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Weird cold-motor lurch
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=3094		 Page 1 of 1
Author:  dog_party [ Sat Oct 29, 2005 1:54 pm ]
Post subject:  Weird cold-motor lurch
I had a strange experience last night. We went to a concert and left after dark. It was about 50 degrees, so I let the truck warm up a little bit before pulling out. We drive about 40 yards to the first traffic light which is red, so I hit the brakes and we come to a nice...slow...stop, at which point the truck lurches forward about a foot and the engine dies. I feel like the truck only went a foot because I was still full-foot on the brake pedal, but I'm not certain of that fact.

For those of you who are as accustomed to driving manual trannys (and as unaccustomed to driving auto trannys) as I, imagine sitting normally at a red light (feet left-clutch/right-brake, tranny in 1st)...now let off the clutch, hold the brake and let the motor stall. That's what the Dog Wagon did last night. But this thing is automatic...(shrug). I mean, I'm not a huge fan of the shifting pattern of this tranny in all driving situations, but that's the nature of an auto tranny...no shift pattern is perfect for everyone. Maybe I'm weird, but I would sure like the truck to stay stopped when I'm telling it to stay stopped.

The engine started right back up and we had no problems after that. But I can see that vehicular behavior being pretty dangerous if one weren't paying attention.

Anyone know what might cause something like this???
Author:  Derek Mc [ Sat Oct 29, 2005 2:02 pm ]
Post subject: 
Mine did the same too, however it was around 60F the and had only 45 miles on her. I started her in the carpark at work let her idle for about 10 secs while I fastened mt belt, selected D and moved about 10 yards to the exit stopped and she did the exact same. I was a bit concerned if anyone can advise.
Also today I took the Jeep for a spin with my baby daughter, along the coastline. After about 40 minutes I started to smell raw diesel but assumed it was from a truck or bus and I ran over it with my tyres. I drove on but the smell persisted and eventually I decided to stop in at the dealer where luckily the workshop was still open. They looked immediately and found the fuel return line had come loose so I was pumping diesel out good style. They have fixed it and steam cleaned underneath but I can still smell it!
Annoying but could have been very serious. :o
Author:  CTKJ [ Sun Oct 30, 2005 9:45 am ]
Post subject: 
It sounds like the computer is down-shifting the tranny back to first gear a little late (the torque made the vehicle lurch). It probably was between first and second gear when you began applying the brakes. Since the vehicle was not completely warm the shift was a little hard and delayed.
Author:  oldnavy [ Sun Oct 30, 2005 10:32 am ]
Post subject: 
VW's TDI automatic's have a built is slippage for cold starts, and it's not really weather related. It about letting fluid circulate and raising the tranny temp to prevent sudden grabbing of clutches. It's strange to get into a car and put into gear and it revs but just barely goes and as it's driven a few feet it gently catchs and off you go. It's all done in the computer software for the tranny or main CPU. I suspect you guys may need a trans computer or the main computer or both reflashed. The initial install of the software may have not properly installed itself, and it needs to be reflashed. In some types of memory used (I'm not sure, but I think this applys here) this is not possiable to do a second time and would require a new trans control module or main CPU to be replaced to correct the problem. Good luck this flashing always requires a service dept to be savy with electronics & computers. That's why the diesel tech is going starting to get short of qualified tech's as most are not into electronics and computers and these are leaving the service dept's bare in people who really understand how to diagnoice and fix problems on the new compurterized car & trucks both gas & diesel.
Author:  bbo [ Sun Oct 30, 2005 8:46 pm ]
Post subject: 
I had an incident real similar to yours ... when I took the CRD in for brake issues they reflashed as an attempt to correct for this.

Don't know if it worked as it only happened once and hasn't happened since ( three weeks between incident and flash ... oct 3rd was service date and no issues since then either ... )
Author:  Derek Mc [ Mon Oct 31, 2005 10:16 am ]
Post subject: 
I have not had it happen again either but I have been aware of the potential so tried to ensure i was ready for it.
so far so good.
Author:  dog_party [ Fri Nov 04, 2005 9:51 am ]
Post subject: 
I think you guys hit it right on the head. Since the original strange incident I've been focusing on the shift patterns and behaviors more. It's definitely more apparent when it's not warmed up, I even had the "put into gear and it revs but just barely goes and as it's driven a few feet it gently catchs and off you go" happen to me in the parking garage one afternoon. But I notice the computer-control trying to do the same thing when it's warm too. I was cruising along at 55 when the light turned red. There was a cruiser sitting at the light, so I decided to test the performance characteristics and structural integrity of the braking system, syspension, and little DC cargo rack by jamming on the brakes. I'd like to report that the brakes work great, the suspension doesn't compress too horribly much, the cargo rack kept a bottle of Diesel911 and a tub of hand degreaser from hitting me in the back of the head, and I only received a squinty-eyed nod from the officer. But the tranny did the downshift-to-first lurch even under heavy braking. I had the truck in line to stop just before the stripe, then, at the last moment, the tranny went down to first and gave me a little extra torque to brake against, taking me an extra foot or so.

Maybe I'm just being picky. I'm so accustomed to driving with a clutch that it feels weird to have the engine pulling against me when I'm braking. I'm taking the truck in for an oil change before too long...I'll ask them to reflash the main and tranny computers and see if that changes anything. Is there a specific certification that I should look for in a diesel mechanic?

Thanks for all the input!!!
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