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Loss of torque

Yahoo Message Number: 16553
I had a strange thing happen while driving my 2000 Intrigue this last weekend. I would appreciate any insight anyone can give me into what it could be.

I was driving up the Grapevine on I5 in California, heading south.
After some heavy climbing, things had leveled off, and I came around a corner and there were workers on the side of the road, so I slowed down. Upon attempting to accelerate, I had no response, and I looked at the Silverleaf and noticed my torque was dropping. I frantically started downshifting, but the torque was still dropping. Finally, the Silverleaf showed me in first gear, with zero torque, despite my applying full throttle. I looked out the rear view mirror and black smoke was POURING out the exhaust.

The sensation was as if the transmission was in a higher gear, even though the Silverleaf indicated first. It was as if the engine was severely lugging down. I managed to coast to the side of the road, where I put it in neutral and set the parking brake. Even idling, it was smoking, but less and less. Finally, after about thirty seconds, it was idling normally. I put it in drive and pulled out, and everything was normal. Torque climbed right up, and it was as if nothing had happened.

If I had been in a place where I could not get off the road, I would have been in trouble. This was scary.

I checked the Silverleaf for any engine diagnostics, and there were no errors. I continued on my trip with no further difficulties.

Anyone have any ideas? FYI, I have the Cummins 350 IHC engine with Allison MD transmission.

Re: Loss of torque

Reply #1 –
Yahoo Message Number: 16554
Quote
I frantically

started downshifting, but the torque was still dropping. Finally, > the Silverleaf showed me in first gear, with zero torque, despite my > applying full throttle. I looked out the rear view mirror and black > smoke was POURING out the exhaust.
We had exactly the same thing happen a few years ago on a 95 Magna. The problem, at least for us, was a stuck valve on the Pac brake. We had to replace the valve - I remember the feeling you described (and the black smoke) all too well.

Diana Powell

2004 Intrigue #11705

Re: Loss of torque

Reply #2 –
Yahoo Message Number: 16564
You can be sure the problem is in your PacBrake. The butterfly valve can stick and cause this problem. I had a 2000 Intrigue with this problem and had it happen on a two-lane crooked road in nothern Arkansas. What a helpless feeling! I found that by rocking the transmission from R to D I could finally break it loose. Cummins actually replaced my fuel pump under warranty before we found the real culprit.

Walt Rothermel
03Allure30811

Re: Loss of torque

Reply #3 –
Yahoo Message Number: 16565
Definitely a stuck Pac brake -- probably sticks only when hot, as you should be able to see it quickly cycle when you watch it and have someone else turn the ignition key on (no need to start engine). I had it stick after a long upgrade, then a short downgrade with the Pacbrake on, followed by the failing upgrade on two different occasions, until I started regular --required-- lubrication of the Pac brake at least every year. Pac Brake sells the lube in a small squeeze bottle. Frightning experience, when it happens.
Herb

2002 Allure #30690

Quote from: allan_colby
I had a strange thing happen while driving my 2000 Intrigue this

last

Quote
weekend. I would appreciate any insight anyone can give me into

what

Quote
it could be.

I was driving up the Grapevine on I5 in California, heading

south.

Quote
After some heavy climbing, things had leveled off, and I came

around

Quote
a corner and there were workers on the side of the road, so I

slowed

Quote
down. Upon attempting to accelerate, I had no response, and I

looked

Quote
at the Silverleaf and noticed my torque was dropping. I

frantically

Quote
started downshifting, but the torque was still dropping. Finally, > the Silverleaf showed me in first gear, with zero torque, despite

my

Quote
applying full throttle. I looked out the rear view mirror and

black

Re: Loss of torque

Reply #4 –
Yahoo Message Number: 16569
I had precisely the same thing happen to me several years ago on SOB with a Cummins C8.3. I was climbing a grade, at high elevation with exhaust brake on, but of course, not deployed because I was all the way into the throttle. Something happened that forced a slow down and thus an acctuation of the exhaust brake. Then, had no power and much black smoke. Sat for a moment, smoke cleared and away I went.

Problem is that high exhaust gas temps cause slight deformations in the exhaust brake so that when deployed it sticks closed. This results in rich mixture and black smoke. Stuck brake releases when cooled and off you go.

I suggest that you lube the exhaust brake per specs and hope that helps/

George Sanders
Allure 31038

Quote from: allan_colby
I had a strange thing happen while driving my 2000 Intrigue this

last

Quote
weekend. I would appreciate any insight anyone can give me into

what

Quote
it could be.

I was driving up the Grapevine on I5 in California, heading south.
After some heavy climbing, things had leveled off, and I came

around

Quote
a corner and there were workers on the side of the road, so I

slowed

Quote
down. Upon attempting to accelerate, I had no response, and I

looked

Quote
at the Silverleaf and noticed my torque was dropping. I

frantically

Quote
started downshifting, but the torque was still dropping. Finally, > the Silverleaf showed me in first gear, with zero torque, despite

my

Quote
applying full throttle. I looked out the rear view mirror and

black

Quote
smoke was POURING out the exhaust.
> The sensation was as if the transmission was in a higher gear, even > though the Silverleaf indicated first. It was as if the engine was > severely lugging down. I managed to coast to the side of the road, > where I put it in neutral and set the parking brake. Even idling,

it

Quote
was smoking, but less and less. Finally, after about thirty

seconds,

Quote
it was idling normally. I put it in drive and pulled out, and > everything was normal. Torque climbed right up, and it was as if > nothing had happened.

If I had been in a place where I could not get off the road, I

would
George in Birmingham
2003 Magna 6298
 

Re: Loss of torque

Reply #5 –
Yahoo Message Number: 16572
Quote from: George Sanders"
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George, et. al.

Let's see if I can add a little to the discussion. Several years ago in an SOB I experienced the same event just as I was leaving town. I didn't know what is was so went to a local freightliner. What a joke! Three bills later I left without the pac=brake working. When I researched and learned how everything worked I removed the air solenoid and found that mud dabbers had plugged the relief port. When clean everything worked fine. Now, another issue. Their was a fued between Jacobs and Cummins regarding backpressure and oil blow-by.
End of story was that I removed the section of exhaust containg the pac-brake and installed a new butterfly. In doing so one has to be carefull to maintain clearance between the edge of the butterfly and the inside of the exhaust chamber. By using a piece of thin shim material this is easily accomplished. I have forgotten the exact thickness of the shim but a call to the pac-brake manufactured should help here. The point of all of this is that through constant use tolerances can change. Removing the entire pac-brake assembly is not too tough, if your bones still bend a bit, and tolerances can be checked. Some minor fileing might be in order to prevent butterfly sticking. JUst a thought or two.

Lyle Wetherholt
04 Intrigue 11740
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