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90 Chevy Silverado - Severe Misfire
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a1handy
User
Mar 1, 2014, 10:26 AM
Post #1 of 15
(2044 views)
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90 Chevy Silverado - Severe Misfire
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I have a 1990 Chevy Silverado that just had the flywheel replaced. When the transmission was reinstalled the truck began to have a severe misfire. This had not happened before, the truck had ran great. What could have possibly be done to create this problem. The engine was not worked on at all. Where can I start? Vaccume leak....
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Hammer Time
Ultimate Carjunky
/ Moderator
Mar 1, 2014, 10:56 AM
Post #2 of 15
(2027 views)
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Re: 90 Chevy Silverado - Severe Misfire
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They may have let the engine hang enough for the distributor to hit the firewall and damage it.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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a1handy
User
Mar 1, 2014, 1:27 PM
Post #3 of 15
(2012 views)
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Re: 90 Chevy Silverado - Severe Misfire
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I repaced the distributor cap and rotor with no change. I have also noticed a lot of fuel useage and backfiring as well. Additionaly, the heater motor is will only run on low and the indicators are only partially working. The alternator shows that it is only charging at about 11 volts. Someone told me I may need to reset the computer? Is this a possibility? Could all of these other issues with the electrical components be related?
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Discretesignals
Ultimate Carjunky
/ Moderator
Mar 1, 2014, 1:32 PM
Post #4 of 15
(2009 views)
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Re: 90 Chevy Silverado - Severe Misfire
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Engine controller has nothing to do with the charging system, indicators, or blower fan. Something happened during your repair. Go back and inspect everything you touched. Visually inspect your grounds, wiring, and connectors. Make sure nothing got pinched or damaged.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Hammer Time
Ultimate Carjunky
/ Moderator
Mar 1, 2014, 1:34 PM
Post #5 of 15
(2006 views)
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Re: 90 Chevy Silverado - Severe Misfire
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No, forget about the computer. You just have to approach this like any other misfire. You first have to identify which cylinders are missing and then why they are missing. That means determine whether it's spark, fuel or compression missing.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 1, 2014, 7:47 PM
Post #6 of 15
(1992 views)
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Re: 90 Chevy Silverado - Severe Misfire
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?? Everything was fine except the flywheel/ring gear which requires trans out and back and now all this from the top.
What engine/trans but not really important. Most common would be the 5.7 and an automatic. Starter motor wires - all that removed, engine would tilt as first said by HT. Trans dipstick (if auto) is on passenger's side along with blower motor I think and that may have been fight.
Now not charging at all if showing 11V. It's going to quit running at all real soon. Wires, hoses and distributor in back all need to be checked for what got pinched, cut, left unplugged or what IMO.
It's NOT CHARGING AT ALL and that alone would quickly make it run like crap and not restart without a boost. Are we on the same page?
T
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a1handy
User
Mar 7, 2014, 2:00 PM
Post #7 of 15
(1968 views)
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Re: 90 Chevy Silverado - Severe Misfire
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Still have not resolved problem. Have notice a couple of new things however. Motor runs great when cold. Alternator charges great when cold. When motor heats up amperage drops and motor loads up. Cannot see anything pinched or unplugged.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 7, 2014, 2:33 PM
Post #8 of 15
(1960 views)
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Re: 90 Chevy Silverado - Severe Misfire
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Try this much. Unhook neg battery cable at battery.
Now go down to starter and take all those wires off, clean them up with sandpaper or wire brush, smear of grease and put them all back exactly as they were. Look for any wrinkled wire insulation on a smaller gauge wire right around there or as far as you can chase them.
Go ahead and clean pos battery cable too while neg is off then put neg back last. May have wire to inner fender right from the neg battery so clean that up too.
You are losing voltage somehow now noted temp sensitive. Not a total surprise as dissimilar metals expand and contract at different amounts.
Ok: Look at main ground cable too to I think side of driver's side block of engine? Wherever it goes.
This stuff got yanked on so even if it was all new took a hit somehow. You've seen 11V (truck's gauge or what?) but when it gets below about 9.5 not much electrical is going to behave. At that point I'm surprised if this would re-start if shut down on purpose.
#1 is this didn't have this problem before so anything that could have been tugged at is in question. IDK, does main battery cable down to starter touch hot exhaust - anything like that,
T
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a1handy
User
Mar 7, 2014, 3:46 PM
Post #9 of 15
(1955 views)
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Re: 90 Chevy Silverado - Severe Misfire
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Is the main ground cable a braided non insulated wire? Maybe about 8-12 inches long. Am I understanding your thinking when you are saying that the conductivity needed is affected by the temperature of the engine/components? Higher temperature decreasing the conductivity and affecting operation of the engine? Would this have a direct effect on the fuel mixture or cause the engine to load up? Thanks
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 7, 2014, 7:42 PM
Post #10 of 15
(1944 views)
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Re: 90 Chevy Silverado - Severe Misfire
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Not braided for that wire and at the age could be moved to anywhere else that is well grounded to block. It's not heat alone like glowing hot causing loss of electrical power rather a maybe of a connection or hot spot doesn't connect well or rugs thru insulation.
It isn't going to run well with improper power as it declines fuel pump, ignition are all under powered as is every sensor for anything that enough to take care of first. For all I know this could be a loose fan belt screwing you up,
T
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a1handy
User
Mar 8, 2014, 6:17 AM
Post #11 of 15
(1920 views)
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Re: 90 Chevy Silverado - Severe Misfire
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The reason I asked if the wire was braided is because I noticed a ground wire not connected during one of my inspections. The wire was flat and not insulated, about 1/4 inches wide and was connected to the compartment on the right side. It was not connected to the engine. I assumed (apparently incorrectly) that this was insignificant. I will connect securely to the engine and see if that helps. I also should mention that when these other problems happened my heater controls went dead. The display will only show parts of what it usually does and these parts change. Also the heater controls are now unresponsive. This could also be a result of a poor ground. Thanks
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 8, 2014, 6:31 AM
Post #12 of 15
(1916 views)
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Re: 90 Chevy Silverado - Severe Misfire
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What you describe probably goes frame to firewall or body metal. They put them all around and not to waste money it was needed or wouldn't be there.
Battery cables since about the 50's have been insulated some with a bare spot to body or frame on way to engine block. Think, most power consuming item in about any vehicle is the starter motor so gets first and strongest shot at battery power. To run it needs everything else,
T
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Hammer Time
Ultimate Carjunky
/ Moderator
Mar 8, 2014, 7:09 AM
Post #13 of 15
(1903 views)
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Re: 90 Chevy Silverado - Severe Misfire
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Definitely not insignificant.
The battery has to be tied to the engine and the engine has to be tied to the body for everything to work.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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a1handy
User
Mar 10, 2014, 2:28 PM
Post #14 of 15
(1883 views)
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Re: 90 Chevy Silverado - Severe Misfire
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Wanted to thank all that offered their help and advice. While searching for any and all weak grounds I noticed a broken sensor, I later was informed by the clerk at Auto Zone that the sensor was an Oxygen sensor. I repalced the sensor and all my troubles disappeared. It seems the Oxygen sensor is important in the amount of fuel distributed to the engine and when this one was damaged it caused the engine to overload. Thanks again
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 10, 2014, 2:38 PM
Post #15 of 15
(1881 views)
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Re: 90 Chevy Silverado - Severe Misfire
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Can't argue the fix if plain broken. Glad it's fixed. Closed to keep spammer out and you can re-open upon request to any moderator,
T
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