Gas Engine Shakes at Startup

Another question I have based on the heat cycling theory, are cars that are predominantly open road driven and/or cars from colder climates as susceptible to HG issues. In both these cases there would be less thermal cycling. Open road cars because the engine is always on above 45mph. In colder climates the ecu won’t let the coolant fall below 121F if the heater is on.

 

Except in startup from ambient, I've never seen the coolant remain or cycle below below 170 F.

 

I was watching my V with my Bluetooth scanner while waiting in line to get the kids the other day. It was chilly outside so the heat was on. As soon as the scanner reported 121F the engine would start, raise the temp by 10 deg give or take then shutdown. I wasn’t calling for maximum heat and the cab was at a comfortable temp so the heater was just maintaining. I wonder if the low limit coolant temp rises if maximum heat is called for.

 

To be clear, I was driving, not parked.

 

This thread has some details on how the ECU adjusts its coolant temperature setpoints under different conditions:

on hunkering, Gen 3 style | PriusChat

 

I'm worried they'll warp your HG. I know it's a coincidence but people usually change their spark plugs around 120k mi, and roughly 30k mi later is the dreaded HG....

A hotter plug is not a hotter burner on the stove, it doesn't distribute it's heat nice and evenly....

 

Engine oil has additives to neutralize acids formed from the combustion process. HG corrosion is usually caused by coolant that doesn’t get changed often enough.

 

Failed or failing water pumps also a big factor, when the coolant isn't flowing properly into the block...what happens? "Nearly" every vehicle that I see come into the shop for HG or engine related service, has a very "tight" water pump impeller or seized one. Everyone's answer is a viable one here, but there's still something else doing it...

 

I always scratch my head as to why this is on the inside back cover of my ‘85 300D diesel Mercedes manual. I hope that Haynes realizes that it uses glow plugs and not spark plugs!

 

A "hotter" plug is one whose own tip stays hotter, because less of it is in contact with the metal threads, and therefore it transfers less heat into the head around it.

 

Thank you for clarifying my misconception!


iPhone ?

 

Is water pump rpm monitored by the ecu.

 

P261B is the waterpump code, the impeller is likely slowing down and the pump failing either because the car ran low on coolant or it's just that time and you have a lot of miles on that Original pump. I'd change it (with alot of miles on the car) before that light comes up if I were you.

 

The three water-pump trouble codes are P261B, P261C, and P261D. The first one is if the monitored pump RPM goes below 900 when the ECM wants it to run faster. The other two are electrical problems monitoring or controlling the pump.

There's also the matter of the fail-safe behaviors the ECM adopts when it has given any of those codes. When it gives a P261C or P261D, it tells the pump to stop. (!) When it gives a P261B, it goes into this cycle where it tells the pump to stop for 30 seconds, run at 85% for 5 seconds, and repeat, like it might be trying to unjam something.

Those fail-safe actions might be helpful for preventing an electrical problem from getting worse, or maybe getting the pump unjammed, but clearly they aren't recipes for cooling the engine really well. So it wouldn't be a good idea to drive around for very long with any of those codes.

Also, with any of those codes showing, the engine will summarily shut off without further warning if the temperature ever hits 105 ℃.

 

^ usually once it detects something that magnet/impeller in the water pump has already failed or gotten so tight it's not flowing enough coolant to sufficiently keep the engine cool any more. It needs to be changed immediately or you WILL blow a head gasket or worse.