2002 VFR800 VTEC Misfiring

Hello all,

I have a 2002 VFR800 Vtec. The bike has started to run poorly and misfiring. I have completed a large amount of required work on the bike since buying it including fitting a larger sized stator and flywheel, an upgraded regulator and rectifier, cat free down pipes and manually adjusted cam chain tensioners. The bike was driving fine after completing all this work until the day came when the bike started to misfire.

I bought a new set of spark plugs and inspected the wiring on the bike and I found the connector connecting the rectifier the loom had burned. I cleaned up these connections and bypassed the silly plastic plug. I also replaced the stator again thinking it might be shorting out. When I put a meter on the battery I'm getting a full charge so I believe my stator and rectifier are fine. I installed the new plugs and the bike is still misfiring?

Might the oversized stator have burned something else? Any ideas? This bike is turning into a money pit!
Any help will be appreciated...

 

Fuel starvation?

Blocked filter?

 

When I turn the key I can hear the fuel pump working and my plugs are black after inspection. The air filter is a Spotless K+N type. Do you mean blocked fuel filter?

 

Typically, an engine misfire under acceleration is an ignition system issue. To start, follow the instructions in the factory service manual to jump the PGM-FI service connector to determine if there are any faults stored in the ECM. If there is no stored data, perform the self diagnoses reset procedure and run the machine again...keep an eye on the FI, or as Honda calls it, the MIL, or multi function indicator lamp. The self diagnoses might point you in the direction of what the problem might be.

 

Ok - I'll give that a go tomorrow. My bike also has a power commander fitted. I did check that map before installing the news plugs. Thanks for your help..

 

Disconnect the PC and put it back to the stock configuration and start from the beginning. The map is only as good as the module it's loaded into.

 

The power commander has been on the bike since I bought it, there might be some connectors missing. I can reset the map back to factory default. In all fairness I don't think the power commander has anything to do with the problem.

 

If you say so. Good luck, hope it all works out for you.

 

Yeah, I like the bike so I'm going to take your advice and test for error codes. Thanks

 

Hello,

I tested for error codes today and I got 9 blinks from the FI light. According to the manual this indicates a faulty IAT sensor in the air box. I checked the connector for a poor connection and cleaned it up. The bike seems to be running a little bit better but still not quite right so I reset the error reports and after doing so the ECU still report a faulty IAT sensor with 9 blinks. So I guess the IAT sensor is indeed faulty and I need to buy a new one?

Thanks for your advice NorcalBoy as I think it's pointed me in the right direction.

Any idea how much I should pay for the sensor?

Cheers,

 

No idea on pricing in UK/Europe, they always seem to be substantially more than what they are in the US. Sometimes the difference can be 4 times the cost.

My initial suspicion was that it was the IAT or the MAP sensor...With any luck, the IAT sensor will fix it...the MAP sensor is a lot more pricey than the IAT. Double check your wiring and connector to the MAP sensor while you're in there, just to make sure it's got a good clean connection. It's difficult to test these sensors without the factory test harness to connect up to the ECM.

 

I have already taken a good luck at the connectors on the map sensor and they appear to be clean with no corrosion. I went over a good few things before posting my problem on VFR World. I'll drop out to Honda parts Ireland tomorrow and try to price a new sensor for the bike as I don't see anything available on ebay or Weemoto.com . Lets see what they quote me and I hope it fixes the bike.

Cheers,

 

Again, best of luck. Fingers crossed it's the IAT and you are back to full power very soon.

 

I'll let you know how it works out with a new sensor.

I have also noticed you are working on a RVF400 restore project! Best of luck with that I too have restored a 1989 VFR400 I found in a scrap yard. It was a hell of a lot of work but the bike now sits in my garage ready to drive anytime I will never sell it

 

That is cool! Thanks for looking at the project. Diving Pete, who's a member here, has a whole herd of them too. Not very common here, but I always thought they were a pretty interesting machine. I will be watching to see how your repair goes, it would be great if it was just the IAT and you were done.

 

Phoned Honda today and the guy quoted a crazy price IAT sensor!

He also said we have never needed to replace that part on a VFR800 VTEC. This got me thinking, so I stripped the IAT connectors and wiring to really make sure I have a good connection. This has now fixed or removed the error code from the ECU after a reset. I had a smile on my face until I started the bike. The bike still runs badly. I'm going to check all the coils tomorrow with a multimeter............

 

Sorry to hear that. You need to get your hands on a test harness so that you can really go through it. Unfortunately, most of the in depth troubleshooting requires it. The horrifying thing about that...they cost 2000 usd. Maybe your local shop has one. I made a set from used harnesses off of EBay, but I no longer have them in my possession.

As far as the price of the IAT...I saw 100 usd from David Silver Spares and 23 usd from Service Honda here in the US....I didn't want to say anything.

My initial thought was the IAT or the MAP sensor, but those were just hunches. I was leaning more towards MAP sensor, but the diagnostic showed IAT. I hope your search just finds a loose wire or connection somewhere, without the test harness, you're kinda dead in the water after that. Typically a backfire is associated with the ignition system, but with ECM controlled motos, and the myriad of sensors they require, it's kind of a catch 22.

 

I have finally fixed my 6th Gen VFR800 Vtec. All of this messing about was caused by a bad earth on the fuel pump. The loom was becoming crazy hot and creating poor connections on the bike.

I ended up doing a repair on some the the wire plugs and installing the "VFRNESS" as the call it. It's seems to have worked out great, I think I have my VFR back now. Happy days

 

Glad you got your bike sorted finally buddy, having a similar type issue with my 5th gen, I know less than nothing really about electrics but I'm hoping mine is just a bad coil, amazing after all that you found your problem was a bad earth.

 

I have clocked up over 1000 trouble free miles since doing the repairs so all is good and I can now relay on my VFR to take me anywhere.