Stalling out when hot.

[cdivine]

Hey all, I'm trying to track down the cause of my intermittent stalling on my 1996 Cutlass Cierra 3.1. No check engine light or trouble codes.

It only stalls out after long driving on a hot day. Verified good fuel pressure while it was up to temp and dying repeatedly. No fuel pressure drops when it died.

Tested ignition coil pack resistance on primary and secondary coils and all 3 tested good when hot and cold. Also I removed the coil packs one by one to see if it would die. It still ran with just 1 coil pack on 2 cylinders so pretty much ruled out the packs.

Swapped ignition control module and no improvement.

Both crank shaft sensors were replaced about 1 year ago.

It seems to me the ignition control module is losing a signal from a sensor and cutting spark. But what I don't know is which sensors the ignition module pulls data from directly. Is there a data logging app I can use to monitor suspect sensors and see when they cut out?

[Pontiac6ksteawd]

You checked for fuel pressure when it stalls out, but did you check for spark?

[cdivine]

I couldn't check for spark unfortunately. When it dies it always starts right back up with a turn of the key. I'll get an inline spark tester on it so I can watch in real time.

[cdivine]

Ok got it hot enough today where it would die repeatedly and I could do some testing. Got my spark tester light on there and had a helper crank it as soon as it died. Sure enough got a few cranks where it would not start but did have spark! Checked all 3 coil packs. So time to get that manifold off and ohm test these injectors. And it finally threw a code today P0301 cylinder 1 misfire. Thanks Pontiac6ksteawd!!

[Pontiac6ksteawd]

With it restarting immediately, it makes it hard to see if the ECM might have failed on the driver. And you having a 96, makes it even harder as thats the year computers for this platform went wonky.

Need to see if the spark is present when it stalls.

Not sure how to tell you to diagnose this one.

[Pontiac6ksteawd]

Although I did just have an idea.... Tack the back end of a screwdriver, and with the engine running, at full operating temp, tap on the MAF. Not enough to break it (obviously), but enough to give it a sharp shake.

Unless you have a spare MAF laying around to swap with.

[tlc1976]

How does it stall? When going down the road? Or when sitting idling? My IAC likes to stick sometimes when it gets hot. Usually cleaning it once a year fixes it, but they’re cheap to replace if needed. At least on my 3.1 mpfi.

[cdivine]

It will usually stall when going down the road. Often at the crest of a hill. When everything's nice and hot (25+ miles driving) it will die at idle and will die repeatedly until it cools off.

[tlc1976]

It does sound like an old sticky IAC valve, at least in my experience. Mine only gets sticky when hot. And of course only when idle speed needs to take over, like when rolling up to a stop sign, or possibly when cresting a hill at a speed low enough that the TCC doesn’t stay engaged to continue to rotate the engine at speed. I learned to be just as proficient driving 2 footed so I can keep tapping the gas to keep it from stalling until the valve catches up and it idles properly. Until I get a chance to clean it, then it lasts another year. That’s on the Celebrity, as I’ve been driving it for 20 years. The Cruiser started doing it last year after my gf wanted Taco Bell and I had to sit in the drive thru for 45 minutes. I replaced it when I took the car out for this year and no more problems. But except for unusual circumstances, I avoid times and places when I know I’ll be sitting in traffic because I hate it. And most of my driving would be for like 200 miles a shot with only a few stop signs, or going to work with only 1 stop sign each way, so I’d just deal with it.

[Keiths1976]

Let’s think all sensors fail at heat when hot , crank position sensor , those prone to crack and get misfire stalling in side the block , there is the wire that connects that to the icm gets brittle and rubs against the block when hot and grounds out to stall and die , the icm also heat prone to fail when it gets hot same as coils , the coils ohm test them when hot see if they are failing normal are 5-6.5 ohms normal and hot . The Iac also are prone to winding breaks down when hot . Also a clogged egr cause cause when hot stalls out . But all of these don’t cause a check engine light either since gm values have room to play . Same as coolant temp and throwing off values to your car running . My best advice is starting out with the coils

[cdivine]

Ok finally getting back to this. Car sat for awhile. Grabbed a full set of injectors from the junkyard. Got the manifold off and tested ohms on the injectors. All were around 12.3 - 12.5 ohms.

Slapped in the junk yard injectors and started it up. Car runs for about 90 seconds and dies. Slid underneath to listen to the fuel pump. I can hear it start to wind down and quit when the car dies.

FIRST thing I did when this all started was verify fuel pressure. Had 40lbs of pressure when it would die. So idk if I made a new issue by tearing stuff apart which is causing the fuel pump to cut out, but I don't think so. I'll get a new pump in and see how that goes.

[DustBro]

So mine used to do this when I first got my 94. I would have to pull up to a light and have my foot slightly depressing the gas while I was stopped. I changed my IAC and TPS and it fixed the issue. I would still look into some simple, free and quick things too. Recently I had a hard start issue and mine was just corrosion on the negative cable to battery. Cleaned it off and no issues since. Have you cleaned your egr? Those get Carbon-ed up pretty quickly, I cleaned mine then changed it then eventually just decided to go without it and it's made a huge difference. Like others have said could be a ICM. Which if you end up needin one get ahold of me I have a spare one I'll give ya for the price of shipping.

[cdivine]

Ain't got no gas in it!

It was pretty low on gas, not quite E but almost. Put a couple gallons in and it ran fine for 10min. I'll have to revisit this next weekend.

[tlc1976]

Has the fuel filter been changed anytime recently? Cheap and easy test, and can’t hurt anyway. They can get junk in them that will slowly stop the flow under pressure, then it falls back out after pressure is relieved. I’ve also had a collapsed filter sock in the tank do this, but if you’re replacing the pump you’ll replace that.

I would see if it’s the pump before I went through the work of dropping the tank. Can you see if there’s voltage trying to run the pump when it’s supposed to be running? Can you jump the fuel pump test connector if the pump won’t run when it’s supposed to? That could help to see if it’s actually the pump or if it’s what controls the pump.

Someone who knows OBD2 better than me could answer this better. Can you jump the fuel pump test connector and leave it while it’s running, without frying anything? If this can be safely done, that would determine if it’s the pump actually cutting out, or if it’s the pump control.