Need help troubleshooting an engine issue: (vibration/miss at WOT, low rpm)

[larry03gt]

I had somewhat of the same problem after the SC install. Changed the regaped factory plugs to the Ford Racing Colder plugs gaped at .32 never had a problem again.

 

[konablue11gt]

doesn't seem to be from the list he posted.

11.5:1 CR in a boosted application???


@ Dustin - well if the rotating assembly is not balanced correctly you could........ (not saying that's the case here)

Yeah apparently he isnt boosted but yes 11:1 CR in boost is done all the time

 

[stkjock]

Yeah apparently he isnt boosted but yes 11:1 CR in boost is done all the time

Yes, but the probability that one would up the CR in a boosted application above 11:1........

 

[skwerl]

I'm interpreting the OP's description as a 'stumble' since he said the vibration was accompanied by a lack of power. It also sounds like it's not a constant vibration but only happens when the motor stumbles. Therefore I'm inclined to look at ignition issues such as plugs or coils. A marginal coil pack going bad can give these types of symptoms (God knows I've had this happen enough in my F150).

 

[captdistraction]

a stumble is a good word for it.

AED wants me to take it to a shop with equipment for looking at misfire counts and check the coils etc.

I have new plugs, I'll check them and install tomorrow and get some video for you guys along with what data I can get from the SCT datalogger software.

 

[BadHabit2Break]

a stumble is a good word for it.

AED wants me to take it to a shop with equipment for looking at misfire counts and check the coils etc.

I have new plugs, I'll check them and install tomorrow and get some video for you guys along with what data I can get from the SCT datalogger software.

You should be able to look at the misfires in SCT's datalog software.

 

[Alfiedagr8]

Also check base oil pressure. At hot ilde. I seen in a few situations low oil pressure cause some low rpm stumble. That's all I can think of Are you still using the VCT? Or locked out? Also my friend just went to this after some cam install. And he found out that a guide was broken. But he did eventually throw a code for that. A compression check can let u know if there is anything wrong with the guides as one bank will generally have higher compression than the other. Sometimes bank to bank fuel trim will vary. Something to look into.


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[stkjock]

VCT - that's for the 4.6L only is it not? the 5.0 is TiVCT?

so not applicable in this situation ?

 

[Alfiedagr8]

Oh shit wasn't aware that this was a 5.0 tread. But they do use them. I guess I'm stumped.


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[captdistraction]

So the new plugs come out of the box at 0.051" gap. How does that sound? Should I gap them closer or leave them alone and install as-is? I haven't removed the existing plugs yet.

Here's an interesting excerpt from the Boss302S manual:
Spark Plugs
BR3E-12405-DA (Heat Range 1) or M-12405-M50 (Heat range 0)
SP519-Motorcraft
GAP= 0.04 (1.0 mm)
Replace after every 6 hours of usage

 

[stkjock]

So the new plugs come out of the box at 0.051" gap. How does that sound? Should I gap them closer or leave them alone and install as-is? I haven't removed the existing plugs yet.

Here's an interesting excerpt from the Boss302S manual:
Spark Plugs
BR3E-12405-DA (Heat Range 1) or M-12405-M50 (Heat range 0)
SP519-Motorcraft
GAP= 0.04 (1.0 mm)
Replace after every 6 hours of usage

I would bring the gap in line with the specs from Ford.

Every 6 hours of use? that must be for racing time?

 

[captdistraction]

I would bring the gap in line with the specs from Ford.

Every 6 hours of use? that must be for racing time?

The spec from Ford on the Mustang GT is 0.051, the Boss302S racecar is .04 (the 6 hour note is given that the 302S is not street legal and is used in racing situations. Interesting that every 6 hours though, seems like a short lifetime even in racing terms)

My engine is closer in design to the Boss302S, but I'm using it in street duty. I'm not sure if having the tighter gap gives up anything, but its sorta worth a shot.

 

[stkjock]

My engine is closer in design to the Boss302S, but I'm using it in street duty. I'm not sure if having the tighter gap gives up anything, but its sorta worth a shot.

I see. A tighter gap can make igniting the a/f mix a bit harder, but at .040 I doubt it will be an issue.

The spec from Ford on the Mustang GT is 0.051, the Boss302S racecar is .04 (the 6 hour note is given that the 302S is not street legal and is used in racing situations. Interesting that every 6 hours though, seems like a short lifetime even in racing terms)

Interesting, I wonder if that has to do with fuels being used.

 

[19COBRA93]

Are they in yet?

 

[Terminator2]

What has your tuner said about your logs?

This. Log the issue and see what is going on.

in a n/a application I would think gap would not matter nearly as much as a FI combo

Not as much but it does matter if his plugs are at 0.065 and the recommended gap is 0.040 it could cause misfires under heavy loads. OP should have P030X codes though.

 

[captdistraction]

Are they in yet?

not yet. Work's keeping me busy for the next couple hours, but will be gathering logs, video and trying the new plugs.

also, here's the driver's bank of plugs:

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[captdistraction]

I hope this was it:

will know soon

 

[stkjock]

That'll do it.

 

[larry03gt]

I hope this was it:

will know soon

That will do it under load. and your other plugs look good.

 

[captdistraction]

That was it. Time to try out the gopro 240fps mode in the plugs' impending demise.