Trottle Body Sync Problems

[AlaskaFJR]

Hello Crew,

Overall the bike starts OK and runs fine at highway speeds. Starts right up when cold and purrs like a kitten during the warm up cycle, then when reaching a certain temp the problem starts in the form of rough idle like not all cylinders are firing. Again, sounds and runs fine on the road until stopping at a traffic light then the problem returns with the weird idle.

Received the warranty notice in the mail for the TPS recall and took it to the shop for the service and asked them to perform a TBS after installing the new TPS. Shop manager called me after his tech (22 years experience) had four hours of labor ($340) in the bike performing the TBS and explained they were stumped and could not find what was causing the problem. I told him to button it up and I would come get it. Following are the techs notes as to what was checked during the trouble shooting process.

1. Checked all injectors in diag mode - OK

2. Fuel pressure @ 36/37 psi (varies 2-3 psi)

3. Swapped #2 and #3 injectors - no change

4. Pinched off press regulator impulse line - no change

5. Changed spark plugs - no change

6. Fuel pump volume test (400cc in 12 sec)

7. Blew out fuel bypass passage in #3

8. Fuel pressure "key on" not running (39 psi) running (36.5 - 37.5 psi)

9. Sync cylinders (mm/hg) #1=29 #2=29 #3=13 #4=29

10. Bypass screw is adjusting flow on cylinders #1, #2, #4 No change on #3

11. Spark checks OK in diag mode.

Any ideas or comments on what to look at next would be highly appreciated. I'm better than average in wrenching skills and have most tools and a good TBS kit. The shop foreman thinks it may be the ECU ($600) causing the problem when the fuel map kicks in after the warm up cycle. This is a 2003 GEN I with low milage as we dont have a long driving season up here. After reading some threads I'm looking at checking the battery (I think its the original) and also the wiring harness corrosion issue. Shop foreman also said I may try a power commander to "tune" out the problem with cylinder #3 but I wanted to tap the brain power of all the super techs out there that may have seen or heard about this problem.

Thanks, Chief

 

[PA1195]

Hello Chief from Gary in Fairbanks. I don't have all the answers, just a few observations. There are many helpful GenI owners here that have much more experience than I.

My GenII '08 is supposed to run at around 47 PSI fuel rail pressure. I don't have a return line from the fuel supply rail like your GenI with an external fuel pressure regulator (mine's in the pump assembly), nor does my '08 Service Manual say what your fuel pressure is supposed to be. Could be faulty fuel pressure regulation only if yours is lower than spec.

Your #3 cylinder appears to have a vacuum leak somewhere, would be my guess (leak = low vacuum reading). Average idle vacuum should be in the mid-20's for all four and needs to be reset if you can get idle bypass control over #3. Possible sources are the rubber head to throttle body coupler (tighten), vacuum line, vacuum test point cap, or a maladjusted throttle plate (all throttle plates should be essentially closed at idle). There are three adjustment screws on the throttle body shaft that set the throttle plate angle for cyl #3 to match 4, 1 to 2, and groups 1 and 2 to 3 and 4. Someone may have fiddled with them at some point. The vacuum leak is a more likely scenario however.

If it were mine I'd do whatever it took to equalize the vacuum readings, and then retest the riding performance. The ECU, battery voltage, or PCIII won't cause or cure a low #3 vacuum or possibly low fuel pressure.

Gary in Fairbanks

 

[AlaskaFJR]

Gary,

Thanks for the input . . . and greetings from the banana belt way down here in the Anchorage bowl. I would hope that for the 350 bones already expended to the local shop, the vacumn leak possibility on #3 would have been explored . . . . . but then again maybe not. It seems plausible and worth looking into. If it is a vacumn leak affecting the idle while hot, its not significant enough to show up while cruising at speed or during the " fuel enriched" cold start up mode.

Chief

 

[FJRBluesman]

I have a Gen1 and have had no such issues with TBS. I too would also suspect vacuum leak, or poorly adjusted throttle plate.

Good luck, let us know what it was.

 

[Silent]

You can spray some carb cleaner around the boots and throtle bodies to find the vacuum leak. when the rpm changes, you know your on it. It's possible that the seals for the rods that control the throttle plates are going out/gone and making a vacuum leak there. kinda hard for a tech to find if there not looking for it.

 

[PA1195]

Gary,Thanks for the input . . . and greetings from the banana belt way down here in the Anchorage bowl. I would hope that for the 350 bones already expended to the local shop, the vacumn leak possibility on #3 would have been explored . . . . . but then again maybe not. It seems plausible and worth looking into. If it is a vacumn leak affecting the idle while hot, its not significant enough to show up while cruising at speed or during the " fuel enriched" cold start up mode.

Chief

That makes sense. Above idle the vacuum may still be lower on cyl #3 if the plate is open more, but not enough to be as noticeable as all cylinders are producing lots of power. Not so at idle. It's at idle where you would likely feel the greatest roughness. There's lots of info here on getting to the throttle bodies for a synch. First check the rubber gasket for cracks and clamp looseness. Hook up a manometer and test for leaks while you tighten the connecting boot. Replace if any cracks are noted. Spray brake cleaner on a crack to test for leaks (brief increased RPM). Make sure the rubber caps that cover the four vacuum ports are in good condition. Also check the vacuum lines and fittings connecting the throttle bodies to the intake pressure sensor for correctness. If you still can't get an even vacuum, try to get a look at the throttle plates to see if #3 is visibly open wider than the rest.

Resetting the plates if #3 is open more at idle may take some work. Normally there's a white paint gob on the three throttle shaft screw heads from the Factory that my allow resetting close to Factory. If that doesn't work, then the job entails setting all four idle bypass screws to about 3/4 turn open, installing a four channel manometer, and adjusting the right shaft screw to first balance #4 (far right) throttle body to #3 (the reference for all four), then balance if required #1 to #2 with the left shaft screw, then #'s 1,2 to 3,4 with the center adjustment screw using the value of ~250 mmHG (or 25 cm HG as your mech noted) as the reference. Takes running the engine, turning it off, rotating the common shaft and twisting the screw 1/8 of a turn max, restarting, and noting any changes +- and correcting. I forget which direction (CW or CCW) balances a low throttle body to a high one. Factory spec is around 250 mmHg at idle +-10 mm. That's about what #3 should be set at with no leaks elsewhere. After the plates are synched, fine tune the values at idle with the brass idle bypass screws. You may have to compromise a bit by closing the plate adjustment a bit if for some reason the vacuum is too low even when the idle screw is fully closed on a particular throttle body. Back and forth until your satisfied or out of beverages.

As far as the fuel pressure, someone else will have to say whether or not it's within spec.

Gary in Fairbanks

 

[wfooshee]

Check the condition of the black boots between the throttle bodies and the engine, and between the throttle bodies and the air box. Any cracked or broken, all clamped tight? No holes drilled by some menacing neighbor kid? (Ok, the last one was a long shot, but still, check the rubber parts for good fit and condition.)

 

[AlaskaFJR]

Thanks to all for your advice . . . . It sounds like the most likely problem (boots, seals) causing the vacumn loss to that individual cylinder. I think the shop was overwhelmed with all the spring maintenance and did'nt want to spend alot of time/effort chasing down the problem.

Personnally I'd rather do the work myself and save the shop rate @ $85 hr. What bothers me was them pointing me towards the ECM failure as a potential cause. My normal instincts are to resist taking my bike to the shop not only due to the high cost but all the new dings and scratches that inevitable show up when you get home. This time I got lucky in that respect with no nasty suprises.

I'll keep the thread posted on the outcome after I get time to dig into it.

Regards, Chief

 

[Silent]

Thanks to all for your advice . . . . It sounds like the most likely problem (boots, seals) causing the vacumn loss to that individual cylinder. I think the shop was overwhelmed with all the spring maintenance and did'nt want to spend alot of time/effort chasing down the problem.
Personnally I'd rather do the work myself and save the shop rate @ $85 hr. What bothers me was them pointing me towards the ECM failure as a potential cause. My normal instincts are to resist taking my bike to the shop not only due to the high cost but all the new dings and scratches that inevitable show up when you get home. This time I got lucky in that respect with no nasty suprises.

I'll keep the thread posted on the outcome after I get time to dig into it.

Regards, Chief

I've had shops charge me several hundred dollars and not fix the problem. I had a broken coil wire inside the insulation on my Ninja that drove both me and the mechs nuts for months. I would loose cylender ramdomly. I finnaly found the problem and it was a $0.05 fix. Just because they work for dealership doesn't mean they know everything about every bike.

Here's hoping that your able to find that $0.05 fix as well

 

[03HiYoSilver]

Alaska,

I had a similar problem but it was #4 that would NOT adjust. After doing all the above mentioned fixes to NO avail under YES, ended up having to replace the Throttle Body Assy (which is all 4 Bodies...not done separately).

This ended up to be my Fix for this situation.

Hopefully, yours will not have to come to this and good luck on your fix.

 

[mattster31]

That sounds strange for sure. I know that when doing a TBS, you need not touch cyl. #3 as the others are matched to it during the procedure. The low reading is bizzare. I use a homemade manometer I copied from "Rickster", which works great. It doesn't give me an actual pressure reading but it "matches" 1-2-4 to 3. as I adjust the screws, the oil level in the third tube does move, so that does indicate a change in pressure. From your post it seems that the #3 cyl. is not moving "pressure wise" at all. If it were me, I would remove the entire assembly and inspect it. Pick up a service manual first. Check the action of the throttle plates, check the rubber boots for cracking and be sure the clamps were tight and the boots seated correctly. If there is a vaccum leak on that cyclinder I would think there might be a visual clue within the throttle body assembly (dirtier than the rest).

I am interested to hear what the issue is once it's resolved. Good luck.

 

[kolar55]

Here's one more thing to look at. Although not totally familiar with the exact setup on the fuel injection system, it would be my guess the screws they tell you to adjust are affecting the air at idle. In the past when working on carburated bikes I have seen some of these screws that were turned in to far and lodged in the throttle body. They can get so tight that when backing them out they will break off and a small piece remains stuck in the seat. If that happens there will no longer be any air adjustment. The result mimmicks your description. Maybe try removing the screw completely and inspect it. Just a thought.

 

[Constant Mesh]

Since it runs OK during warm-up from a cold start the problem may be associated with the cold high idle air valve near the bottom of the throttle body. Maybe that valve is stuck in the open position on the #3 TB and won't close as the coolant temperature rises during warm-up.