Car dies 5 minutes after starting, then runs fine???


Just a good ole boy...
Jun 6, 2003
Over the summer I did a refresh on my engine, re-ringing a cylinder that had gone south due to detonation (the rest of the engine was fine, so I'm guessing a bad injector?). In the process I replaced a few pieces of sketchy wiring, and also installed a brand-new injector wiring harness from caspers and brand new injectors from TT. At first the car ran flawlessly, but in the past few weeks I've noticed a problem, and it seems to be getting worse, both in frequency and severity.

At first, i noticed that occasionally, about 5 minutes or so after starting up, the car would hiccup for a brief second. It would be running fine, then cut out for just an instant, then go right back to running fine again. It only happened maybe every 4th or 5th time i'd drive the car, and always within a few minutes of starting. As time went on, it started to do it more often. Then I noticed sometime it would actually die, not just hiccup. If I cranked it over, it would start back up immediately and continue to run fine. As time has gone on, it now does it almost everytime I first start it up in the morning, dies everytime, and now when i try to restart it, it cranks but wont fire. If i wait a minute or 2, it starts up just fine and will proceed to run fine the rest of the drive. The amount of time I have to wait before it will actually fire seems to be getting longer.

Here's what I know about the problem so far:

-Only ever happens in the first 3-5 minutes. If it hasn;t happened by then it never does, and once I get it restarted again I can drive it for hours with no problem.

-Doesn't seem to matter if i am stopped at idle, crusing at a steady speed, accelerating mildly, or punching it, the problem has happened under all these conditions.

-Runs fine other than this problem: have good compression, getting normal 02 readings, good mileage, nice idle, pulls hard and smoothly, no knock unless i really get on it, etc. Basically a nice-running well mannered GN other than the random die-ing

-When it dies and I try to restart it, it cranks at a normal speed, and I have a full 43 psi of pressure. The injectors have less than 3k miles on them, and the brand new harness looks in great shape still, so I'm doubtful its a fuel system issue

-I doubt its a bad repair-job on the wiring, I replaced some stretches of old wiring and a few of the fusible links because they were old and corroded, with insulation worn through, and corroded connectors. They were all replaced with the proper gauge wiring, with the proper size fusible links. My dad helped me with the actual repair, and he is technical crew chief for the NOAA Hurricane Hunter planes based out of MacDill AFB. If he can do wiring for an airplane that flies through hurricanes, I assume he wouldn't mess up my car :)

-Its a new battery that holds a charge fine and has good voltage

-The car doesn't throw any codes. If it has died, and is still not starting up again, when I scroll through the info on my scanmaster, everything seems what you would expect, except that the AF reads 04 (I would expect it to read 00 if the engine is not running). But then again, if I turn off the car when it is running normally (so whatever problem i have is not acting up) the MAF still reads 04, so maybe its just off its calibration a little bit? I don't know how big a deal this is/isn't.

My first thought was there was a piece of loose wiring somewhere that was randomly grounding out, or something to that effect. Checking what I can with a multi-meter while the problem is acting up however shows everything what I would expect. Also, jiggling wires and harnesses has no effeect on whether the car will restart, while several time i have just sat in the car and waited a few, wthout even popping the hood, and it restarts. It seems time is the determining factor.

My other thought was that some electrical component (sensor, ECM, Ignition Module, Coil, etc.) was gradually going south. Unfortunately I don;t know enough to figure out what to start checking and replacing. Its my understanding that if a cam sensor dies while the engine is running, it'll keep running fine, but once you stop it it won't restart. Since the car actually dies, I was thinking it rules out a cam sensor. Does this sound like a crank sensor problem? Do they fail gradually like this? Just using my intuition I would guess its a problem with the coil/module (I have converted to the 86/87 style of both, as well as ECM). Is there any easy way to test them, or narrow it down to which is the problem? I'd rather not drop the money to replace both if only one is bad.

I'm really at a loss here, and since the car is my daily driver this is really getting to be an inconvenience. Any light you guys can shed is appreciated. Am I barking up the wrong tree thinking ignition? Any other possible fault I may have overlooked? Please share your wisdom:)

Well, the car flat out refuses to start now. I dug out my noid light kit and my spark tester, and the car seems to have good solid spark, but the noid light didn;t do anything, which indicates a fueling issue. Just to re-iterate, the car has good solid fuel pressure, and the injectors and injector wiring harness are brand new. With key on, I probed both sides of the injector plug with the multimeter, and neither one is getting 12v. According to the no-start flow chart, this means "CKT 939 from Ign. feed is open or shorted to ground". Can anyone shed some light on this? does CKT stand for circuit? what do i need to check to fix this? Any help is really appreciated.


Scratch that, I just realized I'd probed it the wrong way and turns out one side of the plug DOES have 12 volts... so back to following the flow chart some more :)
I think I got it figured out, according to the flow chart, its a bad ignition module. I got all the way to page three, and in step 13, following the yes (i did have the proper voltage across the crank sensor terminals) it says its the module... guess I didn;t need to post to the board after all, but hey, now if this same thing happens to someone else, maybe they'll be able to search and find this thread and save themselves the trouble.

since i need to get a new module, are there any brands to steer clear of, or brands to look for? no sense spending $100 if the standard suto-parts store brands are junk.