Car stalls... what does this sound like to you?

[Jonathan]

Took the car out last night and after about 5 miles, it stalled. Caught me by surprise as I looked down and saw the oil pressure needle down and the oil pressure and battery light come on. Pulled over quickly thinking it might have been the belt and not wanting to overheat anything and then had a look.

Absolutely nothing to see out of place. Nothing dripping. No electrical connections looked obviously disconnected. No hoses loose or split or apart. Alt belt is fine.

Tried to restart the car and it did, but then stalled again soon after. Soon after though, not right after.

Here is what it was doing: I start the car and while normally it does that brief little RPM flare up and then settles in nicely at 775 RPM, this time it doesn't do that. It starts and seems to be around 1,000 RPM, then is slowly creeping up to maybe 1,200 RPM or so, then starts to fall off and dips down to around 500 and then quits. And it was repeatable.

I went back around to the engine and checked bulkhead connections, ballast resistor connections, ignition coil connections, fuse block and battery connections. All seem fine. Took the air filter housing off and looked closer at the idle speed microswitch and it appears ok. Throttle lever arm and linkage look ok and no excessive slop when moving. Electrical connectors on top of the frequency valve, cold start valve, pressure regular and idle speed motor all are snug and look fine.

I am at the side of the road, thankfully on a shoulder where I can safely be out of the way, and thinking I might need a tow home. It's not far and the car does start and it stays running if I give it gas. Seems only when in park (my car is an automatic) and your foot isn't on the gas where it stalls soon after starting. If I keep a light pressure on the gas pedal, it stays running and seems fine. So I drive it home. Managed to get home without needing to wait completely stopped at any intersections and so no stalls.

I get home into the garage and put the car in park and now it stays running and doesn't stall. Back to 775 RPM. I shift back in reverse, neutral, drive and I see that the RPM's change based on gear... or load on the engine. And more so when back in park. When I put it back into park, it did this climb back to 1,000 RPM or so. I shut it off and left it as is.

I poked around in the engine bay some more looking for culprits. Looked closer at the vacuum solenoid and the electrical connector on it as well as the two vacuum hoses. They look fine but not sure if it is working correctly or if there are leaks. I don't own a smoke machine for testing the system so have been researching where to get one ($$$, yikes).

What does this sound like to you? Car stalls basically because it isn't idling well. Inconsistently though. Sometimes it does and other times it does not. Might be engine temperature dependent or one of the sensors for engine temperature? Vacuum leak somewhere? Bad vacuum solenoid? Other ideas or suggestions?

Only recent work was getting a new battery. Voltage is good and connections on the battery look fine. I have had this fluttering tach needle at times that another member was recently describing. That's why I got the new battery (old one was 11 years old so seemed time anyway). Fluttering tach never seemed to coincide with actual engine RPM, only the gauge did the strange movement.

Last two seasons or so I have had a brief case of no power when leaving the house. Have thought it might be auto trans fluid level or pressure related, but later felt it was engine idle or fuel related. Not sure. I suspect that ties into this somehow. Basically when leaving the house, it will sometimes feel like you can hit the gas and go, but it won't translate to power going to the wheels, just blah. If I stay in the garage for an extra minute or two before leaving, it doesn't do it. If I knew what was causing that, I'd have fixed it, but been chasing that one for a while. Now I guess I gotta figure it out.

[CFI]

It sounds like my car when I had the fuel mixture adjusted incorrectly. Have you taken any dwell measurements? Out of curiosity, does the problem go away when the O2 sensor is disconnected?

[Jonathan]

It sounds like my car when I had the fuel mixture adjusted incorrectly. Have you taken any dwell measurements? Out of curiosity, does the problem go away when the O2 sensor is disconnected?

I haven't done dwell measurements recently, but can. I have one of the meters from a few years ago when I went into the valley and then put things back together.

I can experiment with the O2 sensor too as that's something else I hadn't explored. What would a normally functioning car do if you disconnected the O2 sensor? Just wondering what to look for or expect to see, good test or failed test.

[Jonathan]

If it was just one thing contributing to this and not ten different things, would a bad idle speed motor microswitch that isn't telling the idle speed motor to turn on when it's needed do this?

[David T]

If it was just one thing contributing to this and not ten different things, would a bad idle speed motor microswitch that isn't telling the idle speed motor to turn on when it's needed do this?

Try a bottle of Techron.

[Jonathan]

Try a bottle of Techron.

Fuel system cleaner? I've done an injector cleaner product before. You think it could be that simple? Any particular type of fuel cleaner? Maybe the one I tried wasn't strong enough or something.

[Bitsyncmaster]

My guess would be something in the idle system is not working. Does your idle motor buzz? I would guess if it's now holding 775 RPM then it is intermittent.

An old common problem with a random stall is the fuel pump stopping because of a bad RPM relay. Broken solder joints in OEM RPM relay are common.

[CFI]

I haven't done dwell measurements recently, but can. I have one of the meters from a few years ago when I went into the valley and then put things back together.

I can experiment with the O2 sensor too as that's something else I hadn't explored. What would a normally functioning car do if you disconnected the O2 sensor? Just wondering what to look for or expect to see, good test or failed test.

The lack of a signal from the O2 sensor would not harm a properly functioning car, you’d simply use more gas and have higher emissions. However, if there is something amiss with the Lambda system with your car, disconnecting the O2 sensor is an easy way to find out as your car would run better with it out of the loop. Many people choose to run without the sensor. I was one of them when I had my car.

[Jonathan]

Nice explanation on the O2 sensor. Between that and the dwell measurements, those'll be my next steps.

I did get a few things done earlier today. One of those was to get a bottle of STP fuel cleaner and put it in (that's pretty much a Techron equivalent in Canada best I can tell). It will take some time and running the engine to see if that makes a difference though.

I also got looking at a few of my electrical connectors closer. On the ballast resistor, I redid the original black plastic quick connector that was still on the left side as I felt like the connector had a small bit of play in it and didn't like thinking that could be it. So now that one is tight for certain. I also took off each of the idle speed motor, cold start valve and fuel pressure regulator connectors and pinched together just a little more each of the tabs inside so that it was making good contact. Did the same for the vacuum advance cable connector on the left side.

When I fired up the car, it roared to life and then settled in pretty well at the usual 775 RPM. It stayed there fairly consistent without moving for maybe half a minute. Car was in park and no foot on the gas. I snapped the gas a couple of times just to see things move and respond and it seems to be reacting now.

Now, my car for the longest time was rock solid at 775 RPM. Not one bit of movement at idle. Today though, it was moving up and down. Not wildly, but more in a gradual search where it would got to 775 and then perhaps up to 900 or so, then down to maybe 650 and then 775 and then repeat. There was a certain rhythm to it. Then after maybe 4-5 minutes of it idling like this, it got searching a bit more, and the lows got lower, and when it got to near 500, it stalled.

So that's new and perhaps related to getting better electrical connections on the idle system? It seems related. Not sure if that is telling me the system is now operating and I can make a mixture adjustment depending on what the dwell readings do. I need to do that part next.

[Bitsyncmaster]

Try increasing the curb idle screw adjustment. I set mine with a hot engine, turn it clockwise until the RPMs go above the 775 idle RPM then back it off about an 1/8 to 1/4 turn.

When it goes above that 775 it means your idle motor is fully closed. A fully closed idle motor has very little torque moving the idle motor.

[Jonathan]

Well, we seem to be back in business for the time being. Hopefully just a 24-hour flu bug thing the old girl had.

I made the small adjustment to the mixture like you suggested and then let it idle for quite some time in the garage. It seemed like it was steady again and didn't stall out another time so I went for my drive. And it was good to go and felt strong too. So maybe that was that.

Again, I think when I went over a bunch of those electrical connections all related to the idle control system, it got some part of that system working again that hadn't been working well or at all before. Then the mixture adjustment was needed and it seems good now.

I'll obviously keep an eye on things a little closer related to this over the next few drives and report back here how it goes.

Thanks for the help.

[Michael]

When I took mine to Pigeon Forge for a DeLorean get together, I stopped in Greeneville at a less than ideal station for gas and for the rest of the tank, the car had a bit of a hard start issue. Once I ran the tank down and refueled, the problem went away.

Point I am making is that maybe run the tank down and refuel and see if the problem is still there.

Are you still running the oe fuel pump?

[Jonathan]

I can definitely run the tank down further before getting the next fill-up. Could be some bad gas in there from the beginning of the season. I think I've gotten 4 fill-ups since the Spring.

My fuel pump is the original design, but not the original one that came with the car. I replaced it with a new one a few seasons ago. Not the combo unit that's available now, but a new pump made to work in the original set-up.