ECU Possibly Dead ('98 VFR800)

Hello all,

My '98 Viffer has been using a heck of a lot of fuel (22 MPG - imperial gaallons, 12.4 L/100km, 17.6 MPG - US gallons, 8.1 km/L - whatever your language, it's really bad)! This is for relatively free-flowing town riding, mainly around 60km/h, but at times up to 80km/h. I usually accelerate quickly to the speed limit (where possible), but I've never hit full throttle, so I'm not exactly ringing its neck... I usually use 3rd gear at 60 or 70 km/h, but sometimes only 2nd (to keep the noise level up, to remind the cage-drivers that I'm there). The exhaust is a Stayintune.

I've put the ECU into diagnostic mode, and it's showing codes for the inlet air temperature sensor (code 9) and the barometric pressure sensor (code 10). When I went through the diagnosis for the IAT sensor, I got to the end, having proven that there's nothing wrong with the wiring and sensor, which means that the ECU is dodgy. What I could diagnose of the Baro sensor (I don't have the special patch harness to do all of the diagnostics) seemed to indicate the same thing. Interestingly, they both feed into pin B2 of the ECU, as does the coolant temperature sensor (which shows up as OK on the diagnostics in the ECU - would be code 7 if it came up).

Is there anyone who can tell me if I'm barking up the wrong tree with the ECU? When warmed up, the engine temp on the instrument cluster shows the mid 80's (deg C) as a minimum, more often the 90's (and into the low 100's when I'm sitting in bad traffic). When I start from cold, it shows "--" until it reaches somewhere in the 30's. I can't find any fuel leaks. The exhaust outlet is quite sooty. The bike has 87,000km on it. My outings usually get the bike up to temp for at least half of the ride (usually more like 90% of the ride is at proper operating temp). Only occasionally will I take it for a short enough ride to have it below operating temp when I turn it off.

Does anyone have any advice/suggestions? If someone has a spare ECU that's known to be good, I'd be interested in buying it.

Cheers,
Danny

 

With your bad mileage I have to ask when was the thermostat replaced? Does it take an unusually long time for it to warm up? If so it sounds like thermostat is the real culprit not the ECU.

 

100 C would be 212 F so it seems the t stat is ok
does the fan kick on??
post a tread in the euro section asking members who might be near you to see if they would be willing to let you try thier ECU.
I would say it is a sensor rather then the ECU

 

AU not EU

In looking at the flag and the .AU designation, the Europeans are as far away as the US. However, the Australian section might help!:thumb:

 

I'm an ASE certified master tech, just so you know where i'm coming from. ECU's very rarely go bad. However they are extremely sensitive to bad connections and poor grounds. Be sure all the connectors in the circuit your ECU is claiming to be faulty are clean and free from corrosion. Be sure the ECU has good ground, whether that be through the harness or through the case. The best way to test for sensor signals are at the ECU harness so you can be sure that the computer is getting all the right signals. Carefully backprobe the ECU connector with a T-pin and measure inputs. Hope this helps you find the issue. Good luck.

 

missed that thanks. :doh:

watch out for those roos

 

Extremely unlikely it is the ECU.
It is solid state.

Forget the codes.
If the computer gave you a code#9 (temp sensor- why not just replace it?)
BTW....Around town riding does use the most gas.
Unplug and plug in the ECU to make sure the connection is not corroded.

 

Eurika! I figured out that there was something lost when Honda translated the service manual into English (I'll give them the benefit of the doubt): If a code's set, you need to clear it again before proceding to the next step in the diagnosis process. If you don't, you could've fixed the problem, but the code will still show up! I cleared the codes, and they haven't come back.

Thanks to everyone for the replies. :biggrin:

So... For the poor fuel consumption... The coolant seems to warm up quickly enough from what I recall (I'll take more notice of it when I go for a ride tonight).

I've given all of the ECU terminals a good clean. There were some small divets on some of the pins (presumably due to fretting). It reminds me why I'm glad I'm a mechanical engineer, not electrical... Sometimes the electrical engineers at work have to deal with fretting corrosion on CAN-bus lines causing intermittent warranty issues in small numbers of the cars we build...

As far as I'm aware, the fan turns on (and stops the temp from going over the low 100's). However, I've never heard it over the stayintune...

Now I'll get back to diagnosing the poor fuel consumption... I'll take it for a nice easy highway ride for an hour or so, and fill it up again to see if it looks like it's in the "normal Viffer" range. If it looks good, perhaps I'll have to be a bit easier on the throttle around town... :wink:

Thanks again to everyone. I'll let you know how it goes.

Cheers,
Danny

 

That mileage is way off tho? Might the end can be the culprit? I'm at a loss as to why every1 keeps saying the bikes running hot and thats the reason for the poor economy? WHAT has that to do with mpg thats this way off? Especially when the temps are perfectly normal!

 

Where the bike running cold it could cause the mileage to be off. Mine is awaiting a thermostat next week and my in town mileage has dropped from 40 to 37 cause they bike tends to run a little on the cold side, around 150 to 160 F as opposed to the normal 165 to 170 F.

 

Pull the plugs and see which one is darker than the rest.if your bike is running rich and your iat is ok your coolant temp is in spec you may have weak spark at one plug,open injector or vacuum leak on a throttle body or intake manifold gasket .
If vacuum is low or leaking it can cause a rich condition along with the other items o stated .

 

i cant beleive no-one has suggested cleaning the PAIR valves in the top of the cylinder heads, these reed valves when leakin cause over fueling which results in poor fuel economy, i blocked mine up 3 years ago as my reeds were leaking even after cleaning and the bike has gone from 22mpg to over 40mpg, i did have to alter the idle to suit, another method of disabling PAIR system is to disconnect the electical connected going to the pair valve solenoid, this will not bring the Fi light on and should bring mpg back to normal

 

Hello again everyone. Thanks for the good info. Sorry for the delay in getting back to you all with the results of the fuel economy checks...

I did a check at 100 km/h (about 62MPH) in top gear, sitting mostly in racing position. I got 5.6 L/100km, which equates to 17.8km/L, 50.3 MPG (imperial gallons), or 41.8 MPG (US gallons). Now, that looks a lot better to me. However, there was something a little alarming that I noticed when I pulled off the freeway to turn around and go back the other way... The temperature was only 68 deg C (154 deg F)... Even more alarming was that the return trip was into the wind, so the temperature started going down, and hit a low of 59 deg C (138 deg F)! Maybe my thermostat isn't quite as good as I thought after all... :frown:

I've also done a "general riding" check. I tried to keep the rev's between 3000 and 4000 around the town (except for the occasional excursion above 4000). A quarter of the riding was freeway riding at 100km/h, a quarter was at 80km/h, and the rest was town riding in 60km/h and 70km/h limits. I got 6.1L/100km, or 16.5km/L, 46.5 MPG (imperial gallons), or 38.6 MPG (US gallons). I've been watching my temperature more closely, and it moves around quite a bit depending on my speed, etc. Again, it seems to indicate that the thermostat needs to be changed.

My new thermostat arrived today, so I'll probably fit it tomorrow night (if I can get away from my wife's list of chores she wants me to do). Perhaps I might also look into blocking the PAIR valves. I've been told that they're "good for nothing", so it would be interesting to see if I get some extra mileage. Thanks to everyone for the suggestions.

Cheers,
Danny

 

Your temp readings are exactly the same as mine, runs at normal temp in town but as soon as you get her cruising at highway speed the temp goes down down down. I've got a thermostat waiting to go in mine, likely wont happen til thanksgiving as you have to remove the fuel injection/throttle bodies to get to it. A month ago when the weather was nice and warm it would run at normal operating temp. My avg MPG(U.S, Gallons) was 40 city 45 highway. Best 47 Highway on a four hour trip. I got 217 miles on that tank...

 

It took me way too long to get around to changing the thermostat, but I'm glad I did. The old one was stuck open. The bike now warms up really quickly. It still uses a bit more fuel than I think it should, but maybe that's because of the pack I always carry on the back of the bike (not exactly aerodynamic)...

 

You need to remember that with those electronic diagnosis that it can also be the connecting wiring.
The barometric sensor is still not a known good part.
You cannot just skip around to other things.
You must find out if the barometric sensor is Good or bad because it can affect the whole food chain.

You need to go step by step.
The sensors are more likely to fail than the ECU which almost never fails because it is all electronic unlike the sensors.
Just a simple Infared gun pointed at each cylinder would tell you much more.

Sooty exhaust? I would be seeing if the (fuel enrichment) is working correctly.
OR the air intake is stuffed up.

 

^ Thanks for the info. As I said in post number 8, I found that some codes are held active even if the fault isn't present. I cleared the codes over a year ago and they've never come back. It was actually a problem in the factory repair manual, failing to say to clear the codes between each diagnostic step.

I actually dug up the old thread to say that I'd finally changed my thermostat, so now all is good.

 

The people that design those computers should read the instructions to see if they make sense and are complete and not make assumptions. If we follow the instructions we should get results.

Just like all corporations should CALL their own business and see what kind of telephone hell the customer has to endure to get any result.

You want a good company? Then answer the phone. Make computers with good instructions. Make good manuals with good instructions.

I have rarely seen a good manual that does not have lots of mistakes, missing photos,or photos that are too dark and you cannot tell what is being pointed to.

Every website should tell what state and city they are located and there should be a good telephone number where a person answers the phone.

If you are receiving too many calls then you better find out WHY.

 

You're certainly right. Trouble is... That would be customer service, and all that companies want to do now is to take your money and run... But that's a topic for a different thread...