On our way to Lake Tahoe up Highway 50 I had probably one of the most scary problems in a motor vehicle in my 54 years of driving! This was almost as heart stopping as the engine failure I had in my Cessna 210 on takeoff!

Just after we had gone past Placerville, and getting close to the summit, Highway 50 goes to 2 lanes, there are turnouts and passing lanes but for the most part is is 2 lanes from there all the way to South Shore, Lake Tahoe. Just before the summit, I passed a couple of 5ers and had gone back to my single lane and I noticed that the speed was starting to increase, the passing lane was upgrade and I was at full throttle and after the passing lane it leveled off a bit so I was surprised to see the speed increase. My first thought was that I had inadvertently triggered the cruise control, (it was set to 70) and I was at 55 but now starting to accelerate fast as we were starting down grade!

I tapped the brakes, NOTHING, I switched off the cruise control, NOTHING, when I put my foot on the accelerator pedal, it was fully depressed and not coming back up. I reached down and pulled up the pedal, I know the cable is a pull only system, but tried it anyway, NOTHING! still accelerating, now up to 60, fortunately, a slight upgrade was helping to keep the speed increase down, I told my wife we had a serious throttle issue and don't be surprised if I make some sudden moves! Told her to stay calm, I had control of the situation.

I was pulsing the brakes very hard then backing off to keep the speed down, and looked for the next turn-out. about 1/2 mile later, found a good place and put the trans in neutral, braked hard and pulled into the turn out! I had gotten the speed down to about 40 before I turned out but the traffic behind me was starting to catch up.

The engine RPM went to top of the governor, about 2700-2800 RPM but that wasn't a big issue, I just got into the turnout, stopped safely, pulled the "E" brake , hit the fourways and then quickly went to the rear to open the bed to get the engine throttled down. YES, I did consider switching off the engine BUT, this is a diesel and it will run all day long at the top of the governor without damage, if I switched off, most like the turbo would suffer damage. (gasoline engines would be a different issue)

Once the bed was up, I reached down and found the throttle stuck in the mechanism somewhere and with a firm yank, got it pulled back into the idle position.

WHEW!

Stopped safe, engine now idling, Now time to get my heart off of full throttle position and relax a bit.

After about 5 minutes of idling I switched off the engine and started to trouble shoot the situation. What I found was the TPS bracket is bolted on to the injection pump with 2 bolts and one of them had backed out, making contact with the throttle linkage, it had back out far enough to prevent the throttle from returning to idle position, probably because I was running at full throttle for long periods of time on the upgrades on Highway 50 the bolt could now back out further and hold the throttle full open without my feeling the interference opening and closing the throttle.

My first thoughts were did I forget something in all the previous work with the TPS system, NO, I had never touched these bolts, no reason to, so this just "happened"??!!

Bolt backed out:


After I got the throttle to idle postion:


Bolt back in showing proper clearance:


I can not say whether or not a previous mechanic had taken out these bolts ( the other was loose!) but I can say I had never touched these bolts. I do know that the TPS linkage was worked on and cobbled up when I bought the coach, so it is possible that these bolts were previously removed.

Is this an isolated incident? probably, BUT, I would strongly recommend any one with this type of TPS bracket, inspect the bolts for tightness at your next opportunity!

Ed, thank God that you both are OK. Must have been a bunch of angels working overtime to keep you safe.
Jim

Wow! Scary.

Are ya gonna drill and safety wire the bolts?

Wow Ed, good job keeping a cool head!!!

I hate to say this, but if it were going to happen, I'm glad it happened to someone with your mind for mechanics and rational action. Otherwise, it could have been catastrophic.

Just curious, were you worried about the turbo starving for oil on a high rev shutdown?

I didn't shut it down until I had it idling for 5 minutes. Sure that was one of my concerns but not one that had an influence on the procedure.

I am watching the boost closer now on the continuing portion of my trip to see if there has been effect of 2-4 minutes at no load full throttle. So far all is good!

Safety wire? Bill how did you know I am an "X" aircraft mechanic? the answer is:

YES