Allpar Forums banner

1 - 3 of 3 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter · #1 ·
So, my new-to-me, 68000 mile Dynasty has picked up one of those terrible little habits that I'm trying to figure out, but I can't get my head around why it's breaking....

It's started to hiccup and act like it's going to die at WOT, but as soon as I back out of it, it goes back to normal. It would be easier if it would store a code when it does this, but it's not storing the code, so...

It improved greatly when I changed the fuel filter, because it would do it when cruising at high speed, but now it's acting a bit more reliably.

The other thing I've noticed, however, is that when it does act up, it has a voltage drop down to what (I'm assuming) is the 12V mark on the voltmeter, and then voltage picks back up when it recovers. That, I can recreate if I give it a jab of throttle when it's cold, and in neutral, and then release suddenly.

I'm pretty reasonably sure it's not a fueling issue, so what else should I be looking for?
 

·
Super Moderator
Joined
·
32,400 Posts
It won't be clear if the voltage drops because it's about to stall, or if it's about to stall because the voltage drops.

I had a situation with my 92 Daytona years ago, where it would skip at highway speeds, and stumble worse at lower speeds. Very quick, sharp event, and sometimes several times a day, sometimes never. It got worse until it skipped 10 times in a few minutes.
I was afraid of a burnt valve, but compression was good. Finally I got a code 13 and momentary CEL. But it turned out, that was a symptom of near-stalling and therefore losing vacuum.

I noticed that when this happened, the voltmeter flicked down, held low for a second or two, then snapped back to normal. Every time. I finally realized that this happened when the cooling fan was turning on. So I measured the motor windings, and they read 0.6 ohms, instead of the normal 2.4 ohms or so. A current probe showed that it drew a spike of 36 amps when the fan turned on, and 13 amps steady-state. I replaced the fan/motor assembly, and it then drew a 13 amp spike and 4 amps steady.

Then it still kept happening. Finally, finding no fault in the wiring harness, but knowing that the wires to the cooling fan were shorting out when the relay was energized, I fabbed a harness of two wires to the fan, mounted a separate relay on the radiator bulkhead, and used male fastons and wire that plugged into the fan's socket in the Power Distribution Center (in the relay coil contacts), so that the external relay was still energized by the socket, and....never had a single problem again. Bypassing the fan wiring between the relay and fan motor with new wiring cured it. Never did find the short.
 

·
Super Moderator
Joined
·
32,400 Posts
1 - 3 of 3 Posts
Top