bizarre intermittent no start- need help!

[SouthernCal GN]

This one has me truly stumped. Installed the new engine about 3 weeks ago, and everything was absolutely fine with starting/running, etc. Did the usual oil changes, put about 500 miles on the car, and all was fine. The only change done to the car's wiring was a relocation of the grounds behind the passenger head to a lengthed cable installed at the front of the block.

Night before last, I went out, and was on cruise control about 65 mph, when I felt the car stumble, and the revs momentarily dropped to about 1800, then the car picked back up to speed. It did it a second time, so I took the cruise control off line, and continued on my way. About 3 minutes later, the engine died without fanfare, and I coasted to a stop.

The car would crank, but not start. I checked the fuse box, all the sensor connectors, and the fuel pressure; after about 10 minutes, the car started, but diied again about 5 minutes later- and wouldn't start. After an hour, I got the car started, and I limped it home.

I replaced the crank sensor with a spare good one, checked the cam sensor cap and rotor, and got the car running well (or so I thought!) Last night, the same thing happened. I swapped the ECM with a new reman I had with me, and for a moment, I got the car running- then it quit. Had it towed home, and with the car cold, it still wouldn't start. 5 minutes ago, I went into the garage, and the car started strong and normally.

When the car dies, it just quits without drama.

ECM/chip- known good.
cam sensor- seems to be ok.
crank sensor- same.
coil pack- did not change.
gauge shows pressure at the fuel rail.

I need some ideas! Thanks...

 

[Quick6'n'-K.C.]

Ignition module getting hot and going out on the fritz...

Works fine cold eh?

Got a spare to try it around the block so you dont have to get towed?

That is the first thing that comes to mind when objects under the hood get hot and start to fail
BW

 

[SouthernCal GN]

I had one with me, but not the tools to swap it. I'm off to swap it out...

 

[charliep]

Loose power wire on starter??

 

[SouthernCal GN]

Car would crank just fine........if it was the fusible link, I would have thought that the car wouldn't start at all.

 

[Rodney87GN]

How about the orange ECM wire from the battery? If you get the car running wiggle it around and see if it dies. Ask me how I know that one.

 

[onslow]

Hi SCGN-

With an engine rebuild, I would believe there is a simple solution here...seems like there are always clinkers to work out.

I like the ideas of (checking, replacing) the ICM and wiggling the ECM wire.

If neither one of those identifies the problem, I suggest the following:

How are EGR and PCV?

Have you checked for vacuum leaks?

Crank Sensor - I know you said you have a new unit. A check would be to wait for the stall or no start to occur.

Then, disable fuel by pulling fuel pump relay or fuse, and crank car. If you get a crank signal/tach of 100 to 200 RPM, you can verify that new sensor is okay.

By the way, does the sensor have black plastic or aluminum towers thru which the interruptor ring runs? Wisdom passed on to me from a 25 year TurboB vet says the aluminum units should be tossed.

MAF - When car will not start, unplug MAF and see if it starts. If so, MAF could be one problem...there could be others.

Verify by swapping with a known working unit, if you can. Swatting it to create stumble does not always disclose a problem.

You might also look to see if yours is filthed up. If so, you might just need to clean it with CRC's MAF spray.

Also, have any screens been removed from it? However, if any were and the car ran fine before the rebuild, and you still have the problem...continue:

Diagnostics - When you get it running long enough, can you give us some numbers in CLOSED loop?
IAC
BLM
MAF
TPS

That should be enough for now.

Please let us know how this works out.

Steve