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2008 BF50 efi backfire from idle to 4500rpm

I

iris

New member
Hi all,
I am new here, only read many posts to see if there is a similar problem, but still haven't solved it.

My recent bought bf50 efi runs well from 4500rpm to woth, and when cold the first 10 min idling.
But, after 10 min of warming up the engine misfires now en then at idle, to a hard backfire at just under 4500rpm.
When acellerating and above the 4500rpm no problems at all.
Changed the plugs, cleaned the fuel/water filter and changed the high pressure filter in the fuel pump which was very dirty.

Am i overlooking something? any help or ideas would be very welcome

Thanks,
Guido
 
This is very unusual. You did not say if it ever ran good since you bought it.

It is always best to start with a compression test.

Check and watch the spark with a spark tester.

Hopefully, you used the correct spark plugs...NGK DR7EB. The wrong spark plugs can cause weird things to happen.

Check your fuel for water. Drain the vapor separator into a glass jar and check. The water will accumulate at the bottom.

Watch fuel pressure to see what it does when it is failing. Should be 41 - 48 psi.

If the "backfiring" is not from water in the fuel, and all else is normal then it could be timing or crossfiring.

Open up all the connectors (especially those associated with spark). Make sure they are all clean and have no corrosion.

You have to check the timing marks (in case the timing belt jumped timing)..

Also, you could put a timing light on each spark plug wire as it is failing and see if there is any difference in the flash pattern.

All that being said, if you are in the US, the motor should still be under warranty. The 50D has a 5 year warranty. You should take it to a dealer to get it checked out. They can also put the HDS on it and to see if any of the sensors etc are out of range. That, in the end, may cost you some bucks (if the problem is not a warranty problem)....but it may save you a lot of aggravation.

If you are going to do you own troubleshooting, then I highly recommend purchasing a Honda Service Manual. http://www.helminc.com/helm/product...result&Style=helm&Sku=61ZZ500E2KIT&itemtype=K It is $84, but well worth the money if you are doing your own work.

Mike
 
hondadude said:
This is very unusual. You did not say if it ever ran good since you bought it.

It is always best to start with a compression test.

Check and watch the spark with a spark tester.

Hopefully, you used the correct spark plugs...NGK DR7EB. The wrong spark plugs can cause weird things to happen.

Check your fuel for water. Drain the vapor separator into a glass jar and check. The water will accumulate at the bottom.

Watch fuel pressure to see what it does when it is failing. Should be 41 - 48 psi.

If the "backfiring" is not from water in the fuel, and all else is normal then it could be timing or crossfiring.

Open up all the connectors (especially those associated with spark). Make sure they are all clean and have no corrosion.

You have to check the timing marks (in case the timing belt jumped timing)..

Also, you could put a timing light on each spark plug wire as it is failing and see if there is any difference in the flash pattern.

All that being said, if you are in the US, the motor should still be under warranty. The 50D has a 5 year warranty. You should take it to a dealer to get it checked out. They can also put the HDS on it and to see if any of the sensors etc are out of range. That, in the end, may cost you some bucks (if the problem is not a warranty problem)....but it may save you a lot of aggravation.

If you are going to do you own troubleshooting, then I highly recommend purchasing a Honda Service Manual. http://www.helminc.com/helm/product...result&Style=helm&Sku=61ZZ500E2KIT&itemtype=K It is $84, but well worth the money if you are doing your own work.

Mike
Click to expand...

Thank you Mike for the detailed information,
Will get home in a few days, and check more things out.
The motor ran even worse when i bought it, it stalled when throttling down from low speeds. Changing the high pressure filter solved that problem.
Under the hood the outboard was very dirty, grease and oil everywhere and some rust on one side on the motor at bolts etc, looking as it had been on its side in a puddle of water... But, i bought it from a dealer, have still 3 months quarantee, the price was right according to state and most important i like a motor which needs TLC..
Did all the "standard" things: plugs, timing, water in fuel etc
Thinking all over, my suspect for now are the injectors. Will try to treat them with injector cleaner, and see how that turns out?
I've read in the manual that the ECU adjusts the fuel/air to a more lean mixture under 4500rpm. Just the range where it backfires.
We live remote (in Europe)from a authorised Honda dealer, but would love to take a look with HDS at it.

Thanking you,
Guido
 
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