Constant miss 86 vert
Thread Starter
Instructor
Joined: Nov 2011
Posts: 147
Likes: 0
From: Florida
Constant miss 86 vert
86 vert
No codes
4+3
It is in stock trim 145k miles
It has had this miss for a while now.
If you are constantly accelerating no miss. If your at highway speeds no miss.
At idle it will sit at @ 800 RPM then start missing. Down to 500 catches itself up to 900 then kinda up and down.
1. New Distributor no change
2. New ESC no change
3. New Fuel pump no change
4. New Plugs no change
Fuel pressure sits at 40 Psi pretty steady nail it it goes to 45 for a second.
any help would be appreciated.
No codes
4+3
It is in stock trim 145k miles
It has had this miss for a while now.
If you are constantly accelerating no miss. If your at highway speeds no miss.
At idle it will sit at @ 800 RPM then start missing. Down to 500 catches itself up to 900 then kinda up and down.
1. New Distributor no change
2. New ESC no change
3. New Fuel pump no change
4. New Plugs no change
Fuel pressure sits at 40 Psi pretty steady nail it it goes to 45 for a second.
any help would be appreciated.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
86 vert
No codes
4+3
It is in stock trim 145k miles
It has had this miss for a while now.
If you are constantly accelerating no miss. If your at highway speeds no miss.
At idle it will sit at @ 800 RPM then start missing. Down to 500 catches itself up to 900 then kinda up and down.
1. New Distributor no change
2. New ESC no change
3. New Fuel pump no change
4. New Plugs no change
Fuel pressure sits at 40 Psi pretty steady nail it it goes to 45 for a second.
any help would be appreciated.
No codes
4+3
It is in stock trim 145k miles
It has had this miss for a while now.
If you are constantly accelerating no miss. If your at highway speeds no miss.
At idle it will sit at @ 800 RPM then start missing. Down to 500 catches itself up to 900 then kinda up and down.
1. New Distributor no change
2. New ESC no change
3. New Fuel pump no change
4. New Plugs no change
Fuel pressure sits at 40 Psi pretty steady nail it it goes to 45 for a second.
any help would be appreciated.
Have you inspected your ignition wires and made sure there are no rips or tears?
It sounds like it's just an idle surge. What is your TPS voltage at idle?
What is your timing set to to?
Did you check for vacuum leaks?
What caused the problem to arise? Out of nowhere?
Clean out your throttle body and IAC.
Do you have access to a scan tool? If you do, what is your computer saying the CTS is reading when it is at operating temperature?
Does it only happen if it is warm, or does it also do it when it is cold?
Pull out your o2 sensor if you can, if it is black or rusted it is bad.
Are there any other problems that you are experiencing? Think about this one, because sometimes multiple issues can be related to be one thing, this will help us further diagnose the problem.
Is your EGR valve stuck open or stuck closed? Can you move the diaphragm with your fingers up and down? If you can't, it is bad.
Also, do you still have a cap over the idle adjustment screw on your throttle body? You will see at the top of your throttle linkage there is a stud that the linkage rests on, on the other side of that stud there is a torx head, this is the idle adjustment screw, don't touch it just tell me if it has a cap over the hole.
Please report back with the results.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Check plug wires. Are all the boots on snug? You can ohm each wire. Also try this.....unplug underhood lights.....start the car at night with all outside light sources off and look for arcing from any of the wire.
Thread Starter
Instructor
Joined: Nov 2011
Posts: 147
Likes: 0
From: Florida
How do you know it is a miss?
Have you inspected your ignition wires and made sure there are no rips or tears?
It sounds like it's just an idle surge. What is your TPS voltage at idle?
What is your timing set to to?
Did you check for vacuum leaks?
What caused the problem to arise? Out of nowhere?
Clean out your throttle body and IAC.
Do you have access to a scan tool? If you do, what is your computer saying the CTS is reading when it is at operating temperature?
Does it only happen if it is warm, or does it also do it when it is cold?
Pull out your o2 sensor if you can, if it is black or rusted it is bad.
Are there any other problems that you are experiencing? Think about this one, because sometimes multiple issues can be related to be one thing, this will help us further diagnose the problem.
Is your EGR valve stuck open or stuck closed? Can you move the diaphragm with your fingers up and down? If you can't, it is bad.
Also, do you still have a cap over the idle adjustment screw on your throttle body? You will see at the top of your throttle linkage there is a stud that the linkage rests on, on the other side of that stud there is a torx head, this is the idle adjustment screw, don't touch it just tell me if it has a cap over the hole.
Please report back with the results.
Have you inspected your ignition wires and made sure there are no rips or tears?
It sounds like it's just an idle surge. What is your TPS voltage at idle?
What is your timing set to to?
Did you check for vacuum leaks?
What caused the problem to arise? Out of nowhere?
Clean out your throttle body and IAC.
Do you have access to a scan tool? If you do, what is your computer saying the CTS is reading when it is at operating temperature?
Does it only happen if it is warm, or does it also do it when it is cold?
Pull out your o2 sensor if you can, if it is black or rusted it is bad.
Are there any other problems that you are experiencing? Think about this one, because sometimes multiple issues can be related to be one thing, this will help us further diagnose the problem.
Is your EGR valve stuck open or stuck closed? Can you move the diaphragm with your fingers up and down? If you can't, it is bad.
Also, do you still have a cap over the idle adjustment screw on your throttle body? You will see at the top of your throttle linkage there is a stud that the linkage rests on, on the other side of that stud there is a torx head, this is the idle adjustment screw, don't touch it just tell me if it has a cap over the hole.
Please report back with the results.
Happens at any constant RPM until you get to about 2000 then steady as she goes. So it is not just at Idle set TPS with VOM.
Set timing to factory specs.
No Vacuum leaks
Has been doing it for years and years has got a little worse.
Bought new TB years ago did not make difference bought new IAC years ago no difference I can remember. But maybe it has gone bad can I just disconnect it ans see what happens.
No codes have been set.
Don't know anyone with a scanner.
Does it warm or cold.
Took EGR stuff off did not make a difference.
It has gotten worse and it seems to take a little longer to start in the morning. I think that is from the fuel pump not being energized for two seconds have not had time to chase that yet.
Cap still on idle screw.
I will check 02 sensor.
Thanks for everyone's reply. The 02 sensor has never been changed so it is close to 30 years old.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
If it is a miss.....it is more than likely electrical and probably not associated with the O2 sensor, fuel, timing, EGR or TB. It would not hurt to replace the O2 sensor with as old as it is.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Here is some information that might help from my files.....
Missfires:
When you hook a timing light lead connector up to an plug wire, one at a time, while the engine is running, it will flash faster or slower, according to the engines rpm speed. That’s a good spark.
I hook up the lead to a plug wire and aim it a dark place, like the hood to watch the flashes from the light as I pull the trigger. I do this for each cylinder wire, one at a time.
If there is a miss on certain cylinder wire, the timing light will not flash as often, or won’t flash with the miss itself. You will see the timing light pause between flashes if its bad.
It’s that easy to use. If the spark is good, the timing light will flash every time, never missing a beat and vary flashes with the engines rpm speed. – Aggrivated4life (Corvette Forum)
--------------------------------------------------------------------------
I use a test light (connected to ground) when I'm trying to find the location of spark leak. I run the side of the test light probe along the wire and boots, if there is a leak, you can hear and see the spark jump to the test light probe, and you don't get shocked. You can also hear the motor stumble when the arc happens. – Agent86
Ohm Spark Plug Wires:
Set the Digital Engine Analyzer on the Ohms setting for 200. Insert test probes into wire ends and take reading in Ohms. MSD 8.5 MM Super Conductor wires should read about 40-50 Ohms per foot. Take reading divided by length of wire times 12 should be in this range for a good wire.
Measure the length of the spark plug wire in inches. Divide the resistance reading by the length of the spark plug wire to determine ohms per inch.
Missfires:
When you hook a timing light lead connector up to an plug wire, one at a time, while the engine is running, it will flash faster or slower, according to the engines rpm speed. That’s a good spark.
I hook up the lead to a plug wire and aim it a dark place, like the hood to watch the flashes from the light as I pull the trigger. I do this for each cylinder wire, one at a time.
If there is a miss on certain cylinder wire, the timing light will not flash as often, or won’t flash with the miss itself. You will see the timing light pause between flashes if its bad.
It’s that easy to use. If the spark is good, the timing light will flash every time, never missing a beat and vary flashes with the engines rpm speed. – Aggrivated4life (Corvette Forum)
--------------------------------------------------------------------------
I use a test light (connected to ground) when I'm trying to find the location of spark leak. I run the side of the test light probe along the wire and boots, if there is a leak, you can hear and see the spark jump to the test light probe, and you don't get shocked. You can also hear the motor stumble when the arc happens. – Agent86
Ohm Spark Plug Wires:
Set the Digital Engine Analyzer on the Ohms setting for 200. Insert test probes into wire ends and take reading in Ohms. MSD 8.5 MM Super Conductor wires should read about 40-50 Ohms per foot. Take reading divided by length of wire times 12 should be in this range for a good wire.
Measure the length of the spark plug wire in inches. Divide the resistance reading by the length of the spark plug wire to determine ohms per inch.
Thread Starter
Instructor
Joined: Nov 2011
Posts: 147
Likes: 0
From: Florida
Here is some information that might help from my files.....
Missfires:
When you hook a timing light lead connector up to an plug wire, one at a time, while the engine is running, it will flash faster or slower, according to the engines rpm speed. That’s a good spark.
I hook up the lead to a plug wire and aim it a dark place, like the hood to watch the flashes from the light as I pull the trigger. I do this for each cylinder wire, one at a time.
If there is a miss on certain cylinder wire, the timing light will not flash as often, or won’t flash with the miss itself. You will see the timing light pause between flashes if its bad.
It’s that easy to use. If the spark is good, the timing light will flash every time, never missing a beat and vary flashes with the engines rpm speed. – Aggrivated4life (Corvette Forum)
--------------------------------------------------------------------------
I use a test light (connected to ground) when I'm trying to find the location of spark leak. I run the side of the test light probe along the wire and boots, if there is a leak, you can hear and see the spark jump to the test light probe, and you don't get shocked. You can also hear the motor stumble when the arc happens. – Agent86
Ohm Spark Plug Wires:
Set the Digital Engine Analyzer on the Ohms setting for 200. Insert test probes into wire ends and take reading in Ohms. MSD 8.5 MM Super Conductor wires should read about 40-50 Ohms per foot. Take reading divided by length of wire times 12 should be in this range for a good wire.
Measure the length of the spark plug wire in inches. Divide the resistance reading by the length of the spark plug wire to determine ohms per inch.
Missfires:
When you hook a timing light lead connector up to an plug wire, one at a time, while the engine is running, it will flash faster or slower, according to the engines rpm speed. That’s a good spark.
I hook up the lead to a plug wire and aim it a dark place, like the hood to watch the flashes from the light as I pull the trigger. I do this for each cylinder wire, one at a time.
If there is a miss on certain cylinder wire, the timing light will not flash as often, or won’t flash with the miss itself. You will see the timing light pause between flashes if its bad.
It’s that easy to use. If the spark is good, the timing light will flash every time, never missing a beat and vary flashes with the engines rpm speed. – Aggrivated4life (Corvette Forum)
--------------------------------------------------------------------------
I use a test light (connected to ground) when I'm trying to find the location of spark leak. I run the side of the test light probe along the wire and boots, if there is a leak, you can hear and see the spark jump to the test light probe, and you don't get shocked. You can also hear the motor stumble when the arc happens. – Agent86
Ohm Spark Plug Wires:
Set the Digital Engine Analyzer on the Ohms setting for 200. Insert test probes into wire ends and take reading in Ohms. MSD 8.5 MM Super Conductor wires should read about 40-50 Ohms per foot. Take reading divided by length of wire times 12 should be in this range for a good wire.
Measure the length of the spark plug wire in inches. Divide the resistance reading by the length of the spark plug wire to determine ohms per inch.
Has anybody replaced the EGR sensor. I took the pump and stuff off but the miss was there before I touched that.
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Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Consuming more fuel and the funny smell different problem than the miss. That could be O2 issue. What does the exhaust pipe look like? Lots of black soot? If the miss is very bad than you could be dumping raw fuel into the exhaust and the cat is trying to burn it up.
Are the injector clips tight on the injectors? It could be an injector wire....think you would need a noid light to test that. Someone else should step in here about that......
Are the injector clips tight on the injectors? It could be an injector wire....think you would need a noid light to test that. Someone else should step in here about that......
Drifting
Joined: Mar 2012
Posts: 1,492
Likes: 61
From: New Jersey
Maybe I am reading his initial post wrong but it seems more like a problem with idle fluctuation and surging (as DanielRicany stated) than what he is calling a "miss". Replace the O2 sensor and check the vacuum lines for cracking and breaks.
Thread Starter
Instructor
Joined: Nov 2011
Posts: 147
Likes: 0
From: Florida
Thanks
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
I would suggest to power balance engine see if cylinder(s) can be isolated. To do it you need a tach, at idle disconnect IAC, O2, & Set Timing connectors. Ecm should not be able to alter running. Then disconnect one injector at a time noting rpm drop. No or very little drop = cylinder(s) to look at.
Thread Starter
Instructor
Joined: Nov 2011
Posts: 147
Likes: 0
From: Florida
Consuming more fuel and the funny smell different problem than the miss. That could be O2 issue. What does the exhaust pipe look like? Lots of black soot? If the miss is very bad than you could be dumping raw fuel into the exhaust and the cat is trying to burn it up.
Are the injector clips tight on the injectors? It could be an injector wire....think you would need a noid light to test that. Someone else should step in here about that......
Are the injector clips tight on the injectors? It could be an injector wire....think you would need a noid light to test that. Someone else should step in here about that......
Heel & Toe
Joined: Aug 2011
Posts: 21
Likes: 0
From: Parsonsfield Maine
After you exchange all your suspected culprits, finially go to autozone and get a rebuilt ECM for $75. Solved all my simular problems.
No codes
4+3
It is in stock trim 145k miles
It has had this miss for a while now.
If you are constantly accelerating no miss. If your at highway speeds no miss.
At idle it will sit at @ 800 RPM then start missing. Down to 500 catches itself up to 900 then kinda up and down.
1. New Distributor no change
2. New ESC no change
3. New Fuel pump no change
4. New Plugs no change
Fuel pressure sits at 40 Psi pretty steady nail it it goes to 45 for a second.
any help would be appreciated.[/QUOTE]
No codes
4+3
It is in stock trim 145k miles
It has had this miss for a while now.
If you are constantly accelerating no miss. If your at highway speeds no miss.
At idle it will sit at @ 800 RPM then start missing. Down to 500 catches itself up to 900 then kinda up and down.
1. New Distributor no change
2. New ESC no change
3. New Fuel pump no change
4. New Plugs no change
Fuel pressure sits at 40 Psi pretty steady nail it it goes to 45 for a second.
any help would be appreciated.[/QUOTE]
Thread Starter
Instructor
Joined: Nov 2011
Posts: 147
Likes: 0
From: Florida
after you exchange all your suspected culprits, finially go to autozone and get a rebuilt ecm for $75. Solved all my simular problems.
You know funny you should say that. That is where my mind has been taking me lately. I believe that will be the next thing i change.
Thanks
no codes
4+3
it is in stock trim 145k miles
it has had this miss for a while now.
If you are constantly accelerating no miss. If your at highway speeds no miss.
At idle it will sit at @ 800 rpm then start missing. Down to 500 catches itself up to 900 then kinda up and down.
1. New distributor no change
2. New esc no change
3. New fuel pump no change
4. New plugs no change
fuel pressure sits at 40 psi pretty steady nail it it goes to 45 for a second.
Any help would be appreciated.
You know funny you should say that. That is where my mind has been taking me lately. I believe that will be the next thing i change.
Thanks
no codes
4+3
it is in stock trim 145k miles
it has had this miss for a while now.
If you are constantly accelerating no miss. If your at highway speeds no miss.
At idle it will sit at @ 800 rpm then start missing. Down to 500 catches itself up to 900 then kinda up and down.
1. New distributor no change
2. New esc no change
3. New fuel pump no change
4. New plugs no change
fuel pressure sits at 40 psi pretty steady nail it it goes to 45 for a second.
Any help would be appreciated.
Thread Starter
Instructor
Joined: Nov 2011
Posts: 147
Likes: 0
From: Florida
update
[QUOTE=DinoBob;1585757943]Dude, check the wires very carefully. That is where my miss was. If it. Is steady and regular I guarantee you it is electrical except if it is a bad injector.[/QUOTE
Bought a new CES no real change.
Bought a new O2 sensor improvement.
Reset timing
Now it runs much better, but still misses a little now and then and once in awhile at idle.
Feels like it is dropping a cylinder now and then.
Only things not changed.
Wires and ECM
Fuel pressure regulator was not changed though a fuel pressure gauge showed no problems in this area.
There is no Fuel pressure when you turn key on, I thought I read that there was a 2 second on for the fuel pump when you turn the key to the on position. Is that correct
So it takes a bit to start when it is cold. Other than that it is running pretty good.
Thanks for all your help
Happy New Year!
Bought a new CES no real change.
Bought a new O2 sensor improvement.
Reset timing
Now it runs much better, but still misses a little now and then and once in awhile at idle.
Feels like it is dropping a cylinder now and then.
Only things not changed.
Wires and ECM
Fuel pressure regulator was not changed though a fuel pressure gauge showed no problems in this area.
There is no Fuel pressure when you turn key on, I thought I read that there was a 2 second on for the fuel pump when you turn the key to the on position. Is that correct
So it takes a bit to start when it is cold. Other than that it is running pretty good.
Thanks for all your help
Happy New Year!