(Engine experts needed) Chirp, Vibe, Pop (What is Wrong?)
- Thread starter toximus
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Maybe... At first I didn't think it did chirp when not up to temp but I think it's because the 42RLE doesn't want to stay in OD when it's cold. As soon as it's warmed up enough to stay in OD it'll make the chirp when under the right conditions.
I ran a scan and found a stored code: P0736. It's been months since I last scanned with the tool so I'm not sure that it's related.
It might have to do with when I accidentally was in 4hi and didn't have enough torque to move the wheels reversing. Idk if that'd throw a code or not.
Remove the sparkplugs and have a look. If you have pre-detonation there will be teeny tiny balls of aluminum on the insulator and ground. Be sure the plugs are the correct temp. Regardless of the recommended number for the boosted application, you should verify efficient burn by plug condition.
I recommend checking the actuating spring on the by-pass-valve butterfly. If there is an external arm on the BPV, make sure it has spring tension and returns without a hitch. Better still if you can remove the spring check it. Check the fluid level in the SC nose, and slack the drive belt and check the nose pulley & shaft for looseness.
While the drive belt is slack, give the idler pulley a spin.
I recommend checking the actuating spring on the by-pass-valve butterfly. If there is an external arm on the BPV, make sure it has spring tension and returns without a hitch. Better still if you can remove the spring check it. Check the fluid level in the SC nose, and slack the drive belt and check the nose pulley & shaft for looseness.
While the drive belt is slack, give the idler pulley a spin.
Reason I ask is what I went through/am going through with my M6 which is a turbo V8. I had predetonation under load but only when well into operating temperature or when I’ve been ragging on it on the highway. I have two step colder plugs, gapped real tight, Downpipes and tune. What we think was happening was a combination of fuel and heat, tune not compensating fuel when the ecu pulls timing. Added half tank of VP MS103 and had no issues. Now I’m running pure 97 from VP and no issues. Points to the issue of timing, fuel and heat. Here in Florida we known to get moisture in the fuel due to the tanks sweating. So I could have a combo of things but if we take what I’ve learned and apply it to the 4.0 which we know runs hot, you could be having heat related, predetonation. Can you throw a few gallons of high octane in and see if it occurs? You’ll need to be in the upper 90s of octane to make a difference.
Still doesn’t change shudder.
The ambient temps yesterday were below freezing so the engine wasn't running super hot but had been running probably 6 hours before the vibration and pop. I can make it chirp within 1/4 mile of driving on a flat road. I don't have anywhere close to me that has an incline long enough to keep the chirp happening while maintaining the same speed. The hottest it's gotten here is 65F and I haven't found any correlation between ambient temp and the chirping.
I've ordered a knock sensor and a couple cans of MMT for ease to boost 91 octane up to 101-105 range to test for predetination.
I will check the spark plugs tomorrow and let you know.
The BPV spring is very strong and returns fast.
I'll check the fluid level tomorrow.
There is no looseness.
I do have a spare idler on order to swap in and test. It should be here in another week.
Toximus- thinking out loud here. You mentioned it doesn't make the chip cold and only starts after warmed up. 42rle changes shift schedules when cold, including lockup and partial lockup of the torque converter clutch. Also of note is the 40-55mph range (depending on final gearing) is when the tranny struggles with staying locked, partially locked up and allowing to slip. Have you tried to force the noise to occur in high load, low rpm conditions with the selector in 2nd? Also have you tried disabling OD ( running in 3rd) to see if the noise still occurs under the same high load, low rpm? I'm wondering if it's a converter issue as others have mentioned or if the torque converter clutch can't currently handle increased power and high load of matting the pedal when in OD with any lockup.
I may be over-simplifying here on the "chi-chi-chi" , but do you still have the stock fan? If so, fan clutch? (since you mentioned idler pully)
The max temp of the engine has been 130F so it's possible that it's not getting up to temp.
I have tried disabling OD and running it in 3rd and the chirping has never happened (other than the squeal when launching but I don't see that as something I ever do normally).
Similarly I had the transmission in 4hi off road and "stalled" (meaning didn't have enough power to turn the wheels without going into 4lo) and the transmission didn't complain.
Does that tell you anything?
I do have the stock fan. I'll take a closer look at it and see if there's any play.
I don't want to discourage you from checking some of the easier items suggested by others, but I do suspect the converter is having issues coping. Sometimes they chirp or squeak, ( I compare the sound to a power steering low on fluid turned to the stops). It checks a lot of boxes as the root cause. The sound, vibration and location of the vibration, overdrive sensitive, and load/rpm based, all are somewhat typical symptoms. It not an easy life for a TC in a trans with a ridiculous gap from 3rd to 4th, to turn 37's with a S/C!!
Aside from stall testing it yourself in the driveway, (which won't tell the whole story), it might be worth scheduling an appointment at a trans shop to diagnose further. Doesn't mean failure is imminent- but it probably will happen sooner than later if don't roll on the gas in OD to lessen the strain as Rubi said.
Hopefully you find it's something else. Keep us posted. Btw I've really enjoyed following your build -nicely done and thanks for documenting!
Aside from stall testing it yourself in the driveway, (which won't tell the whole story), it might be worth scheduling an appointment at a trans shop to diagnose further. Doesn't mean failure is imminent- but it probably will happen sooner than later if don't roll on the gas in OD to lessen the strain as Rubi said.
Hopefully you find it's something else. Keep us posted. Btw I've really enjoyed following your build -nicely done and thanks for documenting!
I'm also inclined to think it's the transmission. Especially when you consider the way the chirp progresses and disappears when it turns into a vibe and then the vibe turns into the pop even though the throttle input and speed don't really change. And it does the exact same sounds and vibe/shudder and progresses the same every time it's in that condition (aside from progressing it into a pop only once).
I'm still going to narrow it down to the transmission but if it is indeed the culprit I'm not sure that I want to invest in the inline 6 platform any more.
The shudder is most likely the torque converter clutch, (electronically modulated converter clutch, or EMCC on the 42rle) trying to apply. A couple more suggestions on converter tests to help narrow it down.
1.) make it shudder then lightly ride the brake at the same time. The EMCC is supposed to disengage when the brake is applied. If the vibration/shuddering stops when the brake is applied, its the converter clutch.
2.) reset the adaptives by disconnecting the battery. Supposedly on the 42rle there in no EMCC within the first 500 miles after a reset. I haven't done this first hand on a 42rle so I cant validate. There is also a brief description of the EMCC function in the FSM which can also give you an idea of the conditions under which is applies.
Unfortunately there's not a lot of options for performance converters for the 42RLE. Perhaps give ATS Diesel a call.
The chirp and shudder for sure happened within the first 500 miles. The chirp always happened ever since I started going fast enough to be in OD, and I remember the shudder happening twice during gear break in. I always lifted off the accelerator to make it go away.
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As I said, I can't vouch for test 2 but Chrysler has previously stated no EMCC during relearn. They've been wrong plenty! Give test 1 a try.
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