Cali rider
Well-Known Member
- Joined
- Oct 7, 2007
- Messages
- 1,328
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- Location
- Buena Park, California
Over the past 6 months I have noticed a slow but steady decrease in fuel efficiency from my 04 FZ with 76000 miles. As I use Fuelly to track mileage it has been easy to see the decline from consistent 52-55 MPG down to the 42-45 MPG mark. I became quite frustrated that this was happening without any obvious symptoms as to the root cause, so I proceeded to do a thorough investigation of many systems to find the cure.
Here is a copy of my troubleshooting document from April 2012:
• Checked valve clearances, every valve was perfect in middle of range.
• Checked spark plugs. Clean, consistent, correct gaps.
• Inspected air filter, good.
• Checked ignition coils, all checked within design specs.
• Found a small restriction in the intake vacuum pressure circuit, cleared but didn’t seem to make a difference.
• Checked vacuum sensor, within range.
• Checked timing rotor, ok.
• Synced throttle bodies, they did not require large adjustments.
• Checked catalytic convertor for fouling, no problems.
• Voltage at ECU, as indicated by the diag display is 11.5 but system voltage measured elsewhere is fine. Might be a weak connection but will wait to see if this changes.
• Looked for mechanical drag, nothing found.
It might be a bad injector, although plugs don’t indicate a rich condition on any cylinder. AIS could be a problem but the reed valves worked and the default solenoid position is closed so this is very unlikely. There is no oil consumption and power delivery is smooth so cylinder/valve wear is unlikely, but a compression test will be next if the fuel mileage doesn’t improve with another load of fuel from a different source.
So, at this point I had no idea what was causing the problem. The mileage really went down as speed increased, which was out of the ordinary for me. On the first weekend of May I had to travel from Los Angeles to the San Fransisco area to visit Lefty and attend the AMA races at Infineon Raceway. I packed very light for this journey, just a tank bag and backpack as I wanted to minimize wind resistance. Going up the infamous (DULL) I-5 that traverses North-South I set a steady 75-80 MPH pace to keep up with traffic. Now the problem just became stupid, watching the fuel gauge drop every 30-35 miles, just pissing me off and making me run through the checklist over and over in my head trying to think of what I must have missed in diagnosing this problem. 2 fuel ups and I am getting right at 41 MPG, this sucks. And just when I thought that I had no ideas left, providence steps in...
I am starting to go up a grade, following and passing other vehicles and speeds were still around 75-80 MPH. As I began a pass and rolled on the throttle I noticed that I couldn't increase speed at all. I throttled down and back up and still no response. At this point it became clear that I had a random misfire on at least 1 cylinder. Backed down the speed and started to accelerate again and the misfire disappeared and returned as speed increased. Ok, bad spark plug(s), I'll replace them as soon as I get into town, but why didn't they appear bad when I checked them just a few days before the trip?? I started thinking some more and I suddenly had a revelation.
Last year, at ~66000 miles, I decided to replace the standard NGK CR9EK plugs with a set of NGK CR9EIX Iridium units. Although the original plugs measured well and looked serviceable I got a great deal from Amazon and changed them as part of a service interval. No problems at that time, and I did a couple of tours last summer without a mileage issue. But since then, it s-l-o-w-l-y got worse, and nothing else was altered.
So, I stopped at the Cycle Gear in San Carlos and bought a new set of CR9EK (non-Iridium) and installed at Lefty's before I began the return journey. Measured at highway speeds since the change I am back to the usual 50+ with no other repairs. After discussing this with Lefty, who also change to Iridium plugs last year, he mentioned that he has also noticed a slow but steady decrease in mileage as well.
After all of this, my conclusion is that the Iridium plugs are not suitable for my FZ. 10000 miles of ever decreasing performance/mileage is unacceptable. I believe that the stock ignition coils on an FZ just don't have the necessary secondary voltage to overcome the deposits and degradation that buildup on the miniscule center electrode. Remember, I measured and closely inspected them less than 300 miles before they failed! When new they work fine but I want longevity out of the parts I put on my FZ.
So, if any of my fellow FZ owners find themselves with a similar set of circumstances, consider putting in a new set of standard non-Iridium NGK CR9EK.
Comments/discussions are welcome on this subject!
Here is a copy of my troubleshooting document from April 2012:
• Checked valve clearances, every valve was perfect in middle of range.
• Checked spark plugs. Clean, consistent, correct gaps.
• Inspected air filter, good.
• Checked ignition coils, all checked within design specs.
• Found a small restriction in the intake vacuum pressure circuit, cleared but didn’t seem to make a difference.
• Checked vacuum sensor, within range.
• Checked timing rotor, ok.
• Synced throttle bodies, they did not require large adjustments.
• Checked catalytic convertor for fouling, no problems.
• Voltage at ECU, as indicated by the diag display is 11.5 but system voltage measured elsewhere is fine. Might be a weak connection but will wait to see if this changes.
• Looked for mechanical drag, nothing found.
It might be a bad injector, although plugs don’t indicate a rich condition on any cylinder. AIS could be a problem but the reed valves worked and the default solenoid position is closed so this is very unlikely. There is no oil consumption and power delivery is smooth so cylinder/valve wear is unlikely, but a compression test will be next if the fuel mileage doesn’t improve with another load of fuel from a different source.
So, at this point I had no idea what was causing the problem. The mileage really went down as speed increased, which was out of the ordinary for me. On the first weekend of May I had to travel from Los Angeles to the San Fransisco area to visit Lefty and attend the AMA races at Infineon Raceway. I packed very light for this journey, just a tank bag and backpack as I wanted to minimize wind resistance. Going up the infamous (DULL) I-5 that traverses North-South I set a steady 75-80 MPH pace to keep up with traffic. Now the problem just became stupid, watching the fuel gauge drop every 30-35 miles, just pissing me off and making me run through the checklist over and over in my head trying to think of what I must have missed in diagnosing this problem. 2 fuel ups and I am getting right at 41 MPG, this sucks. And just when I thought that I had no ideas left, providence steps in...
I am starting to go up a grade, following and passing other vehicles and speeds were still around 75-80 MPH. As I began a pass and rolled on the throttle I noticed that I couldn't increase speed at all. I throttled down and back up and still no response. At this point it became clear that I had a random misfire on at least 1 cylinder. Backed down the speed and started to accelerate again and the misfire disappeared and returned as speed increased. Ok, bad spark plug(s), I'll replace them as soon as I get into town, but why didn't they appear bad when I checked them just a few days before the trip?? I started thinking some more and I suddenly had a revelation.
Last year, at ~66000 miles, I decided to replace the standard NGK CR9EK plugs with a set of NGK CR9EIX Iridium units. Although the original plugs measured well and looked serviceable I got a great deal from Amazon and changed them as part of a service interval. No problems at that time, and I did a couple of tours last summer without a mileage issue. But since then, it s-l-o-w-l-y got worse, and nothing else was altered.
So, I stopped at the Cycle Gear in San Carlos and bought a new set of CR9EK (non-Iridium) and installed at Lefty's before I began the return journey. Measured at highway speeds since the change I am back to the usual 50+ with no other repairs. After discussing this with Lefty, who also change to Iridium plugs last year, he mentioned that he has also noticed a slow but steady decrease in mileage as well.
After all of this, my conclusion is that the Iridium plugs are not suitable for my FZ. 10000 miles of ever decreasing performance/mileage is unacceptable. I believe that the stock ignition coils on an FZ just don't have the necessary secondary voltage to overcome the deposits and degradation that buildup on the miniscule center electrode. Remember, I measured and closely inspected them less than 300 miles before they failed! When new they work fine but I want longevity out of the parts I put on my FZ.
So, if any of my fellow FZ owners find themselves with a similar set of circumstances, consider putting in a new set of standard non-Iridium NGK CR9EK.
Comments/discussions are welcome on this subject!
