Shudder / Shaking Misfire Under Load - not spark plugs

FP tune, catch can, cp-e intercooler. Check my sig line for full list of mods.

At 27k miles my EB started a severe shudder/shaking in 6th gear when accelerated uphill from low rpms. I can cruise at 55-60mph in 6th gear, then floor the go pedal, and the whole vehicle will shudder until it speeds up to a higher rpm when it will smooth out. The whole vehicle will shake, initially feeling almost like an out-of-balance driveshaft or bad u-joint or something. It is NOT the 50-70 mph vibration problem. It only happens under load - I can get it to do it in 5th gear too it's just a lot more significant in 6th - it does not happen at high rpms or when it is coasting. If I wind out the engine without lugging it, it purrs like it's supposed to.

No CEL and no codes thrown.

BTW, I KNOW I'm not supposed to lug the engine but something is wrong and it needs fixed.

I took it to my dealer's service department and they too felt like it was a driveline issue, they called the regional Ford engineer and his long-distance diagnosis said it was the 50-70 mph vibration, but he didn't ride in it and I knew this was different.

I asked them to scan it (just in case) in order to cross off as many possible options before throwing parts at this problem. The service mgr agreed and wanted to do what he called a Mode 6 scan while riding with me and watch the engine on his computer.

The scan tool would not recognize the car because I had the FP tune installed, so I went home and reflashed the car back to stock tune and filled up with 87 octane. I immediately noticed the shudder was not nearly as bad with the lowered power but it was still definitely there and at reduced severity I could tell that it seemed to originate up front of the car. My hopes rose that it was in the engine and would be something they could scan and identify.

Yes and no. The scan tool recognized my Mustang, we went for a ride with the service mgr in the passenger seat looking at his computer while I hit the gas at low rpm going uphill in 6th gear. Bingo, all four cylinders showed misfires until we sped up to higher rpms and it smoothed out again. So it's not driveline related after all.

I am familiar with the spark plug threads here so my first thought was plugs. I buy a set, go home, and pull my plugs. They looked fine, gaps are all good, but just to make sure I replace them with new plugs. The problem is still there. My service manager is stumped and it looks like he wants to keep it awhile to study it. I'd prefer my car has a short stay to get a known problem fixed quickly, not leave it at the dealer for who knows how long.

So it's not a coil or a plug, it's something that affects all of them. In digging through searches I found what may be a similar problem with F150 EBs having a condensation problem in their intercoolers. The intercoolers work so well that in humid conditions they condensate water that gets sucked in the intake to cause the shuddering. The fix seems to be drilling a small 1/8" "weep hole" in the bottom of the intercooler to let oil/condensation water out. Has anyone heard of this in our Mustangs? I really don't want to drill a hole in my intercooler.... or would it do no harm, so what-the-heck give it a try?

Does anyone have any possible ideas what the problem could be, or helpful suggestions where to start looking?

EDIT: SOLVED See post #62. I you are experiencing my problem, have your dual mass flywheel checked.

My money isn't on condensation. That shuddering would happen at all times even idle. Not just this load. Sounds similar almost to mine but I can produce it in 3rd and 4th as well. As long as it's WOT and above 4k rpm it would have like a misfire feeling. Kinda stuttery and all. Let me know what they find

Best guess Evap purge valve upon the top of the engine ! There is a rash of them all of a sudden reprted on the FaceBook pages .

Brian V said:

Best guess Evap purge valve upon the top of the engine ! There is a rash of them all of a sudden reprted on the FaceBook pages .

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Just clarifying but that was a 2.3 motor page?,

Brian V, thanks! Would you please identify the link to the Facebook page it is on? I'd like to read the whole discussion. Just to clarify, this evap purge valve solution is to fix a shudder at low rpm under load? The screen shot you show seems to indicate it is a fix for a start up problem of some sort.

Blyman93 thanks for your input. I've read your posts and am afraid we may not be able to help each other find a fix; mine is only at low rpm under load and from what I understand, yours comes on at 3,700 - 4,000 rpm or so (?). By then, mine has already been running smoothly long before it gets to that rpm level. I have strong suspicion that we don't have the same issue.

GJarrett said:

Brian V, thanks! Would you please identify the link to the Facebook page it is on? I'd like to read the whole discussion. Just to clarify, this evap purge valve solution is to fix a shudder at low rpm under load? The screen shot you show seems to indicate it is a fix for a start up problem of some sort.

Blyman93 thanks for your input. I've read your posts and am afraid we may not be able to help each other find a fix; mine is only at low rpm under load and from what I understand, yours comes on at 3,700 - 4,000 rpm or so (?). By then, mine has already been running smoothly long before it gets to that rpm level. I have strong suspicion that we don't have the same issue.

Click to expand...

Yeah mine is an up-top rpm issue.

Brian V said:

Best guess Evap purge valve upon the top of the engine ! There is a rash of them all of a sudden reprted on the FaceBook pages .

Click to expand...

That's not it. I had mine changed under warranty (after my PCM threw a code for the evap cannister purge valve). My car has started doing the same thing. I took it to the dealer, and they didn't find anything. They checked the plug gap, too (all at spec). The easiest way to duplicate the shutter in mine is to get up to 55 on 5th, let the car coast down a little, and then apply light throttle. I'm at 34,600 miles.

Sounds like we might have the same problem. I believe you have an aftermarket intercooler, right? I may swap my cp-e intercooler back out with the stock intercooler this week just to be able to mark condensation off the list of possibilities.

GJarrett said:

Sounds like we might have the same problem. I believe you have an aftermarket intercooler, right? I may swap my cp-e intercooler back out with the stock intercooler this week just to be able to mark condensation off the list of possibilities.

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Not yet. A bigger IC is definitely on my to do list. I'm wondering, though, since it seems like you don't have a catch can, if we're experiencing intake valve carbon build-up :( P.s. the dealer write-up blamed turbo lag.

I have a catch can.

Im kevin from that facebook page. I fixed my p1450 code with evap valve but im still having issues after 4500rpms.

Interesting I have two trucks and my Mustang all Ecoboost two 3.5 on one 2.3 both trucks have a shudder and a strange noise under acceleration both seem to have started after a air filter change. The noise is hard to describe but it is almost like a moan followed by a drop out of power is this what you are experiencing ?

TxMStang said:

Interesting I have two trucks and my Mustang all Ecoboost two 3.5 on one 2.3 both trucks have a shudder and a strange noise under acceleration both seem to have started after a air filter change. The noise is hard to describe but it is almost like a moan followed by a drop out of power is this what you are experiencing ?

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Nope, just a fair amount of hesitation/rough running (it feels like a driveline vibration). I can confirm that it's not a driveline vibration by shifting into a different gear. It feels like a tire that's out of round or slightly out of balance. For now, I'm keeping an eye on it, as the car is still very driveable. My powertrain warranty should handle it if it turns serious :ford:

It doesn't do it all the time. A very light throttle application when you've been cruising/coasting down at 55 in 5th gear seems to trigger it for me. Your mileage may vary, as I have a performance pack car (3.55 rear end).

I have never had this problem I described in the Mustang only in my two trucks I tend to think it is moisture in the intercooler but it doesn't do it all the time. it is still a strange sound none the less and it started after I put in a K&N filter but not sure if this is the cause or not.

I'm in the process of going back to stock before giving it back to my dealer, in order to remove all possibilities for its cause. I've removed the tune, catch can, and the GT350 CAI that came with the tune has been replaced back with the stock one. So far I still have the problem.

Friday I'll be replacing the cp-e intercooler with the crappy stock one. I will be taking a close look at the cp-e to see if it has any water in it when I remove it.

FYI, I removed my intake in order to more easily get to the catch can lines to remove them off the engine and intake. That catch can does work - my intake looks clean as new, absolutely NO carbon buildup or anything at all for that matter. I wiped down into the engine with my finger and got nothing at all on it.