Return of bucking. A jinx and a curse? Solved!

[TrollFromDownBelow]

do your self a favor ... invest $20.00 in a new TSII and use a smidge of loc-tite on it too. Also get yourself a vacuum gauge...about another $20. If memory serves you should have 18-21" of vacuum. Also, you'd be surprised how much a leaking valve cover gasket can affect how the engine runs. For it to really affect it though, you can tell by looking at the gasket...it will actually get 'sucked in' ... and no, ATV won't work in a pinch if you don't have a new set handy (ask me how I know ... hence why I bought 4 new sets last order from bus depot)

Can't remember ....have you tried swapping out the AFM? Did you test the AFM using an analog volt/ohm meter?If not, let me know ... I might have one stashed that you can borrow to test. Seeing as it is bucking even not under load, I would suspect something electrical...maybe check continuity on the FI wiring harness? Another random thought, you might also have a vac leak around the FI injectors.

Maybe if you could post a comprehensive list of everything that you checked, and just as importantly how you checked it, it will keep the arm chair mechanics like myself from making the same suggestions over and over.

[56ovalbug]

do your self a favor ... invest $20.00 in a new TSII and use a smidge of loc-tite on it too.

I wouldn't use Loc-tite here. The TSII sensor needs good grounding to the cylinder head and the Loc-tite may prevent this.

[bajaman72]

=D> I must applaud you sir. I would of pushed this thing to the pasture by now. No advice, but I am rooting for you

[luftvagon]

:popcorn

[TrollFromDownBelow]

do your self a favor ... invest $20.00 in a new TSII and use a smidge of loc-tite on it too.

I wouldn't use Loc-tite here. The TSII sensor needs good grounding to the cylinder head and the Loc-tite may prevent this.

I would agree with you (hence just a smidge :) ). However, mine kept coming loose; it's the only way I could keep it in place (my threads were a little stripped). I did this last year, and haven't had an issue since.

[aopisa]

do your self a favor ... invest $20.00 in a new TSII and use a smidge of loc-tite on it too. Also get yourself a vacuum gauge...about another $20. If memory serves you should have 18-21" of vacuum. Also, you'd be surprised how much a leaking valve cover gasket can affect how the engine runs. For it to really affect it though, you can tell by looking at the gasket...it will actually get 'sucked in' ... and no, ATV won't work in a pinch if you don't have a new set handy (ask me how I know ... hence why I bought 4 new sets last order from bus depot)

Can't remember ....have you tried swapping out the AFM? Did you test the AFM using an analog volt/ohm meter?If not, let me know ... I might have one stashed that you can borrow to test. Seeing as it is bucking even not under load, I would suspect something electrical...maybe check continuity on the FI wiring harness? Another random thought, you might also have a vac leak around the FI injectors.

Maybe if you could post a comprehensive list of everything that you checked, and just as importantly how you checked it, it will keep the arm chair mechanics like myself from making the same suggestions over and over.

I am waiting to do anything before check the valves. I had a minor medical procedure yesterday that is preventing me from scooting around on my back. Might be another day or two.

I have a new TSll. Will swap it out.

I think I have a vacuum gauge somewhere.

I have tested my AFM using the Bentley and also looking for a voltage drop as I operate the flap (not just the wiper). Although I used a digital meter. Randy in Maine loaned me a spare AFM and his LM-1. I am getting around to doing this soon.

Working on the comprehensive list.

[aopisa]

=D> I must applaud you sir. I would of pushed this thing to the pasture by now. No advice, but I am rooting for you

Believe me I have been tempted many times. I sometimes wave a gas can and pack of matches at it.

The thing is, most of you here would have probably solved this in a couple of hours or a few days at most. Just as some people can pick up a guitar and play it right away while others struggle forever to make that F chord, I struggle with things mechanical. So a bucking bus and my ineptitude are not a good match.

I would like to solve this before the quickly fading summer slips away and get some more camping in. Or else there will be one item on the agenda at 9:00 AM on October 3 when Colin arrives.

So in a way, I'm just getting started on this thing. I have to go through all the things it probably isn't to find the one weird thing that is causing the problem. Have you ever noticed that no two bucking problems on these forums ever seem to have the same cause/solution?

Once again, I am pretty busy with some work deadlines so progress is going to be slow over the next few days.

Thanks to all for sticking with me while I muddle through this.

[drober23]

I have had a few episodes like this with a couple busses. One of them turned out to be very persistent. I had a wire with compromised insulation that would randomly ground out or not. It was the one in the rear left of the engine with the fuse holder on it that goes to the brake light and splits off to the double relay. Colin spotted it after I swore I had checked everything.

Reading the whole thread, I suspect some type of ignition issue (bad ground, bad connection, AFM, or the like). If it were vacuum it would probably not be so darned intermittent. If it were fuel you probabaly would have figured it out by now. But replace the TSII if you have a new one!

Keep the faith and good luck!

[luftvagon]

Colin is a great guy, but what are you going to do 364 days out of the year while he is not around?

[aopisa]

Just what I am doing now, keep learning from my mistakes and new experiences. I am not giving up. I was just saying that there is a chance that I may not track this down before he gets here. Same thing happened last year. This time he may not solve it either. I would have a much greater sense of accomplishment if I can tackle it myself.

Like I said, it's just me in this little Vermont town, you folks and Colin. That's all I have to help me at the moment.

[Lanval]

You're closer than you think. Essentially, when you put on the throttle, you're giving it more gas, air and fire. Figure out which one is failing. Start with gas, 'cause it's the easiest to test and fix. You want to know if the fuel pressure is good under throttle. Then check the injectors.

Then air.

Then fire.

Others might argue the order. I go in order of easy to eliminate. Bottom line, the "only with throttle on" makes it much easier.

You'll get there. Took me weeks to figure out the ECU had died. It's the last thing to go really, but I finally proved what it was. By the end of that go-round, I was an expert on the double relay and checking the ignition.

ML

[luftvagon]

Technically, opening the throttle allows more air to be sucked into the cylinders, and with more air coming into the motor, AFM flap moves, signalling the airflow increase, which results in the increase in injection duration time.

Another thing to check, if you have not already. Pull all four spark plugs out. Take a picture of the tips, and post here.

[aopisa]

Technically, opening the throttle allows more air to be sucked into the cylinders, and with more air coming into the motor, AFM flap moves, signalling the airflow increase, which results in the increase in injection duration time.

Another thing to check, if you have not already. Pull all four spark plugs out. Take a picture of the tips, and post here.

I planned on doing just that since I still cannot get on my back yet to check the valves. Hopefully I can find some time tomorrow to pull the plugs and post a pic.

[aopisa]

You're closer than you think. Essentially, when you put on the throttle, you're giving it more gas, air and fire. Figure out which one is failing. Start with gas, 'cause it's the easiest to test and fix. You want to know if the fuel pressure is good under throttle. Then check the injectors.

Then air.

Then fire.

Others might argue the order. I go in order of easy to eliminate. Bottom line, the "only with throttle on" makes it much easier.

You'll get there. Took me weeks to figure out the ECU had died. It's the last thing to go really, but I finally proved what it was. By the end of that go-round, I was an expert on the double relay and checking the ignition.

ML

Thanks. I hope I am close. I think I will have a good chunk of time this weekend to delve back into the diagnostics.

[aopisa]

I have not had a lot of time lately, but thought I should post an update.

I performed a valve adjustment. I have hydraulic lifters. Everything checked out, probably within the margin of error. At most the adjusting screws backed out 1/8-1/4 turn more after backing off the 1 1/2 turns of preload.

After the adjustment I attempted to time the engine and could not since the engine was bucking badly. Turned it off for a minute to try out a new voltage regulator (no change in alternator light with new VR) and the engine was now running smoothly enough for me to time it and set the idle.

I could not get the spark plugs out. All I have the standard spark plug socket and extensions. I know we put anti-seize on the threads when we installed them. Any suggestions? More elbow grease? A different tool?

Here is the list of what I have done so far as I can recall:

-Checked and cleaned FI grounds, transmission strap, battery cables, double relay
-Installed and removed new double relay
-Installed new fuel pump and filter
-Cleaned starter connections
-Checked old coil resistance cold and warm , all OK
-Installed new coil
-Installed NOS vacuum advance distributor
-Installed new points and condenser
-Adjusted timing
-Checked dwell
-Checked for vacuum leaks
-Checked vacuum with pressure gauge
-Checked AFM for scratches, cleaned AFM board
-Resistance check of AFM per Bentley
-Voltage check of AFM door
-Installed and removed new VR
-Unsuccessful attempt to remove spark plugs
-Valve adjustment
-Checked 2012 temp sensor ll for tightness
-Checked 2012 temp sensor ll resistance
-Checked ECU plug for bent/broken connections

Still to do:

-Remove spark plugs and inspect
-check fuel pressure
-install new 2013 TSll
-install loaner AFM and test with loaner LM-1

Here is something that may not be conclusive at this point. Last year I installed a grounded wire to plug in the TSll as a "limp home" option per Ratwell. When I hooked up this wire to the again new TSll last year, I was able to drive the bus without issue. I think I did something to the existing wire to the ECU as I thought this was the problem. Plugged in the TSll and drove a few hundred miles before the problem returned.

Fast forward to this weekend. I decided to unplug the TSll and plug the wire into the little grounding pigtail that I installed just to see what would happen. It seems that the problem cleared up almost immediately. Now, this problem can frequently go underground, but lately it crops up right away to the point that I cannot drive it more than a few feet. I did not drive it it, but could not seem to get it to buck in the garage as it had only just a few minutes before. I need to do some more testing and get it out for a drive. I live on a high spot and I am very hesitant to go too far since I do not want to be towed home again so my test drives tend to be rather short.

I fear this is just a temporary anomaly, but wanted to post this observation just in case it leads to a path that I should be checking.

Thank you.