# oldsmobile keeps stalling



## lexmarks567 (Aug 13, 2006)

I have a 91 olds cutlass ciera. the engine keeps stalling when it warm. The first time it stalled my mom was driving. it quit in the parking lot of her friends apartment. the car would not restart. after letting it sit for awhile it restarted only to stall a minute later. it restarted right away that time. The next day we were both in the car it stalled in the shopping market parking lot. It restarted right away that time. later that day it almost stalled but my mom was accelerating away from a stop sign the extra fuel prevented it from stalling but you could feel the car jump. took it into a shop.

they replaced the M.A.T. sensor which was reading -4 degrees outside.$202 dollars along with a rusty coolant hose. did not stall the for a few days afterward's but now its back to doing it. its not has bad but still the sensor did not fix the problem. and then yesterday after driving around short distance we overshot our driveway put the car in reverse then forward the front wheels are just touching the driveway the engine quits. Will not fire. my mom puts it in reverse and cost out of the driveway somewhat crooked in the street. after a couple minutes I tell mom to put in in neutral and i will push it to the curb so at least its straght.

She gives the gas pedal a couple pumps and the car starts. what could be the problem. check engine light did not come on. repair shop said they reset it. i took it back to the shop before all this and they said the oh the gas tank is rusty the fuel lines are rusty. the gas pressure while good is going up and down and that the coil "may" be failing. they wanted $500 to replace the tank and pump. they didn't check the engine for vacuum leaks as that can cause faulty fuel readings also.I don't have money to get a 2nd opinion right now sense all shops want to charge to look at it sense they would have to diagnose it. any ideas.


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## Knotbored (Jun 5, 2004)

Just a guess but that sounds like "vapor lock" which is an air bubble in the fuel line caused by heat vaporizing the fuel. It usually used to occur on hot rods when the fuel line was misrouted hear the exhause or when the line was routed up and over something then downward to the carb. The solution was to wrap a wet rag around the highest point you can reach on the fuel line (I also heard of kids keeping a potato to split and put on the line.) The next time it happens immediatly wrap a wet rag on the line and see if it helps-only takes a minute to disolve out the vapor if its the cause.
Also-I see no indication the fuel filter was replaced-if gas is rusty thats an obvious problem.


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## JohnWill (Oct 19, 2002)

I put in a second vote for the fuel filter, that sure sounds like the symptoms. Of course, the mechanic can't make much money replacing that, so it'll be way down the list.


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## mtzlplex (Aug 5, 2002)

I agree with the fuel filter theory, that would be the first thing I would try. For the vapor lock theory, in the old days, we used those wooden spring loaded clothes pins on the fuel line from the fuel pump. we just added them until the vapor lock ceased.


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## lexmarks567 (Aug 13, 2006)

it could be vapor lock as the car only stalls once it warms up not when its cold. once it warms up it seams like its slow. it only wants to stall during idle or slow speed if your doing the speed limit of 40-60 etc its fine cause its getting gas.

to replace the filter i need to de-pressurize the fuel system. how do i do that. do i need a special tool.


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## JohnWill (Oct 19, 2002)

Repressurize the fuel system? What are you talking about? I've never heard of such a thing on a car like a 91 Olds!


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## lexmarks567 (Aug 13, 2006)

that's what i was told. I need to DE-pressurize the fuel system in order to remove the fuel filter.

ok did a search on google. you start the car then pull either the fuel pump fuse or the pump relay. the engine should quit right away and there shouldn't be any pressure in the lines. Im going to replace both the fuel filter and the CTS sensor sense there both $12 each from autozone.


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## Knotbored (Jun 5, 2004)

You are right about that de-pressurizing (I also peeked at Google.)
I saw many cautions indicating fuel spillage- I also saw some unusual locations for that filter for Oldsmobiles (under the drivers seat, next to the fuel tank etc) you might have to check with a dealer to determine where it is on your specific model.
I long for the olden days when you checked the filter by glancing at a plastic bubble-then used a screwdriver to throw away the quarter costing filter-the fittings cost more then that filter then.
Another hint-some Google hits say some models (not all) need a special wrench on the fittings. I usually find a friendly chat with the dealers parts department can be valuable and sometimes they even copy a sketch and instructions from the mechanics manual.


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## JohnWill (Oct 19, 2002)

Never heard of that, learn something new every day.


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## lexmarks567 (Aug 13, 2006)

for the service manaul i can get that from the local library. its the same kind the shops use.


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## lexmarks567 (Aug 13, 2006)

while it stalled 3 times yesterday. all times at a traffic light. first time would not start. after letting it sit awhile and then depressing the gas pedel once and then cranking it starts. go a little ways stalls again. starts back up though. go another little ways quits again. starts back up though. it seams to do it right before the engine is fully warmed up cause so far it does not seam to do it once the engine is FULLY warm. as far as fuel filter location it seams to be located between the driver and passenger door underneath the car according to a diagram on autozones website.


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## Knotbored (Jun 5, 2004)

Well now I am going to go out on a limb and make a guess that you have some water condensed in your gas tank.
reasoning- when warm the gasoline has been sloshed around and the water has been mixed with the water and works.
When the engine is cold the gas/water mix in the lines is adequate strength to work.
While engine is warming up the fuel in the lines (usable fuel) is used up and replaced fuel is from bottom of the tank-water saturated.
My guess is the car was left outside with little fuel and the hot/cold weather drew in moist warm daytime air which condensed in the cold tank at night.
I would drain the gas tank into clean/clear plastic bottles and look for both rust color and water in the bottom of the bottles.


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## JohnWill (Oct 19, 2002)

The condensation is a good possibility, I had that happen in the winter with an SUB I had, it finally froze the fuel line.  

Another issue, back to the fuel filter. When the engine is cold, it's using more fuel, if the filter is restricting the flow, it could be better when it's fully warmed up. A test, after a full warmup, will the car do a full throttle acceleration for at least 10 seconds? That should push enough fuel to either indite or eliminate the fuel filter.


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## Stoner (Oct 26, 2002)

Has anyone run a fuel pressure test?
You could have anything from a weak check valve to a weak fuel pump that is aggravated when warmed up. 

Have you tried loosening the gas cap to see if it's venting properly? Too much of a vacuum can aggravate the before mentioned problems.


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## aka Brett (Nov 25, 2008)

Do you have a check engine light on?
The early fuel injection systems by GM can be checked for codes without tools..by jumping across the diagnostic connector{A and B}..you the count the flashes for the code and then look it up.

The gm fuel injection system is pretty worthy of running with a bad sensor as default values are chosen by the computer//how ever the exception to this is the manifold air pressure sensor or mass air flow sensor..dependent upon which you have...Your drivabilty will suffer however with a bad sensor in that area ..as it is the hardest one for the computer to fake with a default value that is appropriate for most driving conditions

I would get some 89 octane fuel with 10 percent alcohol{they sell it everywhere}...The alcohol will help suspend the water in the event you have any in the tank.....water sinks to the bottom of the tank and can cause a stall when stopping etc as the water can rush beneath the pickup.causing a stall a few seconds later.

In the event you are still having problem....the next step is to drive the vehicle with the diagnostic jumper in place.......the light will now change in accordance with how fuel you are using{in theory} it is basically just a measure of injection open time} so if you were starved for fuel the light wouldnt be realistic.

However it can tell if the car suddenly went lean due to the injectors not having the proper open time...also if you suddenly went rich for reasons unknown.

Even with bad sensors etc the car will almost always pull off an idle ok as the idle air control valve will move in and out as needed to keep the speed where it needs be to stay running...therefore your problem is cause by a sudden change in fuel delivery or a sensor that is failing but has not yet failed.

Some failing sensors can be as follows...A worn throttle position sensor can briefly flood an engine...The voltage changes with the position of the throttle..a failing sensor with have voltage spikes with movements ans interpret it rapid throttle movements...The sign for this is when starting the engine back up its a little rough for a couple to few seconds until it cleans the excess fuel out.

A manifold air pressure sensor...usually dont go bad..but the vacuum hose to it does.......it will suck itself shut...then a false reading is read by the computer...less vacuum is read than there actually is...the symptom of this would be a happy engine at speed,but will start running rich as soon as you stop.......it will get rich enough to start to run poor enough to lower vacuum..the hose will then open back up..the engine will straighten out....it will begin a cycle of this....this happens more with a warm engine as the hose is not as stiff.

A failed temperature sensor will default to a value a little less than a fully warmed engine...it will run fine after warm,,but will be hard to start a cool engine and will suffer hesitations upon acceleration until the engine is warmed.

A failing temp sensor can cause a flood at speed or idle conditions,,however the computer almost always catches it and goes to default value...so its rare.....the same hold true for air temps related to manifold temps.

A failing fuel pump on a gm can show up in many ways from sudden failure{not usually the case}.usually a warning sign. The fuel pump pumps more fuel than is needed and it returned to the tank...the extra fuel pumping is what cools the pump..when the wear of the pump is bad enough there is no extra pressure to have the flow through the return causing extra pump heat and wear....the pump has a very short time remaing in these cases..

A cold pump has less resistance and will have a little more power..so you can have a vehicles that acts up after warmed,with a failing pump.

The voltage to the pump is higher when the engine is running with a healthy alternator....a weak alternator can show a weak pump as it now has a a little more less than a volt going to it.......it dont sound like much a single volt...but the problem compounds itself...lower voltage equals less pumping for cooling,,causing more heat,,creating more resistance electrically thus slowing the pump causing less cooling.{sounds the tax domino effect hey}


Some of these pumps actually carbon track from the positive side wire of the pump down to the pump and much electricity is used by this wire,,thus the voltage drop causes a slow pump...this is a common intermediate problem.just think of it the same as a spark plug wire shooting spark to the engine by leakage through the sparkplug wire....sometimes it does sometimes it dont.

A high mileage gm product will have a pump failure,,the rest of the system is pretty reliable and has an excellent default value setup for failed components{sensors} offering good driveabilty..the exception is the Mass air flow sensor or the manifold air pressure sensor..you will either have one or the other.

Back to the pump and the tank......again water is always possible..water pools together it attracts itself..so in effect you dont have a thin laver at the bottom but rather pools of water with a few large pools and several small ones..these pools can get rushed under the pickup from starts stops and corners.

Junk in the tank.......what can happen is junk can get sucked up to the screen..the engine dies...the fuel pump stops..the junk releases from the screen the car starts back up.......the usual symptoms of this are the longer the car runs it is more apt to have the fuel starvation problem.

Gm tanks are decent as compared to decades ago and its not a major problem...however there have been tanks in your era that suffered like the early tanks.

If you do decide to take down the tank...replace the pump....it is a failure item on a gm.

A few common tools...and a few chosen cuss words{for the hoses not having extra length to make the job easier} and you can do the pump in 2 to 4 hours....45 minutes if you are good.

Without actually having access to your car to be able to check your fuel system...you are describing a failing fuel pump...unless the conditions I have described to various failing sensors apply..you are looking at a fuel pump more than likely...In the event its not the pump... if it is a high mileage car made by gm in your era it is going to fail...you can just call it preventative maintenance.


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## lexmarks567 (Aug 13, 2006)

Stoner said:


> Has anyone run a fuel pressure test?
> You could have anything from a weak check valve to a weak fuel pump that is aggravated when warmed up.
> 
> Have you tried loosening the gas cap to see if it's venting properly? Too much of a vacuum can aggravate the before mentioned problems.


the shop did a fuel pressure test. they said it was within specs but pulsates (10LB-12LB) cylinder number 2 is misfiring and cylinder 4 is misfiring with cold so they think the coil could be failing. the gas tank is rusty and so are the lines but just cause its on the outside does not mean its on the inside.


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## Drabdr (Nov 26, 2007)

Geeze.... where were all you guys back when I would spend all night trying to get my 1979 Chevrolet Silverado going? 

Very nice and helpful posts everyone. :up::up:

Aren't fuel filters directional? Just saying if they are, might want to watch the flow marks.

I have had similar instances. Honestly, it took two or three fillups of gas to get the old out. Then, it would seem to run better.


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## Drabdr (Nov 26, 2007)

lexmarks567 said:


> the shop did a fuel pressure test. they said it was within specs but pulsates (10LB-12LB) cylinder number 2 is misfiring and cylinder 4 is misfiring with cold so they think the coil could be failing. the gas tank is rusty and so are the lines but just cause its on the outside does not mean its on the inside.


If you are in the mood, it might not be a bad idea to get some of that rust off and repaint. Obviously it has nothing to do with the current issue, but may get you some more mileage out of that tank.


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## aka Brett (Nov 25, 2008)

Drabdr said:


> Geeze.... where were all you guys back when I would spend all night trying to get my 1979 Chevrolet Silverado going?
> 
> Very nice and helpful posts everyone. :up::up:
> 
> ...


We were hiding and watching,,,placing bets on how long it would take you to crease the hood when you slammed it from one side


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## Knotbored (Jun 5, 2004)

This whole thread has sure been interesting and illustrates a couple of things.
1. When a mechanic asks an exobitant amount to find a problem he anticipates more then the drivers description ("it makes a funny noise".)
2. The complicated features of a modern engine to satisfy EPA and other emisions situations are bandages making a relatively simple mechanical devise difficult for an amature to analyse.
3. When us old codgers long for "the good ole days" about cars, clothes, computers and building products go ahead and roll your eyes, but give some credit to the fact that it used to be far easier to repair and upgrade all of those.


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## lexmarks567 (Aug 13, 2006)

i've had it in the shop sense before this for other repairs and none said anything about the rusty tank. even pep boys didn't say anything when i took in to have the horn and turn signal fixed. the only other problem they could see was i needed 2 new front tires.when i took it in to have the exhaust pipes replaced he said the ball joint on the front passenger side needed fixing. he didn't say anything about the rusty tank or the fuel lines.


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## Drabdr (Nov 26, 2007)

Hello, Lex!

How long has it been running this way? Do you still have the problem?

Have they read codes off the car, and everything is clear?


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## lexmarks567 (Aug 13, 2006)

they never told me the codes and they reset them. I took it to another shop and hes almost certian that its the ignition modular. He called the other shop sense they cleared the codes and they didn't save the codes for future use. So he has to make the car stall and keep doing it untill he can get a SES light sense the other shop reset it and hopefully get it to produce a code.its still at the shop right now.


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## lexmarks567 (Aug 13, 2006)

ok got it back from the shop. did not get it fixed yet as i do not have the money.its a bad E.C.M. the guy said do not drive it you could damage the engine.
this is the quote from the invoice



> Tech pulled codes they popped up and disappeared very fast. Ran flow chart found bad E.C.M. and idle air control fault. tech needs to replace E.C.M. first and see if idle air control comes back. Check and advise electronic control module.


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## JohnWill (Oct 19, 2002)

Sounds like they're guessing it's the ECM.


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## Mumbodog (Oct 3, 2007)

Vapor lock is out, since fuel injected cars now have an open loop fuel delivery system, this only affected old low pressure closed loop fuel systems.

I would suspect a crank sensor also, they can be weak and cause the symptom without setting a code.


The MAT sensor may not have been bad, but it could be the wiring that connects it to the fuel computer, whenever you read data on that vintage of GM car, high resisitance wiring can cause -4 readings, the sensor is fine, the wiring is bad, no way for a scanner to diagnose this, you must check connections at the sensor for corrosion, and use a DVOM to check the wiring for high resisitance or open circuit.

Clogged fuel filter is at the top of the list. Cheap and easy to replace.

Fuel filter loacation:
Under vehicle, driver side, below seating area near fuel tank, mounted on frame.

.


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## lexmarks567 (Aug 13, 2006)

the computer is saying that the mat sensor is still reading -4 but the sensor was just replaced.


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## Mumbodog (Oct 3, 2007)

> the computer is saying that the mat sensor is still reading -4 but the sensor was just replaced.


Like I said the wiring from the sensor to the fuel computer is damaged, most likely an open circuit (broken wire or damaged terminal end)

Most mechanics these days are parts replacers, the can't "fix" anything.

Find a competent mechanic.

.


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## lexmarks567 (Aug 13, 2006)

well after talking to my mom sense she took the car in the tech said the wiring was bad around the computer.


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## JohnWill (Oct 19, 2002)

Yes, but did fixing the wiring actually solve the problem, or is this yet another guess by yet another mechanic?


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## Mumbodog (Oct 3, 2007)

> well after talking to my mom sense she took the car in the tech said the wiring was bad around the computer.


Are you going to ask for a refund for the MAT sensor replacement?

.


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## crjdriver (Jan 2, 2001)

Just saw this thread. Since this only happens when warm, I would suspect a sensor and or ECM. It really is not all that hard to check out these parts. All of the sensors have either volt or ohm limits. A simple volt/ohm meter works pretty well.

Next here is how I fixed many cars back when I turn wrenches for a living.

While checking the sensor use a hairdryer to heat up the sensor. If the volt/ohm reading varies out of specs when the heat is applied, you have found the problem.

Next I would change the fuel filter just because this thing is 19yrs old. Some filters do use an internal lock that you need to buy a tool for however these are cheap. As to depressurizing, I just wrap a rag around the line and open the fitting. A small amount of fuel will leak out into the rag; that is it. Once the filter is off, cut it open and look at the inside. This will tell you if you have a rusting tank.


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## JohnWill (Oct 19, 2002)

FWIW, I bought a new Buick a long time ago, it was a leftover from the previous year. I went about 20 miles after filling the tank and the fuel filter was clogged to the point that the car could only go at a slow speed and I could hardly accelerate at all. Took several filters to solve the problem.


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## itsjusme (Aug 19, 2006)

Has the vehicle ever quit on the mechanics while they were working on it? In tank fuel pumps can exhibit intermittent problems. As the brushes wear they leave residue in the brush holders, sometimes the brushes hang up in the holders causing it to quit. Fuel sloshing in the tank, jarring the tank, turning the key off and turning it back on may cause the pump to run again. Sometimes hitting the bottom of the tank with a hammer or block of wood will jar it enough to get you back home. I would suggest hooking a fuel pressure gauge to the system and fix it where they can monitor the pressure as you drive. If the fuel pressure drops when it quits then it`s likely the pump, faulty wiring, bad ground, oxidized contacts on a connector or relay/fuse, or ecm. I would check all these other possibilities first.If the tank is rusty as you say then other things may be rusty also creating a bad ground. . To test the ecm or wiring to see if you`re losing power to the pump when it quits, hook a test light to the hot wire going to the pump and monitor while driving. They should also test for spark after it quits. As far as ther pulsating fuel pressure, i would suspect a bad pressure regulator, or a leaking or burned valve, both can cause pulsating fuel pressure, but if the pressure isnt dropping below 12# thats not the problem. A vacuum test will reveal a leaky or burned valve. it will pulsate just like the fuel pressure. Intermittent fuel pump problems can be hard to find if theyre doing all their tests when it happens to be running. One more thing i have found quite often. The gas we get these days will go sour really quickly, leaving behind some pretty nasty brown/green/gummy deposits that can turn hard as rock. I have seen this residue creep into the connections of the pump in the tank, and also the feed through connectors where the harness goes through the tank. This can be a problem if the car sits almost empty more than it sits almost full. Just a few more things to have them check. Good luck, dont just let them keep changing parts till they get the right one.


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