I bought this car used about two months ago. It runs fine most of the time, but once every few days the engine either dies abruptly while I am driving, or fails to start. In either case, it can always be re-started within 15 minutes. More often, I see the "check engine" light come on just as I start it. When this happens, the engine still runs, but I notice some "missing" and hesitation. If, when I first see the "check engine" light I simply turn off the ignition and then turn it on again, the "check engine" light does not come on and the engine runs very smoothly. I took it to a nearby Buick dealer's service, where they ran diagnostics on it and told me that the problem was the ignition module shorting out. I ended up having that repair done by my local mechanic (new, original Delco ignition module), but since then, the problems appear to be exactly the same as before. Naturally, I am leery of taking it for more diagnostics when the original ones led to an expensive dead end. Are there a limited number of good possibilities for what is causing these problems ? I have heard about "sensors" which detect the crankshaft position frequently going bad. Is there anything, such as that, which might be replaced as another troubleshooting step ? I would greatly appreciate any suggestions

Hi!

I had a similiar problem to yours. Filling up corrected it for me. Something else to check is to make sure your gas cap is on correctly and tight as I am told that can sometimes trigger the SES light. I have spent a lot of $$$ on my LeSabre the past year for a rough idle that hasn't been fixed yet so I know how you feel.

refernce your 95 buick if the shop replaced
the igntion module and you still have problems
you might want to see if at the same time he replaced the wires and o2 senser/other possible
problems fuel pump or crank senser

I have the same intermittent problem with my 95 Buick LeSabre. I've been told that this problem may be due to a failing Crankshaft Position Sensor. I am going to try to replace that first and see what happens. I do need to find out where the sensor is located on the engine. Any one know?

Windsurf at Buicks.net

Sorry I delayed so long but was touring South Louisiana for a month. I returned your private email but you gave no response.

Ok first things first. The car will stop because it isn't getting fuel or spark so you have to check for both.

1. When it stops or will not start, is your speedometer at 0 miles per hour or does it go below 0 MPH. ???If you are driving down the road and the engine stops, does the speedometer immediately go to zero or stay at your exhisting speed. If it goes to zero while moving or drops below zero you have other problems and will have to check other things.

2. ???When It stops do you have "spark". Turn the engine off. Pull one wire off of the spark coil, push a paper clip into the spark plug wire boot and have someone crank the engine while holding the wire an eight of an inch from the coil tower. You have to use a long rubber band or rubber vacuum hose to "hold the plug wire" near the coil tower or you will be bitten very paignfully hard. When the engine is running poorly is the best time to do this to find if the spark is the problem.

a. A way to find a missing spark related problem is to wait till it is very dark and look at the plug wires with the engine running. If you see the spark jump from a wire to the engine, you have a bad wire.

b. You may have a plug wire end clip not pushed tightly on to the plug itself. The tips sometimes come off and during the previous plug change, the mechanic just pushed the plug wire boot halfway on causing a large wire to plug gap.

c. Ohm out your plug wires and plugs. GM says the plug wires should not exceed 30,000 ohms. The shortest plug wire should have the least ohms and the longest the most ohms. The average would be 3,000 ohms for the shortest and 20,000 ohms for the longest. Good aftermarket wires may be as little as a thousand ohms for the longest. In other words so many ohms per foot. The plugs should be gapped to the specified gap. High mileage may wear out the gap from 60 thousands to 70thousands or higher and may cause erattic operation. My gap is 60 thousands, later models are 90 thousands. A round gap gage is about a buck at autoparts places. The plugs should ohm out to be about the same resistance and not have excessive resistance. I have purchased new plugs with 3,000 ohms each and some with 6,000 ohms each. I test them as I buy them. Some of them tested out at 15,000 or greater -- the parts person knew what I was doing. If the total resistande is too high the spark may not fire every time and cause this missing when the primary wires are wet or if you have a poor connection in your computer wiring. (A digital volt/ohm meter can be purchased from Harbour Freight for under $4.00 and you will have many uses for it to find your problems over what I am saying here)

d. Check that one of the wires is not sitting on the exhaust pipe. It will burn through the rubber casing and cause intermittent rough running.

3. ???When it stops do you have fuel pressure? To test this the easy way:

a. The fuel pump is located in the fuel tank under the rear seat of the car. When the car is running, listen for the high pitched wine of the fuel pump motor. "REMEMBER the PITCH" of the huming sound. It is just loud enough for you to hear in the car with the door open. If you are not sure put a 2 or 3 foot "listening" stick against the fuel tank located under the car under the rear seat, and the other end to your ear (car stopped in park) so you can hear it.

b. When the engine stops on you, listen for the pump sound. Turn the ignition switch off for 5 seconds, then on (not start). You should hear the pump turn on for a few seconds and then off. Use your memory of the motor pitch to hear if it is running at a similar ptich, barely turning or not running at all. Repeat the ignition off then on several times to confirm this.

c. If the car is hesitating or not pulling and you hear the pump is running at a slower pitch, then the pump is running too slowly to make sufficient fuel pressure or is not getting enough correct voltage to make it run at speed. (The brushes are worn and you need a new pump or there is a bad wire or wire contact in the line that needs to be found.)

d. If the pump is running at speed, not running at speed or barely running then the fuel pressure can be checked on the bicycle valve on the engine fuel rail that connects to the injectors. Have a mechanic check the fuel pressure (with a specially made fuel pressure gage) when the engine is running erratic or not running (this may be a problem since a mechanic is never there when you need them). Fuel presure should be about 35 to 40 pounds at idle. If the mechanic pulls the vacuum hose from the fuel rail pressure regulator the pressure will go up 10 psi. IT 'can' run at 10 to 30psi at idle but if you put the car in gear, stand on the brake pedal and give it 1/4 throttle in drive, the pressure should go up about 10 pounds (not down). If the pressure drops then the fuel pump is not putting out correct pressure and may be actually slowing down or stopping which is why your car stops. (DO NOT put a tire pressure gage on this valve that looks like a tire air valve because it will squirt fuel all over and may light up your life.)
A pump that is nearing the end of it's service life will act intermittent in this manner.

e. If the pump seems to be running at or near speed but the fuel pressure is low then you may have a nearly plugged fuel filter. (about $10 at Auto Zone) Have a mechanically oriented friend change this. The correct procedure is to pull the fuel pump fuse and run the engine till the engine uses up all the fuel pressure and stops on it's own. Then the fuel filter can be unscrewed without squirting fuel several feet. It takes two open end wrenches one about 3/4ths inch in size and the other slightly smaller, I can't remember the sizes but you need both simultaneously, One to hold the filter and the other to unscrew the fuel line on both sides of the filter.

f. The fuel pump pressure switch in the low oil pressure switch is down on the block just above the oil filter. It may be malfunctioning or have a bad plug harness connection. When the oil pressure goes above a few psi it makes electrical contact to send voltage to the fuel pump through one of the wires connected to it. This switch may be intermittent and shut off the engine. This may have to be tested with the voltmeter.

This is enough to get you started.

When you reply copy this message and incert your comments just after each part as to what you did and what you found out so I can see if you missed something.

I had the same problem with my 92, the crank sensor was cracked and would get dampness into the electronics. Check your codes for code 17,it'll say something like crank sensor or ecm fault.