84 vett dies then restarts in 5 minutes

[Swang]

Car usually runs great. Has new plugs, primary coil, cap, Oxygen sensor. When running at about 45 mph, after warm up, it starts to hesitate. Then it just dies. All electrical systems seem to be working. Engine temp is normal, has spark and fuel. Spark seems weak but mat be normal. No codes in the ALDL. Sits for 5 minutes and then will start but dies again after a few minutes. After restart I can usually get it home if I shift to a lower gear and keep my rpms up. Automatic trans is newly rebuilt. Starts fine in the morning. Has 130,00 miles on it.

 

[Ken]

Welcome To The Corvette Action Center Steve Wangemann!

Just guessing (as usual ) but you weren't clear as to whether there is any symptom leading up to the point where it dies. When you say it hesitates, do you mean it feels like it is being strangled and cannot breathe? That being the case it might be your catalytic converters (one or more -- I forget what the '84 comes equipped with) plugging off. When the engines gets to operating temperature and the exhaust temperature is up to where it should be, the cats will plug off, in effect choking the engine to death.

Sometimes they will plug off then open again, as was in my case when mine went bad. The car ran fine as long as they were making noise, but when it got quiet, what happened was they would plug the outlet and kill the engine.

As I said, just guessin' here.

 

[cntrhub]

Is there any way you could get a timing light hooked up to say... #7 plug? This is the closest cylinder on the driver's side. You could drive the car, watch the light (careful) and see if the timing light stops blinking before the engine dies.
You are trying to find out if the ignition is the culprit, or the fuel system is the cause?
If the car dies, and the timing light keeps blinking, well it's fuel. The car dies immediately when the timing light stops flashing = ignition.
Now you kind of know what to chase.
This next diagnosis is going to be way off in left field. Drive the car and when it acts up like it's going to stall, put the Trans in neutral. and see if the engine still runs as if everthing is normal. Now that I think about it, it might be hard to see if when they put the Trans back in, they didn't catch some igniton wire or a sub-harness in between the block and Trans case? It would be wise to give a peek just to make sure. A wire might be grounding, being pinched between the block/Trans housings?

 

[cntrhub]

Good point on the "Cat-Clog" Ken. But I think if Steve can... "get it home if I shift to a lower gear and keep my rpms up."......it wouldn't be the Cat. Now that's a lot of air to backwash in the Cat and shut down the engine really quick.

 

[vettered91]

It seems to me that the your fuel pump is dying. This are tipical symptoms; they start failing after they warm up!

 

[Swang]

Fuel pump

Thanks. Well I suspected the fuel pump, fuel filter, or the cat. I expected the engine to run hotter if the cat was plugged. I changed the fuel filter and noticed that even though the front of the car was up on ramps that fuel kept running out of the gas line when I took the old filter off. The gas stream was not fast, just a slow to moderate trickle. I put a container under it thinking that it would stop once line pressure was reduced. Fuel flow never stopped. Does this still point to the fuel pump?

I also smelled sour exhaust at one point. Like I had bad gas in the tank, but I always run high octane. The smell did not persist and I don't smell it at start up or shut down.

When the car dies it hesitates then recovers, then finally just dies. No unusual sounds.

 

[Ken]

The fuel will siphon from the tank unless the line is disconnected or pinched-off. I know from experience; I felt like the little Dutch boy with his finger in the dyke (shaddup Len! :L) when the fuel would not stop running. (I had the lines completely disconnected! :eek)

_ken

 

[vettered91]

The best way to check the fuel pump is with a fuel pressure gauge and the engine running to see any changes in fuel pressure after the pump warms up!

Sorry Ken Could not avoid it it already happened to me... (changing the fuel filter)

 

[V..rroom]

Try this link, it has some interesting information...it is quite technical, but hey....a Vette is a miracle of American technology...
good luck....
http://www.c4vettes.com/l98.htm

 

[Dave C. '04 Z06]

If it were me, I'd replace the ignition module in the distributor if you haven't already done so. Alot of times when they start to go bad they fail after they get hot, then when they cool off they work again.

Just a thought,

-Dave C.

 

[Corvette-Pilot]

Do the C4's suffer from the good old vapor lock?

 

[Ken]

Do the C4's suffer from the good old vapor lock?

It's not really possible on fuel injected engines because the fuel is always moving in the lines, unlike a carbureted engine where the fuel is only moved as needed (unless you have a return built into the system). Of course, it is always better for the fuel to be as cool as possible so care should still be taken when routing fuel lines to keep them away from sources of heat.

_ken

 

[WhalePirot]

check the fuel pump is with a fuel pressure gauge

Works on the TPI cars but not on the X-fires, which have no factory supplied place to connect.

When my CAT plugged, due to running too rich (the new cam lowered the vacuum, so the ECM figured the throttle was open more than it was, feeding more fuel) I lost power at High RPM. Eventually, the RPM would not exceed 4500 or so.

My guess is fuel, too. As you've already changed the filter, check out the pump, next. Tho probably not heat related, there is a sock-type filter covering the pump intake, inside the fuel tank. If the issue is more related to time passage than actual engine heat, a clogged sock might be part of the problem. You'll see it when you pull the pump assemby out thru the filler door.

Heat related issues can be a bugger to find as misfiring can be due to cracks that show up, under thermal expansion, allowing air or coolant into or out of a place where it's not supposed to pass. Therefore, it might be a temperature related vacuum leak or coolant leak.

If you choose, you might look at each plug carefully, before shelling out dough or a new fuel pump, and see what is going on in each cylinder. Rust indicates coolant is getting in, etc., but the spark plugs can be very revealing on a hole-by-hole basis.

Mike

 

[geekinavette]

Ignition module is certainly a possible culprit, wouldn't be the first time I've heard of one failing when it gets warm. Just remember that the injectors are triggered from the ignition pulse, so if you notice it not spraying fuel when it's in "dead" mode, don't automatically assume that it's a fuel system problem.

Good luck with it.

Bill

 

[Dennis M]

84 dies

I also had the same problem however when I initially started the engine in the morning it would run rough for the first 30 seconds or so. One of the throttle body injectors was leaking. Replaced the injectors and it cured the problem.

 

[Swang]

84 dies

The fuel pump seemed to be a logical place to start but did not cure the problem. So far I have replaced the pump, filter, vaccume lines, coil, cap, rotor, plugs, and cleaned electrical conectors. Most of this I was going to do anyway. I have not replaced the plug wires.

The car ran ok on the first 5 mile road check but on the second it hesitated when I was running at about 50 miles per hour. Just a slight jerking so I slowed down then truned into a driveway to head back home and it died. I was able to restart it immediately by feathering the gas pedal. It died a second time on the way home when I slowed down but started right up again. The check engine light came on but by the time I got home it was off. I did notice some black exhaust smoke the second time I started it after it died. The engine temp was about 197 and it idles at about 600 to 700 rpms. Spark plugs look a little black but do not have alot of carbon built up on them. Always starts ok.

Could it be the EGR valve?

 

[Swang]

Continued 84 dies more info

I also replaced the fuel filter. No popping sounds from the exhaust when it idles but it does have 130,000 mile on it. Idles at 1000 rpm or so from a cold start. The problem does not show up until it is warmed up and has run a few miles. I have let it idle in the driveway to warm up and it does not die. Fresh gas in the tank. No water in the oil. No blue, white or black smoke at stat up. No apparent vaccume leaks around throtle bodies or heads. O2 sensor was also replaced.

 

[cntrhub]

"This is a test. Don't adjust your screen." This might be a driveability problem that may be in the...... "Outer Limits" of your garage.
You may have to bite the bullet and seek a good tune-up shop, or dealer, that has an injector tester harness. This will tell electrically, if an injector is siphoning out just enough fuel to shut the engine down. Not only that, but they could drive the car with the hand held plugged in the ADL and see which code is triggered when the 'CEL" does come on dash.
Have you tried contact cleaner spraying the gasket right behind the throttle butterfly housing? Those gaskets are notorious for air leaks. If the engine revs up or stumbles spraying around that area where the gasket is, this could be triggering a lean condition and fooling the computer to richen up the injectors to stay open longer. Just something to chase before you hand it off to a drivability expert.
The EGR valve could be a problem too. But you could test that by cupping your fingers underneath the EGR, then press the diaphram in and see if it returns. This is done with the engine running, and at idle. If it sticks and stalls out, well, you might have found your problem. Make sure the hose is well sealed on the EGR also. It might be a simple vacuum problem?

 

[geekinavette]

Swang,

Even though the Check Engine Light turned back off, that code is still stored in your ECM. You can retrieve the code with a paper clip by shorting pins A & B of the ALDL connector and turning the ignition on (no need to start the engine). The CEL will flash the code at you. You should get a code 12 first, this just means that the ECM is working and the engine is not running. The CEL will flash once, pause briefly, then flash twice, then pause a little longer, and repeat this cycle two more times (showing you code 12 three times). Any other codes stored will repeat this same pattern.

I'm still leaning towards a possible faulty ignition module. With electronics, frequency = heat. With it just idling in the garage it may not be building up enough heat to fail. Sure you could take the module out and have it tested, but that may or may not show an intermittent problem. The module runs anywhere from $30 to about $60...at 130k miles it can't hurt.

Bill

 

[Eagle85C4]

Steve...
Just for grins and ha-ha's try removing the tach filter and see if that makes a difference....let me know. If it does then you got a free one coming....