Misfire

[Beau75]

When driving my 2005 gt the car will run great but after long amounts of driving or aggressive driving I will get a flashing engine light and the car will run very poorly but only last for about a minute before the engine light goes away and the car will run great after. Any thoughts of what this could be the car has new spark plugs and new oem coil packs.

 

[Dino Dino Bambino]

You'll need to scan the ECU for fault codes (actual and pending). Hopefully that'll help you pinpoint the problem.

 

[86GT351]

You'll need to scan the ECU for fault codes (actual and pending). Hopefully that'll help you pinpoint the problem.

This should always be a first step. Read codes. Check Mode 6 if your scanner has it. Also look at Misfire Data for the counters.

 

[Juice]

Even my crystal ball is hazy on this one. OP didnt even say "it started after plugs" or "new plugs & no change".

 

[Kev555]

Crystal ball Hazy, lol that's funny

 

[Huberoy123]

I'm having a similar issue with my 2006 4.6L. It starts and runs okay, until I try to accelerate quickly. Then it does mild missing, and bogs down. My scan tool showed a pending fault on cylinder 3, and I replaced the coil. I already had the plugs changed at 183,00 and we are at 186,000. I took it back to the dealer who installed the plugs, and they did a diagnosis. 3 plugs needed to be replaced and they wanted to replace a valve cover because the screw holes for some coil packs were becoming compromised. To summarize, they wanted $1,400, with no guarantees that the missing would be addressed. The car was running lean, and they would try to find out why, after the $1,400 robbery without a weapon. I ordered the parts and will do the repair. All the sensors are good, so I'm leaning to something mechanical as the cause for my issue. Any thoughts or suggestions?

 

[StockishS197]

I'm having a similar issue with my 2006 4.6L. It starts and runs okay, until I try to accelerate quickly. Then it does mild missing, and bogs down. My scan tool showed a pending fault on cylinder 3, and I replaced the coil. I already had the plugs changed at 183,00 and we are at 186,000. I took it back to the dealer who installed the plugs, and they did a diagnosis. 3 plugs needed to be replaced and they wanted to replace a valve cover because the screw holes for some coil packs were becoming compromised. To summarize, they wanted $1,400, with no guarantees that the missing would be addressed. The car was running lean, and they would try to find out why, after the $1,400 robbery without a weapon. I ordered the parts and will do the repair. All the sensors are good, so I'm leaning to something mechanical as the cause for my issue. Any thoughts or suggestions?

Need to pull the specific codes to see what else might be causing it.

If it’s running lean, it could be an injector but a misfire will also throw extra fuel on the O2 and could cause a false lean reading if the O2 gets fouled.

I would pull all plugs and inspect, look for variances across plugs and check how the plugs look.

As for the valve cover, it’s easy to strip the coil pack threads given they are cast aluminum. Instead of replacing, you can helicoil it really easily and save yourself a ton of headache. Would be a lot easier to drill and tap than pull the VC unless you want to inspect the cams and followers and get fancy ford racing valve covers

 

[Kev555]

I'm having a similar issue with my 2006 4.6L. It starts and runs okay, until I try to accelerate quickly. Then it does mild missing, and bogs down. My scan tool showed a pending fault on cylinder 3, and I replaced the coil. I already had the plugs changed at 183,00 and we are at 186,000. I took it back to the dealer who installed the plugs, and they did a diagnosis. 3 plugs needed to be replaced and they wanted to replace a valve cover because the screw holes for some coil packs were becoming compromised. To summarize, they wanted $1,400, with no guarantees that the missing would be addressed. The car was running lean, and they would try to find out why, after the $1,400 robbery without a weapon. I ordered the parts and will do the repair. All the sensors are good, so I'm leaning to something mechanical as the cause for my issue. Any thoughts or suggestions?

I was going to replace my valve covers because the threads were away on the coil securing bolts same as yours. The coils pretty much hold in by themselves and had been doing so for a while. I eventually did change the valve covers but I used tec screws that matched the length of the existing bolts and screwed them in with a 1/4 drive ratchet and socket for a better feel of when to stop tightening. That done a temporary fix but would prob have lasted a lifetime. If it was me Id start with compression test and work from there on them cylinders.

 

[whitmanink]

I'm having a similar issue with my 2006 4.6L. It starts and runs okay, until I try to accelerate quickly. Then it does mild missing, and bogs down. My scan tool showed a pending fault on cylinder 3, and I replaced the coil. I already had the plugs changed at 183,00 and we are at 186,000. I took it back to the dealer who installed the plugs, and they did a diagnosis. 3 plugs needed to be replaced and they wanted to replace a valve cover because the screw holes for some coil packs were becoming compromised. To summarize, they wanted $1,400, with no guarantees that the missing would be addressed. The car was running lean, and they would try to find out why, after the $1,400 robbery without a weapon. I ordered the parts and will do the repair. All the sensors are good, so I'm leaning to something mechanical as the cause for my issue. Any thoughts or suggestions?

im wondering if you threw a roller follower and thats causing the miss?
id open the valve cover and look to see whats going on and make sure everything is still in good order,,
then if you still have it , check gaskets and seals around the intake and then the injectors ...