TPS gone bad after starter valves sync

[vladr]

Hello all

 

VfR 800 1999 5th gen

For the past weeks I’ve delved into fixing all the small and complex issues from my vfr, but it seems that I’m completely stuck with some topic in particular.

 

 

Chronological Order of Events:

 

 

1. Initial Symptom:
   - The engine began to exhibit hesitation and jerky movements while maintaining a steady throttle position.

 

2. Diagnostic Code:
   - I’ve got a long blink indicating an error code 10, pointing to an issue with the barometric sensor.

 

3. Sensor Replacement:
   - After conducting some tests, I’ve bought a barometric sensor from a 6th generation model and installed it.

 

4. Resolution of Error Code:
   - The replacement of the sensor eliminated the error code, and normal operation seemed to resume, so I’ve continued with the repairs.

 

5. Throttle Valve Synchronization:
   - During the synchronization of the throttle valves/starter valves, I’ve 

encountered an issue with cylinder number 2.

 

Detailed Issues and Questions:

 

1. Cylinder 2 Synchronization Issue:

   - Cylinder number 2 could not be synchronized; adjusting the screw only decreased the vacuum, and completely unscrewing it did not increase the vacuum beyond 1.8 cmHg.

   - Question: Could the mechanism be broken, or is there another issue I'm overlooking? Is it possible for a vacuum leak to affect only one cylinder's adjustment, despite all four cylinders sharing the same intake from the airbox? The hose from cylinder #2 does not appear to be cracked.

 

2. Power Delivery Delay:
   - After reassembling and testing the bike, a delay in power delivery was experienced during rapid and forceful acceleration, nearly causing a loss of control.

   - Subsequent testing revealed an error code 8, indicating a potential issue with the TPS (throttle position sensor).

   - Question: Can a vacuum leak be related to the issues I'm experiencing, including the inability to adjust cylinder number 2 and problems with the TPS sensor?

 

3. TPS Grounding Concern:

   - Research on various forums suggested that the TPS could be grounded, although the contacts appeared to be correctly in place.

   - A resistance measurement between the negative pole of the battery and the engine block showed approximately 200 milliohms.

   - Question: Is this resistance value normal? I'm not an expert, but having resistance on the engine block itself seems unusual.

 

Please let me know if you need further assistance or clarification on any of these points.

 

And thanks for your help!

[Grum]

Starter valve synch for 5gen.

1 = Master.

2 = Match to 1.

3 = 20mmHg MORE than 1.

4 = 10mmHg MORE than 1.

 

TPS, Baro and MAP have a 5v Vcc voltage on the Pink wire check this voltage is good and the same value at these sensors. See attached drawing.

TPS has a Signal Ground through the ECM on the Green/Orange wire. Confirm all ECM Grounds B1 Green wire, A9 and A20 Green/Pink wires have good continuity back to the Battery Negative terminal.

TPS Signal to ECM is a Light Green wire Confirm Continuity of all three wires back to the ECM.

 

Run the TPS checks in the Service Manual after doing the above basic checks. Assume you have the Service Manual and accurate wiring diagram of your bike..?

 

 - "A resistance measurement between the negative pole of the battery and the engine block showed approximately 200 milliohms"...???? Do you have a special Low Ohm Reading instrument? Shorting your meter leads together might give .2 of an ohm (200 milliohms). Subtract meter lead resistance from your reading. Sounds like you have good main Ground bonding to the engine.

 

- "1. Initial Symptom:
   - The engine began to exhibit hesitation and jerky movements while maintaining a steady throttle position." Spark Plugs or dirty Fuel Filter, water condensation in the tank, or bad fuel can cause this.

 

 - "Cylinder number 2 could not be synchronized; adjusting the screw only decreased the vacuum, and completely unscrewing it did not increase the vacuum beyond 1.8 cmHg. "  Burnt valve maybe, perhaps a compression test might be needed?

 

[vladr]

 

Many thanks, Grum. When I wrote the post, I knew you would be the only one to respond. You're still active on this forum, so many thanks for your service!

 

 

1. I know that the service manual states there should be 20 mmHg more, but based on this forum [1], it seems there should be less due to an incorrect choice of words in the manual.

 

Nonetheless, I will also try, as you've stated, by adding more, but the issue with the 2nd cylinder still persists, so I don't know how I should be able to provide a higher value.

 

My values at the moment are:

- **#1**: 2.2 cmHg
- **#2**: 1.8 cmHg
- **#3**: 2.0 cmHg
- **#4**: 2.1 cmHg

 

After doing this setup, the vibrations after 6k rpm could be felt only on the left footpeg instead of the whole motorcycle (before doing any adjustment), so it's an improvement. I'm assuming the 2nd cylinder being off is what gives those vibrations on the footpeg.

 

I will try as you've suggested and get back to you.

 

2. I will go ahead and follow your recommendations regarding the wires and voltages for all three sensors. Thanks again; those are indeed helpful pieces of information.

 

3. The spark plugs have been changed to iridium ones when doing the valve sync, and there was an amazing difference. The acceleration was much quicker, but I still feel hesitation, most likely due to the TP sensor.

 

I didn't check the fuel filter, so I will do that. Water or bad fuel could be an issue, as after refilling with fresh fuel, the hesitation was less prominent.

 

Also, what I've observed is that if I have a temperature of 80°C, the hesitation does not happen that often. If I go into the city with a temperature of 100°C, then it happens more frequently.

 

4. A burned valve is exactly what I don't want to hear. I will go ahead and do a compression test, but somehow my intuition says that the engine compression is healthy and that this should be related to either the mechanism screw or a vacuum leak (if it's possible).

 

Thanks again, Grum, for everything (I owe you a beer)!

 

[1]

 

 

[vladr]

I’ve come back with some responses:

 

 

1. Voltage Checks:
   - Verified that the **TPS**, **Baro**, and **MAP sensors** have a **5V Vcc

voltage** on the Pink wire, so  voltage is consistent across these sensors.

   - Confirmed that the TPS has a **Signal Ground** through the ECM on the Green/Orange wire, and checked that all ECM Grounds (B1 Green wire, A9, and A20 Green/Pink wires) have good continuity back to the Battery Negative terminal.

 

2. Continuity Tests:
   - Checked the continuity of the **Light Green wire** (TPS Signal to ECM) and found no continuity with the negative terminal.

   - Neither the Orange/Green nor the Green wires had continuity with the negative or chassis, not sure if this is normal or not.

 

3. Grounding and Resistance:
   - All three wires (B1, A9, A20) have continuity with the battery's negative pole.

   - The Green/Orange wire has good continuity with B2.

   - The TPS signal to ECM wire (Light Green) has good continuity with B14.

   - The Pink, Green, and Green/Orange wires have good continuity to the ECM.

 

4. Sensor Resistance:
   - Attempted to verify the resistance in the TPS sensor but couldn't read any values, possible faulty TPS?

   - Similarly, couldn't measure any values for the MAP sensor resistance, which may indicate an issue with the voltmeter or the sensor itself.

 Is this normal or I’m missing something? 

 

5. Throttle Valve Synchronization Issue:

   - Initially, cylinder number 2 could not be synchronized, as adjusting the screw only decreased the vacuum without improvement.

   - After attempting to synchronize the throttle valves as you’ve recommended, the same issue occurred with cylinders 3 and 4, unable to achieve a vacuum higher than 2.1 cmHg, which is the same as the reference cylinder 1.

 

So I’m thinking of any possible leak

 

[Grum]

3 hours ago, vladr said:

2. Continuity Tests:
   - Checked the continuity of the **Light Green wire** (TPS Signal to ECM) and found no continuity with the negative terminal.

   - Neither the Orange/Green nor the Green wires had continuity with the negative or chassis, not sure if this is normal or not.

?? Are you referring to the Green/Orange and the Light Green wires of the TPS? You've already confirmed the Green/Orange is good to the ECM and all Grounds are good.

You've stated the Light Green wire has good continuity to the ECM. Being the TPS Signal to the ECM it shouldn't have continuity to the negative terminal.

3 hours ago, vladr said:

4. Sensor Resistance:
   - Attempted to verify the resistance in the TPS sensor but couldn't read any values, possible faulty TPS?

   - Similarly, couldn't measure any values for the MAP sensor resistance, which may indicate an issue with the voltmeter or the sensor itself.

 Is this normal or I’m missing something? 

 

Are you probing the Light Green TPS to either of the other two and seeing resistance changes as you open and close the throttle, do this with theTPS plug disconnected and probing the terminals on the TPS not the wire harness? If the resistance was so bad you would probably have a active fault code.

 

MAP sensor is a Voltage device, a pressure to voltage transducer! Refer Service Manual for MAP checks. Note - MAP and BARO are the same part numbers and can be swapped over for fault finding. Do you have a MAP fault code?

3 hours ago, vladr said:

5. Throttle Valve Synchronization Issue:

   - Initially, cylinder number 2 could not be synchronized, as adjusting the screw only decreased the vacuum without improvement.

   - After attempting to synchronize the throttle valves as you’ve recommended, the same issue occurred with cylinders 3 and 4, unable to achieve a vacuum higher than 2.1 cmHg, which is the same as the reference cylinder 1.

 

So I’m thinking of any possible leak

Have you removed number 2 SV and tried cleaning with compressed air? Refer Service Manual.

Cylinder 2 also feeds vacuum to the Secondary Air Intake system (flapper valve) if the system has been disabled make sure the vac hose for this is blocked off.

 

3 and 4 provide vacuum to the FPR Fuel Pressure Regulator. Make sure the FPR has no fuel leakage into the vacuum hose and no dripping fuel from the FPR vacuum connection any fuel leak = ruptured diaphragm.

 

Closely inspect all vacuum hoses for cracks or damage and properly connected. Make sure the throttle body boots are tight not cracked or leaky.

 

Good Luck 

[vladr]

Another updated:

 

After disconnecting everything and cleaning the TPS sensor with contact cleaner, it seems that the FI light is no longer on. I've tested it for the past 3 days, covering more than 500 km on a country trip. So, no more errors have been stored after this.

 

I will keep an eye on this topic, but now I would like to focus on the valve sync for the following reason:

 

I tried again to sync the throttle bodies as stated step by step in the service manual, including the pair valve, etc.

 

(One question: the manual states to disconnect hose 1 to 4, meaning that the other 3 hoses should be disconnected from the airbox while I do the sync? I'm asking this because I only have one vacuum gauge. I don't think, and until now, I've been doing it with them connected.)

 

After following your recommendation and after 200 km, the sensation was that everything flowed much better. I was finally able to change gears without that small jerky motion that I've never got the hang of.

 

Everything seemed decent, but I could feel that the power output was much lower, and I had to go full throttle for overtaking other cars. So, smoother but less power. Also, no more running rich and no pops on deceleration.

 

I decided to redo everything as it didn't quite feel perfect (my mistake), and I've got the following new values:

 

- Cylinder #1: 2.0 cmHg
- Cylinder #2: 1.0 cmHg
- Cylinder #3: 2.2 cmHg
- Cylinder #4: 2.1 cmHg

 

After trying various times to get the same values and feeling as before, nothing helped. Now, I have much more power again, but everything is very jerky, and I feel that the response of the acceleration has a slight delay until the action has to be done by the engine, thus jerky when changing gears.

 

So, I'm running out of ideas. I cleaned all the SVs and verified they open synchronously.

 

The flapper valve is still connected and theoretically working. Should I try closing the vacuum hose and test it like that?

 

So, what else could be the culprit in this case, only happening to the 2nd cylinder?

 

Could the TPS sensor have anything to do with this? Is it worth changing the baro sensor (which is from a 6th gen) with the MAP one, maybe it's related?

 

[Grum]

5 hours ago, vladr said:

One question: the manual states to disconnect hose 1 to 4, meaning that the other 3 hoses should be disconnected from the airbox while I do the sync? I'm asking this because I only have one vacuum gauge. I don't think, and until now, I've been doing it with them connected.

Do you have the 4 hoses attached the airfilter housing, OR the five way junction type?

Hoses 1 to 4 must be effectively blocked off while doing SV Synch. Either all connected to a 4 column vac gauge. Or if doing 1 at a time the other 3 must be blocked off, which would be an issue if you have the five way junction type.

- SV's are for base idle, cold idle and small throttle opening. The greater the butterflies open the less the influence of SV's

5 hours ago, vladr said:

So, what else could be the culprit in this case, only happening to the 2nd cylinder?

 

Could the TPS sensor have anything to do with this? Is it worth changing the baro sensor (which is from a 6th gen) with the MAP one, maybe it's related?

 

- Compression checks for number 2 maybe? Body to intake rubber boot leaking or damaged maybe?

- TPS cannot effect only one cylinder.

- Not sure if a 6gen MAP Sensor is the same as the 5th. But as mentioned, the 5gen MAP and BARO sensors are the same part numbers and can be swapped for fault finding.

- The 5gen throttle body is a birds nest of vacuum hoses, make sure all the hoses are in good condition, connected and no cracks or damage.

- Have you read the Technical Features section of the Service Manual? Good explanations of the EFI system and sensors.

 

Sorry I can't offer anything else, have never owned a 5gen.

 

 

[vladr]

On contrary, Grum, many thanks for all the help offered!

 

I have the EU model with the 4 hoses separately for each airbox connection. 
 

I will go ahead right now and try blocking them off totally while doing the sync ( not letting them connected on the air box)

- for the compression test I will have to way to get home

 

- rubber body, I will check those too and see if they fit well onto the airbox

 

- from what I’ve understood the sensors are interchangeable for 5th and 6 th gen, I’ve got a map sensor from 6th gen to the baro of my 5th one and indeed the fi light of one long blink (error code 10 disappeared) but I will try to swap them up to see for any chnages 

 

- at first glance neither of the hose were cracked or twisted and everything seems connected well, the two big tubes from underneath the throttle body, the big one from the front of the airbox and the other one from the breath tube do the cranskshaft (which from the previous photo it seems that there s oil in the passage, something I didn’t recall being there on the first check), the flapper valve and the map sensor.

- I’ve got a beeter understanding now thanks to the technical section from the manual

I will go ahead and check the remaining things, also I will try to block the flapper valve vacuum hose for any change and I will keep you updated. Thanks again grum for everything ! 
 

 

 

UPDATE 2:

 

After syncing the throttle valves again, but this time blocking the other hoses, the engine has power, but the temperature exceeds 100°C at speeds over 80 km/h, even with an ambient temperature of 20°C.

Clearly, this was not the case before, as I'm aware that the VFR runs hot, but it never reached 107°C while riding, not even last summer when it was 40°C.

So now, I'm assuming that because it's the only cylinder not calibrated, it runs rich, and thus, this issue arises.

I'm really considering the burned valves that you told me about. I'm still unable to perform the compression test, but I will proceed with it in the coming days.

So, it could be a burned valve, or the screw mechanism for that cylinder has failed, or any other issue you've mentioned above.

[Grum]

12 hours ago, vladr said:

I will go ahead right now and try blocking them off totally while doing the sync ( not letting them connected on the air box)

 

Aren't the hoses already blocked off when they are attached to the airbox? I thought that the attachment point for the synch hoses at the airbox is simply to store them with the ends blocked? I'm sure there is no passageway that they are plugged into!

 

Hey Vlad. Just reading this whole thread again and noticed there is nothing mentioned of your Air Filter. What is the status of it, how old, how clean? Any doubts Replace it, dirty or poor air flow will cause poor power delivery and possibly rich fueling.

[Terry]

The 4 vacuum tubes do indeed just terminate on blank stubs at the side of the airbox.

[Grum]

41 minutes ago, Terry said:

The 4 vacuum tubes do indeed just terminate on blank stubs at the side of the airbox.

 

Many thanks Terry. I was hoping you'd chime in to confirm this. Not having a 5gen I had a little doubt, but was fairly confident the hose connections were simply storage and blocked off.

Cheers

[vladr]

Thanks everyone for the help! Then my whole life was a lie, I thought the 4 hoses are attached to the airbox to receive air but now I realize that they are vacuum hoses... So stupid. This means that the placebo effect worked and made me think that I can sync the TB more effectively, but it was a lie the whole time...

 

The air filter was new when I bought the VFR one year ago, made around 15K km and I've inspected and cleaned it when I got the sync valve job the first time one month ago. It looked good with only just some normal debris that were cleaned.

I'm riding the VFR every day, and it seems that the jerkiness of the throttle is the same. On low acceleration, it feels like chugging and I need to open the throttle more for it to become 'normal' and resistive. So it seems that all the issue is with the first 25% of throttle.

 

After some more asking around and reading, I come to the following hypothesis:

 

- Valve shims worn off/clearance not in parameters > burnt valves > cannot sync throttle valve for cylinder #2 > incorrect balance of the engine fire times > power output delay > throttle jerkiness/chugging and numb vibrations of the left foot peg (where cylinder 2 is located)

 

Could this be correct?

 

Valve clearance should be checked at 10k and most probably the previous owner did this as the cover gasket seems new.

But as Grum said, I will first start with the compression test to eliminate this possibility.

[vladr]

Oooor the plunger as stated here. Not sure how I should verify them without taking the whole throttle body apart. Probably no other option.

 

 

 

[Grum]

11 hours ago, vladr said:

Oooor the plunger as stated here. Not sure how I should verify them without taking the whole throttle body apart. Probably no other option.

 

 

 

 

You're confusing me Vlad! You said you cleaned All the SV's.

Already mentioned this!

On 5/3/2024 at 11:02 PM, Grum said:

Have you removed number 2 SV and tried cleaning with compressed air? Refer Service Manual.

And your answer!

On 5/6/2024 at 5:44 AM, vladr said:

cleaned all the SVs and verified they open synchronously.

Refer to 5-65 of the Service Manual for SV removal, don't think you'll need to remove the whole TB to remove the SV's. Perhaps a squirt of WD-40 might help if the plungers are sticking in the bore.

 

AND, just incase you intend on cleaning the throttle intakes - WARNING - Be very careful when cleaning the Throttle Body Intakes not to damage the Molybdenum seal coating for the butterflies, do that and you'll end up with high rough idle, you could  also end up needing a replacement throttle body assembly!.

[vladr]

Yep, throttle bodies were cleaned according to the manual. So today I’ve decided to take another look. Removed everything except for the TB per se and made sure that everything is in place again.

Sprayed aerosol all over the air box, funnels and hoses to recheck for any leak, nothing found. 

Double check all the connections to the harness and back, same.

 

Still couldn’t test the compression as I will need to rent one from someone first but power output wise engine runs well.

 

Ive tune again the vacuum to other values:

 

#1: 2.1 cmhg

#2: 1.1 cmhg (instead of max 1.6)

#3: 2.3 cmhg

#4: 2.2 cmhg

 

Runs much smoother but with pops and bangs as well as fire coming out of the exhaust on deceleration. So I will revert back to the previous values.

Inspected the screw mechanism for all cylinder and they seem to work properly, #2 also as I can decrease the value but not increase it.

 

One interesting thing, it seems that from the crankshaft breather there’s unburned gas (see photo), so this makes the speculation of being a burned valve even more plausible.

 

Will get back with a compression test and hope for the best.

 

Thanks again Grum! 

 

[vladr]