[Cheetah2024]

I have been getting a severe misfire while under heavy/full load at 4500-5000RPM. I have a CAI from SCT with a pulley and moderate tune. Last year I had a misfire under any load that was caused by failed coils, 7 of 8 had cracked. Car has been running well after that but I noticed within the last couple months the high load misfire. I have the SC out of the car and have pulled a vacuum on the bypass actuator and it will hold without issue. I have looked over the rest of the vacuum lines and all are good. I have full boost and no check engine light. The code I have is for a bypass valve stuck closed. There are no other codes.

 

[Catmonkey]

Are you pulling a vacuum through your existing line to the actuator? Have you pulled and changed the plugs? I'd start there on a misfire.

 

[The Bone]

I would check your tune. sounds like a rev limiter. Not sure what you mean by a moderate tune.Where did you get your tune from? How many miles on your car? What SC are you using? Cracked coils? That is odd. I could maybe see one but 7 that's huge.

 

[Catmonkey]

I have been getting a severe misfire while under heavy/full load at 4500-5000RPM. I have a CAI from SCT with a pulley and moderate tune. Last year I had a misfire under any load that was caused by failed coils, 7 of 8 had cracked. Car has been running well after that but I noticed within the last couple months the high load misfire. I have the SC out of the car and have pulled a vacuum on the bypass actuator and it will hold without issue. I have looked over the rest of the vacuum lines and all are good. I have full boost and no check engine light. The code I have is for a bypass valve stuck closed. There are no other codes.

After rereading your post, are you saying you're running a CAI tune that comes on the SCT tuning device (i.e. not a custom tune). If you are, you're likely encountering detonation if you're running a pulley to increase boost. You need to get a proper tune if this is the case and you really should stay out of WOT until you get it resolved.

 

[Indy]

A cracked piston might be your prize if Catmonkey is correct, worst case the tunning should show the issue, plugs, spark, injector etc.
A couple hundred might save thousands.

 

[Cheetah2024]

For more info, I have a tune for the CAI and pulley upgrade that I have. Has been installed for 12-13 years without issue. The car has 92k miles and still running all stock intake track other than the CAI. Tune included an CAT/O2 delete for the catless MAC perf exhaust I have. There have been no modifications to the car for at least 10 years. Please let me know if any more info would help. At this point I am thinking about putting the car back together while making sure all the vacuum lines can hold a vacuum after reassembly. Then clear the code and take a drive. This is not my daily so I do not need to hurry for the repair, just really want to avoid mechanics fees if possible. Had to take my truck ('02 F150) to a mechanic Mar and my '15 Explorer has a leaking turbo bearing that Ford says will cost $3000 parts and labor. That leak is fairly small but I still need to get it done. By the way, anyone have a suggestion for a shop in North Seattle - Everett/Marysville areas. Thank you guys much for any and all help.

 

[Cheetah2024]

After rereading your post, are you saying you're running a CAI tune that comes on the SCT tuning device (i.e. not a custom tune). If you are, you're likely encountering detonation if you're running a pulley to increase boost. You need to get a proper tune if this is the case and you really should stay out of WOT until you get it resolved.

I have very much been staying out of WOT, in fact I stay under 10PSI of boost at all times and keep to only a couple PSI as needed for freeway passing or hill climbing.

 

[Catmonkey]

That's a lot of miles. I can think of a few things that would concern me. First, being carbon build up. The pistons on a 5.4 are .1" below the deck and a rather large dish on top of that. Carbon has a whole lot of places it can accumulate. You might consider a compression check to determine high and/or low cylinders. If you have access to a bore scope, you might have a look at the tops of the pistons. Next would be chain stretch. This Ford modular has about 12' of chains driving the camshafts. Surely you have stretch that will come into play. I would love to see the base plate on the intake manifold on a engine with that much mileage just to see what sort of layer of gunk would be sitting on it. If the supercharger is off the car, snap a pic of the intercooler and post it. If there is a lot of build up on the core, you're probably running some fairly high IAT2s. If you have access to a bore scope, I'd remove the IAT2 sensor and have a look at the bottom of the intake.

 

[Cheetah2024]

That's a lot of miles. I can think of a few things that would concern me. First, being carbon build up. The pistons on a 5.4 are .1" below the deck and a rather large dish on top of that. Carbon has a whole lot of places it can accumulate. You might consider a compression check to determine high and/or low cylinders. If you have access to a bore scope, you might have a look at the tops of the pistons. Next would be chain stretch. This Ford modular has about 12' of chains driving the camshafts. Surely you have stretch that will come into play. I would love to see the base plate on the intake manifold on a engine with that much mileage just to see what sort of layer of gunk would be sitting on it. If the supercharger is off the car, snap a pic of the intercooler and post it. If there is a lot of build up on the core, you're probably running some fairly high IAT2s. If you have access to a bore scope, I'd remove the IAT2 sensor and have a look at the bottom of the intake.

I do have a small bore scope but it isn't working, its the kind that connects via wifi and I can't get it to connect... the base plate is under the SC or the intercooler? Here are the pictures. I don't have the means to check the compression. Would there be a relatively easy way to see if the chain is stretched? What is the IAT2 sensor and where would that be? is that a timing sensor? oh, and I do not have the oil separator can either.

 

[Catmonkey]

All chains are going to stretch given enough time and mileage. It's just the nature of the beast and unavoidable. Ford uses tensioners to keep the chain tight, but if it streches enough it will change the cam timing. But you wouldn't be able to determine the point it's stretched enough to cause issues that might effect how it runs. The intercooler looks better than I would have thought, but layer of gunk on the fins is going to reduce it's ability to cool effectively as it did. It can be cleaned, but you have to remove the intake manifold, and it is a bit of a PITA. The base plate is on the bottom of the intake and is the access point for the intercooler. It can only be accessed if the intake is removed. You could take care of the bottom of the intake if you did that too.

A compression tester is not a real expensive piece of equipment. You just need to get an extension that can reach the bottom of the spark plug hole.

The IAT2 sensor is in the dark red circle.

 

[SSGMcIlwain]

I know you noted over the past few months. Not sure if you daily the car or how frequently you drive it but if it is rarely, it could also be as simple as bad/old gas.

 

[Cheetah2024]

I know you noted over the past few months. Not sure if you daily the car or how frequently you drive it but if it is rarely, it could also be as simple as bad/old gas.

I have been driving the car at least once per week for the last couple months, my truck was just down with a misfire from a bad coil that I just got fixed last week, now that it is fixed again I don't drive the GT500 more than once a week. the trips are 40 miles each way so the car can get up to temp though. I have put half a dozen tanks of gas through it over the last few months. I was concerned about the gas at one point so I ran the car down until the trip comp said 10 miles left, that way I could refill almost entirely out of fresh fuel.I will look into a compression tester.

 

[SSGMcIlwain]

I have had bad gas twice (once in my 2014 and once in my 2007). Naturally, your symptoms reminded me of the incident with my 2007, the subsequent detonation obliterated a spark plug but thankfully it didn't cause significant damage to the cylinder (maintained compression).

 

[Catmonkey]

Have you looked at the plugs?

 

[Cheetah2024]

Have you looked at the plugs?

not since I replaced them all last fall. changed all plugs and coils, if I get some time tomorrow I am going to pull a couple and have a look.

 

[The Bone]

Part of your problem is the 02 sensor delete. Why would anyone want to remove that. That's the sensor that keeps your fuel mixture correct. You need to get that back on the car. I can't believe you have been able to go as long as you have. I bet your fuel millage sucks and you may be running to rich. Are your exhaust tips black? i have a CAI and pulley tune. I believe I got my tune from JLT. My 02 sensor is on. Still wondering how you had 7 cracked coils. Why did you remove the SC?

 

[Catmonkey]

Part of your problem is the 02 sensor delete. Why would anyone want to remove that. That's the sensor that keeps your fuel mixture correct.

The car has 4 oxygen sensors. When someone talks about turning off the rear O2 sensors, whose only function is to tell you that your catalyst is bad, it's a non-issue. The front O2 sensors are still there to do their thing. Not that you could get a tuner to turn them off today, it used to be common practice.

 

[The Bone]

The car has 4 oxygen sensors. When someone talks about turning off the rear O2 sensors, whose only function is to tell you that your catalyst is bad, it's a non-issue. The front O2 sensors are still there to do their thing. Not that you could get a tuner to turn them off today, it used to be common practice.

My 07 only has one. That is what I was told when I took my car in for a smog.

 

[AZ21GT500]

I have been driving the car at least once per week for the last couple months, my truck was just down with a misfire from a bad coil that I just got fixed last week, now that it is fixed again I don't drive the GT500 more than once a week. the trips are 40 miles each way so the car can get up to temp though. I have put half a dozen tanks of gas through it over the last few months. I was concerned about the gas at one point so I ran the car down until the trip comp said 10 miles left, that way I could refill almost entirely out of fresh fuel.I will look into a compression tester.

Anyone else concerned about running the car down to the absolute bottom of the tank? I can only imagine what is down there after years of fuel and debris. I had an issue a while back with this on my 16 GT350 I ran it down to 20 miles and after I filled it up the damn thing ran like shit. I ended up having my dealer do an injector cleaning which fixed the issue. Just spitballing here… @Catmonkey could fix it in his sleep.

 

[Catmonkey]

My 07 only has one. That is what I was told when I took my car in for a smog.

So you don't even know how many oxygen sensors your car has and you're posting technical advice in threads?