Crazy engine vibration
 

So, I just completed the 5MT swap and now I have a horrific engine vibration:( :rolleyes: .

I understand the importance of driveline angles, U-joints, and CV joints on the smoothness of the vehicle while driving. HOWEVER, I know that my problem is related to none of the above because it occurs at a stop in Neutral, when none of these components are moving. It also occurs while driving. I cannot troubleshoot any driveline vibrations until I get the engine vibration tamed. Here are the symptoms:

1. Engine codes read 24 (bypass valve), and 19 (fuel injector #6)
2. Even after clearing codes, 19 and 24 are still there
3. At a stop, in gear with clutch disengaged there is a strong vibration that increases intensity with RPM. If I put the car into neutral and engage the clutch at idle, the vibration changes slightly, but is still noticeable. Keep in mind that when I say idle, I mean 2000RPM because I'm having issues with the bypass valve and the 5MT as many members do after the swap

I will check injector #6 by unplugging it and seeing if the problem goes away. Which of the 2 rears is #6? Driver's side? During the 5MT swap, I disconnected a bunch of stuff (of course), but didn't touch the injector connectors. Is there anything that gets disconnected that could make the #6 injector act up?

Any other ideas as to what it may be? Thanks in advance:) !

Mat

If the Inj6 code is current (not historical) that indicates either a open or short circuit, either of which will cause a misfire. Misfires cause engine vibration so the logical step would be to find out what's causing the code to pop up. Note that the code doesn't necessarily mean that the injector itself is bad - emphasis on the word 'circuit'.

Thanks for the insight, Beav. I have a question, though. Last night I went through with the engine running and unplugged each injector one at a time. Each time one was unplugged there was a noticeable degredation in engine smoothness. If this vibration were from a mis-fire, wouldn't it have showed up during that test? Man...it's going to be tough to hunt down a short circuit. Any pointers?

I was also wondering if it's possible that the timing belt slipped a tooth or something during the install of the trans. I've also been recommended to check the dog bone for binding.

Is there any way to test if mounts are bad or bottomed out or something like that?

Mat

Seeing how there was equal change when disabling the injectors I'd say that was a historical code.

Since the vib is there even w/the clutch disengaged and wasn't there before the swap, I'd concentrate on what was changed - incorrectly mounted flywheel/pressure plate, etc.

Did you have that flywheel checked and milled?

did you pull using the wires when/if you unplugged the harnesses on the passenger side in the engine compartment?

Flywheel was resurfaced. I can't say it was checked, but I would've hoped they would've reported any problems based on the resurfacing.

I did disconnect the 2 connectors on the passenger's side, but I didn't pull by the wires.

Unfortunately, my brain is saying it's the flywheel or pressure plate alignment. That sux :( I'm gonna go do a few tests to try to pinpoint the source. Wish me luck and keep providing feedback if you think of anything.

A few other "symptoms" that may or may not be related...

1. Oil seepage from all seals (front, rear, valve covers)
2. Occasionally the starter won't fire

-Mat

Did you brace the front of the engine when removing the auto? I did'nt. The engine rocked forward until it came to a resting position on the radiator fan shroud. This tore my motor mounts in half. :eek: It was very visible.

If the PP and flywheel were'nt aligned, you would'nt be able to get the 5mt fully installed, right?

Testing complete
 

Hey y'all...thanks for the input. I've heeded it all ;)

I did a few different tests to find the source.

I started by disconnecting the dog bone to see if that was the path for vibration transfer. It wasn't. Vibration remained with dogbone disconnected.

Next I removed the exhaust to see if it was a resonance in the new pipes or something coming in through the exhaust mounts. It wasn't. Vibration remained with exhaust removed. And, by the way, car sounded VISCIOUS!!!:D :D

Next I loosened the transmission x-member and jacked the engine up to get it off of the mounts. Vibration remained even with little load on the mounts

Finally, I took out the transmission x-member, jacked the engine up so that the angle between the engine and body was 5.5 degrees (as it is stock), and supported the transmission with a transmission jack. Vibration went away!!!:cool: :D :)

So, there are a few possible causes, still. It could be...

a) the engine and transmission were at slightly different angles. Maybe when I tightened the trans mount to the crossmember, it pulled on the rubber trans mount and strained the joint between engine and trans??

b) transmission mount is a vibration path. I think this is the most likely cause. Will simply increasing the rigidity of the x-member solve this? Also, when all is tightened, I don't want any load on the rubber mount, right? It shouldn't be in compression or tension??? I'm pretty sure that after the original install, the rubber mount was in tension.

Okay...I'm getting close. Looking forward to hearing some advice as to what the best solution would probably be given the test results.

Mat

In my experience a weak trans mount has not caused vibration but a broken one would allow the engine/trans to shift around under changes in inertia.

Tom has suggested people shim the x-member with washers in the past to solve (test for) trans angle issues... perhaps you should try the same to see if it helps.

Purely out of curiosity, what is the uncorrected angle you have?

Can you post a picture of your crossmember? I'm wondering if there isn't enough vibration isolation in your crossmember setup. Do you have anything to dampen vibration besides the actual tranny mount? Is it a stock WRX mount or a Group N mount?

If the car is motionless and just idling and you still feel a vibe until you move the trans I'd be looking for something grounding out - not electrically, but physically touching metal-to-metal. Also check the load on hoses, like that big, fat a/c hose...or even that you're not tugging on the radiator with the upper or lower hose, etc.

Mychailo,
I'm out of town this week, so I can't get a pic of the crossmember up. Here's a description though...

From the front crossbar under the engine, I go straight back about 3/4 of the way to the stock crossmember with thick walled 1.5" piping. At that point, I connect the two "runner" pipes with 2" or 3" wide channel steel (2 pieces welded back to back to create an "I" cross section). This is where the stock WRX rubber mount bolts to. From there, I use a 1/4" thick steel plate about 5" wide to connect to the stock crossmember (it covers about 4" gap). I originally had the 2 runner pipes going all the way back to the stock crossmember, but they interfered with the exhaust. I was thinking about reinforcing the entire structure with 1/2" cold rolled steel. All welds are full seam welds...not spot welded.

Other than the stock WRX rubber mount, I have no other means of vibration absorption (but neither did the stock SVX)

Beav,
I understand what you're suggesting I look for, and I will. However, doesn't my final test point toward either the engine angle or the trans crossmember as the root cause?

Mat

One more thing to add. When I went under the car to remove the x-member, I found that a few of the bolts were not tight. I know, I know...I'm an idiot. But, could that have been the source in itself? I almost think that the vibration rattled them loose...It's not like me to leave bolts un-tightened. Plus, it seems too simple to explain the amount of vibration I was feeling.

Mat

With the exception of "where would the oil be?", it doesn't matter if the engine is upside down or standing on end.