Bucking and Hesitating 96 Park Avenue

[digitalsaw]

Alright guys, this is my first ever post on this forum but I have a lot of faith in numbers. See if I can get some insight into this problem before I replace anymore sensors.
Here are the facts about my problem:

- 1996 Park Avenue 3.8 V-6
- 104,000 miles
- Problem: When it warms up it begins to hesitate (at all speeds) when the accellerator is pushed s-l-o-w-l-y. It bucks and acts like it is kicking in and out. A typical example is rolling down a flat stretch of road at 65 mph with the cruise on. Here comes a small hill. As the vehicle begins going up the hill the cruise automatically tries to accellerate the engine to compensate for the hill. It begins to buck hard. I put my foot on the accellerator and can accellerate through the bucking and it smooths out. A few more facts.
- Problem ONLY happens when it warms up. Typicall this may be as much as 10 miles down the road.
- When it gets fully warm it will hesitate taking off from a stop light. Again, just small short hesitations. Even putting your foot into the accellerator it will not totally smooth it out.
- I have replaced all of the ignition coils, and the ignition module below the coils.
- One other very strange deal. When it was screwing up on me really bad and I was replacing the coils and the modules, I revved it up out of frustration. When I got to 4,000 rmp it began to cycle in and out. Almost like a 'whaaa whaaa whaaa whaaa whaaa and won't go beyond 4,000 rpm.
- The diagnostic guy at Autozone told me it may be the a MAP sensor, the throttle body sensor and my uncle suggested the crank sensor.
Anybody got any ideas? This ole Park Avenue has been

[krazibimmer]

i don't think is the crank sensor. if the crank sensor is bad, ur car won't start. does ur car equipped with a MAF sensor?

[digitalsaw]

I assume you are talking the Mass Air Flow sensor? Yes, my system has one and I have actually experienced one of these going out. The only problem is when this happens usually it won't run right at all even at a constant throttle setting. In my Haines manual for these vehicles I see a MAP sensor monitors the intake manifold pressure changes resulting from changes in engine load ans speed and convets the information into a voltage output. I am thinking this may indeed be the problem. Any thoughts?

[krazibimmer]

Is Ur Engine Light On? Have U Try To Pull Code From The Computer? What About The Spark Plug Wires? Are They Arcing? How The Spark Plugs? If U Have A Dvom, U Could Back Probe The Sensor's Wire To Get The Reading And Compare It To The Spec.

[tman]

krazibimmer- Could you please type out "you" instead of "U." That is frowned upon here and is difficult for some, like me, to read.

digital- Try changing the spark plugs and wires with new Delco ones. Also, Welcome to AF!

[GMMerlin]

The WAA,WAA,WAA is the fuel limiter kicking in to prevent engine destruction.
Remove the plugs and check for signs of carbon tracking (Black lines running down the porcelin part of the plug where the boot attaches.) usually you will find that on the front cylinders.
Definatly changing the plugs and wires is a must (use Delco...far superior than anything out there IMHO)

It sounds like you are experiancing an engine misfire under load...most likely cause is secondary ignition breakdown.

[digitalsaw]

The reason I ruled out the spark plugs and wires is that I replaced all the plugs and wires less than 8 months ago when I was trying to solve the original ignition coil problem. It may be the problem now what I don't understand is why would it do this only when it gets hot? I have always understood that something like this (runs great cold and poor hot) is electrical in nature meaning a sensor or module. I would hate to cough up another $75 - $80 and find out that it was not the problem. The other kicker here is the engine light DOES NOT come on! This is the strangest deal.
With this information in hand would you guys still recommend the plugs and wires? I can take them out and look at them first I guess. It is just a pain and since I have done this not that long ago I had eliminated it from the 'potential problem' list.
Thanks.

[RWALLMOW]

I had a 92 Lesabre doing almost the same thing, Replaceing the Coils would solve the problem for about 6 months and then it would slowly start doing the same thing, It wasnt plugs or wires as I checked those often and they always looked good. I never did figure out what was causing the problem as my transmission died shortly (1yr) after it started happening (tranny died due to collision, not a related problem). I guess I just chalked it up to being very high miles on the car (and I beleive it had the shit beat out of it before my family bought it)

[AFGunGuy]

Check your fittings on TB and fuel pressure regulator. I think GM saved 4 cents on each by going with a cheaper rubber. Mine cracked and caused the hesitation you are talking about.

[Flatrater]

Originally Posted by AFGunGuy

I think GM saved 4 cents on each by going with a cheaper rubber.

You think that is funny? If you only saw the bigger picture than just your little car. Yes 4 cents is nothing for us but when you are dealing with a 100,000 cars that 4 cents sure adds up.

[PAman]

EZ-sleazy...when's the last time you had an O2 sensor? It's what mine needed at about the same miles. By the way, Bosch +4's, wires and O2 sensor all work just fine after installing 20K ago. Coil packs are generally robust.

[AFGunGuy]

Easy Flatrater, I wasn't saying that just GM does it. Economies of scale and just plain money sense say it is the way to save money, but on a car that retails at 34 thousand dollars when new you expect a little more. I know that great strides have been made in newer GM products, just making light of the fact that it could have been done better with the close proximity of a hot engine and being stuck under the plastic cover that holds all of that heat. I love the 3800 series engine, specifically because of the great mileage, longevity, and lack of DOHC. The car is a boat just like old Buicks, or it wouldn't be in my driveway right now.

[RABarrett]

No one has suggested the possibility of a dying fuel pump, filter,etc. This sounds like fuel starvation. Check the pressures, replace the filter and go from there. Ray

[timrice]

digitalsaw: RE: your original post. I recently had the same symptoms on my '91 Park Ave. For me, a new ignition coil pack made an immediate and at least for the past three weeks, lasting difference. I see you'd replaced yours to no avail. I will say that I put up with the problem for a few months, because it started out being a rare occurrence, and it happened more frequently until it got to the point where it almost wouldn't even start. Here's my description of the symptoms - like deja vu after reading your post:

"The car seems to "kick" or "bump" when driving. I have not seen any Service Engine lights. The symptoms have gotten more frequent over the past two weeks.

Most of the time the car will run smoothly out on the highway on level ground, but when going up a slight grade and trying to hold a steady speed, the "kick" will usually happen once or twice. Also, it happens when you are accelerating from a stop as when getting into traffic on the highway. Sometimes it won't do it if you accelerate gently enough.

I have also noticed that the engine will run rough when it is in P at idle and you push down on the accelerator pedal.

The symptoms will occur whether the cruise control is on or not. I have not been able to tell that outside temperature or engine temperature has any effect on it. The only pattern I see is that it does it when you demand a bit more from the engine than just cruising effort."

- Tim

(I hang out more in the LeSabre area of AF - I have three of those and only 1 Park Ave.)

[agrant6]

I had a simular problem with my 96 Park Avenue and it was caused by a bad cam position sensor.