Sudden Cutoff with No Trouble Code

[Skyguy007]

My '96 LT4 engine stalled while idling at a traffic light a few days ago. I managed to get the engine restarted. My scanner turned up a code P0372 (high resolution signal failure from the OptiSpark). After reading the code, I erased the stored trouble code.

The car started today, but stalled after a couple of minutes at idle. I installed a new coil and an ignition module. Once again, the engine started and felt very responsive, but the engine died once I had pulled out onto the street. After about 10 minutes, I was able start the engine and drove the car back into my garage, whereupon the engine died again. I've run a couple of scans, but no trouble code has been set. I thought the computer would set a code whenever there was an engine malfunction, but obviously I'm wrong.

I'd welcome ideas.

 

[FX GS]

Bill, could it be a fuel delivery problem?

 

[Skyguy007]

With no trouble code it's hard to tell. I checked to make sure that the gas cap was secure. When the car starts, it runs just fine - no misses or surges - and the throttle is responsive. When it quits, it simply cuts off. The really wierd thing is that no trouble codes are being set. I haven't timed the running time, but I'd guess that it's in the two to three minute range. It seems to be independent of the engine coolant temp. I have a call into Gordon Killebrew to see what he thinks.

 

[Hib Halverson]

I'd start by checking all wires and connections having to do with the ignition system. The P0372 is a clue but not convincing evidence. Besides, if the ign. looses the high res signal, the system is designed to be able to run on the low res. to get you to where you can make repairs.

That said, anytime you have an abrupt cutoff, it's usually an ign. failure or a loss of B+ electrical power.

 

[Skyguy007]

Thanks for the tip Hib. I've checked out the 4 pin connector that's on the right side of the intake. There's 5 volts at pin B and all of the wires and connectors in and out look solid. I just spoke with Gordon, who said he thinks it's the high-res sensor in the DynaSpark. Although he suggested that I check the conector on the coolant sensor beofre I tear everything down. Apparently, a short or lack of continuity with the coolant sensor can keep the engine from starting an can cause other problems. I think I'm looking at shipping the DynaSpark back to Ft. Wayne if the coolant sensor connection is OK.

 

[sothpaw]

Thanks for the tip Hib. I've checked out the 4 pin connector that's on the right side of the intake. There's 5 volts at pin B and all of the wires and connectors in and out look solid. I just spoke with Gordon, who said he thinks it's the high-res sensor in the DynaSpark. Although he suggested that I check the conector on the coolant sensor beofre I tear everything down. Apparently, a short or lack of continuity with the coolant sensor can keep the engine from starting an can cause other problems. I think I'm looking at shipping the DynaSpark back to Ft. Wayne if the coolant sensor connection is OK.

Hey Sky,

How did this turn out? I'd be interested in the Dynaspark's true durability. If it only lasted you 6 months that is not worth it to me.

 

[Skyguy007]

Wow, this brings back some not-so-fond memories, but I'm happy to provide an update. As it turns out, I had not been careful when routing the vacuum side vent hose on the Dynaspark, which allowed the hose to contact the serpentine belt, which led to the hose being burned through. The un-vented Dynaspark suffered from a buildup of nasty stuff, which caused corrosion and general deterioration under the cap, which pretty much messed it up.

Despite my screwup, Phil at DynaTech rebuilt my Dynaspark at a modest cost with very quick turnaround. The level of caring and service was great -particularly when considering that the failure was a result of my mistake.

Needless to say, I was a lot more careful (and a lot quicker with the job) the second time around. Since then, the Dynaspark has functioned flawlessly. I do periodically pull the vent line and apply vacuum with a hand pump that has a gauge, just to see how fast the vacuum bleeds off.

Would I buy another Dynaspark? Absolutely! It is much more solid than a stock unit. I've done one HPDE and am getting ready for two more. It's nice to not have to worry about Optispark failure while on the track.

Now if someone could just tell me an easy way to swap out spark plugs on my GS....