Hello All. New Member here. PLEASE HELP!! I have searched everywhere for a solution to my problem, hopefully someone out there will be able to help. Here is my issue. The ATV in question is a 2009 Honda TRX420 FPM, FUEL INJECTED with power steering, ONLY 3300 km. The bike starts easily every time, and idles like a champ. It even revs up to about 2000 to 2500 RPM (just guessing) perfectly, HOWEVER, when I try to rev it up any higher, it starts to act like it is being starved for fuel - sputters and runs rough. If I keep giving more gas, it will slowly develop slightly higher RPMs but still sputters. If I back off the throttle quickly, it will often backfire. I have a video for anyone that needs it. PLEASE NOTE, this is FUEL INJECTED and NO ERROR CODES are being displayed on the dash. ALSO, this is a new ATV to me so I do not know the history. I didn't notice any of these symptoms when I purchase the ATV (I have owned many in my 56 years, so I kinda know what to look for). I did, however, PRESSURE WASH the quad when I got it home. Not sure if this is what caused my issue. Here is my TROUBLESHOOTING THUS FAR: 1/ Replaced fuel filter, 2/ Checked valve lash (perfect), 3/ Replaced spark plug 4/ Drained fuel tank, removed petcock and inspected filter screen (it was clean), filled with fresh gas, 5/ Checked fuel pressure (it was 50 psi at idle, similar when attempting to rev). Checked voltage to pump (was 13.8 volts) 6/ Checked voltage at battery (14.2 volts when running), 7/ Inspected PGM FI unit connections. There was a lot of mud around the unit and other relays etc, and I saw evidence of muddy residue inside connections. Cleaned the PGM FI connections, as well as the other connections, with electrical contact cleaner. 8/ Removed muffler (no change) 9/ Replaced injector with new OEM part, 10/ Replaced coil with new aftermarket coil, 11/ Replaced TP/Map sensor with used part, 12/ Cleaned all connections from engine back and re connected using dielectric grease, 13/ Cleaned main ground to frame, 14/ Removed and cleaned throttle body, 15/ Removed and inspected IACV (moved freely), 16/ Replaced PGM FI unit with used part. PLEASE NOTE: Engine seems to rev properly when petcock is closed and just before it runs out of fuel. If petcock is just cracked open just a hair (restricting fuel flow to pump), bike will rev well until it runs out of fuel. To me it appears it is getting too much fuel, which is supported by the fact the plug is black after running for a while attempting to rev. I HAVE NOW RUN OUT OF OPTIONS, AND MONEY FOR PARTS THAT DON'T WORK!! Any help would be greatly appreciated, and thank you all in advance. Will

 

Wow sounds like you have put alot of time and money in this atv..I have done the same above and I know I will get some feedback but trying to help with this issues as I have had an found an bad ingition coil on 4 of these atv with the same issues I know not common on alot of models but in my shop we have had 4 trx 420 with same issues an after alot of time spent on the first one the other 3 was a piece of cake..Good luck an keeps us updated.....Also we check pulse to injector an all was fine

 

Don't you just love EFI. Had it been a 350 you could have fitted a spare carb and if the fault went away, it is a fuel problem, if it didn't, you could then start checking ignition stuff. Have you done a "system re-set", often needed anyway when you swap a TPS. When you are that stuck, just about all you can do is substitution. I usually try to get hold of an identical bike and swap bits until the fault goes off. Please note, Honda changed ECUs in about 2009 and the late one won't work on an early bike (ask me how I know) not sure if ES and manuals have the same ECU either. Did you check battery voltage when the fault is on, i.e. over 2500rpm? If it goes much over 14.5v you will get problems.

 

Looks like you replaced or checked everything except the temperature sensors, IAT and ECT. They can make it run rich or lean.
So maybe look for changes in how it runs cold versus hot.

 

Thanks for the replies everyone. I have given up and sold the bike. I think I will stick to good old fashioned carb bikes from now on!

 

Any updates on this atv?

 

Thanks for the replies. I gave up on the Honda after replacing the PGM FI unit did not work, and sold the quad (yes I disclosed the issue to the buyer). I figure it was time to cut my losses.

 

Hello Everyone. One final post from me on the Honda from heSpam wordSpam word Spam wordSpam word Spam wordSpam word Spam wordSpam word . As I said, I ended up selling the ATV, fully disclosing to the new owner the issue, and all troubleshooting steps I took. I asked if he would let me know what the problem was when he figured it out. He took it to a Honda dealer, who was also stumped. The dealer contacted Honda for a possible solution. It turns out, according to the new owner, that the timing chain jumped a tooth!! I have no idea how or why this would happen. Based on the number of posts I read regarding 420s exhibiting this same behavior, perhaps the 420s are prone to this problem?? Anyway, I hope this will help if anyone experiences the same issue. Cheers.