Stalls out after sitting in traffic too long

gull · Post by **gull** » Mon Jul 31, 2006 2:07 pm

Well, I thought I might have this one licked, but it's cropped up again.

If I get stuck in stop-and-go traffic, or idling completely stopped, for more than 20 minutes or so, the car will start to stall. At idle it cuts out very suddenly, like turning off the switch. If I happen to be rolling forward it will buck and lurch. I'm guessing it's heat-related, since sitting at idle builds up a lot of heat in the engine bay. Even long uphill climbs won't do it, though; it seem to only happen in situations where there's no airflow except that from the radiator fan.

I'm thinking maybe I have a bad ignition coil that opens up when it gets hot, but before I started swapping parts I thought I'd see if anyone else had dealt with a problem like this. It's hard to troubleshoot because it's very intermittent, and it takes a lot of idling to make it happen.

Post by **Calimus** » Mon Jul 31, 2006 4:22 pm

Do you hear a loud buzzing about the time it happens?

If so, and if your cabby has 2 fuel pumps, it may very well be the in-tank pump getting ready to die. Granted, it could be either one, but the in-tank one likes to give up the ghost more often. Good thing to since it's the cheaper of them.

Next time it does it, listen for one of the pumps to get a bit loud shortly before the car stalls.

gull · Post by **gull** » Mon Jul 31, 2006 11:57 pm

I don't remember noticing the fuel pump being louder than usual, when it happens, but I'll have to pay attention. I also haven't had any fuel starvation symptoms at full throttle, which I'd expect with a bad fuel pump.

sixsracing · Post by **sixsracing** » Wed Aug 02, 2006 9:09 am

A couple of questions:

Does the car instantly restart?

Does the car run normally after restart?

Can you keep it from stalling by applying more throttle?

If the car is very warm and you shut it off, does it start harder than usual?

gull · Post by **gull** » Wed Aug 02, 2006 3:05 pm

sixsracing wrote:A couple of questions:

Does the car instantly restart?

Usually. Sometimes it immediately stalls again.

Does the car run normally after restart?

Often, but not always. The likelihood that it will goes down the longer it sits in traffic. It may immediatly stall again, or run normally for a minute or two and then stall. If I'm able to pick back up to normal driving speeds the problem will go away, but if I'm still stuck in stop-and-go traffic it will almost always stall again before long.

It seems to be an all-or-nothing deal...the car either runs fine, or refuses to run at all.

Can you keep it from stalling by applying more throttle?

Nope. Throttle doesn't seem to make any difference.

If the car is very warm and you shut it off, does it start harder than usual?

No, I've never had any problems with that.

sixsracing · Post by **sixsracing** » Wed Aug 02, 2006 3:51 pm

If you have an extra fuel pump relay I would throw it in there just for giggles. If you don't, I would pick one up the next time your in a junk yard, cheap insurance.

I had an ignition problem awhile back and I couldn't diagnose because it would fix itself. I finally wired up a coil complete with harness and bolted it to the left strut mount. If the car died all I had to do was connect the wires to the harness and move the coil wire to the spare. Maybe not a bad idea to do this to yours.

Usually the distributor will either work or not work, same for the ignition control module but this is electricity we are working with here.

Grounds will also heat up and cause nasties.

sixsracing · Post by **sixsracing** » Wed Aug 02, 2006 3:57 pm

You could always move to Maine and then you will NEVER be stuck in traffic for anywhere near 20 minutes.

gull · Post by **gull** » Fri Aug 18, 2006 9:53 pm

It did it to me twice today in stop-and-go traffic, giving me a chance to observe a bit more.

I didn't hear any unusual noise from the fuel pump. I sort of doubt it's fuel pump related, because that doesn't seem to jibe with the sudden on/off/on aspect of it -- I would expect a more gradual sputtering out and sputtering back to life as the fuel system lost pressure.

I also noticed that, during the times when I had no power, but was still coasting in gear, that the tachometer still worked. That neatly rules out the distributor hall effect sender and the ignition module, because a failure in one of those would result in no tach signal. I think it's time to try a new ignition coil.

gull · Post by **gull** » Sun Aug 20, 2006 3:23 am

Got a used ignition coil from a salvage yard and installed it today. It's too early to say if it fixed the problem, of course. I also discovered I'd left off the ground strap from the coil bracket to the valve cover, when I replaced the valve cover gasket a few weeks ago. Doubt that was causing the problem -- its main goal is probably RFI suppression. Still, it can't hurt. The block-to-chassis grounds form the return path for spark current from the plugs to the coil.

Post by **Briano1234** » Sun Aug 20, 2006 4:36 am

no that is to have a common ground for all the componets, without that bonding wire strange things happen.... really strange

gull · Post by **gull** » Sat Aug 26, 2006 8:25 pm

It did it again today. Serves me right for throwing parts at it without proper testing. So, I went to it.

First, I found out that if I got it warmed up and then let it idle in my parking space, it'd die after about ten minutes. So I hooked up a timing light. After discovering the hard way that it wouldn't die unless I closed the hood to trap more heat, I found that the ignition wasn't the culprit -- it works right up until the engine stops.

Main fuel pump and frequency valve both keep running until after the engine comes to a stop, when the safety cut-off turns them off. This ruled out the fuel pump relay.

I'd earlier noted a slight enrichment (65-70% duty cycle) at the Lambda test connector, yet the engine has always seemed to run rich -- the tailpipe has a pretty thick layer of soot. So I decided to test the O2 sensor. I disconnected it and hooked up my DVM, and got around 700 mV, indicating a rich condition. I hooked the sensor back up, and I suddenly started getting a massive correction to the lean side -- 5.2% duty cycle. But it's running as rich as ever, maybe more. Gray smoke from the exhaust, and coughs and quiet pops from the tailpipe at idle.

With the Lambda system already calling for full lean, I can't think of anything other than a mechanical fuel system problem that could be causing a rich condition. I also ruled out the thermo-time switch by disconnecting it. I think I've gone as far as I can without a fuel pressure gauge.

I'm still not sure if this new(?) issue is at all related to the old one, but I suppose it's possible...I've noted in the past, on L-Jet systems, that an overly rich mixture will sometimes cause an engine to cut out remarkably suddenly when it gets warm enough.

sixsracing · Post by **sixsracing** » Mon Aug 28, 2006 8:29 am

A couple things to throw at ya,

Pull the plugs and check for uniformity, do they all look as black?

Check the return line for blockage or crimped between two components.

Have you performed a spray pattern test on the injectors?

Compression check?

None of these cost money and can help narrow down the issue.

Keep posting, we'll figure this out

gull · Post by **gull** » Mon Aug 28, 2006 1:56 pm

Thanks for the list of stuff to check. I've parked the car for now because this week is looking like a busy one, but hopefully I'll be able to work on it more next weekend. I also ordered a CIS fuel pressure gauge set; I figure if I'm going to work on one of these cars I should have one.

gull · Post by **gull** » Sun Sep 10, 2006 5:00 pm

Got finished moving into my new place last weekend, so today I had some time to mess with it.

Pulled all the injectors and did a spray pattern test. (We're all in trouble if Corona ever stops using clear bottles.) #4 looked a little poor, the rest seemed OK. None dripped when I released the sensor plate. Is it best to replace these as a set, so they all match, or are onesies acceptable?

System pressures all look acceptable:

Engine cold: System 71 psi, Control 26 psi, ambient temperature 69 F.
Engine warm: System 72 psi, Control 50 psi.

Residual pressure was just a little low:
10 minutes: 36 psi
20 minutes: 34 psi
Probably a marginal check valve at the pump. I already verified that the injectors and CSV don't leak.

Haven't pulled the spark plugs yet. I will when the engine cools down. I never pull plugs from an aluminum head unless it's cold.

Does anyone know where the Lambda control unit is located on this car? I'd like to unplug the connector and check the wiring harness for shorts. The O2 sensor voltage seems to drop to nothing when I plug it into the Lambda harness.

gull · Post by **gull** » Sun Sep 10, 2006 6:18 pm

Pulled all four spark plugs. They're all about equally black and sooty.