95 Sierra bucking violently

[donc]

Hi, new member here.

I have a 95 Sierra 5.0L 5 speed pickup w/61000 miles. While downcoasting or trying to maintain a low speed my truck bucks violently. This occurs after the truck has warmed up. I've noticed that when this happens and I throw in the clutch, the idle will be something like 1200-1500 RPM; normal idle is around 730.
I've already replaced the plugs, wires, dist cap & rotor, O2 sensor and Throttle Position Sensor.

Would appreciate any suggestions before I bring it in to the dealer. Thanks in advance.

[Doug Rodrigues]

It could be anything but the first thing I'd check is for vacuum leaks at the fuel injector body. When those gaskets crack, the idle increases while the mixture becomes too lean. That's the easiest thing to check first. Get back and tell us what you found.

[workaholic2001]

your problem is your ignition coil, when you replaced the dist cap did you remove the groung strap that was in the old one and put it in the new one, or did it even have one? get a new coil, and a new ground strap and your problem will go away

[donc]

Well, it took a long time but the bucking problem has finally been fixed. After replacing O2 sensor, MAP sensor, Coolant Temp sensor and the Throttle Position sensor it turned out to be an intermittent in the ECM. As time went on, the problem progressed from the violent bucking leading to the engine stalling after running like only 4 cylinders were firing.
Hope my pains will help someone else out.
Don

[Doug Rodrigues]

Thanks for your feedback. An intermittent problem is the toughest kind of problem to find. Sure sounded expensive! Glad you fixed the problem.