Chevrolet Repair: 1997 k1500 silverado extra cab 4wd, nose dives, google search

Question
hello my name is Cameron Rockett i am 18 and i live in Georgia and i work at a shop called DJ's Auto Repair we have had this truck for a few weeks now and we cant seem to figure out that the problem is. it seems to have a really bad miss. when you are driving it at about 30mph it will cut off for almost a second and throw you into the dash. we have also put it in gear in the shop with the parking break on with the computer hooked up torquing it out and all 4 cylinders on the right side of the motor show a quick miss. what i have noticed is that when i keep the motor in a closed loop as if it were cold it wont fall on its face. but as soon as i turn it to open loop as if it was hot and running properly and torque it out she will miss again. we have taken it to the dealership and they said it was fuel volume messing up and it needed a fuel pump but the only time the fuel volume messed up was when it nose dives. it has a 100,000 miles on it and looks brand new. i have done a complete tune up on it tried a new computer, new wiring harness, temp sensor, you name it i most likely have tried it. so if you have any advice or what you think it is, we will be very appreciative for giving us your time.

Answer
Hi Cameron.... Do you have a lab scope, if you do connect it to the ign module and set the parade as slow as you can get on your scope. load up the engine and watch the parade, note what it looks like when it misses...if you can freeze it and print would even be better... there is a web site that you can go to, and compare waveforms against known good ones...i can't think of the name of the web site but i am sure a google search would find it. if waveform turns out to be good for the ign module you will need to look farther in the ign system. you don't say what engine and ign system it has, so i will assume that it is a 5 L with dist ign.... take a look at the dist check bushing in the dist shaft, i have run across that when they have excessive wear in that bushing, the dist will have too much run out under load causing the reluctor to touch the pick up creating a miss...another problem i have run into on those trucks in in the cap...even brand new ones...check for crossfire in the cap under load. also one i just did one that drove us nuts was kinda the same problem ended up being the plug at the coil having intermittant loss of contact in the plug under load...it also would go down the road then stumble and quit but restart right away...we changed the plug in at the coil and problem solved...hope this helps...

Bob