Attention: TDR Forum Junkies I asked Piers what causes the bucking I have observed three times in the last 18 months when towing with my 97 automatic. He thought the problem was probably throttle return springs. I searched the TDR site and found:
http://216.235.147.117/forums/showthread.php?s=&threadid=28253&highlight=throttle+return+springs
There is a 1997 TSB, TSB 18-29-97A, that is for bucking with 5 speed transmissions. The TSB costs about $200 and has revised throttle arm and springs. Apparently when you bomb an automatic, you can also get conditions of low rpm (1200-1500 rpm) and light throttle with TC lockup that can initiate throttle oscillation and bucking as observed with the 5 speeds.
Issue 18, page 22, of the TDR has an article on bucking and changing the throttle return springs to cure it. I went to the dealer and found that the part numbers for heavier throttle return springs has changed in the last 5 years.
The current number for 94-96 vehicles is 4874476. This is a double spring, one spring inside the second spring. This double spring replaces the original single throttle return spring. The new spring is about $3.
The 97-98 12 valve engines have two side-by-side throttle return springs. The TDR issue 18 article called out replacement of the throttle return spring toward the outside of the engine/pump. The curent part number for the outside spring is 5003737AA and about $30. 00. The current part number for the inside spring is 4883996AA and about $5. 00.
The inside spring appears the same as the two original springs The expensive outer replacement spring is larger diameter wire and coil and appears to be about 3 times as stiff as the original spring.
I replaced both springs on my 97 and found the inside spring had been stretched out about 3/8 inch (since original installation?). After installation the accelerator pedal pressure appears to be 2-3 times higher than before. Hopefully this will prevent any future bucking.
http://216.235.147.117/forums/showthread.php?s=&threadid=28253&highlight=throttle+return+springs
There is a 1997 TSB, TSB 18-29-97A, that is for bucking with 5 speed transmissions. The TSB costs about $200 and has revised throttle arm and springs. Apparently when you bomb an automatic, you can also get conditions of low rpm (1200-1500 rpm) and light throttle with TC lockup that can initiate throttle oscillation and bucking as observed with the 5 speeds.
Issue 18, page 22, of the TDR has an article on bucking and changing the throttle return springs to cure it. I went to the dealer and found that the part numbers for heavier throttle return springs has changed in the last 5 years.
The current number for 94-96 vehicles is 4874476. This is a double spring, one spring inside the second spring. This double spring replaces the original single throttle return spring. The new spring is about $3.
The 97-98 12 valve engines have two side-by-side throttle return springs. The TDR issue 18 article called out replacement of the throttle return spring toward the outside of the engine/pump. The curent part number for the outside spring is 5003737AA and about $30. 00. The current part number for the inside spring is 4883996AA and about $5. 00.
The inside spring appears the same as the two original springs The expensive outer replacement spring is larger diameter wire and coil and appears to be about 3 times as stiff as the original spring.
I replaced both springs on my 97 and found the inside spring had been stretched out about 3/8 inch (since original installation?). After installation the accelerator pedal pressure appears to be 2-3 times higher than before. Hopefully this will prevent any future bucking.
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