Someone PLEASE help me with this!!
Thread Starter
Heel & Toe
Joined: Jul 2011
Posts: 17
Likes: 0
From: Fort Worth Texas
Someone PLEASE help me with this!!
1990 Corvette
Auto tranny
132k miles
Fires right up
Throwing ZERO codes
My problem: While at idle in drive my Vette will kick/jump rapidly. Somedays worse than others. At a red light it just kicks and kicks. Seems to be worse when the AC is on. Seems like the higher the AC, the worse the kick. With the AC off, the kick is still there but is minor in comparison. I'm trying to sell this car but this random problem popped up and I refuse to sell anyone a car w/ a mechanical issue. Please help me with this. I just changed the cap and rotor and checked all the plug wires. Any suggestions? Any help?
God Bless all of you, thank you in advance!!
If I left anything out, tell me what ya need and it's yours
Auto tranny
132k miles
Fires right up
Throwing ZERO codes
My problem: While at idle in drive my Vette will kick/jump rapidly. Somedays worse than others. At a red light it just kicks and kicks. Seems to be worse when the AC is on. Seems like the higher the AC, the worse the kick. With the AC off, the kick is still there but is minor in comparison. I'm trying to sell this car but this random problem popped up and I refuse to sell anyone a car w/ a mechanical issue. Please help me with this. I just changed the cap and rotor and checked all the plug wires. Any suggestions? Any help?
God Bless all of you, thank you in advance!!
If I left anything out, tell me what ya need and it's yours
Thread Starter
Heel & Toe
Joined: Jul 2011
Posts: 17
Likes: 0
From: Fort Worth Texas
During acceleration she cuts out ridiculously depending on how much I give her. She'll hesitate and thudder while going. It's unbarable for me to watch this car drive like a PoS ricer.
Random part is there will be days that she drives like a 2010 Vette then the next day back to this. (my son has a '10 so I can say that
)
Random part is there will be days that she drives like a 2010 Vette then the next day back to this. (my son has a '10 so I can say that
)
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
You have an ignition misfire going on yet in 1 or 2 cylinders.
Replace all the ignition wires & spark plugs.
You replaced the distributor cap & rotor already.
If the intermittent bucking continues,
suspect bad fuel injectors.
Brian
Replace all the ignition wires & spark plugs.
You replaced the distributor cap & rotor already.
If the intermittent bucking continues,
suspect bad fuel injectors.
Brian
Thread Starter
Heel & Toe
Joined: Jul 2011
Posts: 17
Likes: 0
From: Fort Worth Texas
So does that explain how th AC affects the performance of it? If the AC is on, it runs like trash. Just so jumpy. But I'm in Texas and it topped out at 108 today. AC is required XD
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
Air Conditioning On throws a heavy extra load on the engine at idle RPM's of 625 to 750 RPM's.
That A/C compressor takes around 16 - 20 Horsepower to turn at speed.
If you have a misfire in 1 or 2 cylinders, A/C on will show the ugly side effects of an engine cylinder(s) misfire.
Complete your ignition tuneup 1st.
Let me know & others on C4.
Old time mechanics had Snap On Counsler Ignition Oscilloscopes & SUN Oscilloscopes.
I have them both & use them yet today for troubleshooting engine misfires.
Most of those old time mechanics are gone.
I remain today.
But I am in IL.
You are in Texas.
You have C4 for help & me when I am online here on C4 tech along with everyone else.
Brian
That A/C compressor takes around 16 - 20 Horsepower to turn at speed.
If you have a misfire in 1 or 2 cylinders, A/C on will show the ugly side effects of an engine cylinder(s) misfire.
Complete your ignition tuneup 1st.
Let me know & others on C4.
Old time mechanics had Snap On Counsler Ignition Oscilloscopes & SUN Oscilloscopes.
I have them both & use them yet today for troubleshooting engine misfires.
Most of those old time mechanics are gone.
I remain today.
But I am in IL.
You are in Texas.
You have C4 for help & me when I am online here on C4 tech along with everyone else.
Brian
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Also, you might want to backtrack a bit, go over what you've already done & be sure of firing order etc. Were you experiencing this before you changed the cap & rotor? If not then most likely your problem is in something you did/replaced.
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Burning Brakes
Joined: May 2011
Posts: 838
Likes: 2
From: Louisville Ky
maybe have two wires crossed at the cap. happened recently -two different guys! posted here.
you have to trace every wire, not just the numbes on the dist.
1 and 3, 5, 7 or any others. or wires shorting to metal brackets, tubes, manifold, etc.
** misread or didn't read the entire post; crossed wires would not perform normal anytime. shorting to ground is possible. but not crossed. mea culpa.
Last edited by joe paco; Aug 5, 2011 at 09:37 AM. Reason: add ***
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
I don't think it would be crossed wires because he says some days it drives great , other days it runs like crap. Crossed wires would do it all the time.. The question we need to address is what would cause this problem intermittently?..I have seen Coils and Ignition Control Modules work intermittenly,also like mentioned above, when my injectors started going bad they would work ok one time and lousy the next until they finally got to the point where they just made it run crappy all the time.......WW
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
I don't think it would be crossed wires because he says some days it drives great , other days it runs like crap. Crossed wires would do it all the time.. The question we need to address is what would cause this problem intermittently?..I have seen Coils and Ignition Control Modules work intermittenly,also like mentioned above, when my injectors started going bad they would work ok one time and lousy the next until they finally got to the point where they just made it run crappy all the time.......WW
But a leaking spark plug ignition wire will act intermittent also with changes in Ambient temps, humidity, and engine driving loads.
Worn out spark plug electrodes with rounded off gaps double or triple factory recommendation does not help the cause likewise.
Why I said for him to complete his full ignition tuneup with ignition wires & spark plugs 1st.
He has already replaced the distributor cap & rotor.
Burning Brakes
Joined: May 2011
Posts: 838
Likes: 2
From: Louisville Ky
I don't think it would be crossed wires because he says some days it drives great , other days it runs like crap. Crossed wires would do it all the time.. The question we need to address is what would cause this problem intermittently?..I have seen Coils and Ignition Control Modules work intermittenly,also like mentioned above, when my injectors started going bad they would work ok one time and lousy the next until they finally got to the point where they just made it run crappy all the time.......WW
don't recall a crossed wire running normal part of the time, except at idle, maybe..joe
Race Director
Joined: Jan 2000
Posts: 16,488
Likes: 25
From: USA. Northern Virginia
Replace your wires and ensure they are routed correctly. Check your coil and you might want to look around the engine bay for any opened leads or a bad vacuum leak---check the EGR-that will give you a bad stumble once the systems goes into a closed loop mode. While you are in the area, check your plugs, you might have a couple fouled or too old to be firing right
I'll put $$$ that its in the plug wires.
I'll put $$$ that its in the plug wires.
Thread Starter
Heel & Toe
Joined: Jul 2011
Posts: 17
Likes: 0
From: Fort Worth Texas
All of that has been done already in the past two years. This is how long I've been trying to fix this damn thing. The only thing I haven't replaced is the pick up coil.
Thoughts?
Thoughts?
Melting Slicks
Joined: Mar 2003
Posts: 2,512
Likes: 49
From: Franklin IN
Sometimes at night in a dark garage (with the door open)hood up you may see the spark jump between wires. Esp when the AC kicks in because of the load on the engine. The spark will always take the path of least resistance.
Intermediate
Joined: Dec 2008
Posts: 27
Likes: 0
From: Grants Pass Oregon
My problem was similar, but occasionally stumbling from a stop light but in the past couple of weeks it got worse until it quit running. Before it totally died it would buck like it was firing on only four cylinders during idle.
Problem turned out to be a cracked coil casing. You could see the spark jump from the coil to the bracket when trying to start. Replaced coil and module at it runs GREAT! (see more info on my post today) ART
Problem turned out to be a cracked coil casing. You could see the spark jump from the coil to the bracket when trying to start. Replaced coil and module at it runs GREAT! (see more info on my post today) ART
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
I have a suggestion for you to try and it is free, your mention of the heat made me think of it. Get an ice pack, wrap it in a rag or towel, something to keep condensation from getting everything wet. Place the pack close to or on your ecm. This will keep the ecm cool, my '85 would drive like a champ on any day the heat was below 80 but anything above 80 and it would do similar things like yours is doing. I searched for weeks with no luck when a friend of mine suggested the ecm may be acting up when it gets hot. I got a new ecm and the problem went away. If your car drives & runs okay with the ice pack on the ecm you have found your problem.