Grid heater shake / miss / vibrate / jolt

[g_dog1]

Hi guys.

I have a 2007 5. 9 and the engine shakes/jolts/misses (I don't know what other word to use to describe it) when the engine is cold and the grid heater is cycling in the morning. Only once in a while when the grid heater is cycling does this happen. Basically I start the truck on a cold morning, it idles at the low (750 RPM idle, so the temperature is slightly above freezing), and while I'm sitting there for a couple grid heater cycles, the odd one will really cause a hard miss or jolt just as the grid heater or maybe it is the relay shuts off and/or turns on. I think I could actually hear the engine knock. I don't like this. I'm afraid I'll break the crankshaft with a jolt that hard.

I watch the battery gauge, and the "miss" occurs instantaneously as the voltage begins to rise again (or as soon as the grid heater shuts off).



Could it be a bad grid heater relay, or maybe a voltage regulator in the alternator?

Or have the only solutions been bad batteris and sensors?



If I let the grid heater cycle 5 times, this might happen once or twice. There is never any consistancy. I was even thinking it might be the PCM.



Any ideas?

 

[HBarlow]

It's nothing more than the grid heater cycling off and on as programmed. The grid heater draws about 90 amps which loads the alternator heavy. When the high current draw loads the alternator engine speed slows. The ECM senses rpm drop and bumps it back to normal idle speed. They all do it. Nothing to worry about.

 

[MChrist]

Hmmm, I start my truck in frigid temps all winter and haven't experienced any shudder when the grid heater cycles. The only indication that it is cycling is watching the volt meter drop down and the lights dim slightly.
Maybe somebody up near you has more info??

 

[Hoefler]

How old are your batteries?? I would bet you have one weak or bad. Have them load tested. When the grid heater cycles, the draw can cause a low voltage spike, starving other necessary electronics of needed power.

 

[g_dog1]

Hi guys. It comforts me a little bit to hear that this happens to others vehicles, and I agree with what Harvey said. But I am wondering why every once in a while I will get a much more violent shake than other times within one warmup period. And it seems to happen when the heater turns off. The truck has done this every winter for the past couple years. I disconnected the batteries for 24 hrs then checked the voltage of each battery and they were both really close. 12. 78V and 12. 69V. A load test would be a much more apropriate test. The batteries are original from 2007. The truck is very clean (no corrosion) and the grounds all look good. Is it possible to deactivate the grid heater without getting the check engine light? Can I just pull the two little wires (not the large ones going to the battery) off the relay? I understand that this relay is a double relay, and I want to isolate one side to see if one side causes this issue.

 

[HBarlow]

I know exactly what you are describing. It is a more abrupt jerk as you described. My '08 has done that a few times also. It is just one of those minor events that happens and goes without notice. I don't remember how many times mine has done that or if it still happens.

Hoeffler raised a good question. One of my OEM batteries failed early a year or two ago. The violent jerk could have happened only during the time I had a weak battery on one side and had not yet detected it. I've never thought about it and don't remember the last time it occurred.

It might be a good idea to have your batteries load tested by a shop with professional equipment. If the batteries are okay forget about it. No dealer is going to be able to diagnose it for you and will only waste your time.

My truck has just under 120k trouble free miles.

 

[JJPage]

With all you've stated I would suspect a failing relay(if bats are good), especially since it happens when the contacts are breaking because that's when an arc will occur. One of the relays could be starting to corrode, usually they will weld themselves shut, then they drain your battery or worse, melt conductors.

There was a thread awhile back about replacement relays available at large truck shops(Freightliner/Kenworth), that were heavier duty than the OEM's, and the price was better than the Dodge dealers. I never have much luck with the search forum, but you can try... change the "find posts" to "any date", may get better results.

Jess

Here's a link with some info,
https://www.turbodieselregister.com/forums/search.php?searchid=72253
https://www.turbodieselregister.com/forums/showthread.php?142915-1994-No-Intake-heater&pp=15

 

[EDankievitch]

my 05 did this same thing after I replaced the injectors. never did it with the old ones. never figured out why.

 

[g_dog1]

So what actually causes the jolting effect? Is it the grid heater robing power from the ECU, ultimately affecting the injectors (or injector relay), or is it the response of the alternator to the draw in current from the grid heater? I have experianced the jolting feeling both when the grid heater turns on and shuts off. The jolting feels like much more than just the rotational drag of the alternator pulley. It is as if the ECU does some kind of knee jerk reaction, ultimatey affecting the fuel injection events.

 

[sag2]

I would check all high current connections, powers and grounds. Remove them, clean and tighten again.

 

[B.G. Smith]

Mine is doing the same thing and takes more turning over to start when it is cold.(not really cold here, maybe 35 or so a few mornings) The jerk/jolt mine does I figured it was a complete missfire in one cylinder. Hope someone can figure it out. bg

 

[DonFitzwater]

My old 06 did it occasionally and it was remedied upon replacement of a bad injector that would hang up at idle (not firing randomly)

 

[B.G. Smith]

My old 06 did it occasionally and it was remedied upon replacement of a bad injector that would hang up at idle (not firing randomly)

That is my suspecion, I had some missfireing when it was new but couldn't/didn't ever really get a solution from dealer except adding Mopar fuel addative. It has a about 82000 miles now. bg

 

[FourBarR]

Just replaced the pair on my 98.5 OEM p/n 56026842. These are made by Borg Warner p/n R4811. Supplied by local parts store and were in stock price 110.00 cdn. They are exact replacement with the bracket.

 

[JJPage]

Just replaced the pair on my 98.5 OEM p/n 56026842. These are made by Borg Warner p/n R4811. Supplied by local parts store and were in stock price 110.00 cdn. They are exact replacement with the bracket.

Thank you FourBarR, do you know if these will also fit on a CR?

 

[Wingate]

if you think you ahve an injector hanging when cold, simply pour a bottle of two cycle engine oil in the fuel tank. If it ceases to act up on a cold start, then yes, its an injector not liking winter blend fuel and cold temps.
If it continues, I would suspect a weak battery causing voltage to drop too low when the grids cycle on.
If you ahve a block heater on it, try plugging it in and see how it starts in the morning.

 

[g_dog1]

With the Sanp-on Solus scan tool, I was watching the ECM voltageduring the grid heater cycling. While the voltage would fluctuate from 11.8V to 15V, the miss, would seem to be very intermitant. When it jolts, everyone within 10 ft of the truck knows it. I suspect that the Voltage regulator in the alerternator causes a dirty voltage signal to go the ECM, or the ECM gives a bad signal to the injectors or to the wrong injector for some reason. I had the batteries load tested and they tested good. I don't think it is a loose connection somewhere, as I drove over some rough roads and never have issues or glitches. Would a voltage regulator in the alternator interupt signals from a cam sensor or crank position sensor? I wonder if a temp sensor changing temp values would cause that violent miss.
By the way, I had all new injectors installed, and nothing changed.

 

[jgillott]

I had a similar issue with my '07 a few years ago. After a lot of trial and error and finally a P0193 (Fuel Rail Sensor High) code, it ended up being a bad connection between the wiring harness and the fuel pressure sensor on the back of the rail. Every once in a while under the right conditions, cold damp, after a heavy rain, rough road, it would start to miss/surge/jolt. It took us a while to isolate it as a connection issue, but what we ended up noticing was a great spike or drop in the rail pressure signal for a split second when the miss would occur. Cleaned the connector and used dielectric grease and haven't had a problem since.

 

[g_dog1]

JGillott. I will check this out right away. I haven't gotten any codes, and I wish I would just to indicate where to start looking. So your engine would Miss while driving down the road also? I will keep you posted. Thank-you for the feedback.

 

[jgillott]

Yes, it would miss and stumble while driving and under load. Sometimes slight and sometimes very violently. Then it would go away for days or weeks at a time and then come back again.