2003 Thunderbird engine miss. Not cop problem (just changed them)

John Hayman

John Hayman

Active Member
Bronze Member
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Joined
Mar 15, 2017
Thunderbird Year
2003
My engine has developed a miss. It is most evident when I have cruise control on at 40 to 45, but is there at all speeds. Not as bad when I stomp on the gas, though. Any diagnostic thoughts? Thanks.
 

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My thoughts, just because the cops have been changed doesnt mean 1 or 2 may not be firing. Also could be fuel injection issue, where one injector may be in need of cleaning.
 
I had major miss issues until I changed all the coils out, since then my bird runs like a singer sewing machine,...very smooth.
 
Make ABSOLUTELY sure you didn't pinch ANY wires if you actually changed the spark plugs and COPs yourself. A pinched injector wire being cut by the hold down screw hence grounding it to the block causes the injector to constantly send fuel into that cylinder making the car act like a bad COP.
 
Transporter said:
Make ABSOLUTELY sure you didn't pinch ANY wires if you actually changed the spark plugs and COPs yourself. A pinched injector wire being cut by the hold down screw hence grounding it to the block causes the injector to constantly send fuel into that cylinder making the car act like a bad COP.
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The miss started before I changed plugs and COPs to 'cure' the miss. Two weeks earlier, the Ford dealer worked on the radiator thermostat and hoses....???
 
the only time that happened to me was when i put off brand gasoline in. Next time i filled it with Mobil it started to purr again!
 
John Hayman said:
The miss started before I changed plugs and COPs to 'cure' the miss. Two weeks earlier, the Ford dealer worked on the radiator thermostat and hoses....???
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Couple quick questions to make sure we are all on the same page. 1) was it missing before taking it to Ford for the thermostat and hoses? 2) If it started missing after, was it that day or days/weeks later? 3) Did you get a Check Engine Light after it started missing? 4) If CEL was on, did you read the Code? If yes, what Code did the Tbird throw? 5) Do you own an OBDII handheld or an OBDII dongle with an App? If not, they are worth every penny you pay for them. 6) Is the CEL on now?

John you are missing my point in my reply. Think about it this way:
Tbird is shuttering/missing because of a bad COP. You change your COPs so you know you have 8 good ones. Assume you got the bad COP. You drive the Tbird and it still shutters like it is missing or has a bad COP, but you just shotgunned all of them. Time to think maybe something went wrong during the shotgunning of the COPS. One of my neighbors is a BMW mechanic and he gets the pleasure of changing number 4 or number 8 if it isn't an emergency (plus he is better and faster at it EXCEPT when he shorts an injector lead to the engine block). This is what I am suggesting you should look for. Any wire near the COPS, Injectors, or Fuel Rail that might have gotten pinched when the COPS were changed. Why? Because an injector that constantly sends fuel to a cylinder causes the same symptom as a bad COP, a shutter or miss feeling during driving.

If you find no pinched wiring and the CEL is not on, it is time to try to make it throw a code. I have found hills work best, IE putting a load on the engine right from the start. Find a steep hill you can come to a complete stop on. Then start driving again but aggressively feather the throttle on and off so the engine gets loaded up again after losing momentum. I drove for two weeks with on and off missing never getting a code. One trip down to the river and back up to the top of the ridge above the river and I had my Code!
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Transporter said:
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Couple quick questions to make sure we are all on the same page. 1) was it missing before taking it to Ford for the thermostat and hoses? 2) If it started missing after, was it that day or days/weeks later? 3) Did you get a Check Engine Light after it started missing? 4) If CEL was on, did you read the Code? If yes, what Code did the Tbird throw? 5) Do you own an OBDII handheld or an OBDII dongle with an App? If not, they are worth every penny you pay for them. 6) Is the CEL on now?

John you are missing my point in my reply. Think about it this way:
Tbird is shuttering/missing because of a bad COP. You change your COPs so you know you have 8 good ones. Assume you got the bad COP. You drive the Tbird and it still shutters like it is missing or has a bad COP, but you just shotgunned all of them. Time to think maybe something went wrong during the shotgunning of the COPS. One of my neighbors is a BMW mechanic and he gets the pleasure of changing number 4 or number 8 if it isn't an emergency (plus he is better and faster at it EXCEPT when he shorts an injector lead to the engine block). This is what I am suggesting you should look for. Any wire near the COPS, Injectors, or Fuel Rail that might have gotten pinched when the COPS were changed. Why? Because an injector that constantly sends fuel to a cylinder causes the same symptom as a bad COP, a shutter or miss feeling during driving.

If you find no pinched wiring and the CEL is not on, it is time to try to make it throw a code. I have found hills work best, IE putting a load on the engine right from the start. Find a steep hill you can come to a complete stop on. Then start driving again but aggressively feather the throttle on and off so the engine gets loaded up again after losing momentum. I drove for two weeks with on and off missing never getting a code. One trip down to the river and back up to the top of the ridge above the river and I had my Code!
.
Click to expand...
 
I appreciate your interest. I thought the miss (stutter) was the same before and after the mass changeout of plugs and coils. I put fuel system cleaner in today and ran the hell out of it - no better. Seems to miss more at steady lower speeds. I guess a wire could have been pinched as you said and resulted in the same miss?
 
John Hayman said:
I appreciate your interest. I thought the miss (stutter) was the same before and after the mass changeout of plugs and coils. I put fuel system cleaner in today and ran the hell out of it - no better. Seems to miss more at steady lower speeds. I guess a wire could have been pinched as you said and resulted in the same miss?
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Yes, it feels so much identical it can even fool a mechanic with 30 years of modern fuel injected car experience. What happens with the now grounded injector is that it doesn't receive any signals on when and how much fuel, it just sends fuel constantly. So when it is time for that cylinder to fire there is to much fuel to burn so it causes the same shutter or missing feeling (the shutter from a bad COP is caused by unburned fuel because the COP didn't fire at all or didn't fire hard enough for a full burn). The only reason it doesn't immediately break a rod (it will eventually) is that unlike water the engine heat causes enough vaporization plus what gets discharged using the exhaust phase to be just enough to cause the shutter but not immediately snap a rod like when water is trapped in a closed cylinder during the compression phase and water can not be compressed. So when and if it ever happens, find it fast, and thank the stars it is fuel and not water because fuel does compress to a point, it vaporizes, it does burn as much as possible during the firing phase, with excess leaving during exhaust phase. Like I said if it is a pinched wire it can damage things by either burning out your CAT or eventually snap a rod, or both.
 
Transporter said:
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Yes, it feels so much identical it can even fool a mechanic with 30 years of modern fuel injected car experience. What happens with the now grounded injector is that it doesn't receive any signals on when and how much fuel, it just sends fuel constantly. So when it is time for that cylinder to fire there is to much fuel to burn so it causes the same shutter or missing feeling (the shutter from a bad COP is caused by unburned fuel because the COP didn't fire at all or didn't fire hard enough for a full burn). The only reason it doesn't immediately break a rod (it will eventually) is that unlike water the engine heat causes enough vaporization plus what gets discharged using the exhaust phase to be just enough to cause the shutter but not immediately snap a rod like when water is trapped in a closed cylinder during the compression phase and water can not be compressed. So when and if it ever happens, find it fast, and thank the stars it is fuel and not water because fuel does compress to a point, it vaporizes, it does burn as much as possible during the firing phase, with excess leaving during exhaust phase. Like I said if it is a pinched wire it can damage things by either burning out your CAT or eventually snap a rod, or both.
Click to expand...
I really need some help here! I took it to Hertrich Ford today. They had it all day (I also printed out your thoughts for them to consider). They now think that the replacement coils were bad. "1&4, 6&8". I seriously doubt their abilities to diagnose our Bird. What now?
 
Transporter said:
.
Yes, it feels so much identical it can even fool a mechanic with 30 years of modern fuel injected car experience. What happens with the now grounded injector is that it doesn't receive any signals on when and how much fuel, it just sends fuel constantly. So when it is time for that cylinder to fire there is to much fuel to burn so it causes the same shutter or missing feeling (the shutter from a bad COP is caused by unburned fuel because the COP didn't fire at all or didn't fire hard enough for a full burn). The only reason it doesn't immediately break a rod (it will eventually) is that unlike water the engine heat causes enough vaporization plus what gets discharged using the exhaust phase to be just enough to cause the shutter but not immediately snap a rod like when water is trapped in a closed cylinder during the compression phase and water can not be compressed. So when and if it ever happens, find it fast, and thank the stars it is fuel and not water because fuel does compress to a point, it vaporizes, it does burn as much as possible during the firing phase, with excess leaving during exhaust phase. Like I said if it is a pinched wire it can damage things by either burning out your CAT or eventually snap a rod, or both.
Click to expand...
I really need some help here! I took it to Hertrich Ford today. They had it all day (I also printed out your thoughts for them to consider). They now think that the replacement coils were bad. "1&4, 6&8". I seriously doubt their abilities to diagnose our Bird. What now?
 
John Hayman said:
I really need some help here! I took it to Hertrich Ford today. They had it all day (I also printed out your thoughts for them to consider). They now think that the replacement coils were bad. "1&4, 6&8". I seriously doubt their abilities to diagnose our Bird. What now?
Click to expand...

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Hi John
I would really like to help you if I could. I asked 6 questions in a previous reply to your post, yet you didn't answer any of them?
Another question, why/what was the reason given that the replacement COPS are bad? I can't see 50 percent new COPS bad.
 
Transporter said:
.
Hi John
I would really like to help you if I could. I asked 6 questions in a previous reply to your post, yet you didn't answer any of them?
Another question, why/what was the reason given that the replacement COPS are bad? I can't see 50 percent new COPS bad.
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I thought I had answered your queries - sorry. Here are the answers: 1) was it missing before taking it to Ford for the thermostat and hoses? No it was not to the best of my knowledge 2) If it started missing after, was it that day or days/weeks later? Fairly soon after, but I could not see how a radiator could cause a miss 3) Did you get a Check Engine Light after it started missing? The check engine light has not come on. 4) If CEL was on, did you read the Code? NA. If yes, what Code did the Tbird throw? NA5) Do you own an OBDII handheld or an OBDII dongle with an App? No. If not, they are worth every penny you pay for them. I assume the Ford dealer has such a device, and cannot ID this problem 6) Is the CEL on now? No.

I agree that it is highly unlikely for several of the new cops to be bad. It would seem more likely something entirely different, such as MAS or ??
 
The dealer said there were 'drops' on those cylinders...... whatever that means...
 
John Hayman said:
The dealer said there were 'drops' on those cylinders...... whatever that means...
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If it were me, I would call the dealership and ask for the actual mechanic that looked at your Tbird to call you back. Ask for specifics in layman terms what was meant by Drop. The only time I have used or heard the term "Drop" when it comes to cylinders is when I was running the quarter mile and lost due to a loss of power because I "dropped" a cylinder. The other term with engines with "drop" is a compression test IE losing compression due to bad rings or a burnt piston, but that has nothing to do with COPS.

If anybody owns a 1996 or newer vehicle should own an OBD II handheld or a wifi/bluetooth dongle. The OBD II can save you multitude of dollars over what the unit costs in self diagnostics.
 
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