'bird started stumbling and even backfired once. My wife stopped and someone came to get me at the next corner where we were waiting (radio comms between point and rear guard.) When I got there it started and ran fine for me. I have a PCII on it and had dyno'ed it last year. I thought the ECU had finally rebelled against the Power Commander so I took it out and plugged the stock harness back in. As a side note, the FI light was always on when I had the PCII installed. I had called Dynojet years ago and they said it was just something to live with and that 'they all did that.' It ran like that since 2003 with no trouble at all, just the light on all the time. When I took it out of the circuit the FI light went out so I thought the problem had been fixed. Then I took it for a test run about a mile or so each way. I tried it lugged going uphill, reving going uphill and I even tried to see if it would pop on the way downhill. It ran fine. So we took off again. About 20 minutes later we stopped for a water break for about 10 minutes then left. Five minutes later it started doing it again and my wife decided she didn't want to ride it like that because it was surging on her. We went back to the gas station and drained the tank because we thought it was bad gas (even though the Tiger was running great on the same gas). Put 5 gallons of fresh gas into it and it started and ran fine. We took secondary roads on the way home and about 20 miles from home she took the lead and got on the interstate. She was HAULING ASS. It was running fine for about ten miles. Just before we exited from that highway onto the other for the last leg home it started stumbling and backfiring again. She limped it to a gas station and I committed a cardinal sin: I went home and got a trailer for my 'Bird. So now I am offshore for another week or so, unable to tinker on it at all and I decided to turn to this bunch for advice. Again, this is a '99 with about 48k on it. I have a K&N, Micron slip-ons and it was just dynoed with the PCII last April and has run fine ever since. I even changed the plugs in it right after the dyno run because it had been running rich and the guy reccomended it. Any and all suggestions would be appreciated.

Thanks and have a great week!

[redxxrdr]

How is the battery and charging system?

[ActionStarCBRxx]

Not sure of your location... but here in Texas its been 100 degree days. Could it be the vacuum line/pressure relief line/valve from the gas tank building up too much pressure? Each time you stopped it looks like you popped the top on the tank to either fill/replace the gas. The other time was when you swapped out the PCI. Did you pop the top on the tank then as well?

[urloozn]

The battery is about 5 years old. Didn't think of that one. I'll have to check it out.

Now that you mention it, we did pop the top a few times. Otherwise it had time to sit and maybe bleed down any vacuum that may have built up. I'll have to look into that as well. My brother also told me about a problem a friend had with similar symptoms. I don't remember the exact chain of events but it ended up being a stuck thermostat causing the FI to think the engine was cooler that it was and running on 'choke.' He said after they changed the $8 thermostat the truck ran with no problems. Since my thermostat is now 10 years old it may be worth looking at.

Keep the suggestions coming!

[urloozn]

Bump.

C'mon guys, going home in a few days. So far, check battery and charging system, vent lines on the tank and from another thread the fuel pressure regulator. Any other suggestions?

[cbrxxquad]

I did not answer cause your not giving any info...

what year?

have you done the loom fix if under 01?

is #2 and #three plugs black

pull the line from the fpr vacuum and plug and see if it runs fine????

what have you done so far?

and where the fuck are you????

and yes I can read and look it up if I wanted

and if the fi light is on somethings wrong, even with the pc, and the pc done right will not turn it on but programed wrong it will.

[urloozn]

It's a 99 with about 48k-ish. Wifes's been riding it so I'm not exactly sure anymore. It all happened the day before I went offshore for 14 days so I haven't been able to get into it at all. No 'loom fix' as I didn't think that was the problem. The light was on all the time and it ran fine for years until now. I am fishing for suggestions to start checking when I get home.

[cbrxxquad]

corrosion in the loom will cause a fi light as it is largely ground connections. But not entirely. It may not be the problem but should be the first suspect in that model. check both and prove they are correct and clean and pack with dielectric grease and re wrap. Then check the fpr for problems. If the vent lines are open and not crimped then check the plugs and coils for visual indicators of problems.

keep notes.

[urloozn]

Hello boys and girls! Sorry for the delay on an update. Here's the deal on the problem:

- Checked FPR - No leaks and producing proper pressure.

- Checked all four plugs - Looked good so cleaned, re-gapped and put 'em back in.

- Checked coils as per manual - all up to spec.

- Finally looked into the loom plug and there she be. One of the pins had shortd out and burned up. It was black and the plug had been melting away. Fortunately (or unfortunately depending on how you look at it) it was on the corner so it didn't affect any of the other pins. But I think that is the reason it was intermittent. It would run well for a little while then start stumbling and backfiring. Mind you, this all happened within an afternoon so I wasn't riding it for a month with a possible engine detonation. Anyway, I researched here and on other forums and found a link to a fix with pictures. The author of the link is a guy I've met before (porterb123) so I have no reason to not trust his handiwork. I did the fix (took about 2 hours...yeah, I know. I'm slow but VERY detail oriented and a perfectionist) and rode it up and down the highway in front of my houe for about a half hour. It's a 4 mile stretch from the two turn around points I chose and I rode it one way tached up to 7k at 50 mph, then back in 6th gear at 45mph to see if it would give me any trouble..none. Then my wife and I rode to Baton Rouge (120 miles rount trip)to meet some friends Thursday again with no trouble. The one that closed the book on the problem for me was that we did almost 500 miles yesterday without a hiccup.

BUT......the FI light still comes on. I read up on how to pull the codes (neutral, idling, kickstand down) and found that it was the knock sensor. I really like that little add on in the system. You can check the codes without any special tools....like a paper clip in the test loom for a Suzuki. So the manual says that it would run fine without the sensor but I'm not playing that game anymore. I was able to replicate the same code every time so I'm reasonably sure that its correct. I ordered a new one and will put it in as soon as I get it.

[rockmeupto125]

If the plugs are the iridium tipped plugs, they don't gap well, as bending the electrode cracks the iridium coating. You may never notice anything, but its an FYI to file away for next time.