Author Topic: violent stammering at 3500 ~4000+ RPM in 5th Gear (Read 8416 times)

jdirty · « **on:** May 31, 2011, 12:48:25 AM »

i was driving my e30 again lately and i noticed that whenever i go beyond 3500 rpm.. roughly 75mph.. (i'm not really sure about the speed coz my speedo is broken) the car would shake so bad it would almost feel like it's going to fall apart. if i slow down, the car would calm down. aside from that, the car also pulls to the right. last thing i did was replaced the front calipers, rotors and pads. could i have fucked the alignment..? and another the car would jolt. when going into reverse and then stopping, the car would seem to jolt as if giving you a mini whiplash effect. in either going reverse or forward.

can't really go under the car yet due to injury but what do you guys suspect?

bmwman91 · « **Reply #1 on:** May 31, 2011, 01:16:58 AM »

Does the crazy vibration only occur when you are moving at 75mph+, or any time your RPM is over 3500RPM? If it is only speed-dependent, it sounds like an unbalanced driveshaft. Have you had the 2 halve separated recently? If you don't put them back together EXACTLY like they originally were, then it is out of balance. It is usually easy to fix...there are usually painted alignment marks covered in dirt.

It might also be the driveshaft support bearing/bushing, or the guibo.

It could also be a wheel bearing, but that seems less likely. Check that all wheels spin freely to rule out brakes. If one wheel has a lot more dust than the other, that is also a hint of a seized caliper.

jdirty · « **Reply #2 on:** May 31, 2011, 06:05:54 PM »

it is actually strictly on 75+ mph speeds and over 3500 rpm is pushing it.. higher than that.. the car would seem to be running on a bed of small rocks. i have no clue what the previous owner tried to do when he had it but ever since, it has always been that way with the shuddering. you know what i actually replaced the calipers.. because the previous owner didn't know they were seized and so did i until a replaced the calipers and rotors.

bmwman91 · « **Reply #3 on:** May 31, 2011, 06:18:41 PM »

Hmm, in that case I'd investigate the driveshaft. See if you can ask him if he had the halves separated. I made that mistake once, years ago. It made the car feel like it was going to vibrate itself to death when I drive 35MPH or more though (I had the halves really disoriented).

Are you saying that if you were in neutral and revved the motor above 3500RPM, or were over 3500RPM in 2nd gear that the car also stammers? Or is this strictly at 75mph, regardless of engine speed? If it happens ONLY when moving at 75mph+, it sounds like it is probably just the driveshaft. Worst case, if the alignment marks are gone, some specialty shops can re-balance it for $100-150.

jdirty · « **Reply #4 on:** May 31, 2011, 06:30:06 PM »

the vibration would only happen in motion specifically 75mp / 3500+ rpm.
at a stand still, i can revv the engine as much as i want,
other gears than the 5th, the car is perfectly fine.

the 1st owner might have passed away 2nd owner said it was a really old guy.. 2nd owner said he just held onto the car (though i believe he fucked up the car),
i'm the 3rd. and recently found out it's a salvage.

bmwman91 · « **Reply #5 on:** June 01, 2011, 12:41:30 AM »

Sorry to be playing 20 questions. So if you go 75 mph in 4th gear (or push in the clutch & coast), everything is fine? If that's the case, then it is not an unbalanced driveshaft since that would be speed-dependent only.

If it is a salvage, it could be busted suspension bushings, motor mounts, tranny bushings, diff mount, driveshaft support bearing/bushing or a bent driveshaft. Unfortunately, you'll most likely need to get in there & really look around. Do the seams on the doors/hood/trunk look even & consistent?

If it requires both 75mph AND 3500RPM in 5th gear, I'd put my bet on trashed motor mounts, or tranny mounts.

jdirty · « **Reply #6 on:** June 01, 2011, 06:49:10 PM »

i haven't really noticed if i'm going 5k rpm in 4th gear... does that translate to 75 mph?
because i'm really not for sure what my speeds are most of the time.
(..only speeds i'm only familiar with is 35 mph/2.5 k rpm. 45 mph/2.2k rpm. 65mph/3.2k rpm. 75mph/3.5k rpm all these are just guesses and a cop telling me what speed i was doing at one point..)

only noticeable thing is passenger fender. the hood isn't straight particularly near the fender and also the top side being battered.

old fender semi close up when i replaced my lamps and painted my grilles.

side view of the fender when i replaced rotors, calipers and pads.

notice passenger side fender and hood aren't flush.

somebody mentioned before, somewhere that my lamps were way into the grille than normal?

i'll try going faster on 4th gear later to verify because i can't really remember how it was when i drove it home from CA. i remember gunning it and being on 4th gear majority of the time.. hmm.

jdirty · « **Reply #7 on:** June 02, 2011, 12:48:20 PM »

tried going 75+mph on 4th gear and there was no vibration. different issue but this morning.. the car started hesitating on low rpms. like its getting bogged down. sputtering to higher rpm. i opened the hood while the car was on neutral, gave it some gas ans i noticed on low rpm the engine was shaking. so the shaking is the motor mount but sputtering..? could that be cause by my faulty throttle cable..? i recently just repaced the o2 sensor, fuel pump, fuel filter and fpr. and 3 months back, the spark plugs. wtf! -_-

DesktopDave · « **Reply #8 on:** June 02, 2011, 02:36:29 PM »

Check the resistance on the AFM flap. I think it's pins 1 & 2. Should smoothly progress from high to low IIRC. Do you have the BMW books like the ETM and the Bentley e36?

jdirty · « **Reply #9 on:** June 03, 2011, 01:48:04 AM »

yep. did the whole resistance testing and came up with inconsistent values, up and down. so i popped it open and checked the carbon track. and sure enough its was like thinned out on the spots where resistance was off... long story short, i kinda fucked my afm.

bmwman91 · « **Reply #10 on:** June 03, 2011, 11:45:43 AM »

Interesting. I had a similar issue years ago, but it didn't seem to be quite as RPM dependent. Hopefully a "new" AFM will solve your issues!

DesktopDave · « **Reply #11 on:** June 03, 2011, 01:44:24 PM »

Seems like you're getting a lot closer on this one...good to hear.

Realign the resistor pickup heads if possible. I've only had the older ones apart, I heard the newer ones aren't quite so adjustable. Post some pics!

jdirty · « **Reply #12 on:** June 03, 2011, 09:18:53 PM »

i opened it again and last night then realized it had been tampered with. i guess the previous owner was already trying to remedy the afm. ground wire for the wiper arm was brittle. had to resolder a new one and double checked the tracks.. went to work this morning no change. but on my way home just now, i kept gunning the car on high rpms... and when i was nearing home the stumbling stopped but would still come up sometimes. i need a "new" afm for sure. -_-

makes me think because of the stumbling, it intensifies the worn out mounts and bushings of the car making everything vibrate even more. i'll still look into the drive shaft soon as i can crawl under it.

92BMW318is · « **Reply #13 on:** June 03, 2011, 09:22:01 PM »

Quote from: jdirty;104206

i was driving my e30 again lately and i noticed that whenever i go beyond 3500 rpm.. roughly 75mph.. (i'm not really sure about the speed coz my speedo is broken) the car would shake so bad it would almost feel like it's going to fall apart. if i slow down, the car would calm down. aside from that, the car also pulls to the right. last thing i did was replaced the front rotors and pads. could i have fucked the alignment..? and another the car would jolt. when going into reverse and then stopping, the car would seem to jolt as if giving you a mini whiplash effect. in either going reverse or forward.

can't really go under the car yet due to injury but what do you guys suspect?

Check Break calipers and rotors on the right front side mine was doing this when the piston on the caliper was locking up. also it could be a ball joint. or wheels are unbalanced.

If you are in neutral on a hill and you cannot roll backwards its defiantly the calipers

jdirty · « **Reply #14 on:** June 03, 2011, 09:41:52 PM »

it's the ball joint from what i recall when i looked at it. i actually replaced my front calipers. just forgot to put it. i didn't think of the wheels being unbalanced. thanks.