Can not figure it out
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Cruising
Joined: Nov 2015
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From: Killeen Texas
Can not figure it out
I have a C5 with the 5.7
I have been trying to figure out why it is missing not having any luck. Read a couple of post that said crank variation relearn can someone tell me what this is.
I have been trying to figure out why it is missing not having any luck. Read a couple of post that said crank variation relearn can someone tell me what this is.
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2020 Corvette of the Year Finalist (performance mods)
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we need more info... could be fouled or improperly gapped plugs, bad plug wires, problems in the coil harness wiring, broken valve spring, lots of things can cause a misfire... when did it start and did you do any work to the car before you noticed the issue?
Le Mans Master
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From: OK
Thread Starter
Cruising
Joined: Nov 2015
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From: Killeen Texas
Can not figure it out
I put new plugs in the car put new wires also check to see if all the injectors were working so I just unplugged the wire to the injector and heard if there was a drop in the engine all but #5 would drop and now the car is smoking out the tail pipe.
Thread Starter
Cruising
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From: Killeen Texas
Jefferyrivera
Thank you I have did this and the code P0300 still comes up as soon as I clear code
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take the plug wire off from the plug but leave it connected to the coil and see if there is spark present... if not, visually inspect the coil/injector harness especially where it goes behind the intake... there is a bracket that is known for rubbing on this harness and causing issues... if there is spark and you have brand new plugs you might pull the driver side valve cover just for peace of mind that a spring isn't broken
Thread Starter
Cruising
Joined: Nov 2015
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From: Killeen Texas
I took a 6 hour drive to northern texas got there and everything was fine. a day later I got in the car started it up and it started missing so I checked a couple of things under the hood. no fuses were burnt, there was a hose that comes off the EAVP along side of the intake on the driver side that was off so I put it back on then drove it back 6 hours running with a miss just to get back home. Before this I found there was a miss connection in the wiring harness for the driver side door cause it would roll down or up and the lock stop working when I tried to lock the door.
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Cruising
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From: Killeen Texas
jefferyrivera
take the plug wire off from the plug but leave it connected to the coil and see if there is spark present... if not, visually inspect the coil/injector harness especially where it goes behind the intake... there is a bracket that is known for rubbing on this harness and causing issues... if there is spark and you have brand new plugs you might pull the driver side valve cover just for peace of mind that a spring isn't broken
I will try these two things right now.
Thread Starter
Cruising
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From: Killeen Texas
Thread Starter
Cruising
Joined: Nov 2015
Posts: 14
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From: Killeen Texas
Tech Contributor
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
What PLUGS and What Wires did you use?
Measure the battery voltage directly on the battery terminals with a volt meter ENGINE ON and ENGINE OFF.
Examine the voltage reading on the DIC and IPC Analog Volt meter. ENGINE ON and ENGINE OFF
Compare the voltages. They SHOULD be very close to each other.
Use the schematics provided and examine the primary coil POWER and GROUND and circuit wires.
Measure the ground terminal on each coil harness bank plug to CHASSIS GROUND & ENGINE GROUND and report OHM READING
Examine the GROUND WIRE on the back of the drivers cylinder head and make sure its TIGHT and the wires are properly secured in the eyelet.
Pull the FUSES for the coil circuits and examine the fuses and fuse sockets. Fuse should be clean and fit in the connection TIGHT! Each FUSE has two TEST SLOTS on top of the fuse.
Turn on the IGNITION SWITCH and measure both fuse test slots to Engine Ground and Chassis ground for all the fuses. Report those voltage readings.
HEAD GROUND FOR COILS:
COIL SCHEMATICS:
Measure the battery voltage directly on the battery terminals with a volt meter ENGINE ON and ENGINE OFF.
Examine the voltage reading on the DIC and IPC Analog Volt meter. ENGINE ON and ENGINE OFF
Compare the voltages. They SHOULD be very close to each other.
Use the schematics provided and examine the primary coil POWER and GROUND and circuit wires.
Measure the ground terminal on each coil harness bank plug to CHASSIS GROUND & ENGINE GROUND and report OHM READING
Examine the GROUND WIRE on the back of the drivers cylinder head and make sure its TIGHT and the wires are properly secured in the eyelet.
Pull the FUSES for the coil circuits and examine the fuses and fuse sockets. Fuse should be clean and fit in the connection TIGHT! Each FUSE has two TEST SLOTS on top of the fuse.
Turn on the IGNITION SWITCH and measure both fuse test slots to Engine Ground and Chassis ground for all the fuses. Report those voltage readings.
HEAD GROUND FOR COILS:
COIL SCHEMATICS:
Thread Starter
Cruising
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From: Killeen Texas
Jefferyrivera
Men of this great forum I personnely thank you for helping me figure this problem out. I did everything that everyone had suggested and came up with the same problem. After finding out that I had a defective pressure gage, I used one that my friend had and there was no yes I said no pressure build up in the number 5 cyl. So I took off the valve cover off to find that the push rod for the intake valve was broken in half. Everything looked good except for that rod. I replaced that rod and had no other problems. The runs great with no faults. Now my question is why did that one push rod break, the owner that I bought the car from said that the push rods were all changed at 64,000 miles with brand new ones. Looking at all the other push rods none of them were damaged nor bent to the degree of this one. Again thank you for all your help and knowledge.
Melting Slicks
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From: Round Rock Texas
Men of this great forum I personnely thank you for helping me figure this problem out. I did everything that everyone had suggested and came up with the same problem. After finding out that I had a defective pressure gage, I used one that my friend had and there was no yes I said no pressure build up in the number 5 cyl. So I took off the valve cover off to find that the push rod for the intake valve was broken in half. Everything looked good except for that rod. I replaced that rod and had no other problems. The runs great with no faults. Now my question is why did that one push rod break, the owner that I bought the car from said that the push rods were all changed at 64,000 miles with brand new ones. Looking at all the other push rods none of them were damaged nor bent to the degree of this one. Again thank you for all your help and knowledge.
Tech Contributor
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Something on that valve had a bind. I would look at the spring, the ROCKER ARM.. Make sure that the rocker arm isnt missing any if its needle bearings. Look at the rocker arm and see if its sitting SQUARE on the head of the valve. No off to one side.
Bill
Bill
Thread Starter
Cruising
Joined: Nov 2015
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From: Killeen Texas
jefferyrivera
Bill, When I inspected the rocker arm it looked fine and did sit square on the top of the spring and on the push rod. No ware on the top of the valve tip or on the side of it. As far as over tighting the rocker, I see no way that you can overtighten it has a torque and that is it. Cause it is not like a 350 chevy eng in a K5 the rockers on the bottom dont rest on the bottom like these do. Please correct me if i am wrong and i am going to look more into it right now.