Bucking and Hesitating 96 Park Avenue

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

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?

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?

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.

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!

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.

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.

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)

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.

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.

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.

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.

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

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.)

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

I'm having same problem on my 99 lesabre.
I would like to verify the spark plug wiring map. Does anyone know
and can tell me the true routing of the spark plug wires On:
1999 buick lesabre V6 3800 EFI engine
( appears 3 coils with 2 wires each)

I have a 95 ultra (80k miles) that seems to do that after the engine warms up under light acceleration from any speed.. I have always gotten about 14mpg overall ( but I do have a heavy foot). the dealer has replaced ( for various reasons) fuel pump, crank sensor, catalytic converter because they said the performance was off.. this problem came back a couple of days later...any suggestions ( plugs and wires were replaced when I bought car 30k ago or so). I thought tranny, but it runs great cold..( for 10 minutes or so :>)

lglm8, superchargers usually conk out after 80000 miles. You'll probably need a new one.

I had the same problem with my 1992 LeSabre it was without a doubt the Cam Shaft Position Sensor. The reason it messes up under heavy acceleration is because when the engine RPM's increase this sensor must produce more pulses for the computer. If a cam shaft position sensor has an intermittant failure, the percentage of "bad signal pulses" will increase with engine RPM because it is producing more pulses in a given period of time. The computer gets a bad pulse more often at higher RPM's and it has a more dramatic affect. At lower RPM's the computer still gets a bad signal, but not as often, so the performance problem isn't noticable when you aren't pushing the throttle, although your bad gas milage is a clear indication that you have a problem all of the time. Most Cam Shaft Position sensors fail when they get hot, one tell tail way to check this problem is to rig up a simple system that will dump some cold water on the sensor while you are driving. You can do this by pulling the hose off of the sprayer for teh winshield washer, then fill your washer tank with ice cubes and water. Get a cheap piece of vacuum hose and hook it up to the output of the washer pump and run it in a safe place across the engine compartment to the Cam Sensor. Once you have the hose so that it squirts the cold water on the sensor, take your car for a drive. When the vehicle starts acting up, wash your windows, lol. The cold water will spray down on the sensor and cool it off, if the CPS sensor is the problem the cold ice water will improve temporarily improve or fix the problem. Give it a shot, this is how I finally found the problem with my CPS and it worked great. I spent almost two years trying at one point or another to track down the problem.

can you have a flakey cam position sensor like that and still get no codes...?

The one and only code that can be set for the camshaft position sensor is code 41. I'll re-type the exact paragraph for code 41 and the camshaft sensor for you from my gm shop manual.

Circuit Description:
During cranking, the ignition module monitors the dual crank sensor sync signal. The sync signal is used to determine the correct cylinder pair to spark first. After the sync signal had be processed by the ignition module, it sends a fuel control reference pulse to the PCM. When the PCM recieves this pulse it will command all six injectors to open for one priming shot of fuel in all cylinders. After the priming, the injectors are left off for the next six fuel control reference pulses from the ignition module (two crankshaft revolutions). This allows each cylinder a chance to use the fuel from the priming shot. During this waiting period, a cam pulse will have been received by the PCM. Now the PCM begins to operate the injectors sequentially based on true camshaft position. However, if the cam signal is not present at startup, a Code 41 will set and the PCM will start sequential fuel delivery in random patterns with a 1 in 6 chance that fuel delivery is correct. Code 41 is set when the following conditions are met.
1. Engine is running
2. Cam sensor signal not received by PCM for last 5 seconds.

In general they tell you to use a volt meter or a Tech 1 scanner to monitor the signal, but the problem is, code 41 won't set unless the computer believes it has lost a signal for at least 5 seconds. But I can take two wires and short them together and fake a cam signal by sending an on-off voltage back to the computer. An intermittant signal won't confuse the computer because it can often interpret a screwy signal as a real one and try to use it to sequence the fuel injectors, basically this means the wrong cylinders will be getting fuel at the wrong times. But interestingly enough as the paragraph says there are only six cylinders on this car, the injectors are shooting fuel thousands of times every minute, and so it has a one in six chance of getting fuel in the correct cylinder and firing. But of course the other 5 times will cause severe driveability problems and loss of power and also a heavy loss of fuel, hence the bad gas milage. Newer versions of the 3800 monitor this cam signal more carefully and actually compare the signal it gets to one that is reasonable so that a strange signal will tip the computer off that something is wrong.
The manual doesn't say how this "sensor" works, but I know from experience that a hall effect sensor of any kind uses a permanent magnet that is fixed to the rotating object usually, and a wire coil that is held still or mounted within "range" of the rotating magnet. As the magnet passes the wire coil it induces a voltage in the coil and the sensor can use this voltage to either go straight back to the comptuer or as I can only assume in this case to trip a solid state relay circuit that grounds a very stable signal voltage inside the sensor. When the sensor package heats up, these tiny connections inside can expand and cause a poor signal, or the tightly wound coil can short out and produce a weak signal. Either way, the only way to tell for sure is to try and cool down the sensor or heat it up to see if it changes the behavior. You can use a hair dryer or heat gun on the sensor to see if you can make it act up, but remember that it may only cause a noticable problem at high RMP's under load, thats why I suggested the more "real time" test with the washer fluid idea. As long as you don't care about having a window washer for a while, and as long as you mount the little tube well out of the way of moving or hot parts, you can drive around like this for a long time until the thing acts up.

Thanks for the info.. I'll let you know what happens.. :>)

code 34 map sensor or maf sensor, where is the map sensor?

My problem, which was the same as digitalsaw's seems to have been a bad plug wire. I changed all the plugs ( found one with carbon tracking) and wires (found a destroyed wire corresponding to bad plug, in the process) and regapped the plugs to .60( they were at .68 for some reason) and as an aside, changed the O2 sensor. The problem is gone now.. too bad the coolant bypass fitting broke ( old age) and my battery went south ( 4yrs old) in the process.. oh well, sooner or later I will be able to enjoy speeding again. Maybe tonite :>)

@ pcmos if the cam sensor is working but has no reference signal a code 26 "quad driver b failure" can also come up thats the code ive had and the shop diagnosed it finally

Gspot, check the dates of the posts you are responding to....they are old.....

I have a 96' buick Park Ave with the 3800 series 2 motor.
My car starts right up every morning but after driving for a while and I park the car for say 10 to 15 minutes it will not start. When I turn the key it tries to start and if it does the motor is chugging and miss firing I assume then dies. So if I get out of the car for 1/2 hr and come back it will start right up like there was not a problem. Its happening mor frequently now. If I replace the CKP and the ICM sensors would that do?

You might reference this thread that was so popular(?) it had to be padlocked:
"95 LeSabre Dies Without Warning". It might help you. Grab a cup, can, or bottle of whatever you like to drink, and start in. It reaches a conclusion in post #56. After that, I think it's mostly diminishing returns.

Another possibility I have run into while driving the wheels off five LeSabres and a Park: the fuel pump failing--flaky when it's hot, works for a while when cool. A very strong word of advice if it does turn out to be your fuel pump. Do NOT put an aftermarket pump in. I learned the hard way that you are better off getting the OEM part and paying the extra for it.

Might consider the possibility of a coil going out, too, though when I've had bad coils, I don't recall any problems starting...only while driving, especially up slight grades where the engine works a bit harder.

I wish you luck on your diagnosis!

If the forum will permit me a moment of sentimental reflection...
I would like to honor a few of my heroes:

2004 LeSabre (daily driver: 136,000 mi.)
2000 LeSabre (backup unit: 181,000 mi.)
1995 LeSabre (167K before passing away in a nasty T-bone wreck )
1991 Park Ave. (177K, sold)
1990 LeSabre (rusty but trusty: orig. trans died at 330K; original motor)
1989 LeSabre (170K, sold)

They took out three deer between them, so that's another plus.

Well, you can just change parts and hope that fixes the problem, or you can diagnose it......

When the car won't start, that is when you do the diagnosis........

A couple things to check.......pull the vac line off the f/p regulator and smell or see fuel in the line....if there, replace the f/p regulator(very easy, just remove the horse shoe clip and remove the "guts" of the regulator and replace......also try starting with the MAF sensor disconnected....if it starts, shut off....reconnect....try to restart....if it doesn't you need a MAF.....

Check fuel pressure with a gage.....check for spark on all cylinders.....check for injector pulse....if possible, check for codes....