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Discussion Starter · #1 · (Edited)
Welcome all my puzzle solvers, for I have quite the challenge.
Quick back story. Recently undertook a massive project on my 03 E46 M3. ~147k miles. I essentially did a big overhaul and been wanting to auto/track the M (Big dream of mine).

Problem:
Rough idle/cabin shake @ 850rpm with warm engine. When I bring above 950-1k rpm it smooths out.
I have no initial start-up problems and runs super smooth. As it warms and rpm starts to decline, the shake sets in.

Parts I've upgraded or cleaned:
Engine:
  • VANOS (rattle kit/o-rings/oil line/timing chain guide)
  • Valve adjustment / timing
  • Spark plugs (NOT INGINITION COILS) <--- Initial start to fix shake/idle
- Did a coil/plug change about 4-5yrs / 10-15k miles ago.
  • Cleaned and tested fuel injectors
  • Cleaned ICV
  • Removed ITB's and thoroughly cleaned. (new o-rings)
  • Rod bearing w/ ARP bolts
  • New oil pump
  • Fuel filter
  • REVSHIFT Poly engine mounts (95A)
  • Chase bays Power steering kit.
  • New O2's
  • PSDesigns Velocity Stacks w/ IAT and TTFS Alpha-N tune. (Tune is just a basic one for I can't really go to them to have them specifically tune it. Plan will be to take to local tuner).

Transmission:
  • Flywheel w/ new bolts(changed about 4-5yrs / 10-15k. Looked in good condition and had no need to change.)
  • New clutch/pressure plate
  • Input/output seals
  • Select rod seal
  • REVSHIFT trans mounts (95A)

Exhaust?
  • Fabspeed catless headers
  • Status Gruppe Sec 1&2 (poorly made, going to upgrade to Supersprint)
  • Supersprint Sport Muffler

There is a ton more. I may be forgetting some stuff or it's not needed for the issue at hand. So please ask away. I am seriously stuck. She drives beautifully, engine not only sounds strong, but feels amazing. Your ideas or inputs will be greatly appreciated.

Notes:
I have done everything myself. Always made sure to torque-to-spec (At least I believe, keep second guessing myself).
I understand with these firm mounts I would be receiving more feed back from the engine/trans, but I don't think to this extent?
I have ordered a new ICV and Coils.
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Rough idle/cabin shake @ 850rpm with warm engine.
No engine error codes?

Rough only with warm engine: check with INPA software to see the long and short term fuel trim data. Could be a bad intake air temperature sensor or bad MAF.

Smooth when cold: DME ran in opened loop control and no O2 sensor feedback; but after warming up and in closed loop, a bad sensor can cause the closed loop to be unstable and a shaking engine.
 

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Discussion Starter · #3 ·
No engine error codes?

Rough only with warm engine: check with INPA software to see the long and short term fuel trim data. Could be a bad intake air temperature sensor or bad MAF.

Smooth when cold: DME ran in opened loop control and no O2 sensor feedback; but after warming up and in closed loop, a bad sensor can cause the closed loop to be unstable and a shaking engine.
Zero codes.

I have INPA but ill have to take a look for that since I've never payed attn to it. Also IAT shouldn't have faulted, but I can give it a clean and check wires. When at idle its very stable. No bumps, no "going to die" moments.

Has all new O2's. They're from FCP so lifetime for the win, but I feel like I need proof they faulted.
 

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Discussion Starter · #5 ·
you meant only when engine was cold, and DME controlled with opened loop (rich mixture)?
Nope. This is for both cold/warm engine. I can drive around and and when I want to come to a stop, idle comes down normally.

I watched some videos last night about fuel trim and it was quite interesting. The only things I think of when coming around for that test is that I've done a smoke test with no leaks, and again, brand new O2's.
 

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Discussion Starter · #6 ·
you meant only when engine was cold, and DME controlled with opened loop (rich mixture)?
I have attached some photos in the original post. O2's are fluxin between .0v and .7v. Short terms were moving, but the long term was steady. I hope this may give you some more information to my issue.
 

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I agree that most probably it's the maf or maybe the iat. You can easily check if the iat works from inpa. Maf diagnosis isn't so simple though.
One simple trick you can to is disconnect the maf and try to reproduce the problem. If it won't occur, voila, your maf is soft failing
Also, a vacuum smoke test wouldn't hurt. You can also check the fuel pressure

Edit ; now I see that you have an alpha n tune. I believe that's your problem. Something isn't perfect in the tune
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seeing how shake is only at the lower 850rpm and goes away at 950rpm it sure sounds like the tune is causing those 95A poly engine and transmission mounts to transmit the vibration to the seat/cabin.

S54 is a heavy engine. there are trade-off using poly over stock M3 rubber fluid filled heavy duty engine mounts.

i’m Not saying it’s definitely the firm poly mounts, but it’s something that certainly comes to mind. I’m guessing the engine & trans mounts were done together with the rest of the build? so you can’t really compare what incremental changes caused what.

as a last resort you can always raise the idle’s tune if you don’t figure it out.
 

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Discussion Starter · #9 ·
I agree that most probably it's the maf or maybe the iat. You can easily check if the iat works from inpa. Maf diagnosis isn't so simple though.
One simple trick you can to is disconnect the maf and try to reproduce the problem. If it won't occur, voila, your maf is soft failing
Also, a vacuum smoke test wouldn't hurt. You can also check the fuel pressure

Edit ; now I see that you have an alpha n tune. I believe that's your problem. Something isn't perfect in the tune
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I had an issue prior where I had did this test and there was a difference when I disconnected it.

I've had a gut feeling about the tune. I'm not faulting the company, it just with all the modifications I've done a basic tune won't do it.
 

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Discussion Starter · #10 ·
seeing how shake is only at the lower 850rpm and goes away at 950rpm it sure sounds like the tune is causing those 95A poly engine and transmission mounts to transmit the vibration to the seat/cabin.

S54 is a heavy engine. there are trade-off using poly over stock M3 rubber fluid filled heavy duty engine mounts.

i’m Not saying it’s definitely the firm poly mounts, but it’s something that certainly comes to mind. I’m guessing the engine & trans mounts were done together with the rest of the build? so you can’t really compare what incremental changes caused what.

as a last resort you can always raise the idle’s tune if you don’t figure it out.
I knew there was a trade of when doing poly bushings, but I didnt think there would be this much vibration. Or i'm just crazy and there is and I just gotta live with it. But like you said worst case I just raise the idle. Don't see much harm in that.
 

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I had an issue prior where I had did this test and there was a difference when I disconnected it.

I've had a gut feeling about the tune. I'm not faulting the company, it just with all the modifications I've done a basic tune won't do it.
Well the word that troubles me is basic. The tune needs to be spot on, perfect in every rpm and situation, else you will have problems. Maybe not severe, but noticable. But Alex323 may be right. Polyurethane engine mounts considerably affect roughness at low rpms, so it may be that simple. And when it's cold the rpms stay high, so it's a warm engine only problem. You have some things to do, unplug the maf maybe, swap mounts to pinpoint the problem, or keep the idle raised, etc

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Discussion Starter · #12 ·
As stated, I've ordered new ignition coils and an new ICV. So I will keep this updated on how everything is performing.
 

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Discussion Starter · #13 ·
Well the word that troubles me is basic. The tune needs to be spot on, perfect in every rpm and situation, else you will have problems. Maybe not severe, but noticable. But Alex323 may be right. Polyurethane engine mounts considerably affect roughness at low rpms, so it may be that simple. And when it's cold the rpms stay high, so it's a warm engine only problem. You have some things to do, unplug the maf maybe, swap mounts to pinpoint the problem, or keep the idle raised, etc

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Yeah I can think of a better word than just that. When I bought this kit it was included, but the tuners were across the county(USA) and I was new to my area and had no idea of local tuners. There is a tuner that I will be going to get it dialed in.

I wish I kept my old mounts 🙃 Did the ole "I ain't gonna be needing these things anymore!" and tossed them.
 

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Yeah I can think of a better word than just that. When I bought this kit it was included, but the tuners were across the county(USA) and I was new to my area and had no idea of local tuners. There is a tuner that I will be going to get it dialed in.

I wish I kept my old mounts Did the ole "I ain't gonna be needing these things anymore!" and tossed them.
I see and I hear you about the old mounts hahah, we get wiser with those hiccups though. Hope you to solve it

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Discussion Starter · #15 ·
Just an update. I decided to drive the M into work due to having a nice day. While I was in the parking lot I was coming to a stop and I pushed my clutch in and car just died. Almost like the fuel pressure just went away completely. Tried to start it up and there was no luck. After tinkering with it my starter literally went out. Talk about a double whammy. I'm kinda thinking that the rough idle was something to do with that. I've never changed the FPR and don't really know how to test it. I will have to wait for the starter motor so I can test the pressure. Also I can hear the fuel pump priming. Maybe I'm missing something? No leaks and doesn't fuel smell anywhere.
 

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Discussion Starter · #16 ·
Just an update for this post. I have got in contact with Revshift and asked if I had "somehow" messed up the installation. Something about pre-loading and what not. The gentleman was awesome and pretty much summed up the "rough idle". So since it took me a hot minute to really find this information. 95A Poly mounts will cause pretty heavy shaking! While at idle that is. Most of the vibration you feel is from the transmission mounts since they are located right under your seat. I've ordered some used oem trans mounts to do some testing.

For the weird shut off. I have no idea on what the cause was and still has me kinda worrying about taking it out for a drive. Worst case, I drive and hope it never happens again with all the replacements i've done, or it does happen again and I try to diagnose issue. Hopefully closer to the house so i can push it. Otherwise here comes towing fee :/

I have another post going about my fuel pressure: Fuel pressure dropping while idle... Other fuel issues. Which I dont know if it was part of the problem.
 
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