O/T 1992 Buick (Update) (POS)

greenmachineman · Aug 28, 2009

Ok guys... last night changed the plugs and wires with new ac delco plugs and wires. Still does the exact same thing. Just continues to idle rough, or pulling away from a stop light a little hesitation/stumble then it will take off. Refuses to idle smooth. Drove it for at least an hour last night. Came home and did another diagnostic and got no codes. When driving it runs great, has great power and is a smooth as glass down the highway. I am stumped.

glennster · Aug 28, 2009

vaccuum leak maybe? see if you can get a gauge on it and check vaccuum at idle. if its got a leak it would pull too much air aat idle and cause your problem, but when the throttle plate is opened, it would show up as much.

ted regentin · Aug 28, 2009

Check for vacuum leaks and air intake leaks. Many times these problems don"t set a code. Live data stream on a good scan tool can be very helpful. You might also try substituting a known good mass air flow sensor.
Hope this helps.

Allan in NE · Aug 28, 2009

Have you owned this car since new?

The meanest one I ever dove into had the ECM replaced by another garage. They stuck in a used unit out of a salvage yard and it was a California Emmisions ECM. Was continually opening that EGR at the wrong times.

The greatest demand/stress on the engine is at idle and launch.

Might be time to run 'er past the dealer to let him get a grasp on what is going on with this rascal? His scanner can read and snap all the primeters.

Allan

Allan in NE · Aug 28, 2009

Dunno Glen,

A vacumn leak usually shows up as a "fast idle". Darned fuel trim just dumps in more juice to compensate.

Allan

Gene Stevens · Aug 28, 2009

Spray some WD40 around the carb and on other vac areas. If it starts to run smoth you found the vac leak.

lucas boy · Aug 28, 2009

ID CHECK THE OHMS ON THE INJECTORS.SHOULD BE ABOUT 10 OHMS EACH

Janicholson · Aug 28, 2009

With a safe location outside, and the shrouding, if any, removed to get at the top of the engine, use a propane torch with the nozzle removed to test for a vacuum leak. The propane will supply fuel to the leak allowing it to smooth the stumble. Transmission vacuum control sensors diaphrams, and hoses are also suspect locations for leaks. Pulling hoses and plugging lines one at a time can also work.
Intake manifole leaks (internal) will also make it happen.
If it is a pair o fcylinders doing it, Pulling one plug wire at a time (stopped and grounded to the block before starting) will direct the search. JimN

hay · Aug 28, 2009

just a little note here. just because new plug wires are installed does not mean they are any better than the old ones. i had that happen on a 1975 chevy p/u. drove me crazy until i checked each wire with an ohmmeter and compared values. any wire with even a bit too much resistance is likely to be bad. however, it is a slim possibility that the new wires are defective, so i think a trip to the diagnostic shop would help a great deal. they should be able to pinpoint the problem.

jay-eye-see · Aug 28, 2009

I would check the EGR valve. It is not called for at idle but will sometimes stick open due to carbon etc. and cause engine to idle rough. At higher RPMs when the valve normally opens, such as when going down the road, engine will run smooth.

greenmachineman · Aug 28, 2009

I'm thinking of using dynamite to check for leaks. : )

bradk · Aug 28, 2009

Have you checked the ignition coil resitance?

There are two types of coils in that year.Delco and Magnavox.Delco has three individual coils mounted on top of the ignition module and should spec out at 5-7 ohms between coil towers.Magnavox has a one piece design and towers across from each other should test out at 11-13 ohms.

What did it run like with the MAF sensor unplugged?

tlak · Aug 28, 2009

Head gasket.

railhead · Aug 28, 2009

A buddy had a 95 crown vic nearly same symptoms. we exhausted all our and the local mechanics knowledge on it(and all our beer) so, went bought more beer and it ended up like these cars:

http://www.youtube.com/watch?v=oS6NZ-hRnoU

only thing is we did not have a vid camera or we could have been on you toob too. If you're gonna blow it to smithereens, you may as well get famous for it.

railhead · Aug 28, 2009

A buddy had a 95 crown vic nearly same symptoms. we exhausted all our and the local mechanics knowledge on it(and all our beer) so, went bought more beer and it ended up like these cars:

http://www.youtube.com/watch?v=oS6NZ-hRnoU

only thing is we did not have a vid camera or we could have been on you toob too. If you're gonna blow it to smithereens, you may as well get famous for it.

greenmachineman · Aug 28, 2009

where is the egr on it?

Anonymous-0 · Aug 28, 2009

I am on my 5th GM EFI vehicle with over a 100K. Generally a piece of black tape over the check engine light and holding my foot on the throttle to keep the RPM above 700 is the only way I get them to idle smooth with that much mileage. I probably should replace all of the sensors, but in about another 10 - 12 months this vehicle will have a new home and at that point I plan to be a "former" GM owner. And yes, I had to fix the gas gauge on it a year ago. The dealer offered to do a diagnostic for $75.00, I found a shop that pulled the tank and fixed it for under $300.00.

dhermesc · Aug 28, 2009

Actually I was thinking INTAKE MANIFOLD gasket.

There are two kinds of 3800 engines, those that have had the intake manifold gasket replced and those that will have it replaced.

Anonymous-0 · Aug 28, 2009

Spray some carb cleaner around intake , any hoses, brake booster etc. If rpm picks up you found vac leak .not to say that it could not be intake leak . You can short cylinders by taking 6 , two inch pieces of 7/32 vac hose . Put hose on each coil tower , then plug wire on hose . Get about a 2 foot jumper wire hook to good ground , then other end to metal part of screw driver . Place tip of driver on each hose , one by one , note the difference as each cylinder is shorted . if you find one that the rpm does not drop theres your bad cylinder .

Brian Jasper co. Ia · Aug 28, 2009

Being a tech at a GM dealer I can say what you describe is likely a leaking EGR valve, vacuum leak, dirty injectors, not necessarily in that order. When looking for vacuum leaks don't overlook the brake booster as a potential source of un metered air.
The EGR valve is a round thing about the size of a pop can with a wire connector on top and metal tubes going into the bottom, one from the rear exhaust manifold the other going to the intake on a 3.8. On all others, it will be an internal passage on the corner of the intake. It is fairly close to the brake booster.

tlak · Aug 28, 2009

3100 is bad about head gaskets, whatever he has. I would use Barg stop leak, just pour in the liquid part and it would go strait to the bad cylinder and cause a more pronounced miss. Unless he lucks out and the stop leak/head gasket sealer actually works for him.

glennster · Aug 28, 2009

odd one to figure out alan. we have a 98 malibu here at the shop with a stumbling problem . owner said autozone scanned it and it was an 02 sensor. he brought it in, we scanned it with our modus, and have random cylinder misfire, cat efficiency low bank one, evap emission system failure. owner bought the car used last february. found plug #3 is a standard plug, all rusted, the rest are platinums. the whole coil pack was bolted to the motor below where it should be, and found an open vacuum line so far. looks like the fuel rail had been removed in the past and the car was just slapped together.

John M · Aug 28, 2009

Sounds like my grannys Lumina, had something to do with the torque converter lockup switch.

gab · Aug 28, 2009

Sometimes an intake gaskit can leak on bottom side too. Take the oil fill cap off with it running, should'nt be a big sucking sound. Spray a little carb. cleaner in the oil fill hole and see if it smooths out any.

buickanddeere · Aug 28, 2009

How does a machine with 18 years of hard service. And has enough miles on it to have traveled around the world 6+ times. Qualify as being a POS ?
It's old and worn out.

EGR · Aug 28, 2009

Valve

Anonymous-0 · Aug 29, 2009

Bonehead famous

O/T 1992 Buick (Update) (POS)

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