3.8 Series II Oldsmobile Shaking Violently

[vonVeezelsnider]

Hi All,

I'm posting this on behalf of my friend who owns a Naturally Aspirated 3800 Series II 1996 Oldsmobile Eighty Eight LS with about 175K Kms (108K Miles) and he says that when he comes to a complete stop at a stoplight and sits there in gear, the engine starts shaking real violently and the check engine light comes on. I haven't had the opportunity to witness the problem first hand but he's described it in this way... He's taking the car into an indie mechanic but I know that alot of you guys have 3800 H-Bodies and I was wondering if you can give any insight.

He says he's gonna turf the car in favour of a LeSabre or Park Avenue if the cost of the repairs are any more than 1000$... So what are some possible causes?

Keep in mind he witnessed the infamous Upper Intake Manifold Failure and the coolant leaked into his engine, causing it to seize just last June... The engine has been rebuilt as of July 07, and the head gasket had failed as a result of the coolant leak as well and was replaced at the same time...

So far we put our heads together and got the following possibilities:

-Bad Spark Plug

-Bad Spark Plug Wire

-Bad Valve

-Bad Piston

-Head Gasket Leak

-Cracked or Leaking Head

-Bad Powertrain Control Module (PCM)

Are there any other possibilities you can think of and also... Do you think it would be prudent for me to advise him (and for him to do as I say) to take the Olds to a GM Dealer and have them run a compression test as well as have the dealer run the codes on it??

Any other suggestions as to what is causing this are appreciated as well as perhaps a notation of what you'd expect to pay in the USA for the problems I've already sourced would help him out greatly as well.

Thanks!

/CP

[76ChevyTrucker]

With 108,000-ish miles on it, its tune-up time. The shaking comes from at least one cylinder (probably one or some other odd number of cylinders misfiring), which means that the engine runs unevenly, causing the shake. If your friend has had no other real problems with the car, then its probably tune up time and don't think anything of it. Repair bill shouldnt' be more than a couple hundred, dependant on the standard labor rate for whatever shop its taken to. I know here in Alabama, the "normal" labor rate is right about $65.00 per hour with a minimum charge of one hour.

[SuperSport623]

my last motor in the nova that just came out shook most under 800 RPM... ( it was a 350, but same principal..) i had one cylinder out at first and slowly started to lose the rest... hopefully that turns out to be just needing a tune up... my problem turned out to be the motor eating cam lobes so the valves werent opening..

[Drew Dowdell]

take each spark plug wire off, one at a time and replace it before moving to the next, while the engine is running. Note any changes in engine beat. Could be a coil pack.

[vonVeezelsnider]

Does it happen while he's decelerating? It may be his torque converter not unlocking if it is.

Nope, only when the car is not moving.

[daves87rs]

I was thinking either

-need a tune up

- coil pack

-EGR (either cleaned or replaced)

I'd do the tune up first....

[vonVeezelsnider]

Coil pack could be it...

He's having this other problem, when he turns the steering wheel @ low speed the car makes a terrible groaning noise that I can only liken to a dying beached whale... any chance both problems are connected?

[daves87rs]

Coil pack could be it...

He's having this other problem, when he turns the steering wheel @ low speed the car makes a terrible groaning noise that I can only liken to a dying beached whale... any chance both problems are connected?

power steering pump?

Could be a hose too...

[vonVeezelsnider]

Well... Brace Yourselves.

Computer Said No Compression in Cylinder One... So it's a 3.8L V5 now. The sad part is that his dad says that enough money has gone into the car already (nearly 3600$ Y.T.D.) so there will be no more repairs and nothing but oil changes and gasoline in expenditures... When the engine finally gives up the ghost a Buick will be bought... Such a sad ending. If I was in a better financial condition I'd buy the car and plop a new engine into it to rescue it as there are no other problems, but alas now is not the time for a 5th Car... So I guess it's a slow and painful death for das Kubelwagen

[Drew Dowdell]

None?! That's unusual unless there is a valve stuck open somehow. IDK if the 3800 is an interference engine or not... not something that generally comes up with OHV engines.

[vonVeezelsnider]

None?! That's unusual unless there is a valve stuck open somehow. IDK if the 3800 is an interference engine or not... not something that generally comes up with OHV engines.

None, and the computer isn't displaying any valve-related codes...

[76ChevyTrucker]

First things first, the computer wouldn't show compression, only a compression gauge screwed into the spark plug hole with the engine cranking over would show if you have compression or not. And also the computer wouldn't display any codes related to the valves since they are a purely mechanical part of the engine. Someone is yanking their chain, sorry to say it. As far as everying else is concerned, it could be no spark on cylinder one, if so, then you've either got a bad plug, plug wire, or coil. Easy test for that, either do like said above, remove the suspect plug, in this case #1 would be the first one on the front bank of the engine (first being first nearest to the belt), and see if the engine seems to change its idle and lower rpm qualities. If it does, then you can more easily narrow things down by checking to see if the spark plug is fouled out. That's an easy test, just pull the plug and look at it. If its all gummed up looking or the tip is badly worn, then its time to replace the plugs (don't ever just replace one, do them all you'll be thankful in the end). If is a bad coil, since it has three coil packs you just swap the coils around and see if the skip moves. If it does, then you now know that you've got a bad coil. As far as plug wires, you can check them by removing a wire from a spark plug, inserting a screwdriver into the end of the wire, then hold it down near a metal object (to act as a grounding point) and have someone crank the engine over. Your spark color should be bluish-white, if its any other color, then suspect a bad coil of plug wires. You can also resistance test the spark plug wires with an ohm meter. If I remember right, any plug wire that shows more than 50,000 ohms of resistance is bad and should be replaced. Plug wires are like spark plugs, just buy a set and do them all you'll be happier in the long run.

[vonVeezelsnider]

He says the engine has calmed down recently and is not doing this as much at all so god only knows what was wrong with it... but for now the Olds lives.

[loki]

BAD batch of gas?

[vonVeezelsnider]

BAD batch of gas?

Could be, but this was over the course of at least 3 tanks.

[76ChevyTrucker]

Bad gas wouldn't have lasted more than a tank, maybe in the most extreme of circumstances, two tanks.