Hi,
I have a thread on the General Tec forum about my problems with my 2003 CBR600 F4i, ( https://cbrforum.com/forum/general-t...-story-162338/ ), but I still have a problem with it running very rich that I am hoping someone on here can help me with?
All 4 cylinders are turning the plugs black within only a few hours of run time. The plugs were new a few months back and have only done a couple of hundred miles. The plugs in cylinders 1 and 2 are coming out black and sooty, but the plugs in 3 and 4 are black but also wet with fuel.
What would cause all 4 cylinders to run rich and 2 of them to have unburnt fuel left in there?
I have already replaced the FPR, the MAP sensor, and all injectors are refurbished replacements that were tested before installing. I've replaced all vacuum lines, (nothing wrong with them that I could find, they were just old), and adjusted the valve clearances. I tested the air temp sensor with a voltmeter and its right in the middle of the spec range. The TPS also gives voltage readings comfortably within spec. The bike has OEM exhaust headers but a slip on muffler/silencer.
The bike starts and idles without problem, but with the fouled plugs it bogs down as soon as load is put on the engine and backfires when you give it more throttle to stop it stalling out.
Has anyone had this issue and fixed it? I see in a lot of the older threads that others have said to install a power commander - but thats $400 that I don't have right now. Can anyone help? Thanks.

 

Well, I don't have an actual answer but have a power commander 3 that I'd be willing to sell for less than half that if you're interested (mods you can remove that part if needed since this isn't the for sale section). Only down side is - it may not fix the issue. Slim, but always a chance, you have leaking injectors.
I know one of the other, more advanced, will be along soon to help out.

 

Don't replace perfectly-working parts with brand-new perfectly-working parts. NOTHING will change and symptoms will persist!

Instead, test and measure and compare numbers you measured with values given in manual. Even sensors could be victim of bad, broken, corroded wires and connectors. Measure at ECU connector:

- MAP sensor's output voltage & reference-voltage and ground/short tests according to manual. Also do additional tests with vacuum-gauge connected. Could very well be leaking vacuum-hose leaking vacuum. This causes MAP-sensor to think load is higher-than-actual. It will output higher-than-normal signal to ECU and ECU will end up injecting additional fuel for what it thinks is higher-load. Very, very common.

- measure vacuum going to MAP-sensor at idle and with key ON, bike OFF. What are these vacuum numbers?

- FPR, lowers fuel-pressure according to load. At idle, vacuum is highest and fuel-pressure lowest. At WOT, vacuum is lowest and fuel-pressure highest. Again, measure vacuum going to FPR at idle. What is vacuum?

- actual fuel-pressure in rail at idle and WOT. Basically functional test of FPR and vacuum-lines. What's these pressure-readings?


These are factors that determine fueling amounts. One or more of these numbers may be off, thus skewing your fuel amounts injected.

 

@dannoxyz - thanks for the advice, this is truly helpful.
I took the voltmeter to the bike today and everything is within spec except the voltage between one pair of wires in the connection to the MAP:



I'm only getting 4.1 to 4.2V between the Gr/Ye and the Gr/Or wires..... all the other readings are good. Do you think this is really enough to cause the over rich condition?

I don't have the tools for the fuel pressure test or the vacuum test (I only have the crappy eBay gauges that are only useful for showing the relative vacuum between throttle bodies).

Any suggestions on how I find a loose or poor contact in this wiring loop? Thanks again.

 

There are only 2 connectors besides the one actually on the sensor where you could have a bad connection. On the ECM 22 pin Light Gray connector, or the 10 pin Gray connector in the wiring harness.

 

Thanks - I checked continuity between the MAP and the main plug connector, and from the connector to the ECM and they both have continuity, (approx. 0.5 Ohm) - what else can I do if its not got the spec voltage?
I have used the paperclip stuck into the connection method to test the ECM terminals and they are within the spec voltage too.
The battery is measuring at 13.4V. I would love for this to be the issue thats causing the rich running - but I am at a loss on how to fix it.

 

This morning I checked the voltage at the sub harness connector with the bike ON and the MAP sensor removed and it was reading 2.7-2.8V, which pretty much matches the 2.7V I measured at the ECM terminals.
it could be an issue with the sub harness wiring somewhere or even the plug connection to the MAP. I ordered an used replacement on eBay this morning, and I'll update this thread if it solves the problem... unless anyone else has a suggestion for me to try? Thanks.

 

Not sure what line you're measuring 2.7-2.8v if MAP-sensor's disconnected? We want signals from MAP-sensor itself. Most likely not MAP sensor itself is bad. In 40-years of working on bikes and turbo cars, and blowing up plenty of engines, I've only seen one go bad.

1. Did you measure reference-voltage leaving ECM to verify if it's within 4.7-5.2v? It might be OK there, but corrosion or loose connectors on way to MAP sensor may have lowered ref-voltage.

2. You'll also want to measure vacuum at MAP-sensor, because leaking lines will throw off sensor-output and trick ECU into injecting way too much petrol.

In end, you'll want to combine all your measurements into graph and compare with standard MAP-output for various vacuum-levels. As mentioned, there are MANY possible causes of signals deviating that has nothing to do with MAP-sensor itself, but its inputs. I bet there's a vacuum-line that's leaking causing all of this.




Sync-gauges should be fine for measuring vacuum if they have numerical dial. Use vacuum-T to tap into MAP-sensor line and see what idle-vacuum is. Should be in 20-24 in.Hg range at idle. If less, than MAP-sensor would be reporting higher loads than normal and ECU injects more fuel.

Get one of these vacuum-tester/pumps. You can measure vacuum on bike and bench-test MAP-sensor and verify it outputs proper signal at various vacuum-levels. Current MAP one on bike is most likely fine, replacement must also be tested to verify it's good. Replacing perfectly-working parts with brand-new perfectly-working parts changes nothing and symptoms will persist because you haven't found actual problem yet.

One thing we know for sure is ref-voltage line at MAP-sensor is way off. Thus any signal MAP-sensor outputs to ECU will be out-of-range as well, even for perfectly-working MAP-sensor. Like any data-processing, garbage-in = garbage-out. Could be those connectors IDoDirt pointed out. So next test really should be

1. measuring reference-voltage output at ECU itself to verify it's sending put proper 4.8-5.2v. If it is there, then there's some degradation on way to MAP-sensor due to broken, corroded wiring or connector terminals. Sometimes, terminals gets pushed out of connectors resulting in bad signals. Swapping perfectly-working MAP-sensor for new one does nothing to fix that.

 

Does this bike have any piggyback interceptors like Power Commander or Bazzaz?

3. send injectors to https://mrinjector.us for cleaning. Very well could be clogged injectors being lazy or even stuck open. Thus too much fuel being injected. Their before and after flow-test numbers will be valuable info to figure out this issue.

While injectors are away, measure other sensors that may be sending erroneous signals to ECU:

4. test and measure IAT sensor according to manual. Also at 0C and 100C

5. test and measure ECT sensor according to manual. Also at 0C and 100C

 

Wow - thats a lot of info - many thanks.

To answer some of your questions, I followed the maintenance manual when checking the MAP and its connections. The ECM voltage that I measured at 2.7V-2.8V matches the the troubleshooting part of the manual shown here:

I wanted to try an eliminate either the main wiring harness or the fuel injector sub-harness as the cause of the low voltage, so I took a voltage reading at the connector end of the same wires and got a similar reading to the one I measured at the ECM, so it might be a wiring issue in the sub-harness somewhere.
I thought the same thing about the injectors and have already sent them away to a company that cleans and tests them.
I have tested the IAT using the maintenance manual methods and it shows that its comfortably within spec. I haven't managed to get to the ECT yet, but my gut tells me that it isn't the problem as my dash temp display shows the temps I'd expect to see... but I will take some time at the weekend to get the voltmeter on that also.
Lastly, I replaced all the vacuum lines just a couple of weeks ago, and checked them all again last weekend - everything is connected and secure. Nothing is blocked, and there are no signs of fuel or any other liquid in the lines. I will try the carb cleaner spray trick when I have the bike running again to see if there is a leak anywhere.

Thanks again for all the advice - I will report back on what I find. I am really hoping its the MAP sensor wiring/voltage issue and a wiring harness swap will fix it, otherwise I have a lot more investigating to do.