I have a 93, convertible. I chased an intermittent stalling problem for a year. Someone on this forum pointed out it might be a VATS problem. I bought a VATS bypass device on ebay but it came without instructions.

Then I looked my key and the electrode thing was very worn. Could it be that simple after replacing the opti, the coil twice and the ignition module twice?

I haven't been able to find out. In the middle of all this I brought out my alarm clicker, which had broken years ago and been unused ever since. It wouldn't lock and unlock the car but I could hear some clicking. And yes, I replaced the battery, no change.

Before I got to road test the new key, the battery completely discharged, no nothin, no dummy lights, nothin. So now I need to trouble shoot a short before I can drive the thing long enough to see if it dies for no apparent reason anymore. I have a volt meter and a test light but I have no idea where to start with the short. Any advice?

 

VATS won't cause your car to stall. It will prevent it from starting. Once the engine is running the ECM never looks at the VATS input again.

One way to test for a short is to remove a fuse and put your test light across the fuse contacts in the fuse panel. If the circuit is drawing power the light will light.

I'm not sure on a '93, but there may be some power drawn at key off by the radio and some computer modules (to maintain the memory). Keyless entry also is active.

 

Not much to go on, but starting from scratch, here's some basic electrical troubleshooting steps I would take to get pointed in the right direction:

Of course, you'll need to charge the battery, assuming the battery is good. (Ya might have to take it to be charged and tested; WalMart has done that for me a couple times.)

Then, with the freshly charged battery, you'll want to clean the terminals, if not already done in the previous exercise, and fire it up and see if the charging system is working. A voltage across a fully charged battery is around 14.6. (Anything above 12.8 on a battery badly needing a charge indicates the system is attempting to charge it. But, do not attempt to charge a "dead" battery with the car's charging system, as the poor diodes in the rectifier will get very hot and one might "bust a gut", resulting in having to repair/replace the alt...Just a thought.) If charging OK, and fully charged (around 14.6 (cold)), you're ready to move on to the next step(s)

Note: If you might try Cliff's approach using the light. If the current drain is high enough to run the test light, then that will set you on the right path. Then you'll just need the FSM to trace down the draw. However, you can have excessive drain which may or may not turn the light on. In that case you may want to continue with the following.)

1. Measure current draw with the engine off to verify you don't have more than about 25-35 mA "keep alive" current. GM says under 50mA is OK, but I find that is actually higher than anything I've seen a car draw when everything is working properly, FWIW.)
2. Check current draw by setting your meter to Amperes config.
3. Disconnect the positive lead from the battery.
4. Attach the red lead to the positive post on the battery and attach the black lead to the positive battery cable. Under 50mA (GM spec) you're OK. If more than 50mA, then something is "leaking".
5. I use alligator leads (from Radio Shack, or the like) to attach the meter leads to the battery and positive cable so I can position the meter where I can read it, as I pull one fuse at a time to see which circuit has excessive draw. When the excess goes away, you know which path to take. Now we need the FSM to see where to start breaking the circuit down to see which leg has the draw.

FYI...VATS is not a problem if the car will start. But, far as your key goes, if the contacts on the key's chip are worn down to the point it is intermittently making contact, or you just want another spare, the keys are numbered according to the resistance (ohms) measured across the contacts on the chip. The chart below is a list of the VATS key numbers, according to resistance, which the key maker will need to know to make you the right key:



Well, this should get you started. By way of "blood sweat and tears", I am of the opinion that to maintain these sweet but older toys, one should invest in an OBD-I capable scanner, an FSM, and a good digital volt meter. I can tell ya that my scanner has paid for itself many, many times over in avoided repair bills. (My first clue was after the dealer had my car for a week and there was "no problem found" - only to have the problem crop up again on my way home with the car.) I figured I needed my own scanner so I could stop being at the mercy of some idgit at some dealership. BTW, there are some nifty (free) downloads available too, if you want to use a laptop to check things out. Tunerpro, comes to mind. Just a thought.

Well, good luck. See whatcha find!

P.

 

Couldn't have said it better myself.

Other than the 14.6 volt thing. A fully charged battery is 12.6volts. This is measured by the battery just sitting, key off. AND...doing the draw test on the positive side. Technically, supposed to be done on the negative side. Other than that ok. I would start there as suggested.


FYI, to all, if your taking your C4 to a dealership, especially if you do not know if they have a C4 experienced guy, that is just dumb. Do you really think they are going to support a 15 year old or older vehicle? Dream on. I work on Nissan products, I can count on maybe two hands the number of pre-2000 vehicles I work on in a year. That being said, yes they might be older, but they are still just cars. It can be figured out, but most mechanics do not want to be bothered with that. Why, because they loose money...evidently that is THE most important thing to them.

My advice, work on it yourself or find someone who can and is knowledgeable on the car.

As was said, a good OBD-1 scan tool (not a code reader), a FSM, and a DMM will take you very far on a C4.

 

One other thing that may be important about the short. The right headlight seems to have some issue with the retracting mechanism. When I jump start the car, yes I let the alternator re-charge my dead battery, it clicks about 5-10 times. It does the same thing when I turn the lights off. It sounds like it's trying engage a gear but the retraction of the light is fine and the light works fine.

I've gotten a lot of different opinions on VATS. From what I've been able to gather, if vats fails to maintain a signal, it will cut off the injectors and the car will stall and not start. I get no codes when the car dies and I have 60 lbs of fuel pressure at the rail. I'd even consider bringing it to a dealer but I can't get it to fail on any predicable basis. I've driven 30-40 miles and had no problem. Other times I drive 10 miles and it dies. Other times I drive 3 miles, let it sit for 2 hours and it won't start again. The car is useless to me because the only time I consider driving it anymore is when I know I don't have to be anywhere and I can sit on the side of the road for hours. In other words, never.

 

Well, just to be clear, 14.6 volts refers to what is measured across a fully charged battery if and when the alt is running...is what the point is I was trying to make. I that 12.6 ish is normal, as long as the battery has had a chance to stabilize after being charged. (It will sometimes read a bit higher when first the charger is removed, due to the "surface charge" effect.)

As for which side of the battery the current test is done, it doesn't matter because all of the current loops out or the battery, and all of the current returns to the battery. So, "technically" the current flowing to or from either side can be measured, one just has to be aware of the polarity.

That said, if the negative post is more easily accessed, then after the negative cable is removed from the battery, the red lead of the meter is attached to the negative cable (or any convenient chassis ground point) and the black lead is attached to the negative post of the battery.

I think we're in "violent agreement".

P.

 

I get your point about the voltage on the battery.
The only reason I mentioned the negative thing, I was taught that way. It is also is this way in my electrical test book. I guess it depends on it you think conventional theory is correct or election theory.

To get back on topic, are there any codes in the CCM? You can access codes directly thru the instrument cluster. Instructions are found in the FSM, you might find them here doing a search. I think you have two issues a current draw (you call it a short, but technically its a draw, shorts blow fuses, etc..., but whatever I know what you mean) and a intermittent stalling issue.

I would trace down the current draw first. Charge the battery, keep it charged as you find the current draw. Hook the DMM in line with the negative side of the battery. Keep the doors open, keys out, and wait like an hour. Interior lights should go off. Then note the draw on the meter, and start pulling fuses one by one until the draw does away. From there you can disconnect components on the fused circuit.

This is all but impossible without a FSM.

Also, what is the status of your security light? On all the time, flashing, etc...?

From reading the description it sounds like to me the Pass Key only is for start up, stalling later maybe something else.

Hope this helps.

 

The problem with the headlight is the plastic bushings in the motor are shot. They will be totally disintegrated into a powder. You can buy 2 sets of bushings for about $ 12.00 from the vendors and install both sets in one afternoon. If one headlight is bad the other will need replacing also. There are plenty of write ups on the forum with instructions. This would have nothing to do with your battery going dead.

 

I could quote so much on this thread an don't know where to begin so I will focus on the initial problem. Stalling and discharging battery.

As said for reasons above, its not a VATS problem.

Some of the common things to check are door switches and hood lights. Are all lights going off when the doors are closed (there might me a 20 second delay which is normal). The under hood lights should be off when the hood is down 50-70% down.

I guess it is possible if the headlights are not working properly as describes in the thread, it might continue to draw current it there was no mechanical stop in the headlight gears. Just as a thought.

Fix the simple and obvious things first like the headlight gears. See if some things get resolved and then move on to the other problems.

The stalling problem has symptoms of a bad ICM. If the car does not start, you have to at least check for spark from the coil. You need to have some hard data to go on. Perhaps there is a fuel pump problem.

And what do you mean by the "alarm clicker". Is it the passive key FOB. Did you try to program the car for it?

 

i would deffinitly do some checking the next time the car does stall. Check for spark and fuel at this point. When it does stall what exactly happens? Will the engine still turn over and just not start or will it not even turn over?

 

Yes the car will turn over and the one time I was able to get it to not start when I was near my garage I got 60 lbs of fuel at the rail with the key on and it went down shortly after the initial pulse.

I thought it was a heat related ignition module problem. I've replaced the module twice and the coil twice. I put washers between the heat sync and the head to create air space for additional cooling. I also got the correct heat sync grease at Radio Shack.

It does turn over fine when it's in its stalling mode.

I feel more confident about tracking down the battery drain problem than I do about the other problem. The reason why I thought VATS is because I could still have good fuel pressure but if the injectors were shut down the car would die. Whoever said it can't be VATS because it only matters at start up needs to read some of these VATS forum posts. There are a bunch of people who have had the same problem I have and solved it by disconnecting VATS. I'm not going to say it absolutely isn't a spark problem. I had a bad coil on this car one time and I could still get the plug wire to arc a white spark. I could see it but it didn't have that snapping sound. It had spark but it was too weak to ignite the fuel.

 

60 pounds sounds high for a LT1, you should have fuel pressure all the time key on, cranking, running, etc...I would investigate that further.