*Need help with violent engine shaking*

[KLars]

Hi everybody,

I am new here. I recently inherited a 1994 Grand Am GT 2dr couple with the 3.1L V6. (by marriage) It currently has just over 130,000 miles on the odometer.

First off, great website! Tons of info here-I have been cruising the site for the last couple of hours.

Anyway, onto my problem and questions.

This problem just started happening in the last week. It has not been a gradual progression. The car was fine and then it wasn't sort of thing. I don't know if it is a coincidence, but I just ran a bottle of Techron fuel injector cleaner through the car.

1. The main problem going on with the GA is a serious shuddering/shaking of the engine at cruise. It doesn't seem to matter how fast you are going. It is more dependant on engine speed. Cruising along with slight throttle about 1500-2000rpm on a slight incline or flat ground results in the rpms of the engine dropping and the engine going into some sort of violent shuddering that shakes the whole car. Letting off the throttle or pushing on the throttle (resulting in a downshift) makes the engine smooth out normally. Also, the idle has become much rougher and the oil pressure needle now shakes at idle. I have also noticed a loss of power.

I have found about three other posts on this exact problem on this exact engine but there wasn't a clear-cut solution. (actually just noticed a similiar one below but for a different engine.)

Is this problem related to the egr carbon buildup problem in the intake manifold/throttle body that I have been reading about in the 3100 section of the site?


2. How can I read trouble codes of the ECM on the '94? (I saw the post in the FAQ about pre 94, however, no mention of later vehicles that I saw)

3. What is between the CAT and the mufflers on this car? Some sort of resonator? It is making tons of racket at idle. (Loud clanging noises, quite embarrassing)

4. The driver's side power window motor is behaving very strange. Most of the time it works fine, but on a few occasions it goes down fine, but when you try to get it back up it moves about 2 in and stops. Releasing the button and repressing it results in about another 2in up and then it stops again and so on. Is this a sign the motor is going out? It is really weird because a hour later it will work perfectly normal. Is this the window regulator problem? It seems different because that problem seems like the window stops working completely.

5. The driver's side mirror motor seems to only move the mirror left and right but not up and down. Replace the motor?

Sorry this post is so long but I am the type person (as I'm sure you all are) that likes my vehicles to be in working order.

Kevin

[LargeFish]

You can't read the codes yourself unless you have a scanner that supports OBD 1.5 and they tend to be very expesive AFAIK. Yes, there is a resonator behind the cat. A number of us have removed it.

[DEMonte1997]

As per your engine inquiry:

A friend of mine had the same symptoms occur with his Buick Century, although he had the 90 degree 3800 V6 in his car.

Turned out to be a bad cam. Would have costed a lot to fix, so he just let it be. The car ended up running for over 60K miles on the cam. He even sold it with the bad cam.

Does the gas pedal get mushy and lose it's tension when the shaking occurs? If that's the case, it sounds very similar to what my friend went through.

Good luck.

[KLars]

Originally posted by LargeFish
You can't read the codes yourself unless you have a scanner that supports OBD 1.5 and they tend to be very expesive AFAIK. Yes, there is a resonator behind the cat. A number of us have removed it.

Thanks for the info!

What does removing the resonator result in? More Horsepower? Better sound? Or are you just removing in to prevent having to buy a new one when it begins to rattle?

[KLars]

Originally posted by DEMonte1997
As per your engine inquiry:

A friend of mine had the same symptoms occur with his Buick Century, although he had the 90 degree 3800 V6 in his car.

Turned out to be a bad cam. Would have costed a lot to fix, so he just let it be. The car ended up running for over 60K miles on the cam. He even sold it with the bad cam.

Does the gas pedal get mushy and lose it's tension when the shaking occurs? If that's the case, it sounds very similar to what my friend went through.

Good luck.

Thanks for the reply. The gas pedal does not get mushy or lose its tension.

Kevin

[DEMonte1997]

I have one more suggestion.. I certainly don't want to lead you off-base, but it might be a clogged air filter. It happened to my Olds Ciera. I know, it sounds silly. What I noticed was that if I gave the car partial throttle, the car would buck, shake and act as if it wanted to stall. Idle was pretty rough too. Of course, I had a pretty bad air cleaner situation: turned out that some little animal tried to make a nest in it and my filter became totally clogged. :lol: Thus, the engine was running amazingly rich because of the lack of O2.

Just another option for you. You also might want to change all the spark plugs, check the fuel filter and maybe run some top-engine cleaner through a vaccuum line (that might get rid of any carbon build-up in the throttle body).

Resonators are usually installed by the factory to help with the exhaust note. Removing it might help performance, but I doubt it. I'm not sure about the 3.1L engine, but I know that on my 3.4 the exhaust note becomes extremely raspy if the resonator is removed and aftermarket mufflers are put on. 3.1L engines might sound better w/out them.

Hope this helps.

[LargeFish]

It makes it louder, I don't expect it affects power much. I put on a 2.25" catback that eliminated the resonator. I don't know the exact effect in a 3.1 though...

Originally posted by KLars
What does removing the resonator result in? More Horsepower? Better sound? Or are you just removing in to prevent having to buy a new one when it begins to rattle?

[KLars]

Originally posted by KLars
1. The main problem going on with the GA is a serious shuddering/shaking of the engine at cruise. It doesn't seem to matter how fast you are going. It is more dependant on engine speed. Cruising along with slight throttle about 1500-2000rpm on a slight incline or flat ground results in the rpms of the engine dropping and the engine going into some sort of violent shuddering that shakes the whole car. Letting off the throttle or pushing on the throttle (resulting in a downshift) makes the engine smooth out normally. Also, the idle has become much rougher and the oil pressure needle now shakes at idle. I have also noticed a loss of power.

I have found about three other posts on this exact problem on this exact engine but there wasn't a clear-cut solution. (actually just noticed a similiar one below but for a different engine.)

Is this problem related to the egr carbon buildup problem in the intake manifold/throttle body that I have been reading about in the 3100 section of the site?


OK, guys. I am bumping this thread to try and get some more help with the above problem.

I have tried the following:

New Fuel Filter
Another bottle of Injector cleaner
New Platinum Spark Plugs
New Spark Plug wires

No luck. These things did nothing to help my GA. Next on my list is coil packs. If that doesn't work I have to think it is the injectors. However, as stated above, I don't know if this is related to the egr build up problem.

Thanks, Kevin

[92CamaroRS]

my guess would be motor mounts.

[4kQuad]

Another guess.......
You hear ratteling from the resanator...I wonder if it is clogging the exhaust causing too much back pressure.

Did you gap the plugs or just put them in?

Air filter can also cause such problems.

Also listen for a sucking sound or like a straw with a small hole in it when you blow through it. Vacumm leaks cause a lot of problems.

Have you looked at the trany fluid. It should be bright red and not smell burnt. It should smell like oil stuff of course, but not burnt.

Lift the hood at night and look around the spark plug wires for sparks. some times wires go bad and leak there spark.

[92CamaroRS]

Originally posted by 4kQuad

Lift the hood at night and look around the spark plug wires for sparks. some times wires go bad and leak there spark.


JUST LOOK DO NOT GRAB!!!! that stuff hurts. i know from experiance.

[Blylock]

well to clarify some things, does the engine hesitate? does it seem like the engine is running smooth when the shuttering occurs? or does it seem like its skipping, then the shuttering happens.

[4kQuad]

Now if you like to take your shoes off and stomp on rocks....you might like grabbing a bad wire or two. J/K

[KLars]

Originally posted by 4kQuad
Another guess.......
You hear ratteling from the resanator...I wonder if it is clogging the exhaust causing too much back pressure.

Did you gap the plugs or just put them in?

Air filter can also cause such problems.


Thanks for the reply.

The car has a newer air filter (6months?).

I gapped the plugs to .060-that is what the counter guy told me to gap them to.

About the resonator...I was thinking the same thing. If a piece of it is clogging the exhaust then I would think the car would act almost like a clogged cat. I plan on getting the resonator removed and replaced with straight pipe ASAP.

[KLars]

Originally posted by Blylock
well to clarify some things, does the engine hesitate? does it seem like the engine is running smooth when the shuttering occurs? or does it seem like its skipping, then the shuttering happens.

The engine seems like it is running smooth until the shuttering occurs. It is like the engine is fine and then it suddenly drops in rpm and begins to shutter. This occurs when the engine is "cruising" about 2100rpm and under light throttle just to hold speed. It does not seem to be specific to a certain gear. It happens in D and 3.

I can hear the engine miss every 5s or so at idle.

Also, there is a noticeable lack of power. Even when the engine seems like it is behaving OK, if I get on it, the engine feels real lazy.

If a coil pack is going, does it just completely fail? Or does it become an intermitent problem?

Thanks for you help guys.
Kevin

[Blylock]

is it throwing any codes, or backfiring at all. or any noticible spitting sounds upon throttle? or just feel like its not getting enough fuel? generally if its a spark problem, the car would spit or backfire, for the fuel will still be pumped in the cylinders when it skips spark, causing it when it does fire to spit or backfire due to too much fuel upon ignition. a fuel problem generally will bog down the motor, waiting for some more fuel to get going, with seldom spits or backfires. my car (92GA Quad4) was experiencing problems. i found out after mass research and a few changed parts, it was the ignition coil module. my friend works at the dealer said its purpose is mainly for spark, but if it fails, it also communicates with the ECM to control fuel intake, and will on rare occasions tell the ECM to stop pumping fuel to the motor due to spark failures. Im not familiar with the 3.1, but if its set up with a coilpack like my Q4, take the ICM to autozone, they test it for free. if its throwing codes, would be nice to know the numbers

[KLars]

Originally posted by Blylock
is it throwing any codes, or backfiring at all. or any noticible spitting sounds upon throttle? or just feel like its not getting enough fuel? generally if its a spark problem, the car would spit or backfire, for the fuel will still be pumped in the cylinders when it skips spark, causing it when it does fire to spit or backfire due to too much fuel upon ignition. a fuel problem generally will bog down the motor, waiting for some more fuel to get going, with seldom spits or backfires. my car (92GA Quad4) was experiencing problems. i found out after mass research and a few changed parts, it was the ignition coil module. my friend works at the dealer said its purpose is mainly for spark, but if it fails, it also communicates with the ECM to control fuel intake, and will on rare occasions tell the ECM to stop pumping fuel to the motor due to spark failures. Im not familiar with the 3.1, but if its set up with a coilpack like my Q4, take the ICM to autozone, they test it for free. if its throwing codes, would be nice to know the numbers

Don't know if it is throwing any codes because I can't pull them without special equipment. I will check out the ICM. Isn't that the piece that sits right under the coil packs? If so, I already took it off once for the plugs.

No backfiring, spitting or other. Just the engine shudder and I can sense an occasional misfire at idle.

Thanks for the tip on the ICM.

KL

[Blylock]

yes its that flat electronic piece that the coilpacks plug into, take it out and bring it to autozone. keep me posted. btw its around 120 bucks for a new one. short out the 2 upper right pins on your diag connector with a paperclip, turn the key on but dont start it. count the flashes of your service engine light, should start with a 1 flash pause then 2 flashes, thats 12. that means your ECM is operating ok, should do that 3 times, then if you have others it will follow. example 3 flashes pause 2 flashes, thats 32 and so on. if it still does the 12 code, means you have no codes.generally the ICM will not give you a code, but if it screws up bad like mine, it will give you 42 and 43. spark timing circuit and ignition circuit failure.

[LargeFish]

Blylock, there is no test terminal on the 94s, you have to use a scanner...

[Blylock]

Originally posted by LargeFish
Blylock, there is no test terminal on the 94s, you have to use a scanner...


well thats good to know :) thanks. i thought it was from 89-94 i must be wrong

[Hackedtodeath]

i think i might now what that could be i have a freind who has a areostar and his car putters and does all the same things as your and its his cats you might want to check that cause to much back pressure and it can make your car run hard and ruff. Also what you might want to check is motor mounts but i really doubt that cause it mike shake but if you are losing power then its not a motor mount.

[RocketFast321]

Have you tried a italian tune-up? Our malibu does that. It shakes and drops rpm(s) under no load. Turn the a/c on it it runs fine, very little rpm drops. But with it off and the engine warmed up it looks like someone is pulling on the engine. I give it an italian tune up and it runs fine for the week

[cocobob]

Next time it does the same symptoms hook-up a spark plug spark tester inline. If no spark is found on one of the cylinders its either the plug or the coil. You said you replaced the plugs (and double checked the gap spec) so that leaves the coil or module. Substitute the coil with one that worked. If the faulty coil now works in it's new position its the module. If it doesn't work in its new position its the coil.
The problem here on this diagnosis is the lack of space to check the plugs close to the firewall if your car yr is the same as mine (97').
Hope this helps

Cheers

[mikem220153]

From the symptoms you describe, it sounds like you may have more than 1 problem. I haven't seen anyone mention this but, for the shaking and RPM drop off, you might want to look at the crankshaft postition sensor and the camshaft postition sensor. Both of these sensors help control your spark timing on the 3.1 engine. Also don't discount the possibility that you may have 1 or more fuel injectors going out.

The rough idle and lack of power could be from a dirty throttle bodyor as pointed out in a previous response to this post, excessive back pressure from a blocked exhaust system. You need to get the exhaust checked as soon as you can because excessive back pressure can cause burnt exhaust valves.

[jazzman]

well if you want to try diff coil packs and wires. I have some perfect used ones, came off my old engine, worked just fine. If your interested let me know.

Derek

[KLars]

First off, let me say....thank you for all of the responses I got on this thread.

I wanted to report back with the progress. Many of the responses on the forum indicated this problem may have been ignition related. I replaced the plugs and wires with no success.

I then found all three coil packs and Ignition Control Module on ebay from a '96 with 27K miles. I bought it and replaced the ICM and all three coil packs with the ones I bought off ebay.

The problem immediately subsided and it was very obvious that the car was back to idling and accelarating very smoothly.

Again, thanks.

Kevin

[beendead666]

It sounds like I have a similar problem as you. I have done a lot to try and fix it though. Here is what mine does. I step on the gas to give it a little go not much and the whole engine bucks until I really press the gas and make it go. When I press it hard, the throttle will give intermittent bursts of acceleration. It is like it accelerates then bogs goes then bogs. I can cruise along fine I have driven like this for a while but it is just when I give it a slight press of the pedal.
Anyway, here is what I have done with no solution to my problem. I have changed the coil packs housing etc. I have replaced the fuel rail with new injectors, Changed TPS, I change my air filter regularly new plugs all the good stuff, my Fiance's brother is a mechanic and he is baffled.
Cleaned the Throttle body, checked for vaccum leaks. All this and no fix.
My codes say misfire on cylinder (skips around each time I have it checked) Catalyst below threshold. Each time I have it checked it throws a different code.
Im stumped and it is really getting to me, this car has been good to me with 182K on it. I have kept it running strong and now I cannot figure this one out.