Rough Running Engine

Tiny
CNTRLFRK
  • MEMBER
  • 1997 CHEVROLET SILVERADO
Engine Performance problem V8 Four Wheel Drive Automatic 350000 miles

I have a Silverado C1500 with a 5.7L 350 Vortec engine. The engine will idle fine, but rough and will run so rough going down the road that it will literally shake the entire truck. Power has dropped and passing someone on the highway is nearly impossible.

I've changed plugs, wires, distributor cap, rotor, coil and fuel filter. I've even pulled both upstream O2 sensors to see if I possibly had a plugged Converter or Muffler, but this did not seem to help.

I know this truck has a lot of miles, but has always run well, and I've run out of ideas. The OBD scan shows "Manufacturer Ignition Control or Misfire" or something similar.

Any ideas?
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Tuesday, June 24th, 2008 AT 10:32 AM

116 Replies

Tiny
MERLIN2021
  • EXPERT
If you have the actual error code it would be helpful, but with 350,000? miles, it can be valve springs or other internal engine parts, start with a compression test, wet and dry! post results here...

This guide can help

https://www.2carpros.com/articles/engine-misfires-or-runs-rough
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Tuesday, June 24th, 2008 AT 5:45 PM
Tiny
CNTRLFRK
  • MEMBER
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?
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Thursday, June 26th, 2008 AT 8:25 AM
Tiny
MERLIN2021
  • EXPERT


http://www.2carpros.com/forum/automotive_pictures/62217_Ignition_testa_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_Ignition_testb_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_Ignition_testc_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_Ignition_testd_1.jpg

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Thursday, June 26th, 2008 AT 1:42 PM
Tiny
CNTRLFRK
  • MEMBER
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.
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Friday, June 27th, 2008 AT 8:43 AM
Tiny
JWIN9569
  • MEMBER
Im having the same problem any fixes?
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Tuesday, March 21st, 2017 AT 2:26 AM
Tiny
KEN
  • ADMIN
These trucks had a problem with the injectors. Replace all of the injectors or just the ones over the cylinders with the black spark plugs.

Please let me know if you need anything else to get the problem fixed.

Best, Ken
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Thursday, March 23rd, 2017 AT 7:45 AM
Tiny
ALASKABOBB
  • MEMBER
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.
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Friday, October 19th, 2018 AT 9:38 AM
Tiny
KEN
  • ADMIN
Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help

Cheers, Ken
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Friday, October 19th, 2018 AT 11:33 AM
Tiny
KILMERONE
  • MEMBER
  • 1997 CHEVROLET SILVERADO
  • 170,000 MILES
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!
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
FIXITMR
  • MEMBER
What motor?
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
KILMERONE
  • MEMBER
Its a 5.7 vin#R
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
CHEVYFORLIFE
  • EXPERT
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?
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
FIXITMR
  • MEMBER
No CEL on?
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
ZDIETRICH
  • MEMBER
  • 1997 CHEVROLET SILVERADO
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?
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
JACK42
  • MEMBER
There were problems with the Crank Angle Sensors in those CPI engines. Caused no starts and intermittent stalling
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
ZDIETRICH
  • MEMBER
Not familar with a crank angle sensor. What is involved in repair/replacement? Is there a specific brand/type sensor you would recommend?
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
JACK42
  • MEMBER
Should be in the bottom of the timing chain cover. Very easy to replace yourself
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
MAMALONSISIMO
  • MEMBER
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.
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
ZDIETRICH
  • MEMBER
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.
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Friday, October 19th, 2018 AT 11:34 AM (Merged)
Tiny
CVG1MAK
  • MEMBER
  • 1992 CHEVROLET SILVERADO
  • 210,000 MILES
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.
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Friday, October 19th, 2018 AT 11:35 AM (Merged)

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