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High Idle "Hic-Up/Fishbite"

ak diesel driver said:
what about the wires to your toggle
Click to expand...

I think I eliminated the toggles as a possible problem by jumping directly from the ECM connector to the battery and still had the biting.

Chevylover said:
OR especially your ENGINE COOLANT SENSOR (the one for the ECM) ??

Cu,
Sven
Click to expand...

Brooklyn Tow said:
X2....Coolant temp sensor adjusts timing and idle on cold start.

2 Cents - JMO
Click to expand...

This is the one is the T-stat crossover, right?

Well, I know it's at least functioning (and it's about 3 years old) because the engine responded appropriately when I disconnected it... Engine idle went higher by itself (w/o using the HI toggle or manually pushing down the pedal). Also, this morning (with heater plugged in for about 3 hours) it started as I expected it would. Idle didn't stay as high, less noise, etc.

How well it's functioning, I don't know.
 
POSSIBLY FIXED

I started the truck this morning (didn't plug it in last night) - it was about 20* out. NO BITING! I'll have to do it a few more times to be sure (I hope I'm not jinxing myself).

Here's the deal: Two years ago I replaced all battery/alternator/starter/ECM cables and upsized them, too. I also replaced and upsized the grounds (in addition to adding more).

So, when this biting issue came up, I checked the connections at the battery and the grounds (as some suggested) and they were tight and clean. BUT, I never thought to to check the alternator lug/connection. IT WAS LOOSE (my own fault)! The wire was loose inside the lug - I never properly crimped it. Now it is soldered and crimped.

I only stumbled upon this because my truck wouldn't start about a week ago and I traced it to this bad connection.

So, does this make sense to you guys? Could the bad alternator wire connection explain the biting?
 
So what do you think it was then. The starting amp draw plus the longer glow when cold drops voltage some? And the alternator is charging but slower than normal due to high resistance of marginal connection???

Or a variation of voltage / amps from vibration on lug connection while the alternator is quick charging the initial drain of cranking (worse when really cold). Then during surge of charge the PDM/FSD hiccups or something. Once recovered initial drain it clears itself up???

Keep us posted. Grounds and battery connections are harped on a lot but the alternator not as much.
 
schiker said:
So what do you think it was then. The starting amp draw plus the longer glow when cold drops voltage some? And the alternator is charging but slower than normal due to high resistance of marginal connection???

Or a variation of voltage / amps from vibration on lug connection while the alternator is quick charging the initial drain of cranking (worse when really cold). Then during surge of charge the PDM/FSD hiccups or something. Once recovered initial drain it clears itself up???

Keep us posted. Grounds and battery connections are harped on a lot but the alternator not as much.
Click to expand...

Hmmm. Good questions. Admittedly, I didn't really know what to think about how the loose wire caused the problem. I would like to know, if for no other reason than just for "knowledge sake".

It was 33* out this morning, so I didn't try it. As soon as it gets cold again, I'll try starting it w/o having it plugged in the night before.
 
UPDATE UPDATE UPDATE

It was finally cold this morning - 14*. NO fishbite! :D

Thanks everyone!!!! Really, really appreciate all the help and guidance! :grouphug:
 
Good glad its fixed. Wonder what the root of the problem was? I am still kind of thinking it was temperature/afterglow/voltage(or amps) related. Could have been a hiccup of FSD due to power issues but am leaning more towards the afterglow wasn't as strong with less charge from alternator and a little cold natured.

If it ever happens similarly again maybe a way to tell would be hook up 1 or 2 more batteries so you have more umph after cranking while really cold. Even though you were probably spinning fast enough some reduced power output of batteries could have reduced heating of the glow plugs during the quick afterglow cycles. ????
 
Well, I will say that now that the batteries are fully charged, I do notice a difference in how quickly the thing spins up. I didn't notice it before - at least not until it was obvious. But now, it sure does sound faster than it was before.
 
It did it again - the truck was sitting for about 2 weeks. I'm surprised that that is long enough to draw the battery down enough to cause a problem. I did this a while back, but I'm going to check battery draw again. I might experiment with taking voltage readings and then letting the interior lights on overnight - then taking another reading in the morning and starting it up. Then charge it up fully and repeat.

I dunno? Does that sound like a good game plan?
 
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