3.4L Engine/Transmission Vibration

[IceHammer]

Ok guys, I just bought a 94 Firebird, because I just got in an accident with my 94 Camaro. I'm working on tuning up the new car, and I've become stumped on something.

When the engine is on, and you shift into drive or reverse (Auto) and have the brake on, the car has a fairly good sized vibration. This same vibration occurs when it shifts to overdrive (past 45 mph). When idling and not in gear, the vibration cannot be felt in the cabin, but may still be occuring. No load on the engine there so it really isnt the same condition. My old Camaro (R.I.P) had the same thing going on, but not nearly as bad. I never addressed it in my old car as it never was bad enough to bother me, however the new car has it bad enough that I may go crazy if I drive it that way.

Anyone have any ideas on what the problem may be / have the same problem?

A little more info, the previous owner just had the Tranny fluid changed, so could anything in the transmission be causing a problem? I've found if someone is selling a used car and it has new Tranny fluid they are probably trying to cover up a problem. The engine will be getting new plugs, wires, air filter, and probably an oil change today, so I'll let you know if any of that solves it.

Now that I'm thinking of it, I once tried to use injector cleaner to solve the problem on the old car, and that had a mildly positive effect. Could the fuel injectors be the problem?

Any ideas would be appreciated.

[nascar24jd]

Re: 3.4L Engine/Transmission Vibration

What is the idle RPM in gear and also in neutral?

[3.4grapeofwrath]

Re: 3.4L Engine/Transmission Vibration

Check the transmission mount/ exhaust mount at the tail section for any metal on metal contact. The mount might be shot.

[speedyx14]

Re: 3.4L Engine/Transmission Vibration

My car suffers from the exact symptoms, only it doesn't shake at higher speeds.Only in drive and reverse when the car is at idle. From what I've gathered this is a common problem with the 93-96 Camaro/Firebirds. If you search this forum you will find various topics about the issue. Few people have actually solved it. And one proven solution might not work for someone else.
I have heard it could be motor mounts, rod's etc. Many folks just kind of deal with it, or throw the car in neutral at a stop light.

[tkoforpresident]

Re: 3.4L Engine/Transmission Vibration

My car suffers from the exact symptoms, only it doesn't shake at higher speeds.Only in drive and reverse when the car is at idle. From what I've gathered this is a common problem with the 93-96 Camaro/Firebirds. If you search this forum you will find various topics about the issue. Few people have actually solved it. And one proven solution might not work for someone else.
I have heard it could be motor mounts, rod's etc. Many folks just kind of deal with it, or throw the car in neutral at a stop light.

YES!!! it's amazing how my car runs so much better in neutral and it shakes violently in drive idling even though theres no misfiring.

[IceHammer]

Re: 3.4L Engine/Transmission Vibration

At idle in gear the Tach reads about 600, about 800 not in gear. As far as I can tell, the tach is giving me the wrong reading, it also shows about 1250 at 45 mph in OD. My other 94 would read 1450, so I'm guessing right now that the tach is giving me a reading about 200rpm low.

Do you know what those other threads on this topic are titled? I did quite a few searches before I posted this thread to see if there was something similar and I wasn't able to find too much.

[tkoforpresident]

Re: 3.4L Engine/Transmission Vibration

another Buffalo winter warrior!! :rock:

[IceHammer]

Re: 3.4L Engine/Transmission Vibration

Haha thats right. Snow doesn't have anything on us! Who needs traction anyways, sliding is much more fun.

[tkoforpresident]

Re: 3.4L Engine/Transmission Vibration

Haha thats right. Snow doesn't have anything on us! Who needs traction anyways, sliding is much more fun.

lol, i put my bird away on tuesday actually, i drove it once when there was snow on the ground and i thought i was gonna die.

my birds a garage queen in the buffalo winters, except of course when it's parked on my back patio and i'm tearing apart the top end in the middle of january like last year :banana:

[speedyx14]

Re: 3.4L Engine/Transmission Vibration

Do you know what those other threads on this topic are titled? I did quite a few searches before I posted this thread to see if there was something similar and I wasn't able to find too much.

Here are a couple of threads that highlight this problem. I got these when I searched "car vibrates idle".
http://forum.camarov6.com/showthread...ngine+vibrates
http://forum.camarov6.com/showthread...ngine+vibrates

There are even more threads than this. Simply search "car vibrates at idle" and join the masses who have yet to solve this one.

[blackandgold]

Re: 3.4L Engine/Transmission Vibration

My car was doing the same thing for a long time, I finally replaced the wires, and it turned out that my #5 wire was completely melted through, check your wires and plugs, it may be an easy fix.

[IceHammer]

Re: 3.4L Engine/Transmission Vibration

Ok, I just changed the fuel pressure regulator in attempting to fix an unrelated problem, but it seems to have lessened the vibration. However, it is not entirely gone.

After looking around the forums some more, the best idea I've heard for the vibration cause is the main crank bearings being worn. Other legit ideas included engine mounts and a misfire, but there is no misfire in my current bird or the camaro I just lost, both of which had this vibration. In either case, the vibration is on the back burner while I figure a different problem.

I just had a new Cat put in because the old one was burnt out and the inside was rattling around inside. We determined that the engine was getting way too much fuel. Which lead to the replacement of the pressure regulator. Not it doesn't seem to be running too rich. However, the engine bogs down at some times. It isn't terribly consistent, and all of a sudden it will stop bogging and let loose running like it has no problems. Anyone have any ideas on this?

Another issue I found is that the Oil Pressure gauge reads 70-80psi from a cold start. This is clearly wrong and about double what it should be. It doesn't have too much oil. Can the gauge be reading incorrectly? Or is the sending unit out of control?

Any ideas on any of these would be helpful.

[speedyx14]

Re: 3.4L Engine/Transmission Vibration

I had an oil pressure sending unit that was leaking and giving me incorrect readings. I would go from 20psi at start up to 0psi at idle when warm. I now get 60psi at start up and about 23psi at a warm idle. Of course the reading rises when I'm driving though.

What is your oil pressure reading when the car is completely warm? It probably isn't a serious problem as long as it drops to a reasonably safe range.

[IceHammer]

Re: 3.4L Engine/Transmission Vibration

When warmed up and idling, it'll come down to 40psi, but hit the gas and it shoots back to 80psi. I'm not terribly concerned at this point as its probably the sending unit giving me false readings. In my camaro with the same engine it would do a cold start at 45 and warm idle a little over 20, so thats why I think its wrong.

Any ideas on the intermittent bogging problem I described above?