Rough Running Engine

I only did a dry compression test. I can do a wet test if needed, I just didn't have anything handy to get oil into the cylinders.

I pulled out all plugs, stuck a screwdriver in the air intake to hold it open, and pulled the coil wire, then cranked the engine about 5 times and took my readings.

All were between 170-180psi, except cylinder 4 which was 162. I think these readings are acceptable considering the mileage on this truck.

Oddly the plugs from cylinders 5 and 6 were already very black (only in for two weeks) 6 was probably non-functional, as it was just a big glob of tar like substance on it. The engine does not use a lot of oil, and does not smoke.

I cleaned the plugs, checked the gap at.06 and replaced the plugs.

Now the truck won't start at all.

It does not seem to have any spark at all. Perhaps I have finally found my problem or maybe caused a new one. I double checked all the wires, and made sure I hadn't bumped anything while working and didn't see anything. With a screwdriver in the end of a wire, I got no spark at all when turning the motor over.

Is it possible I harmed the coil?

Is there a way to test the coil and/or ignition module with a standard multimeter?

Thanks.

That is a very helpful and thorough, step by step procedure.

I kinda got thrown off on step 5, since the coil connector is not labeled, I assumed the 'pink' wire was 'C' and was chasing my tail until I looked at a wiring schematic. Then I assumed the 'black/wht' wire was 'C' since it was connected to the control module.

Assuming that is correct, I then proceeded down to until I got to step 12, where I did not show the 1-4 VAC, I only showed about.4 VAC on my meter.

I was not sure which connector was the 'VCM C3' connector, or which terminal was the ignition control (IC) circuit as described in steps 15-17, but I did disconnect all plugs from the module, then re-connect.

At this point, I am assuming it is the VCM since I do not seem to be getting hardly any AC control voltage to the Ignition Control Module.

If you have any other ideas, I would appreciate it.

Im having the same problem any fixes?

Hi, I found out that the distributors on the vortecs wear out and cause these problems, some say only 100,000 miles. Mine is 243,000, but a new one fixed it. The OEM are plastic and the shaft starts to wobble as they wear and age and produce misfires. Got a new one made from aluminum with cap and sensor for $34 on eBay, works great. I first had changed everything from sensors to filters and injectors, but it was the distributor. To set the new one on a vortec you have to use a scan tool, you are really setting the cam sensor since the engine is self timing. Instead I bought an app, Car Gauge Pro and a obd2 blue-tooth adapter I got on eBay (BAFX) and set mine for under $35.

97 k1500 silverado 5.7 I had to crank the engine over for about 30 seconds until it finally started. After that it starts right up and seems to idle fine and it seems fine when I step on the gas in park. When I took it for a drive it spits and sputters. I changed plugs and wires but still spits and sputters. Please help!

Its a 5.7 vin#R

You could have a fuel pump bleeding down. Get a pressure gague on it and turn the key on and then off and then see if the pressure drops very fast?

97 Silverado 1500, 40,000 miles, 5.7L with auto trans, 2wd. Over the past month the truck has turned itself off (died) 3 times. All 3 times, I dropped it into Neutral and it re-started without a problem. The first time was at a red light, the next time was while going about 20mph, and the last time was while driving about 40mph. I don't notice the truck running rough or any other indications of trouble right before or right after it happens. I'm not real sure what is going on, but am affraid that eventually it won't re-start. Any ideas?

Not familar with a crank angle sensor. What is involved in repair/replacement? Is there a specific brand/type sensor you would recommend?

Ive had this same problem 4 the last 2 years, I have changed the gas pump, distributor, crank shaft sensor and the problem has not gone away, the computer will not show faults. Let me know if you have an answer for this problem and good luck.

Mamalonsisimo.I'm going to start with the crank angle sensor and see what happens. Hopefully that will fix the problem. I saw your post and see that you already replaced this along with several other things and you're still having trouble. Thats no bueno.

I just rebuilt my chevrolet Chevrolet K-2500 350 5.7L T.B.I. V-8 out of my 1992 K-2500. The engine had locked up so I rebuilt from the bottom up. When I start the engine the idle is rough and only keeps running with assistance. After about thirty seconds the engine will die no mater what
Engine is in initial start up and break in phase of rebuilding.
New piston Rings, main bearings, rod bearings, TPS, oil pressure sending unit, cam bearings, new stock camshaft, lifters, valve seals, professionally cleaned all engine parts, qualified all non replaced engine components, new timing chain.
Adjusted rocker arms, checked timing, verified vacuum hoses are in good order and correctly placed. Crankshaft was professionally ground and polished to 10/10.