[lexmarks567]

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.

[Knotbored]

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.

[JohnWill]

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.

[IMP49]

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.

[lexmarks567]

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.

[JohnWill]

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

[lexmarks567]

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.

[Knotbored]

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.

[JohnWill]

Never heard of that, learn something new every day.

[lexmarks567]

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

[lexmarks567]

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.

[Knotbored]

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.

[JohnWill]

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.

[Stoner]

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.

[aka Brett]

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.