Random engine stalls

[teahouse]

Hey everyone - first post here. I'm driving a rusty ol' 97' Outback Impreza Sport, 2.2, automatic (wish it were manual). The rust is considerable, but I've kept on the engine... and am only at about 165k at this point.

 

Ok, so here is the issue - for some reason it will just randomly die... this can happen whether I'm idling or driving on the highway, and anywhere in between. I just replaced the spark plugs and fuel filter, hoping for an easy fix. While it is much peppier now, as these needed replacing anyways, it didn't fix the problem.

 

The car starts instantly every time after it stalls. I looked for arcing sparks, and found none. I ran every accessory (heater, lights, etc) to see if the alternator was failing, but it powered everything like a champ. Since the car starts every time after stalling, it makes be think it isn't an issue with the fuel pump - but correct me if I'm wrong.

 

I did notice, yesterday, that when I took it for a test drive after replacing the fuel filter, it ran like a champ. Then I tried it again after it began to rain outside, and it stalled about 10 times within a couple miles. Sometimes it doesn't die right away, but stutters and revs up and down erratically as I try to give it more gas... then just dies. Also, it usually keeps stalling consistently for a little bit, then magically after a few minutes it seems to run well again.

 

I have no idea what component I should go after next... and I'm hoping someone here has a suggestion or may have had the same thing happen to them before. I'm waiting to bring it to a mechanic, because I am very limited on funds right now... thus I'm just trying to fix it myself right now.

 

Any help is appreciated, and I apologize if I've left out any critical info.

[bstone]

Sounds like a fuel delivery issue. Has the fuel pump ever been replaced?

[Fairtax4me]

Fuel pump is possible. Just went through something similar with a friends car. Occasionally it would just cut off while driving. If idling it would stumble for a few seconds hen cut off. Wait a few minutes and it would start and run fine for a few miles then do it all over again.

replaced the fuel pump and it hasn't done it in two weeks or so. Kind took a gamble since we couldn't get it to duplicate the problem when we had a pressure gauge hooked up to it, but it seems to have fixed it.

 

If you can get your hands on a fuel pressure gauge make sure the pump is making the right pressure when this is happening. If it drops suddenly or is low the pump could be bad.

[Recian]

fuel pumps are easy to change on this car too. When it starts back up after dying does it have an extended crank time? if it fires right up i wouldnt suspect fuel for one main reason. If it dies due to lack of fuel it means your lines are empty since it loses all the pressure. The 1-second run time the fuel pump has when you turn the key isnt enough to re-pressurize the entire fuel system. It takes about 5 second crank time to fill the lines back up. That being said if it starts right back up i'd look at an intermittent cmp/ckp or coil pack. It isnt common but it fits the description. But like was said before having a fuel pressure gauge in line never hurts to diag before spending money on ignition and you can splice it into your lines at the pump and run it to the front of the car so you can monitor it while driving without having a line running from under the hood. Also the fact that moisture in the air seems to make it worse leads me to believe that you have a failing coil pack. Happened to me on my old buick 3800.

[teahouse]

Thanks for the replies everyone.

 

if it fires right up i wouldnt suspect fuel for one main reason. If it dies due to lack of fuel it means your lines are empty since it loses all the pressure.

 

My thoughts exactly... every time it dies, it fires right back up... maybe I'll go replace the coil pack, at a throw of the dice, to see what happens...

 

You don't think it could be the distributor, alternatively? The thing that makes me think it may not be that is how well it runs, when it does run... IDK.

[Recian]

No since these cars use cmp/ckp sensors to monitor cam and crank position and fire the coil through the ecm based on imputs. If those 2 sensors cause this ull have a 340 or 335 code.

[teahouse]

Hmm, I don't have a way to determine whether I have that code read-out or not... that is, unless I bring it to the dealer... do I?

[bstone]

Gosh I hope you don't go to the dealer to get a code read. That'll cost for $100 at least.

 

Go to Auto Zone or Advance Auto Parts. They read codes for free. Your car is a 97, so it's OBD-II compliant.

[teahouse]

Eh, I just called around - can't get the code readout done by anybody BUT the dealer here in Cali (stupid).

[bstone]

So to go Advance and buy one. Buy it online and use a coupon code.

[teahouse]

Are they pretty accurate at telling what the problem is?

[bstone]

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_3020-OBD-II-CAN-Scan-Tool-Innova_10181921-P_N3389_T|GRP2018_____

 

google for an online coupon code. cheaper than paying the dealer.

[teahouse]

Are these usually accurate enough to narrow a problem down to say, a fuel pump or coil pack, for example? I've never used one...

 

Thanks for the link.

[Fairtax4me]

No it's a code reader. It will display and CEL codes that are stored in the ECU, but it can not diagnose a problem with the fuel pump. If the CEL is on, you need to get the codes read or buy a scanner for yourself and find out what they are. It may help, but it won't tell you if a coil or fuel pump is the cause. the Check Engine Light is there for emissions, and that's all.

 

Fuel pump failure does not mean the lines go completely empty. The only time the lines go empty is when the tank tuns dry.

The problem may be that it just can't produce enough pressure to keep the engine running. And this can happen intermittently. When the key is turned to start the pump primes the fuel lines and the pressure builds to normal during the half second or so that the engine is cranking. Then the pump may run indefinitely or for only a second before it slows and the pressure starts to drop again.

When pressure gets low the injectors do not spray properly, fuel doesn't burn completely, which causes the stumbling and loss of power. Eventually the pressure gets low enough that the fuel doesn't "spray" anymore, it just kinda dribbles out, then the engine dies. All depends on how the pump wants to act. But the point is, the pump is still running, just not as well as it should be. If the pump is cut off for a second it may return to normal operation.

[teahouse]

Ah, very good info - maybe I'll go after the pump next then.

 

I do have a few more interesting points to add, after just testing a few more things:

 

1. I just noticed that the engine dies consistently when I close the hood, while it is idling.

 

2. The engine also died when I brought the RPMs up to 4k, then let off gas completely. However, it ran smooth and clean at full RPM... just when the rpms dropped quickly did it die, but this doesn't happen consistently.

 

3. I took the ignition coil pack off and inspected the contacts, and tested them with a voltmeter. Both banks read almost exactly equal, the contacts looked like new, and the unit it's self had no cracks... which leads me to believe it likely is NOT the coil pack.

 

4. I check the air flow sensor, and it looks clean.

 

5. I misted water over the coils, sparks, etc... and saw no spark nor did the engine die or stutter.

 

To me, number 1, the engine dying when closing the hood, MUST mean something??

 

**edit** - also, as of right now, there is no check engine light on.

Edited April 27, 2012 by teahouse

[teahouse]

Well I bought a new fuel pump based on the recommendations here... its being shipped to me, so it will be a few days before I can put it in and post results. I also picked up a diagnostic reader and an air filter for another 2 dollars, using a nice $50 discount.

[Fairtax4me]

Gotta love it when you can spend a few dollars more (funny, I'm watching For a Few Dollars More) and get something else practically for free.

[GeneralDisorder]

If it dies due to lack of fuel it means your lines are empty since it loses all the pressure. The 1-second run time the fuel pump has when you turn the key isnt enough to re-pressurize the entire fuel system.

 

Not true. The lines are not empty after losing pressure. Without pressure the fuel will not flow through the injectors - it will just stay in the lines and the filter. 1.5 to 2 seconds is plenty of time to repressurize the the lines.

 

May not be a fuel pressure issue at all - but the logic used above is flawed.

 

GD

[GeneralDisorder]

1. I just noticed that the engine dies consistently when I close the hood, while it is idling.

 

Check your crank and cam sensor wiring.

 

GD

[davebugs]

Check your crank and cam sensor wiring.

 

GD

 

My guess is crank.

 

When I've had weird problems like this it was often the crank sensor.

 

Especially with intermittent no starts.

 

Perhaps because it's the hardest one to remove around here in the rust belt.

 

While you are diagnosing this issue a shot of your favorite penetrant arouind the crank sensor won't hurt anything and may make the removed easier if needed later.

[teahouse]

Alright, I'll check it out -- any way to check if it's faulty? Perhaps with a voltmeter, for example?

 

Also, I have no intermittent no starts... it starts up every time. It's just that, occasionally, it will only stay running for a few seconds, struggle to keep RPMs up, then die again.

Edited April 28, 2012 by teahouse

[Fairtax4me]

Crank sensor is usually all or nothing, meaning if it doesn't work the engine doesn't even start. Plus you usually get a code for it. Intermittent stumbling is either fuel related, bad MAF sensor or a sticky IAC.

[teahouse]

Swam through all the grease just now to find and unplug the crank sensor. While dirty on the outside, the contacts looked perfect, and the wires look good. MAF sensor looked good too. IAC -- there's a new idea. I'll give it a look.

 

If I were to take the MAF sensor out, is there a way to check it using a voltmeter?

[Recian]

maf cant be checked due to it's complex integrated circuits. however if you unplug it and start the car it goes into failsafe but that only works at idle to see if it's a problem. You cant rev it with it unplugged or it dies. However letting off gas causing a stall sounds lke fuel. My landlord's truck wouldnt start on her today and she had the same symptoms. Stalls when you dont give it gas. The injectors open at a higher pulse width at higher rpm allowing the lower fuel pressure to not be a problem because they open so fast the fuel can get into the cylinders. As i said about dry lines it's true it wont completely drain the lines but it will only leak down until the injectors drain the fuel system at the lowest possible PSI to keep it running then it dies. What i referred to by that would be the fact that the pump usually cant re-pressurize the system instanly. If it drops to say 25 while running and 35 at idle and if it goes under those conditions the car cant possibly run then what's the odds the pump can in it's 1-2 second prime time when he re-cranks can accomidate 10-20 psi through the entire (however many cubic centimeters long) section of fuel line it has to fill from back to front with fuel hence it would have a long crank time as it builds faster than the injectors releive pressure until it hits that 35 psi mark again.

Edited April 28, 2012 by Recian

[GeneralDisorder]

You check the cam sensor? Cam and crank are both prone to having damaged wiring.

 

GD