'91 Buick Les LTD stumbling/stalling

How about a '91 Buick Lesabre LTD, 180K miles, 3.8 eng. This car is plagued with stumbling on hiway and occasionally dies coming up to corner. normally, idles and runs perfect and smooth, and when it dies, I can go to neutral and restart on the run. Have replaced fuel pump,filter, and regulator, crank, oil press, coolant, and o2 sensors, ign mod, coil pack assy, plugs, wires, and maybe some things I don't remember. nothing changed. Today, I unplugged connector from solenoid on top of fuel cannister, and it ran fine. Anyone know about these things? What they do,how they're activated, How to check it, and symptems of its failure? No gas smell or plugged filter on bottom of cannister. Could this have been my problem for last 2 years? Could it be creating a vacuum in fuel tank?? Thanks, Huey286

Have you ever had any work done to the fuel lines? Ever, at all? It sounds like the vapor line may have been switched with the vacumn line. The hose on the solenoid should lead to the throttle body, and the other hose to the gas tank. I'm not really sure if it actually makes that big of a differance, but check just to be sure. The solinoid may have also gone bad.

Because you asked, the purpose of the cannister is to pull the vapors out of the gas tank, and put them into the throttle body, which get sucked into the air manifold, so it will create a vacumn in the fuel tank. Some newer cars even have a SES light that comes on if the fuel cap isn't put on properly, beacuse it creates an air leak, prevent a vacumn from being in the tank, and thus decreasing gas mileage. You may notice that when you take the fuel cap off, it hisses. If not, the line that goes up to the canister may possibly be leaking, plugged, not correctly connected, or the solinoid might be dead. The canister itself may even be cracked. You said that there was no gas smell, so I think you can rule out a tank leak. Just in case, I would check for moist spots on the fuel tank.
That is all I can think of. Hope this helps.

I had posted a little further down about rough running at 55 mph and I received some good suggestions. While out on the road the other day I slipped the tranny out of OD and into D. Accelerationi was smooth and powerful. I have a few questions. Would this be an OD problem in the trans? Also would adding some "snake oil" like Sea Foam, Lucus Gas Treatment etc help in the fuel lines?

Hi
I have a94 lesabre and had the same problem since last dec. never got a code for the EGR until about a week ago after the check engine light started coming on everyday, the scantool said EGR pintel circuit !??. I took a chance and bought one at the wrecking yard for $45.00, put it on and it hasn't missed or stumbled or stalled since.
I am delighted, Hope this finds you before you get too much more money into this.
Rick

The canister you mention is the Evaporative Emission Control System Charcol Canister. Functions as described above. The lines do have to be connected in the correct fashion, or you will have problems. I know detailed instructions for checking it are listed in the begining of chapter 4 (Driveability and Emissions) of the Chilton manual for 86-99 LeSabres.

As for the transmission. The reason your acceleration was "smooth and powerful" when you shifted the transmission from OD to D is not indicative of a transmission problem. The fact is, you were going 55 MPH, so the transmission was likely already in OD. When you step down on the accelerator hard in OD, you cause a "detent shift" causing your transmission to downshift to D to give you more power.

This is why you tow a trailer in D, to keep you transmission to shifting rapidly between D and OD because the transmission doesn't have the power to pull the trailer in OD but wants to. By shifting to D and forcing the transmission to remain in D, you simply increased your engine RPM to transmission output, thereby increasing the amount of power/torque generated by the transmission and given to the wheels.

"Detent shift" is most noticeable if while driving at 55-65MPH you press the accelerator down more than half way. At that speed, a reading from the TPS (Trottle Position Sensor) of 50+% will cause a (4-2 detent shift." E.g. Your transmission will shift from OD to 2. There will be a momentary pause, then you'll hear your engine rev hard to 4000 RPM and there will be the sudden jerk from the added power as your car accelerates very quickly.

Also. I believe what creslevi replaced is the EGR Valve... will be a round unit with one steel tube leading from the exaust manifold and another steel tube leading to the intake manifold. Mounted on the front of the engine, near the valve cover, lower than the intake manifold, higher than the exaust manifold. Let me know if I'm correct on that Rick.

Hi
That sound like a pretty good discription to me, only 2 nuts and 1 plug and it lifts right off, it's amazing the engineer's made it soo simple, even easier than the serpitene belt replacement, I even used the old gasket.
Rick

PS
It's strange that I have been looking for this miss/stumble problem since last Dec. and had it scanned several times by the same guy and same scanner, With no codes about the EGR, So go figure the comp/Diagnostic worked but it was about 10 months too late

Also remember that the fault has to be detected by the computer and occur during 2+ driving cycles before it will set the code and light the lamp. It's only been since 1996 that they have had to monitor those components within a tighter realm, or at all. So... that makes it difficult.

And then you have the EGR on my car. ---- thing keeps lighting the SES light, annoying the piss out of me. Three different solinoids, and the light still comes on. New vacumn line, and the light still comes on. New valve, and the light still comes on. Bad wiring? Bad connectors? Only God knows at this point. I've done tests by the book, and nothing relevent can be determined. aaarrrrrrrrrg.

egr valve?therory of operation....

EGR stands for Exaust Gas Recirculation. The EGR valve opens when your engine is below operating temp to introduce exaust gases into your intake manifold for the purposes of heating the incoming air. By heating the incoming air, a better air to fuel mix is created producing more efficiency.

That, and it also recirculates the exhaust to help burn off any unburned gasses.

How about a '91 Buick Lesabre LTD, 180K miles, 3.8 eng. This car is plagued with stumbling on hiway and occasionally dies coming up to corner. normally, idles and runs perfect and smooth, and when it dies, I can go to neutral and restart on the run. Have replaced fuel pump,filter, and regulator, crank, oil press, coolant, and o2 sensors, ign mod, coil pack assy, plugs, wires, and maybe some things I don't remember. nothing changed. Today, I unplugged connector from solenoid on top of fuel cannister, and it ran fine. Anyone know about these things? What they do,how they're activated, How to check it, and symptems of its failure? No gas smell or plugged filter on bottom of cannister. Could this have been my problem for last 2 years? Could it be creating a vacuum in fuel tank?? Thanks, Huey286
I have replaced the purge valve/solenoid on top of cannister, old one was sticking. Did some checking for/with vacuums, I can pull vacuum in tank with hand vac pump hooked to vent hose to tank. pumpes a few times, then unscrewed gas cap and heard hiss. And I get about 20 Hg vav at bottom of purge valve, so now know it's working right. But cannot detect vacuum in cannister, so it can't pull any vacuum in tank, rather just pulls in fresh air in through bottom of cannister. should I be able to get vacuum built up in cannister, and how much? don't know what's in these except air filter and charcoal. Any check valve, etc, that would allow vacuum build-up to create vacuum in tank? Not on this '91. Thanks for any help. After replacing purge solenoid, ran well for a day, now detecting slight return of problem. :confused:

A Haynes or Chilton manuals Drivability and Emissions section will cover testing the EVAP canister in detail.

Depending on the car, there is either a vacuum line or a couple wires that control a solinoid, which presses on diaphram. All have two other lines, one vacuum and a vapor line to the gas tank (labeled as a fuel line).

Wow, just came home from Autozone with new plugs, harness, coil (one of three) and tried the interenet, amazing aint it!

My trusty 93 Lesabre is missing at 45 mph and sundry speeds.

I will also try to disconnect the whatchamacallit thing too if all of these parts dont work.

Will let you all know

I have replaced the purge valve/solenoid on top of cannister, old one was sticking. Did some checking for/with vacuums, I can pull vacuum in tank with hand vac pump hooked to vent hose to tank. pumpes a few times, then unscrewed gas cap and heard hiss. And I get about 20 Hg vav at bottom of purge valve, so now know it's working right. But cannot detect vacuum in cannister, so it can't pull any vacuum in tank, rather just pulls in fresh air in through bottom of cannister. should I be able to get vacuum built up in cannister, and how much? don't know what's in these except air filter and charcoal. Any check valve, etc, that would allow vacuum build-up to create vacuum in tank? Not on this '91. Thanks for any help. After replacing purge solenoid, ran well for a day, now detecting slight return of problem. :confused:
After replacing purge valve/solenoid,on top of cannister, I believe stumbling has ceased, so far anyway. But yesterday again it died while coasting down slight grade to stop sign, about 30 mph, in OD, so guess engine was near idle speed, (no tach). Slip into neutral, and starts right up, before stopping for sign. Considering all the parts I've replaced, (origional thread), do you have any clue what could be causing this? Thanks again

How about a vacuum leak? Have you checked all your vacuum lines to insure they are in good order.

Before all the extra sensors were added to engines, vacuum lines controlled a lot of functions, 50% of the devices controlled by this vacuum could feasably cause stalling, rough idle, etc.

I'm the 1991 has plenty of vacuum lines to check, at 180,000 miles, I would just replace all the vacuum lines. The vacuum lines on a 1991 should control the EGR and fuel pressure regulator directly, as well as the transmission modulator, EVAP canister, and provide vacuum to the brake master cylindar.

I'm replacing the couple rubber lines on my 1995 today in fact, as they have completely degraded. I'm not even sure vacuum was being provided to fuel regulator any more. However, on my 1995, most of the rubber lines have been replaced with PVC tubing, which has stood up to heat and time a lot better. My environmental controls are still recieving the vacuum needed to work despite the ugly hose, but the fuel pressure line was just barely hanging there. Quite disturbing.